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<title>erl_nif</title>
<prepared>Sverker Eriksson</prepared>
<responsible>Sverker Eriksson</responsible>
<docno>1</docno>
<approved></approved>
<checked></checked>
<date>2009-11-17</date>
<rev>PA1</rev>
<file>erl_nif.xml</file>
</header>
<lib>erl_nif</lib>
<libsummary>API functions for an Erlang NIF library</libsummary>
<description>
<p>A NIF library contains native implementation of some functions
of an Erlang module. The native implemented functions (NIFs) are
called like any other functions without any difference to the
caller. Each NIF must also have an implementation in Erlang that
will be invoked if the function is called before the NIF library
has been successfully loaded. A typical such stub implementation
is to throw an exception. But it can also be used as a fallback
implementation if the NIF library is not implemented for some
architecture.</p>
<marker id="WARNING"/>
<warning><p><em>Use this functionality with extreme care!</em></p>
<p>A native function is executed as a direct extension of the
native code of the VM. Execution is not made in a safe environment.
The VM can <em>not</em> provide the same services as provided when
executing Erlang code, such as preemptive scheduling or memory
protection. If the native function doesn't behave well, the whole
VM will misbehave.</p>
<list>
<item><p>A native function that crash will crash the whole VM.</p></item>
<item><p>An erroneously implemented native function might cause
a VM internal state inconsistency which may cause a crash of the VM,
or miscellaneous misbehaviors of the VM at any point after the call
to the native function.</p></item>
<item><p>A native function that do <seealso marker="#lengthy_work">lengthy
work</seealso> before returning will degrade responsiveness of the VM,
and may cause miscellaneous strange behaviors. Such strange behaviors
include, but are not limited to, extreme memory usage, and bad load
balancing between schedulers. Strange behaviors that might occur due
to lengthy work may also vary between OTP releases.</p></item>
</list>
</warning>
<p>A minimal example of a NIF library can look like this:</p>
<p/>
<code type="none">
/* niftest.c */
#include "erl_nif.h"
static ERL_NIF_TERM hello(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
{
return enif_make_string(env, "Hello world!", ERL_NIF_LATIN1);
}
static ErlNifFunc nif_funcs[] =
{
{"hello", 0, hello}
};
ERL_NIF_INIT(niftest,nif_funcs,NULL,NULL,NULL,NULL)
</code>
<p>and the Erlang module would have to look something like
this:</p>
<p/>
<code type="none">
-module(niftest).
-export([init/0, hello/0]).
init() ->
erlang:load_nif("./niftest", 0).
hello() ->
"NIF library not loaded".
</code>
<p>and compile and test something like this (on Linux):</p>
<p/>
<code type="none">
$> gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
$> erl
1> c(niftest).
{ok,niftest}
2> niftest:hello().
"NIF library not loaded"
3> niftest:init().
ok
4> niftest:hello().
"Hello world!"
</code>
<p>A better solution for a real module is to take advantage of
the new directive <seealso
marker="doc/reference_manual:code_loading#on_load">on_load</seealso> to automatically
load the NIF library when the module is loaded.</p>
<note><p>A NIF does not have to be exported, it can be local to the module.
Note however that unused local stub functions will be optimized
away by the compiler causing loading of the NIF library to fail.</p>
</note>
<p>A loaded NIF library is tied to the Erlang module code version
that loaded it. If the module is upgraded with a new version, the
new Erlang code will have to load its own NIF library (or maybe choose not
to). The new code version can however choose to load the exact
same NIF library as the old code if it wants to. Sharing the same
dynamic library will mean that static data defined by the library
will be shared as well. To avoid unintentionally shared static
data, each Erlang module code can keep its own private data. This
private data can be set when the NIF library is loaded and
then retrieved by calling <seealso marker="#enif_priv_data">enif_priv_data</seealso>.</p>
<p>There is no way to explicitly unload a NIF library. A library will be
automatically unloaded when the module code that it belongs to is purged
by the code server.</p>
<p><marker id="lengthy_work"/>
As mentioned in the <seealso marker="#WARNING">warning</seealso> text at
the beginning of this document it is of vital importance that a native function
return relatively quickly. It is hard to give an exact maximum amount
of time that a native function is allowed to work, but as a rule of thumb
a well-behaving native function should return to its caller before a
millisecond has passed. This can be achieved using different approaches.
If you have full control over the code to execute in the native
function, the best approach is to divide the work into multiple chunks of
work and call the native function multiple times, either directly from Erlang code
or by having a native function schedule a future NIF call via the
<seealso marker="#enif_schedule_nif"> enif_schedule_nif</seealso> function. Function
<seealso marker="#enif_consume_timeslice">enif_consume_timeslice</seealso> can be
used to help with such work division. In some cases, however, this might not
be possible, e.g. when calling third-party libraries. Then you typically want
to dispatch the work to another thread, return
from the native function, and wait for the result. The thread can send
the result back to the calling thread using message passing. Information
about thread primitives can be found below. If you have built your system
with <em>the currently experimental</em> support for dirty schedulers,
you may want to try out this functionality by dispatching the work to a
<seealso marker="#dirty_nifs">dirty NIF</seealso>,
which does not have the same duration restriction as a normal NIF.</p>
</description>
<section>
<title>FUNCTIONALITY</title>
<p>All functions that a NIF library needs to do with Erlang are
performed through the NIF API functions. There are functions
for the following functionality:</p>
<taglist>
<tag>Read and write Erlang terms</tag>
<item><p>Any Erlang terms can be passed to a NIF as function arguments and
be returned as function return values. The terms are of C-type
<seealso marker="#ERL_NIF_TERM">ERL_NIF_TERM</seealso>
and can only be read or written using API functions. Most functions to read
the content of a term are prefixed <c>enif_get_</c> and usually return
true (or false) if the term was of the expected type (or not).
The functions to write terms are all prefixed <c>enif_make_</c> and usually
return the created <c>ERL_NIF_TERM</c>. There are also some functions
to query terms, like <c>enif_is_atom</c>, <c>enif_is_identical</c> and
<c>enif_compare</c>.</p>
<p>All terms of type <c>ERL_NIF_TERM</c> belong to an environment of type
<seealso marker="#ErlNifEnv">ErlNifEnv</seealso>. The lifetime of a term is
controlled by the lifetime of its environment object. All API functions that read
or write terms has the environment, that the term belongs to, as the first
function argument.</p></item>
<tag>Binaries</tag>
<item><p>Terms of type binary are accessed with the help of the struct type
<seealso marker="#ErlNifBinary">ErlNifBinary</seealso>
that contains a pointer (<c>data</c>) to the raw binary data and the length
(<c>size</c>) of the data in bytes. Both <c>data</c> and <c>size</c> are
read-only and should only be written using calls to API functions.
Instances of <c>ErlNifBinary</c> are however always allocated by the user
(usually as local variables).</p>
<p>The raw data pointed to by <c>data</c> is only mutable after a call to
<seealso marker="#enif_alloc_binary">enif_alloc_binary</seealso> or
<seealso marker="#enif_realloc_binary">enif_realloc_binary</seealso>.
All other functions that operates on a binary will leave the data as read-only.
A mutable binary must in the end either be freed with
<seealso marker="#enif_release_binary">enif_release_binary</seealso>
or made read-only by transferring it to an Erlang term with
<seealso marker="#enif_make_binary">enif_make_binary</seealso>.
But it does not have to happen in the same NIF call. Read-only binaries
do not have to be released.</p>
<p><seealso marker="#enif_make_new_binary">enif_make_new_binary</seealso>
can be used as a shortcut to allocate and return a binary in the same NIF call.</p>
<p>Binaries are sequences of whole bytes. Bitstrings with an arbitrary
bit length have no support yet.</p>
</item>
<tag>Resource objects</tag>
<item><p>The use of resource objects is a safe way to return pointers to
native data structures from a NIF. A resource object is
just a block of memory allocated with
<seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.
A handle ("safe pointer") to this memory block can then be returned to Erlang by the use of
<seealso marker="#enif_make_resource">enif_make_resource</seealso>.
The term returned by <c>enif_make_resource</c>
is totally opaque in nature. It can be stored and passed between processes
on the same node, but the only real end usage is to pass it back as an argument to a NIF.
The NIF can then call <seealso marker="#enif_get_resource">enif_get_resource</seealso>
and get back a pointer to the memory block that is guaranteed to still be
valid. A resource object will not be deallocated until the last handle term
has been garbage collected by the VM and the resource has been
released with <seealso marker="#enif_release_resource">enif_release_resource</seealso>
(not necessarily in that order).</p>
<p>All resource objects are created as instances of some <em>resource type</em>.
This makes resources from different modules to be distinguishable.
A resource type is created by calling
<seealso marker="#enif_open_resource_type">enif_open_resource_type</seealso>
when a library is loaded. Objects of that resource type can then later be allocated
and <c>enif_get_resource</c> verifies that the resource is of the expected type.
A resource type can have a user supplied destructor function that is
automatically called when resources of that type are released (by either
the garbage collector or <c>enif_release_resource</c>). Resource types
are uniquely identified by a supplied name string and the name of the
implementing module.</p>
<marker id="enif_resource_example"/><p>Here is a template example of how to create and return a resource object.</p>
<p/>
<code type="none">
ERL_NIF_TERM term;
MyStruct* obj = enif_alloc_resource(my_resource_type, sizeof(MyStruct));
/* initialize struct ... */
term = enif_make_resource(env, obj);
if (keep_a_reference_of_our_own) {
/* store 'obj' in static variable, private data or other resource object */
}
else {
enif_release_resource(obj);
/* resource now only owned by "Erlang" */
}
return term;
</code>
<p>Note that once <c>enif_make_resource</c> creates the term to
return to Erlang, the code can choose to either keep its own
native pointer to the allocated struct and release it later, or
release it immediately and rely solely on the garbage collector
to eventually deallocate the resource object when it collects
the term.</p>
<p>Another usage of resource objects is to create binary terms with
user defined memory management.
