<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE cref SYSTEM "cref.dtd">
<cref>
<header>
<copyright>
<year>2001</year><year>2009</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<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>
<warning><p>The NIF concept was introduced in R13B03 as an
EXPERIMENTAL feature. The interfaces may be changed in any way
in coming releases. The API is still sparse and contains only
the most basic functions to read and write Erlang terms.
</p><p><em>R13B04</em>: The function prototypes of the NIFs
have changed to expect <c>argc</c> and <c>argv</c>
arguments. The arity of a NIF is by that no longer limited to
3.</p>
<p>enif_get_data renamed as enif_priv_data.</p>
</warning>
<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>
<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!");
}
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>
<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 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="erl_nif#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. A NIF library will also be unloaded if it is replaced
by another version of the library by a second call to
<c>erlang:load_nif/2</c> from the same module code.</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 value. The terms are of C-type <c>ERL_NIF_TERM</c>
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></item>
<tag>Resource objects</tag>
<item><p>Resource objects are a way to return pointers to native data
structures from a NIF in a safe way. A resource object is just a block
of memory allocated with <seealso marker="erl_nif#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="erl_nif#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 processses
on the same node, but the only real end usage is to pass it back as argument to a NIF.
The NIF can then do <seealso marker="erl_nif#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="erl_nif#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 or applications to be distinguishable.
A resource type is created by calling
<seealso marker="erl_nif#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 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 also 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. Resource types are uniquely identified by a supplied name string.
</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 operates on the supplied
arguments. As soon as you access a shared state either through static
variables or <seealso marker="erl_nif#enif_priv_data">enif_priv_data</seealso>
you need to supply your own explicit synchronization.</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>
</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>
</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 able to keep a state between NIF
calls. <c>enif_priv_data()</c> will return this pointer.</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="reload"/>int (*reload)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info)</tag>
<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>
<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 no previously loaded library for this module
code, BUT 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. 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.</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. A variable of
type <c>ERL_NIF_TERM</c> is only valid until the NIF call, where it was
obtained, returns.</p>
</item>
<tag><marker id="ErlNifEnv"/>ErlNifEnv</tag>
<item>
<p><c>ErlNifEnv</c> contains information about the context in
which a NIF call is made. This pointer should not be
dereferenced in any way, but only passed on to API
functions. An <c>ErlNifEnv</c> pointer is only valid until
the function, where is what supplied as argument,
returns. There is thus useless and dangerous to store <c>ErlNifEnv</c>
pointers in between NIF calls.</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[]);
} 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).</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>
</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. 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="erl_nif#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>
</taglist>
</section>
<funcs>
<func><name><ret>void*</ret><nametext>enif_alloc(ErlNifEnv* env, 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(ErlNifEnv* env, unsigned size, ErlNifBinary* bin)</nametext></name>
<fsummary>Create a new binary.</fsummary>
<desc><p>Allocate a new binary of size of <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="erl_nif#enif_release_binary">enif_release_binary()</seealso>
or ownership transferred to an erlang term with
<seealso marker="erl_nif#enif_make_binary">enif_make_binary()</seealso>.
An allocated (and owned) <c>ErlNifBinary</c> can be kept between NIF
calls.</p>
<p>Return false if allocation failed.</p>
</desc>
</func>
<func><name><ret>void*</ret><nametext>enif_alloc_resource(ErlNifEnv* env, 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>int</ret><nametext>enif_compare(ErlNifEnv* env, 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_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(ErlNifEnv* env, 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>int</ret><nametext>enif_get_atom(ErlNifEnv* env,
ERL_NIF_TERM term, char* buf, unsigned size)
</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>. 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_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> or return 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> or return 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_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> or return false if <c>list</c> is not a non-empty
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> 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_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>.
Return 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
<c>encode</c>. 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 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> 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_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> 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_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 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 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_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(ErlNifEnv* env, 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_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_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>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 C-string <