<seealso marker="#enif_make_resource_binary">enif_make_resource_binary</seealso>
will create a binary term that is connected to a resource object. The
destructor of the resource will be called when the binary is garbage
collected, at which time the binary data can be released. An example of
this can be a binary term consisting of data from a <c>mmap</c>'ed file.
The destructor can then do <c>munmap</c> to release the memory
region.</p>
<p>Resource types support upgrade in runtime by allowing a loaded NIF
library to takeover an already existing resource type and thereby
"inherit" all existing objects of that type. The destructor of the new
library will thereafter be called for the inherited objects and the
library with the old destructor function can be safely unloaded. Existing
resource objects, of a module that is upgraded, must either be deleted
or taken over by the new NIF library. The unloading of a library will be
postponed as long as there exist resource objects with a destructor
function in the library.
</p>
</item>
<tag>Threads and concurrency</tag>
<item><p>A NIF is thread-safe without any explicit synchronization as
long as it acts as a pure function and only reads the supplied
arguments. As soon as you write towards a shared state either through
static variables or <seealso marker="#enif_priv_data">enif_priv_data</seealso>
you need to supply your own explicit synchronization. This includes terms
in process independent environments that are shared between threads.
Resource objects will also require synchronization if you treat them as
mutable.</p>
<p>The library initialization callbacks <c>load</c>, <c>reload</c> and
<c>upgrade</c> are all thread-safe even for shared state data.</p>
</item>
<tag><marker id="version_management"/>Version Management</tag>
<item><p>
When a NIF library is built, information about NIF API version
is compiled into the library. When a NIF library is loaded the
runtime system verifies that the library is of a compatible version.
<c>erl_nif.h</c> defines <c>ERL_NIF_MAJOR_VERSION</c>, and
<c>ERL_NIF_MINOR_VERSION</c>. <c>ERL_NIF_MAJOR_VERSION</c> will be
incremented when NIF library incompatible changes are made to the
Erlang runtime system. Normally it will suffice to recompile the NIF
library when the <c>ERL_NIF_MAJOR_VERSION</c> has changed, but it
could, under rare circumstances, mean that NIF libraries have to
be slightly modified. If so, this will of course be documented.
<c>ERL_NIF_MINOR_VERSION</c> will be incremented when
new features are added. The runtime system uses the minor version
to determine what features to use.
</p><p>
The runtime system will normally refuse to load a NIF library if
the major versions differ, or if the major versions are equal and
the minor version used by the NIF library is greater than the one
used by the runtime system. Old NIF libraries with lower major
versions will however be allowed after a bump of the major version
during a transition period of two major releases. Such old NIF
libraries might however fail if deprecated features are used.
</p></item>
<tag><marker id="time_measurement"/>Time Measurement</tag>
<item><p>Support for time measurement in NIF libraries:
<list>
<item><seealso marker="#ErlNifTime"><c>ErlNifTime</c></seealso></item>
<item><seealso marker="#ErlNifTimeUnit"><c>ErlNifTimeUnit</c></seealso></item>
<item><seealso marker="#enif_monotonic_time"><c>enif_monotonic_time()</c></seealso></item>
<item><seealso marker="#enif_time_offset"><c>enif_time_offset()</c></seealso></item>
<item><seealso marker="#enif_convert_time_unit"><c>enif_convert_time_unit()</c></seealso></item>
</list></p>
</item>
<tag>Long-running NIFs</tag>
<item><p><marker id="dirty_nifs"/>Native functions
<seealso marker="#lengthy_work">
must normally run quickly</seealso>, as explained earlier in this document. They
generally should execute for no more than a millisecond. But not all native functions
can execute so quickly; for example, functions that encrypt large blocks of data or
perform lengthy file system operations can often run for tens of seconds or more.</p>
<p>If the functionality of a long-running NIF can be split so that its work can be
achieved through a series of shorter NIF calls, the application can either make that series
of NIF calls from the Erlang level, or it can call a NIF that first performs a chunk of the
work, then invokes the <seealso marker="#enif_schedule_nif">enif_schedule_nif</seealso>
function to schedule another NIF call to perform the next chunk. The final call scheduled
in this manner can then return the overall result. Breaking up a long-running function in
this manner enables the VM to regain control between calls to the NIFs, thereby avoiding
degraded responsiveness, scheduler load balancing problems, and other strange behaviours.</p>
<p>A NIF that cannot be split and cannot execute in a millisecond or less is called a "dirty NIF"
because it performs work that the Erlang runtime cannot handle cleanly.
<em>Note that the dirty NIF functionality described here is experimental</em> and that you have to
enable support for dirty schedulers when building OTP in order to try the functionality out.
Applications that make use of such functions must indicate to the runtime that the functions are
dirty so they can be handled specially. To schedule a dirty NIF for execution, the
appropriate flags value can be set for the NIF in its <seealso marker="#ErlNifFunc">ErlNifFunc</seealso>
entry, or the application can call <seealso marker="#enif_schedule_nif">enif_schedule_nif</seealso>,
passing to it a pointer to the dirty NIF to be executed and indicating with the <c>flags</c>
argument whether it expects the operation to be CPU-bound or I/O-bound.</p>
<note><p>Dirty NIF support is available only when the emulator is configured with dirty
schedulers enabled. This feature is currently disabled by default. To determine whether
the dirty NIF API is available, native code can check to see if the C preprocessor macro
<c>ERL_NIF_DIRTY_SCHEDULER_SUPPORT</c> is defined. Also, if the Erlang runtime was built
without threading support, dirty schedulers are disabled. To check at runtime for the presence
of dirty scheduler threads, code can use the <seealso marker="#enif_system_info"><c>
enif_system_info()</c></seealso> API function.</p></note>
</item>
</taglist>
</section>
<section>
<title>INITIALIZATION</title>
<taglist>
<tag><marker id="ERL_NIF_INIT"/>ERL_NIF_INIT(MODULE, ErlNifFunc funcs[], load, reload, upgrade, unload)</tag>
<item><p>This is the magic macro to initialize a NIF library. It
should be evaluated in global file scope.</p>
<p><c>MODULE</c> is the name of the Erlang module as an
identifier without string quotations. It will be stringified by
the macro.</p>
<p><c>funcs</c> is a static array of function descriptors for
all the implemented NIFs in this library.</p>
<p><c>load</c>, <c>reload</c>, <c>upgrade</c> and <c>unload</c>
are pointers to functions. One of <c>load</c>, <c>reload</c> or
<c>upgrade</c> will be called to initialize the library.
<c>unload</c> is called to release the library. They are all
described individually below.</p>
<p>If compiling a nif for static inclusion via --enable-static-nifs you
have to define STATIC_ERLANG_NIF before the ERL_NIF_INIT declaration.</p>
</item>
<tag><marker id="load"/>int (*load)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info)</tag>
<item><p><c>load</c> is called when the NIF library is loaded
and there is no previously loaded library for this module.</p>
<p><c>*priv_data</c> can be set to point to some private data
that the library needs in order to keep a state between NIF
calls. <c>enif_priv_data</c> will return this pointer.
<c>*priv_data</c> will be initialized to NULL when <c>load</c> is
called.</p>
<p><c>load_info</c> is the second argument to <seealso
marker="erlang#load_nif-2">erlang:load_nif/2</seealso>.</p>
<p>The library will fail to load if <c>load</c> returns
anything other than 0. <c>load</c> can be NULL in case no
initialization is needed.</p>
</item>
<tag><marker id="upgrade"/>int (*upgrade)(ErlNifEnv* env, void** priv_data, void** old_priv_data, ERL_NIF_TERM load_info)</tag>
<item><p><c>upgrade</c> is called when the NIF library is loaded
and there is old code of this module with a loaded NIF library.</p>
<p>Works the same as <c>load</c>. The only difference is that
<c>*old_priv_data</c> already contains the value set by the
last call to <c>load</c> or <c>reload</c> for the old module
code. <c>*priv_data</c> will be initialized to NULL when <c>upgrade</c>
is called. It is allowed to write to both *priv_data and *old_priv_data.</p>
<p>The library will fail to load if <c>upgrade</c> returns
anything other than 0 or if <c>upgrade</c> is NULL.</p>
</item>
<tag><marker id="unload"/>void (*unload)(ErlNifEnv* env, void* priv_data)</tag>
<item><p><c>unload</c> is called when the module code that
the NIF library belongs to is purged as old. New code
of the same module may or may not exist. Note that <c>unload</c> is not
called for a replaced library as a consequence of <c>reload</c>.</p>
</item>
<tag><marker id="reload"/>int (*reload)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info)</tag>
<note><p>The reload mechanism is <em>deprecated</em>. It was only intended
as a development feature. Do not use it as an upgrade method for
live production systems. It might be removed in future releases. Be sure
to pass <c>reload</c> as <c>NULL</c> to <seealso marker="#ERL_NIF_INIT">ERL_NIF_INIT</seealso>
to disable it when not used.</p>
</note>
<item><p><c>reload</c> is called when the NIF library is loaded
and there is already a previously loaded library for this
module code.</p>
<p>Works the same as <c>load</c>. The only difference is that
<c>*priv_data</c> already contains the value set by the
previous call to <c>load</c> or <c>reload</c>.</p>
<p>The library will fail to load if <c>reload</c> returns
anything other than 0 or if <c>reload</c> is NULL.</p>
</item>
</taglist>
</section>
<section>
<title>DATA TYPES</title>
<taglist>
<tag><marker id="ERL_NIF_TERM"/>ERL_NIF_TERM</tag>
<item>
<p>Variables of type <c>ERL_NIF_TERM</c> can refer to any Erlang term.
This is an opaque type and values of it can only by used either as
arguments to API functions or as return values from NIFs. All
<c>ERL_NIF_TERM</c>'s belong to an environment
(<seealso marker="#ErlNifEnv">ErlNifEnv</seealso>). A term can not be
destructed individually, it is valid until its environment is destructed.</p>
</item>
<tag><marker id="ErlNifEnv"/>ErlNifEnv</tag>
<item>
<p><c>ErlNifEnv</c> represents an environment that can host Erlang terms.
All terms in an environment are valid as long as the environment is valid.
<c>ErlNifEnv</c> is an opaque type and pointers to it can only be passed
on to API functions. There are two types of environments; process
bound and process independent.</p>
<p>A <em>process bound environment</em> is passed as the first argument to all NIFs.
All function arguments passed to a NIF will belong to that environment.
The return value from a NIF must also be a term belonging to the same
environment.
In addition a process bound environment contains transient information
about the calling Erlang process. The environment is only valid in the
thread where it was supplied as argument until the NIF returns. It is
thus useless and dangerous to store pointers to process bound
environments between NIF calls. </p>
<p>A <em>process independent environment</em> is created by calling
<seealso marker="#enif_alloc_env">enif_alloc_env</seealso>. It can be
used to store terms between NIF calls and to send terms with
<seealso marker="#enif_send">enif_send</seealso>. A process
independent environment with all its terms is valid until you explicitly
invalidates it with <seealso marker="#enif_free_env">enif_free_env</seealso>
or <c>enif_send</c>.</p>
<p>All contained terms of a list/tuple/map must belong to the same
environment as the list/tuple/map itself. Terms can be copied between
environments with
<seealso marker="#enif_make_copy">enif_make_copy</seealso>.</p>
</item>
<tag><marker id="ErlNifFunc"/>ErlNifFunc</tag>
<item>
<p/>
<code type="none">
typedef struct {
const char* <em>name</em>;
unsigned <em>arity</em>;
ERL_NIF_TERM (*<em>fptr</em>)(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
unsigned flags;
} ErlNifFunc;
</code>
<p>Describes a NIF by its name, arity and implementation.
<c>fptr</c> is a pointer to the function that implements the
NIF. The argument <c>argv</c> of a NIF will contain the
function arguments passed to the NIF and <c>argc</c> is the
length of the array, i.e. the function arity. <c>argv[N-1]</c>
will thus denote the Nth argument to the NIF. Note that the
<c>argc</c> argument allows for the same C function to
implement several Erlang functions with different arity (but
same name probably). For a regular NIF, <c>flags</c> is 0 (and
so its value can be omitted for statically initialized <c>ErlNifFunc</c>
instances), or it can be used to indicate that the NIF is a <seealso
marker="#dirty_nifs">dirty NIF</seealso> that should be executed
on a dirty scheduler thread (<em>note that the dirty NIF functionality
described here is experimental</em> and that you have to enable
support for dirty schedulers when building OTP in order to try the
functionality out). If the dirty NIF is expected to be
CPU-bound, its <c>flags</c> field should be set to
<c>ERL_NIF_DIRTY_JOB_CPU_BOUND</c>, or for I/O-bound jobs,
<c>ERL_NIF_DIRTY_JOB_IO_BOUND</c>.</p>
</item>
<tag><marker id="ErlNifBinary"/>ErlNifBinary</tag>
<item>
<p/>
<code type="none">
typedef struct {
unsigned <em>size</em>;
unsigned char* <em>data</em>;
} ErlNifBinary;
</code>
<p><c>ErlNifBinary</c> contains transient information about an
inspected binary term. <c>data</c> is a pointer to a buffer
of <c>size</c> bytes with the raw content of the binary.</p>
<p>Note that <c>ErlNifBinary</c> is a semi-opaque type and you are
only allowed to read fields <c>size</c> and <c>data</c>.</p>
</item>
<tag><marker id="ErlNifPid"/>ErlNifPid</tag>
<item>
<p><c>ErlNifPid</c> is a process identifier (pid). In contrast to
pid terms (instances of <c>ERL_NIF_TERM</c>), <c>ErlNifPid</c>'s are self
contained and not bound to any
<seealso marker="#ErlNifEnv">environment</seealso>. <c>ErlNifPid</c>
is an opaque type.</p>
</item>
<tag><marker id="ErlNifPort"/>ErlNifPort</tag>
<item>
<p><c>ErlNifPort</c> is a port identifier. In contrast to
port id terms (instances of <c>ERL_NIF_TERM</c>), <c>ErlNifPort</c>'s are self
contained and not bound to any
<seealso marker="#ErlNifEnv">environment</seealso>. <c>ErlNifPort</c>
is an opaque type.</p>
</item>
<tag><marker id="ErlNifResourceType"/>ErlNifResourceType</tag>
<item>
<p>Each instance of <c>ErlNifResourceType</c> represent a class of
memory managed resource objects that can be garbage collected.
Each resource type has a unique name and a destructor function that
is called when objects of its type are released.</p>
</item>
<tag><marker id="ErlNifResourceDtor"/>ErlNifResourceDtor</tag>
<item>
<p/>
<code type="none">
typedef void ErlNifResourceDtor(ErlNifEnv* env, void* obj);
</code>
<p>The function prototype of a resource destructor function.
A destructor function is not allowed to call any term-making functions.</p>
</item>
<tag><marker id="ErlNifCharEncoding"/>ErlNifCharEncoding</tag>
<item>
<p/>
<code type="none">
typedef enum {
ERL_NIF_LATIN1
}ErlNifCharEncoding;
</code>
<p>The character encoding used in strings and atoms. The only
supported encoding is currently <c>ERL_NIF_LATIN1</c> for
iso-latin-1 (8-bit ascii).</p>
</item>
<tag><marker id="ErlNifSysInfo"/>ErlNifSysInfo</tag>
<item>
<p>Used by <seealso marker="#enif_system_info">enif_system_info</seealso>
to return information about the runtime system. Contains currently
the exact same content as <seealso marker="erl_driver#ErlDrvSysInfo">ErlDrvSysInfo</seealso>.</p>
</item>
<tag><marker id="ErlNifSInt64"/>ErlNifSInt64</tag>
<item><p>A native signed 64-bit integer type.</p></item>
<tag><marker id="ErlNifUInt64"/>ErlNifUInt64</tag>
<item><p>A native unsigned 64-bit integer type.</p></item>
<tag><marker id="ErlNifTime"/>ErlNifTime</tag>
<item>
<p>A signed 64-bit integer type for representation of time.</p>
</item>
<tag><marker id="ErlNifTimeUnit"/>ErlNifTimeUnit</tag>
<item>
<p>An enumeration of time units supported by the NIF API:</p>
<taglist>
<tag><c>ERL_NIF_SEC</c></tag>
<item><p>Seconds</p></item>
<tag><c>ERL_NIF_MSEC</c></tag>
<item><p>Milliseconds</p></item>
<tag><c>ERL_NIF_USEC</c></tag>
<item><p>Microseconds</p></item>
<tag><c>ERL_NIF_NSEC</c></tag>
<item><p>Nanoseconds</p></item>
</taglist>
</item>
<tag><marker id="ErlNifUniqueInteger"/>ErlNifUniqueInteger</tag>
<item>
<p>An enumeration of the properties that can be requested from
<seealso marker="#enif_unique_integer">
enif_unique_integer</seealso>.</p>
<taglist>
<tag><c>ERL_NIF_UNIQUE_POSITIVE</c></tag>
<item><p>A positive integer</p></item>
<tag><c>ERL_NIF_UNIQUE_MONOTONIC</c></tag>
<item><p>A
<seealso marker="time_correction#Strictly_Monotonically_Increasing">strictly
monotonically increasing</seealso> integer corresponding to creation time</p></item>
</taglist>
</item>
</taglist>
</section>
<funcs>
<func><name><ret>void *</ret><nametext>enif_alloc(size_t size)</nametext></name>
<fsummary>Allocate dynamic memory</fsummary>
<desc><p>Allocate memory of <c>size</c> bytes. Return NULL if allocation failed.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_alloc_binary(size_t size, ErlNifBinary* bin)</nametext></name>
<fsummary>Create a new binary</fsummary>
<desc><p>Allocate a new binary of size <c>size</c>
bytes. Initialize the structure pointed to by <c>bin</c> to
refer to the allocated binary. The binary must either be released by
<seealso marker="#enif_release_binary">enif_release_binary</seealso>
or ownership transferred to an Erlang term with
<seealso marker="#enif_make_binary">enif_make_binary</seealso>.
An allocated (and owned) <c>ErlNifBinary</c> can be kept between NIF
calls.</p>
<p>Return true on success or false if allocation failed.</p>
</desc>
</func>
<func><name><ret>ErlNifEnv *</ret><nametext>enif_alloc_env()</nametext></name>
<fsummary>Create a new environment</fsummary>
<desc><p>Allocate a new process independent environment. The environment can
be used to hold terms that is not bound to any process. Such terms can
later be copied to a process environment with
<seealso marker="#enif_make_copy">enif_make_copy</seealso>
or be sent to a process as a message with <seealso marker="#enif_send">enif_send</seealso>.</p>
<p>Return pointer to the new environment.</p>
</desc>
</func>
<func><name><ret>void *</ret><nametext>enif_alloc_resource(ErlNifResourceType* type, unsigned size)</nametext></name>
<fsummary>Allocate a memory managed resource object</fsummary>
<desc><p>Allocate a memory managed resource object of type <c>type</c> and size <c>size</c> bytes.</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_clear_env(ErlNifEnv* env)</nametext></name>
<fsummary>Clear an environment for reuse</fsummary>
<desc><p>Free all terms in an environment and clear it for reuse. The environment must
have been allocated with <seealso marker="#enif_alloc_env">enif_alloc_env</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_binary_to_term(ErlNifEnv *env, ErlNifBinary *bin, ERL_NIF_TERM *term)</nametext></name>
<fsummary>Convert a term from the external format</fsummary>
<desc>
<p>Returns a term that is the result of decoding <c>bin</c>
according to the Erlang external term format.</p>
<p>See also:</p>
<list>
<item><seealso marker="erlang#binary_to_term-1"><c>erlang:binary_to_term/1</c></seealso></item>
<item><seealso marker="#enif_term_to_binary"><c>enif_term_to_binary</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_compare(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)</nametext></name>
<fsummary>Compare two terms</fsummary>
<desc><p>Return an integer less than, equal to, or greater than
zero if <c>lhs</c> is found, respectively, to be less than,
equal, or greater than <c>rhs</c>. Corresponds to the Erlang
operators <c>==</c>, <c>/=</c>, <c>=<</c>, <c><</c>,
<c>>=</c> and <c>></c> (but <em>not</em> <c>=:=</c> or <c>=/=</c>).</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_cond_broadcast(ErlNifCond *cnd)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_cond_broadcast">erl_drv_cond_broadcast</seealso>.
</p></desc>
</func>
<func><name><ret>ErlNifCond *</ret><nametext>enif_cond_create(char *name)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_cond_create">erl_drv_cond_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_cond_destroy(ErlNifCond *cnd)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_cond_destroy">erl_drv_cond_destroy</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_cond_signal(ErlNifCond *cnd)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_cond_signal">erl_drv_cond_signal</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_cond_wait(ErlNifCond *cnd, ErlNifMutex *mtx)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_cond_wait">erl_drv_cond_wait</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_consume_timeslice(ErlNifEnv *env, int percent)</nametext></name>
<fsummary></fsummary>
<desc><p>Give the runtime system a hint about how much CPU time the current NIF call has consumed
since last hint, or since the start of the NIF if no previous hint has been given.
The time is given as a <c>percent</c> of the timeslice that a process is allowed to execute Erlang
code until it may be suspended to give time for other runnable processes.
The scheduling timeslice is not an exact entity, but can usually be
approximated to about 1 millisecond.</p>
<p>Note that it is up to the runtime system to determine if and how to use this information.
Implementations on some platforms may use other means in order to determine consumed
CPU time. Lengthy NIFs should regardless of this frequently call <c>enif_consume_timeslice</c>
in order to determine if it is allowed to continue execution or not.</p>
<p>Returns 1 if the timeslice is exhausted, or 0 otherwise. If 1 is returned the NIF should return
as soon as possible in order for the process to yield.</p>
<p>Argument <c>percent</c> must be an integer between 1 and 100. This function
must only be called from a NIF-calling thread and argument <c>env</c> must be
the environment of the calling process.</p>
<p>This function is provided to better support co-operative scheduling, improve system responsiveness,
and make it easier to prevent misbehaviors of the VM due to a NIF monopolizing a scheduler thread.
It can be used to divide <seealso marker="#lengthy_work">length work</seealso> into
a number of repeated NIF-calls without the need to create threads.
See also the <seealso marker="#WARNING">warning</seealso> text at the beginning of this document.</p>
</desc>
</func>
<func>
<name><ret>ErlNifTime</ret><nametext>enif_convert_time_unit(ErlNifTime val, ErlNifTimeUnit from, ErlNifTimeUnit to)</nametext></name>
<fsummary>Convert time unit of a time value</fsummary>
<desc>
<marker id="enif_convert_time_unit"></marker>
<p>Arguments:</p>
<taglist>
<tag><c>val</c></tag>
<item>Value to convert time unit for.</item>
<tag><c>from</c></tag>
<item>Time unit of <c>val</c>.</item>
<tag><c>to</c></tag>
<item>Time unit of returned value.</item>
</taglist>
<p>Converts the <c>val</c> value of time unit <c>from</c> to
the corresponding value of time unit <c>to</c>. The result is
rounded using the floor function.</p>
<p>Returns <c>ERL_NIF_TIME_ERROR</c> if called with an invalid
time unit argument.</p>
<p>See also:</p>
<list>
<item><seealso marker="#ErlNifTime"><c>ErlNifTime</c></seealso></item>
<item><seealso marker="#ErlNifTimeUnit"><c>ErlNifTimeUnit</c></seealso></item>
</list>
</desc>
</func>
<func>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_cpu_time(ErlNifEnv *)</nametext></name>
<fsummary></fsummary>
<desc>
<p>Returns the CPU time in the same format as <seealso marker="erlang#timestamp-0">erlang:timestamp()</seealso>.
The CPU time is the time the current logical cpu has spent executing since
some arbitrary point in the past.
If the OS does not support fetching of this value <c>enif_cpu_time</c>
invokes <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.
</p>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_equal_tids">erl_drv_equal_tids</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_free(void* ptr)</nametext></name>
<fsummary>Free dynamic memory</fsummary>
<desc><p>Free memory allocated by <c>enif_alloc</c>.</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_free_env(ErlNifEnv* env)</nametext></name>
<fsummary>Free an environment allocated with enif_alloc_env</fsummary>
<desc><p>Free an environment allocated with <seealso marker="#enif_alloc_env">enif_alloc_env</seealso>.
All terms created in the environment will be freed as well.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_atom(ErlNifEnv* env, ERL_NIF_TERM term, char* buf, unsigned size, ErlNifCharEncoding encode)</nametext></name>
<fsummary>Get the text representation of an atom term</fsummary>
<desc><p>Write a null-terminated string, in the buffer pointed to by
<c>buf</c> of size <c>size</c>, consisting of the string
representation of the atom <c>term</c> with encoding
<seealso marker="#ErlNifCharEncoding">encode</seealso>. Return
the number of bytes written (including terminating null character) or 0 if
<c>term</c> is not an atom with maximum length of
<c>size-1</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_atom_length(ErlNifEnv* env, ERL_NIF_TERM term, unsigned* len, ErlNifCharEncoding encode)</nametext></name>
<fsummary>Get the length of atom <c>term</c></fsummary>
<desc><p>Set <c>*len</c> to the length (number of bytes excluding
terminating null character) of the atom <c>term</c> with encoding
<c>encode</c>. Return true on success or false if <c>term</c> is not an
atom.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_double(ErlNifEnv* env, ERL_NIF_TERM term, double* dp)</nametext></name>
<fsummary>Read a floating-point number term</fsummary>
<desc><p>Set <c>*dp</c> to the floating point value of
<c>term</c>. Return true on success or false if <c>term</c> is not a float.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_int(ErlNifEnv* env, ERL_NIF_TERM term, int* ip)</nametext></name>
<fsummary>Read an integer term</fsummary>
<desc><p>Set <c>*ip</c> to the integer value of
<c>term</c>. Return true on success or false if <c>term</c> is not an
integer or is outside the bounds of type <c>int</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_int64(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifSInt64* ip)</nametext></name>
<fsummary>Read a 64-bit integer term</fsummary>
<desc><p>Set <c>*ip</c> to the integer value of
<c>term</c>. Return true on success or false if <c>term</c> is not an
integer or is outside the bounds of a signed 64-bit integer.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_local_pid(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPid* pid)</nametext></name>
<fsummary>Read an local pid term</fsummary>
<desc><p>If <c>term</c> is the pid of a node local process, initialize the
pid variable <c>*pid</c> from it and return true. Otherwise return false.
No check if the process is alive is done.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_local_port(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPort* port_id)</nametext></name>
<fsummary>Read an local port term</fsummary>
<desc><p>If <c>term</c> is the port of a node local port, initialize the
port variable <c>*port_id</c> from it and return true. Otherwise return false.
No check if the port is alive is done.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_list_cell(ErlNifEnv* env, ERL_NIF_TERM list, ERL_NIF_TERM* head, ERL_NIF_TERM* tail)</nametext></name>
<fsummary>Get head and tail from a list</fsummary>
<desc><p>Set <c>*head</c> and <c>*tail</c> from
<c>list</c> and return true, or return false if <c>list</c> is not a
non-empty list.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_list_length(ErlNifEnv* env, ERL_NIF_TERM term, unsigned* len)</nametext></name>
<fsummary>Get the length of list <c>term</c></fsummary>
<desc><p>Set <c>*len</c> to the length of list <c>term</c> and return true,
or return false if <c>term</c> is not a proper list.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_long(ErlNifEnv* env, ERL_NIF_TERM term, long int* ip)</nametext></name>
<fsummary>Read an long integer term</fsummary>
<desc><p>Set <c>*ip</c> to the long integer value of <c>term</c> and
return true, or return false if <c>term</c> is not an integer or is
outside the bounds of type <c>long int</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_map_size(ErlNifEnv* env, ERL_NIF_TERM term, size_t *size)</nametext></name>
<fsummary>Read the size of a map term</fsummary>
<desc><p>Set <c>*size</c> to the number of key-value pairs in the map <c>term</c> and
return true, or return false if <c>term</c> is not a map.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_map_value(ErlNifEnv* env, ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)</nametext></name>
<fsummary>Get the value of a key in a map</fsummary>
<desc><p>Set <c>*value</c> to the value associated with <c>key</c> in the
map <c>map</c> and return true. Return false if <c>map</c> is not a map
or if <c>map</c> does not contain <c>key</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* type, void** objp)</nametext></name>
<fsummary>Get the pointer to a resource object</fsummary>
<desc><p>Set <c>*objp</c> to point to the resource object referred to by <c>term</c>.</p>
<p>Return true on success or false if <c>term</c> is not a handle to a resource object
of type <c>type</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_string(ErlNifEnv* env,
ERL_NIF_TERM list, char* buf, unsigned size,
ErlNifCharEncoding encode)</nametext></name>
<fsummary>Get a C-string from a list</fsummary>
<desc><p>Write a null-terminated string, in the buffer pointed to by
<c>buf</c> with size <c>size</c>, consisting of the characters
in the string <c>list</c>. The characters are written using encoding
<seealso marker="#ErlNifCharEncoding">encode</seealso>.
Return the number of bytes written (including terminating null
character), or <c>-size</c> if the string was truncated due to
buffer space, or 0 if <c>list</c> is not a string that can be
encoded with <c>encode</c> or if <c>size</c> was less than 1.
The written string is always null-terminated unless buffer
<c>size</c> is less than 1.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_tuple(ErlNifEnv* env, ERL_NIF_TERM term, int* arity, const ERL_NIF_TERM** array)</nametext></name>
<fsummary>Inspect the elements of a tuple</fsummary>
<desc><p>If <c>term</c> is a tuple, set <c>*array</c> to point
to an array containing the elements of the tuple and set
<c>*arity</c> to the number of elements. Note that the array
is read-only and <c>(*array)[N-1]</c> will be the Nth element of
the tuple. <c>*array</c> is undefined if the arity of the tuple
is zero.</p><p>Return true on success or false if <c>term</c> is not a
tuple.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_uint(ErlNifEnv* env, ERL_NIF_TERM term, unsigned int* ip)</nametext></name>
<fsummary>Read an unsigned integer term</fsummary>
<desc><p>Set <c>*ip</c> to the unsigned integer value of <c>term</c> and
return true, or return false if <c>term</c> is not an unsigned integer or
is outside the bounds of type <c>unsigned int</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_uint64(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifUInt64* ip)</nametext></name>
<fsummary>Read an unsigned 64-bit integer term</fsummary>
<desc><p>Set <c>*ip</c> to the unsigned integer value of <c>term</c> and
return true, or return false if <c>term</c> is not an unsigned integer or
is outside the bounds of an unsigned 64-bit integer.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_get_ulong(ErlNifEnv* env, ERL_NIF_TERM term, unsigned long* ip)</nametext></name>
<fsummary>Read an unsigned integer term</fsummary>
<desc><p>Set <c>*ip</c> to the unsigned long integer value of <c>term</c>
and return true, or return false if <c>term</c> is not an unsigned integer or is
outside the bounds of type <c>unsigned long</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_getenv(const char* key, char* value, size_t *value_size)</nametext></name>
<fsummary>Get the value of an environment variable</fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_getenv">erl_drv_getenv</seealso>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_has_pending_exception(ErlNifEnv* env, ERL_NIF_TERM* reason)</nametext></name>
<fsummary>Check if an exception has been raised</fsummary>
<desc><p>Return true if a pending exception is associated
with the environment <c>env</c>. If <c>reason</c> is a null pointer, ignore it.
Otherwise, if there's a pending exception associated with <c>env</c>, set the ERL_NIF_TERM
to which <c>reason</c> points to the value of the exception's term. For example, if
<seealso marker="#enif_make_badarg">enif_make_badarg</seealso> is called to set a
pending <c>badarg</c> exception, a subsequent call to <c>enif_has_pending_exception(env, &reason)</c>
will set <c>reason</c> to the atom <c>badarg</c>, then return true.</p>
<p>See also: <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>
and <seealso marker="#enif_raise_exception">enif_raise_exception</seealso>.</p>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_inspect_binary(ErlNifEnv* env, ERL_NIF_TERM bin_term, ErlNifBinary* bin)</nametext></name>
<fsummary>Inspect the content of a binary</fsummary>
<desc><p>Initialize the structure pointed to by <c>bin</c> with
information about the binary term
<c>bin_term</c>. Return true on success or false if <c>bin_term</c> is not a binary.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_inspect_iolist_as_binary(ErlNifEnv*
env, ERL_NIF_TERM term, ErlNifBinary* bin)
</nametext></name>
<fsummary>Inspect the content of an iolist</fsummary>
<desc><p>Initialize the structure pointed to by <c>bin</c> with one
continuous buffer with the same byte content as <c>iolist</c>. As with
inspect_binary, the data pointed to by <c>bin</c> is transient and does
not need to be released. Return true on success or false if <c>iolist</c> is not an
iolist.</p>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is an atom</fsummary>
<desc><p>Return true if <c>term</c> is an atom.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_binary(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a binary</fsummary>
<desc><p>Return true if <c>term</c> is a binary</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_empty_list(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is an empty list</fsummary>
<desc><p>Return true if <c>term</c> is an empty list.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_exception(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is an exception</fsummary>
<desc><marker id="enif_is_exception"/>
<p>Return true if <c>term</c> is an exception.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_map(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a map</fsummary>
<desc><p>Return true if <c>term</c> is a map, false otherwise.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_number(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a number (integer or float)</fsummary>
<desc><p>Return true if <c>term</c> is a number.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a fun</fsummary>
<desc><p>Return true if <c>term</c> is a fun.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_identical(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)</nametext></name>
<fsummary>Erlang operator =:=</fsummary>
<desc><p>Return true if the two terms are identical. Corresponds to the
Erlang operators <c>=:=</c> and
<c>=/=</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_on_dirty_scheduler(ErlNifEnv* env)</nametext></name>
<fsummary>Check to see if executing on a dirty scheduler thread</fsummary>
<desc>
<p>Check to see if the current NIF is executing on a dirty scheduler thread. If the
emulator is built with threading support, calling <c>enif_is_on_dirty_scheduler</c>
from within a dirty NIF returns true. It returns false when the calling NIF is a regular
NIF running on a normal scheduler thread, or when the emulator is built without threading
support.</p>
<note><p>This function is available only when the emulator is configured with dirty
schedulers enabled. This feature is currently disabled by default. To determine whether
the dirty NIF API is available, native code can check to see if the C preprocessor macro
<c>ERL_NIF_DIRTY_SCHEDULER_SUPPORT</c> is defined.</p></note>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_pid(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a pid</fsummary>
<desc><p>Return true if <c>term</c> is a pid.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a port</fsummary>
<desc><p>Return true if <c>term</c> is a port.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_port_alive(ErlNifEnv* env, ErlNifPort *port_id)</nametext></name>
<fsummary>Determine if a local port is alive or not.</fsummary>
<desc><p>Return true if <c>port_id</c> is currently alive.</p>
<p>This function can only be used in a from a NIF-calling thread.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_process_alive(ErlNifEnv* env, ErlNifPid *pid)</nametext></name>
<fsummary>Determine if a local process is alive or not.</fsummary>
<desc><p>Return true if <c>pid</c> is currently alive.</p>
<p>This function is only thread-safe when the emulator with SMP support is used.
It can only be used in a non-SMP emulator from a NIF-calling thread.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_ref(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a reference</fsummary>
<desc><p>Return true if <c>term</c> is a reference.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_tuple(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a tuple</fsummary>
<desc><p>Return true if <c>term</c> is a tuple.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term)</nametext></name>
<fsummary>Determine if a term is a list</fsummary>
<desc><p>Return true if <c>term</c> is a list.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_keep_resource(void* obj)</nametext></name>
<fsummary>Add a reference to a resource object</fsummary>
<desc><p>Add a reference to resource object <c>obj</c> obtained from
<seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.
Each call to <c>enif_keep_resource</c> for an object must be balanced by
a call to <seealso marker="#enif_release_resource">enif_release_resource</seealso>
before the object will be destructed.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_atom(ErlNifEnv* env, const char* name)</nametext></name>
<fsummary>Create an atom term</fsummary>
<desc><p>Create an atom term from the null-terminated C-string <c>name</c>
with iso-latin-1 encoding. If the length of <c>name</c> exceeds the maximum length
allowed for an atom (255 characters), <c>enif_make_atom</c> invokes
<seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.
</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_atom_len(ErlNifEnv* env, const char* name, size_t len)</nametext></name>
<fsummary>Create an atom term</fsummary>
<desc><p>Create an atom term from the string <c>name</c> with length <c>len</c>.
Null-characters are treated as any other characters. If <c>len</c> is greater than the maximum length
allowed for an atom (255 characters), <c>enif_make_atom</c> invokes
<seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.
</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_badarg(ErlNifEnv* env)</nametext></name>
<fsummary>Make a badarg exception</fsummary>
<desc><p>Make a badarg exception to be returned from a NIF, and associate
it with the environment <c>env</c>. Once a NIF or any function
it calls invokes <c>enif_make_badarg</c>, the runtime ensures that a
<c>badarg</c> exception is raised when the NIF returns, even if the NIF
attempts to return a non-exception term instead.
The return value from <c>enif_make_badarg</c> may be used only as the
return value from the NIF that invoked it (directly or indirectly)
or be passed to
<seealso marker="#enif_is_exception">enif_is_exception</seealso>, but
not to any other NIF API function.</p>
<p>See also: <seealso marker="#enif_has_pending_exception">enif_has_pending_exception</seealso>
and <seealso marker="#enif_raise_exception">enif_raise_exception</seealso>
</p>
<note><p>In earlier versions (older than erts-7.0, OTP 18) the return value
from <c>enif_make_badarg</c> had to be returned from the NIF. This
requirement is now lifted as the return value from the NIF is ignored
if <c>enif_make_badarg</c> has been invoked.</p></note></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)</nametext></name>
<fsummary>Make a binary term</fsummary>
<desc><p>Make a binary term from <c>bin</c>. Any ownership of
the binary data will be transferred to the created term and
<c>bin</c> should be considered read-only for the rest of the NIF
call and then as released.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_copy(ErlNifEnv* dst_env, ERL_NIF_TERM src_term)</nametext></name>
<fsummary>Make a copy of a term</fsummary>
<desc><p>Make a copy of term <c>src_term</c>. The copy will be created in
environment <c>dst_env</c>. The source term may be located in any
environment.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_double(ErlNifEnv* env, double d)</nametext></name>
<fsummary>Create a floating-point term</fsummary>
<desc><p>Create a floating-point term from a <c>double</c>. If the <c>double</c> argument is
not finite or is NaN, <c>enif_make_double</c> invokes
<seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_existing_atom(ErlNifEnv* env, const char* name, ERL_NIF_TERM* atom, ErlNifCharEncoding encode)</nametext></name>
<fsummary>Create an existing atom term</fsummary>
<desc><p>Try to create the term of an already existing atom from
the null-terminated C-string <c>name</c> with encoding
<seealso marker="#ErlNifCharEncoding">encode</seealso>. If the atom
already exists store the term in <c>*atom</c> and return true, otherwise
return false. If the length of <c>name</c> exceeds the maximum length
allowed for an atom (255 characters), <c>enif_make_existing_atom</c>
returns false.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_existing_atom_len(ErlNifEnv* env, const char* name, size_t len, ERL_NIF_TERM* atom, ErlNifCharEncoding encoding)</nametext></name>
<fsummary>Create an existing atom term</fsummary>
<desc><p>Try to create the term of an already existing atom from the
string <c>name</c> with length <c>len</c> and encoding
<seealso marker="#ErlNifCharEncoding">encode</seealso>. Null-characters
are treated as any other characters. If the atom already exists store the term
in <c>*atom</c> and return true, otherwise return false. If <c>len</c> is greater
than the maximum length allowed for an atom (255 characters),
<c>enif_make_existing_atom_len</c> returns false.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_int(ErlNifEnv* env, int i)</nametext></name>
<fsummary>Create an integer term</fsummary>
<desc><p>Create an integer term.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_int64(ErlNifEnv* env, ErlNifSInt64 i)</nametext></name>
<fsummary>Create an integer term</fsummary>
<desc><p>Create an integer term from a signed 64-bit integer.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list(ErlNifEnv* env, unsigned cnt, ...)</nametext></name>
<fsummary>Create a list term</fsummary>
<desc><p>Create an ordinary list term of length <c>cnt</c>. Expects
<c>cnt</c> number of arguments (after <c>cnt</c>) of type ERL_NIF_TERM as the
elements of the list. An empty list is returned if <c>cnt</c> is 0.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list1(ErlNifEnv* env, ERL_NIF_TERM e1)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list2(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list3(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list4(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list5(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list6(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list7(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list8(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list9(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)</nametext></name>
<fsummary>Create a list term</fsummary>
<desc><p>Create an ordinary list term with length indicated by the
function name. Prefer these functions (macros) over the variadic
<c>enif_make_list</c> to get a compile time error if the number of
arguments does not match.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list_cell(ErlNifEnv* env, ERL_NIF_TERM head, ERL_NIF_TERM tail)</nametext></name>
<fsummary>Create a list cell</fsummary>
<desc><p>Create a list cell <c>[head | tail]</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_list_from_array(ErlNifEnv* env, const ERL_NIF_TERM arr[], unsigned cnt)</nametext></name>
<fsummary>Create a list term from an array</fsummary>
<desc><p>Create an ordinary list containing the elements of array <c>arr</c>
of length <c>cnt</c>. An empty list is returned if <c>cnt</c> is 0.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_long(ErlNifEnv* env, long int i)</nametext></name>
<fsummary>Create an integer term from a long int</fsummary>
<desc><p>Create an integer term from a <c>long int</c>.</p></desc>
</func>
<func><name><ret>unsigned char *</ret><nametext>enif_make_new_binary(ErlNifEnv* env, size_t size, ERL_NIF_TERM* termp)</nametext></name>
<fsummary>Allocate and create a new binary term</fsummary>
<desc><p>Allocate a binary of size <c>size</c> bytes and create an owning
term. The binary data is mutable until the calling NIF returns. This is a
quick way to create a new binary without having to use
<seealso marker="#ErlNifBinary">ErlNifBinary</seealso>. The drawbacks are
that the binary can not be kept between NIF calls and it can not be
reallocated.</p><p>Return a pointer to the raw binary data and set
<c>*termp</c> to the binary term.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_new_map(ErlNifEnv* env)</nametext></name>
<fsummary>Make an empty map term</fsummary>
<desc><p>Make an empty map term.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_map_put(ErlNifEnv* env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value, ERL_NIF_TERM* map_out)</nametext></name>
<fsummary>Insert key-value pair in map</fsummary>
<desc><p>Make a copy of map <c>map_in</c> and insert <c>key</c> with
<c>value</c>. If <c>key</c> already exists in <c>map_in</c>, the old
associated value is replaced by <c>value</c>. If successful set
<c>*map_out</c> to the new map and return true. Return false if
<c>map_in</c> is not a map.</p>
<p>The <c>map_in</c> term must belong to the environment <c>env</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_map_update(ErlNifEnv* env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM new_value, ERL_NIF_TERM* map_out)</nametext></name>
<fsummary>Replace value for key in map</fsummary>
<desc><p>Make a copy of map <c>map_in</c> and replace the old associated
value for <c>key</c> with <c>new_value</c>. If successful set
<c>*map_out</c> to the new map and return true. Return false if
<c>map_in</c> is not a map or if it does no contain <c>key</c>.</p>
<p>The <c>map_in</c> term must belong to the environment <c>env</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_map_remove(ErlNifEnv* env, ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM* map_out)</nametext></name>
<fsummary>Remove key from map</fsummary>
<desc><p>If map <c>map_in</c> contains <c>key</c>, make a copy of
<c>map_in</c> in <c>*map_out</c> and remove <c>key</c> and associated
value. If map <c>map_in</c> does not contain <c>key</c>, set
<c>*map_out</c> to <c>map_in</c>. Return true for success or false if
<c>map_in</c> is not a map.</p>
<p>The <c>map_in</c> term must belong to the environment <c>env</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_pid(ErlNifEnv* env, const ErlNifPid* pid)</nametext></name>
<fsummary>Make a pid term</fsummary>
<desc><p>Make a pid term from <c>*pid</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_ref(ErlNifEnv* env)</nametext></name>
<fsummary>Create a reference</fsummary>
<desc><p>Create a reference like <seealso marker="erlang#make_ref-0">erlang:make_ref/0</seealso>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_resource(ErlNifEnv* env, void* obj)</nametext></name>
<fsummary>Create an opaque handle to a resource object</fsummary>
<desc><p>Create an opaque handle to a memory managed resource object
obtained by <seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.
No ownership transfer is done, as the resource object still needs to be released by
<seealso marker="#enif_release_resource">enif_release_resource</seealso>,
but note that the call to <c>enif_release_resource</c> can occur
immediately after obtaining the term from <c>enif_make_resource</c>,
in which case the resource object will be deallocated when the
term is garbage collected. See the
<seealso marker="#enif_resource_example">example of creating and
returning a resource object</seealso> for more details.</p>
<p>Note that the only defined behaviour of using a resource term in
an Erlang program is to store it and send it between processes on the
same node. Other operations such as matching or <c>term_to_binary</c>
will have unpredictable (but harmless) results.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_resource_binary(ErlNifEnv* env, void* obj, const void* data, size_t size)</nametext></name>
<fsummary>Create a custom binary term</fsummary>
<desc><p>Create a binary term that is memory managed by a resource object
<c>obj</c> obtained by <seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.
The returned binary term will consist of <c>size</c> bytes pointed to
by <c>data</c>. This raw binary data must be kept readable and unchanged
until the destructor of the resource is called. The binary data may be
stored external to the resource object in which case it is the responsibility
of the destructor to release the data.</p>
<p>Several binary terms may be managed by the same resource object. The
destructor will not be called until the last binary is garbage collected.
This can be useful as a way to return different parts of a larger binary
buffer.</p>
<p>As with <seealso marker="#enif_make_resource">enif_make_resource</seealso>,
no ownership transfer is done. The resource still needs to be released with
<seealso marker="#enif_release_resource">enif_release_resource</seealso>.</p>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_reverse_list(ErlNifEnv* env, ERL_NIF_TERM list_in, ERL_NIF_TERM *list_out)</nametext></name>
<fsummary>Create the reverse of a list</fsummary>
<desc><p>Set <c>*list_out</c> to the reverse list of the list <c>list_in</c> and return true,
or return false if <c>list_in</c> is not a list. This function should only be used on
short lists as a copy will be created of the list which will not be released until after the
nif returns.</p>
<p>The <c>list_in</c> term must belong to the environment <c>env</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_string(ErlNifEnv* env, const char* string, ErlNifCharEncoding encoding)</nametext></name>
<fsummary>Create a string</fsummary>
<desc><p>Create a list containing the characters of the
null-terminated string <c>string</c> with encoding <seealso marker="#ErlNifCharEncoding">encoding</seealso>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_string_len(ErlNifEnv* env, const char* string, size_t len, ErlNifCharEncoding encoding)</nametext></name>
<fsummary>Create a string</fsummary>
<desc><p>Create a list containing the characters of the string <c>string</c> with
length <c>len</c> and encoding <seealso marker="#ErlNifCharEncoding">encoding</seealso>.
Null-characters are treated as any other characters.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_sub_binary(ErlNifEnv*
env, ERL_NIF_TERM bin_term, size_t pos, size_t size)</nametext></name>
<fsummary>Make a subbinary term</fsummary>
<desc><p>Make a subbinary of binary <c>bin_term</c>, starting at
zero-based position <c>pos</c> with a length of <c>size</c> bytes.
<c>bin_term</c> must be a binary or bitstring and
<c>pos+size</c> must be less or equal to the number of whole
bytes in <c>bin_term</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple(ErlNifEnv* env, unsigned cnt, ...)</nametext></name>
<fsummary>Create a tuple term</fsummary>
<desc><p>Create a tuple term of arity <c>cnt</c>. Expects
<c>cnt</c> number of arguments (after <c>cnt</c>) of type ERL_NIF_TERM as the
elements of the tuple.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple1(ErlNifEnv* env, ERL_NIF_TERM e1)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple2(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple3(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2, ERL_NIF_TERM e3)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple4(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple5(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple6(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple7(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple8(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)</nametext></name>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple9(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)</nametext></name>
<fsummary>Create a tuple term</fsummary>
<desc><p>Create a tuple term with length indicated by the
function name. Prefer these functions (macros) over the variadic
<c>enif_make_tuple</c> to get a compile time error if the number of
arguments does not match.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_tuple_from_array(ErlNifEnv* env, const ERL_NIF_TERM arr[], unsigned cnt)</nametext></name>
<fsummary>Create a tuple term from an array</fsummary>
<desc><p>Create a tuple containing the elements of array <c>arr</c>
of length <c>cnt</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_uint(ErlNifEnv* env, unsigned int i)</nametext></name>
<fsummary>Create an unsigned integer term</fsummary>
<desc><p>Create an integer term from an <c>unsigned int</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_uint64(ErlNifEnv* env, ErlNifUInt64 i)</nametext></name>
<fsummary>Create an unsigned integer term</fsummary>
<desc><p>Create an integer term from an unsigned 64-bit integer.</p></desc>
</func>
<func>
<name><ret>ERL_NIF_TERM</ret><nametext>enif_make_unique_integer(ErlNifEnv *env, ErlNifUniqueInteger properties)</nametext></name>
<fsummary></fsummary>
<desc>
<p>Returns a unique integer with the same properties as given by <seealso marker="erlang#unique_integer-1">erlang:unique_integer/1</seealso>.</p>
<p><c>env</c> is the environment to create the integer in.</p>
<p>
<c>ERL_NIF_UNIQUE_POSITIVE</c> and <c>ERL_NIF_UNIQUE_MONOTONIC</c> can
be passed as the second argument to change the properties of the
integer returned. It is possible to combine them by or:ing the
two values together.
</p>
<p>See also:</p>
<list>
<item><seealso marker="#ErlNifUniqueInteger"><c>ErlNifUniqueInteger</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_ulong(ErlNifEnv* env, unsigned long i)</nametext></name>
<fsummary>Create an integer term from an unsigned long int</fsummary>
<desc><p>Create an integer term from an <c>unsigned long int</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_create(ErlNifEnv *env, ERL_NIF_TERM map, ErlNifMapIterator *iter, ErlNifMapIteratorEntry entry)</nametext></name>
<fsummary>Create a map iterator</fsummary>
<desc><p>Create an iterator for the map <c>map</c> by initializing the
structure pointed to by <c>iter</c>. The <c>entry</c> argument determines
the start position of the iterator: <c>ERL_NIF_MAP_ITERATOR_FIRST</c> or
<c>ERL_NIF_MAP_ITERATOR_LAST</c>. Return true on success or false if
<c>map</c> is not a map.</p>
<p>A map iterator is only useful during the lifetime of the environment
<c>env</c> that the <c>map</c> belongs to. The iterator must be destroyed by
calling <seealso marker="#enif_map_iterator_destroy">
enif_map_iterator_destroy</seealso>.</p>
<code type="none">
ERL_NIF_TERM key, value;
ErlNifMapIterator iter;
enif_map_iterator_create(env, my_map, &iter, ERL_NIF_MAP_ITERATOR_FIRST);
while (enif_map_iterator_get_pair(env, &iter, &key, &value)) {
do_something(key,value);
enif_map_iterator_next(env, &iter);
}
enif_map_iterator_destroy(env, &iter);
</code>
<note><p>The key-value pairs of a map have no defined iteration
order. The only guarantee is that the iteration order of a single map
instance is preserved during the lifetime of the environment that the map
belongs to.</p>
</note>
</desc>
</func>
<func><name><ret>void</ret><nametext>enif_map_iterator_destroy(ErlNifEnv *env, ErlNifMapIterator *iter)</nametext></name>
<fsummary>Destroy a map iterator</fsummary>
<desc><p>Destroy a map iterator created by
<seealso marker="#enif_map_iterator_create">enif_map_iterator_create</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_get_pair(ErlNifEnv *env, ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM *value)</nametext></name>
<fsummary>Get key and value at current map iterator position</fsummary>
<desc><p>Get key and value terms at current map iterator position.
On success set <c>*key</c> and <c>*value</c> and return true.
Return false if the iterator is positioned at head (before first entry)
or tail (beyond last entry).</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_is_head(ErlNifEnv *env, ErlNifMapIterator *iter)</nametext></name>
<fsummary>Check if map iterator is positioned before first</fsummary>
<desc><p>Return true if map iterator <c>iter</c> is positioned
before first entry.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_is_tail(ErlNifEnv *env, ErlNifMapIterator *iter)</nametext></name>
<fsummary>Check if map iterator is positioned after last</fsummary>
<desc><p>Return true if map iterator <c>iter</c> is positioned
after last entry.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_next(ErlNifEnv *env, ErlNifMapIterator *iter)</nametext></name>
<fsummary>Increment map iterator to point to next entry</fsummary>
<desc><p>Increment map iterator to point to next key-value entry.
Return true if the iterator is now positioned at a valid key-value entry,
or false if the iterator is positioned at the tail (beyond the last
entry).</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_map_iterator_prev(ErlNifEnv *env, ErlNifMapIterator *iter)</nametext></name>
<fsummary>Decrement map iterator to point to previous entry</fsummary>
<desc><p>Decrement map iterator to point to previous key-value entry.
Return true if the iterator is now positioned at a valid key-value entry,
or false if the iterator is positioned at the head (before the first
entry).</p></desc>
</func>
<func>
<name><ret>ErlNifTime</ret><nametext>enif_monotonic_time(ErlNifTimeUnit time_unit)</nametext></name>
<fsummary>Get Erlang Monotonic Time</fsummary>
<desc>
<marker id="enif_monotonic_time"></marker>
<p>Arguments:</p>
<taglist>
<tag><c>time_unit</c></tag>
<item>Time unit of returned value.</item>
</taglist>
<p>
Returns
<seealso marker="time_correction#Erlang_Monotonic_Time">Erlang
monotonic time</seealso>. Note that it is not uncommon with
negative values.
</p>
<p>Returns <c>ERL_NIF_TIME_ERROR</c> if called with an invalid
time unit argument, or if called from a thread that is not a
scheduler thread.</p>
<p>See also:</p>
<list>
<item><seealso marker="#ErlNifTime"><c>ErlNifTime</c></seealso></item>
<item><seealso marker="#ErlNifTimeUnit"><c>ErlNifTimeUnit</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>ErlNifMutex *</ret><nametext>enif_mutex_create(char *name)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_mutex_create">erl_drv_mutex_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_mutex_destroy(ErlNifMutex *mtx)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_mutex_destroy">erl_drv_mutex_destroy</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_mutex_lock(ErlNifMutex *mtx)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_mutex_lock">erl_drv_mutex_lock</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_mutex_trylock(ErlNifMutex *mtx)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_mutex_trylock">erl_drv_mutex_trylock</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_mutex_unlock(ErlNifMutex *mtx)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_mutex_unlock">erl_drv_mutex_unlock</seealso>.
</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_now_time(ErlNifEnv *env)</nametext></name>
<fsummary></fsummary>
<desc><p>Retuns an <seealso marker="erlang#now-0">erlang:now()</seealso> timestamp.
The enif_now_time function is <em>deprecated</em>.</p></desc>
</func>
<func><name><ret>ErlNifResourceType *</ret><nametext>enif_open_resource_type(ErlNifEnv* env,
const char* module_str, const char* name,
ErlNifResourceDtor* dtor, ErlNifResourceFlags flags, ErlNifResourceFlags* tried)</nametext></name>
<fsummary>Create or takeover a resource type</fsummary>
<desc><p>Create or takeover a resource type identified by the string
<c>name</c> and give it the destructor function pointed to by <seealso marker="#ErlNifResourceDtor">dtor</seealso>.
Argument <c>flags</c> can have the following values:</p>
<taglist>
<tag><c>ERL_NIF_RT_CREATE</c></tag>
<item>Create a new resource type that does not already exist.</item>
<tag><c>ERL_NIF_RT_TAKEOVER</c></tag>
<item>Open an existing resource type and take over ownership of all its instances.
The supplied destructor <c>dtor</c> will be called both for existing instances
as well as new instances not yet created by the calling NIF library.</item>
</taglist>
<p>The two flag values can be combined with bitwise-or. The name of the
resource type is local to the calling module. Argument <c>module_str</c>
is not (yet) used and must be NULL. The <c>dtor</c> may be <c>NULL</c>
in case no destructor is needed.</p>
<p>On success, return a pointer to the resource type and <c>*tried</c>
will be set to either <c>ERL_NIF_RT_CREATE</c> or
<c>ERL_NIF_RT_TAKEOVER</c> to indicate what was actually done.
On failure, return <c>NULL</c> and set <c>*tried</c> to <c>flags</c>.
It is allowed to set <c>tried</c> to <c>NULL</c>.</p>
<p>Note that <c>enif_open_resource_type</c> is only allowed to be called in the three callbacks
<seealso marker="#load">load</seealso>, <seealso marker="#reload">reload</seealso>
and <seealso marker="#upgrade">upgrade</seealso>.</p>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_port_command(ErlNifEnv* env, const ErlNifPort* to_port, ErlNifEnv *msg_env, ERL_NIF_TERM msg)</nametext></name>
<fsummary>Send a port_command to to_port</fsummary>
<desc>
<p>This function works the same as <seealso marker="erlang#port_command-2">erlang:port_command/2</seealso>
except that it is always completely asynchronous. This call may return false
if it detects that the port is already dead, otherwise it will return true.
</p>
<taglist>
<tag><c>env</c></tag>
<item>The environment of the calling process. May not be NULL.</item>
<tag><c>*to_port</c></tag>
<item>The port id of the receiving port. The port id should refer to a
port on the local node.</item>
<tag><c>msg_env</c></tag>
<item>The environment of the message term. Can be a process
independent environment allocated with
<seealso marker="#enif_alloc_env">enif_alloc_env</seealso> or NULL.</item>
<tag><c>msg</c></tag>
<item>The message term to send. The same limitations apply as on the
payload to <seealso marker="erlang#port_command-2">erlang:port_command/2</seealso>.</item>
</taglist>
<p>Using a <c>msg_env</c> of NULL is an optimization which groups together
calls to <c>enif_alloc_env</c>, <c>enif_make_copy</c>, <c>enif_port_command</c>
and <c>enif_free_env</c> into one call. This optimization is only usefull
when a majority of the terms are to be copied from <c>env</c> to the <c>msg_env</c>.</p>
<p>The call may return false if it detects that the command failed for some reason. Otherwise true is returned.</p>
<p>See also:</p>
<list>
<item><seealso marker="#enif_get_local_port"><c>enif_get_local_port</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>void *</ret><nametext>enif_priv_data(ErlNifEnv* env)</nametext></name>
<fsummary>Get the private data of a NIF library</fsummary>
<desc><p>Return the pointer to the private data that was set by <c>load</c>,
<c>reload</c> or <c>upgrade</c>.</p>
<p>Was previously named <c>enif_get_data</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_raise_exception(ErlNifEnv* env, ERL_NIF_TERM reason)</nametext></name>
<fsummary>Raise a NIF error exception</fsummary>
<desc><p>Create an error exception with the term <c>reason</c> to be returned from a NIF,
and associate it with the environment <c>env</c>. Once a NIF or any function it calls
invokes <c>enif_raise_exception</c>, the runtime ensures that the exception it creates
is raised when the NIF returns, even if the NIF attempts to return a non-exception
term instead. The return value from <c>enif_raise_exception</c> may be used only as
the return value from the NIF that invoked it (directly or indirectly) or be passed
to <seealso marker="#enif_is_exception">enif_is_exception</seealso>, but
not to any other NIF API function.</p>
<p>See also: <seealso marker="#enif_has_pending_exception">enif_has_pending_exception</seealso>
and <seealso marker="#enif_make_badarg">enif_make_badarg</seealso>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_realloc_binary(ErlNifBinary* bin, size_t size)</nametext></name>
<fsummary>Change the size of a binary</fsummary>
<desc><p>Change the size of a binary <c>bin</c>. The source binary
may be read-only, in which case it will be left untouched and
a mutable copy is allocated and assigned to <c>*bin</c>. Return true on success,
false if memory allocation failed.</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_release_binary(ErlNifBinary* bin)</nametext></name>
<fsummary>Release a binary</fsummary>
<desc><p>Release a binary obtained from <c>enif_alloc_binary</c>.</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_release_resource(void* obj)</nametext></name>
<fsummary>Release a resource object</fsummary>
<desc><p>Remove a reference to resource object <c>obj</c>obtained from
<seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.
The resource object will be destructed when the last reference is removed.
Each call to <c>enif_release_resource</c> must correspond to a previous
call to <c>enif_alloc_resource</c> or
<seealso marker="#enif_keep_resource">enif_keep_resource</seealso>.
References made by <seealso marker="#enif_make_resource">enif_make_resource</seealso>
can only be removed by the garbage collector.</p></desc>
</func>
<func><name><ret>ErlNifRWLock *</ret><nametext>enif_rwlock_create(char *name)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_create">erl_drv_rwlock_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_rwlock_destroy(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_destroy">erl_drv_rwlock_destroy</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_rwlock_rlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_rlock">erl_drv_rwlock_rlock</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_rwlock_runlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_runlock">erl_drv_rwlock_runlock</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_rwlock_rwlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_rwlock">erl_drv_rwlock_rwlock</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_rwlock_rwunlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_rwunlock">erl_drv_rwlock_rwunlock</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_rwlock_tryrlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_tryrlock">erl_drv_rwlock_tryrlock</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_rwlock_tryrwlock(ErlNifRWLock *rwlck)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_rwlock_tryrwlock">erl_drv_rwlock_tryrwlock</seealso>.
</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_schedule_nif(ErlNifEnv* env, const char* fun_name, int flags, ERL_NIF_TERM (*fp)(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]), int argc, const ERL_NIF_TERM argv[])</nametext></name>
<fsummary>Schedule a NIF for execution</fsummary>
<desc>
<p>Schedule NIF <c>fp</c> to execute. This function allows an application to break up long-running
work into multiple regular NIF calls or to schedule a <seealso marker="#dirty_nifs">dirty NIF</seealso>
to execute on a dirty scheduler thread (<em>note that the dirty NIF functionality described here is
experimental</em> and that you have to enable support for dirty schedulers when building OTP in
order to try the functionality out).</p>
<p>The <c>fun_name</c> argument provides a name for the NIF being scheduled for execution. If it cannot
be converted to an atom, <c>enif_schedule_nif</c> returns a <c>badarg</c> exception.</p>
<p>The <c>flags</c> argument must be set to 0 for a regular NIF, or if the emulator was built the
experimental dirty scheduler support enabled, <c>flags</c> can be set to either <c>ERL_NIF_DIRTY_JOB_CPU_BOUND</c>
if the job is expected to be primarily CPU-bound, or <c>ERL_NIF_DIRTY_JOB_IO_BOUND</c> for jobs that will
be I/O-bound. If dirty scheduler threads are not available in the emulator, a try to schedule such a job
will result in a <c>badarg</c> exception.</p>
<p>The <c>argc</c> and <c>argv</c> arguments can either be the originals passed into the calling NIF, or
they can be values created by the calling NIF.</p>
<p>The calling NIF must use the return value of <c>enif_schedule_nif</c> as its own return value.</p>
<p>Be aware that <c>enif_schedule_nif</c>, as its name implies, only schedules the
NIF for future execution. The calling NIF does not block waiting for the scheduled NIF to
execute and return, which means that the calling NIF can't expect to receive the scheduled NIF
return value and use it for further operations.</p>
</desc>
</func>
<func><name><ret>ErlNifPid *</ret><nametext>enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)</nametext></name>
<fsummary>Get the pid of the calling process</fsummary>
<desc><p>Initialize the pid variable <c>*pid</c> to represent the
calling process. Return <c>pid</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_send(ErlNifEnv* env, ErlNifPid* to_pid, ErlNifEnv* msg_env, ERL_NIF_TERM msg)</nametext></name>
<fsummary>Send a message to a process</fsummary>
<desc><p>Send a message to a process.</p>
<taglist>
<tag><c>env</c></tag>
<item>The environment of the calling process. Must be NULL if and
only if calling from a created thread.</item>
<tag><c>*to_pid</c></tag>
<item>The pid of the receiving process. The pid should refer to a process on the local node.</item>
<tag><c>msg_env</c></tag>
<item>The environment of the message term. Must be a process
independent environment allocated with
<seealso marker="#enif_alloc_env">enif_alloc_env</seealso>.</item>
<tag><c>msg</c></tag>
<item>The message term to send.</item>
</taglist>
<p>Return true on success, or false if <c>*to_pid</c> does not refer to an alive local process.</p>
<p>The message environment <c>msg_env</c> with all its terms (including
<c>msg</c>) will be invalidated by a successful call to <c>enif_send</c>. The environment
should either be freed with <seealso marker="#enif_free_env">enif_free_env</seealso>
of cleared for reuse with <seealso marker="#enif_clear_env">enif_clear_env</seealso>.</p>
<p>This function is only thread-safe when the emulator with SMP support is used.
It can only be used in a non-SMP emulator from a NIF-calling thread.</p>
</desc>
</func>
<func><name><ret>unsigned</ret><nametext>enif_sizeof_resource(void* obj)</nametext></name>
<fsummary>Get the byte size of a resource object</fsummary>
<desc><p>Get the byte size of a resource object <c>obj</c> obtained by
<seealso marker="#enif_alloc_resource">enif_alloc_resource</seealso>.</p></desc>
</func>
<func>
<name><ret>void</ret><nametext>enif_system_info(ErlNifSysInfo *sys_info_ptr, size_t size)</nametext></name>
<fsummary>Get information about the Erlang runtime system</fsummary>
<desc><p>Same as <seealso marker="erl_driver#driver_system_info">driver_system_info</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_term_to_binary(ErlNifEnv *env, ERL_NIF_TERM term, ErlNifBinary *bin)</nametext></name>
<fsummary>Convert a term to the external format</fsummary>
<desc>
<p>Returns a binary data object that is the result of encoding <c>term</c>
according to the Erlang external term format.</p>
<p>See also:</p>
<list>
<item><seealso marker="erlang#term_to_binary-1"><c>erlang:term_to_binary/1</c></seealso></item>
<item><seealso marker="#enif_binary_to_term"><c>enif_binary_to_term</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_thread_create(char *name,ErlNifTid *tid,void * (*func)(void *),void *args,ErlNifThreadOpts *opts)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_create">erl_drv_thread_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_thread_exit(void *resp)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_exit">erl_drv_thread_exit</seealso>.
</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_thread_join(ErlNifTid, void **respp)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_join">erl_drv_thread_join </seealso>.
</p></desc>
</func>
<func><name><ret>ErlNifThreadOpts *</ret><nametext>enif_thread_opts_create(char *name)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_opts_create">erl_drv_thread_opts_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_thread_opts_destroy(ErlNifThreadOpts *opts)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_opts_destroy">erl_drv_thread_opts_destroy</seealso>.
</p></desc>
</func>
<func><name><ret>ErlNifTid</ret><nametext>enif_thread_self(void)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_thread_self">erl_drv_thread_self</seealso>.
</p></desc>
</func>
<func>
<name><ret>ErlNifTime</ret><nametext>enif_time_offset(ErlNifTimeUnit time_unit)</nametext></name>
<fsummary>Get current Time Offset</fsummary>
<desc>
<marker id="enif_time_offset"></marker>
<p>Arguments:</p>
<taglist>
<tag><c>time_unit</c></tag>
<item>Time unit of returned value.</item>
</taglist>
<p>Returns the current time offset between
<seealso marker="time_correction#Erlang_Monotonic_Time">Erlang monotonic time</seealso>
and
<seealso marker="time_correction#Erlang_System_Time">Erlang system time</seealso>
converted into the <c>time_unit</c> passed as argument.</p>
<p>Returns <c>ERL_NIF_TIME_ERROR</c> if called with an invalid
time unit argument, or if called from a thread that is not a
scheduler thread.</p>
<p>See also:</p>
<list>
<item><seealso marker="#ErlNifTime"><c>ErlNifTime</c></seealso></item>
<item><seealso marker="#ErlNifTimeUnit"><c>ErlNifTimeUnit</c></seealso></item>
</list>
</desc>
</func>
<func><name><ret>int</ret><nametext>enif_tsd_key_create(char *name, ErlNifTSDKey *key)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_tsd_key_create">erl_drv_tsd_key_create</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_tsd_key_destroy(ErlNifTSDKey key)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_tsd_key_destroy">erl_drv_tsd_key_destroy</seealso>.
</p></desc>
</func>
<func><name><ret>void *</ret><nametext>enif_tsd_get(ErlNifTSDKey key)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_tsd_get">erl_drv_tsd_get</seealso>.
</p></desc>
</func>
<func><name><ret>void</ret><nametext>enif_tsd_set(ErlNifTSDKey key, void *data)</nametext></name>
<fsummary></fsummary>
<desc><p>Same as <seealso marker="erl_driver#erl_drv_tsd_set">erl_drv_tsd_set</seealso>.
</p></desc>
</func>
</funcs>
<section>
<title>SEE ALSO</title>
<p><seealso marker="erlang#load_nif-2">erlang:load_nif/2</seealso></p>
</section>
</cref>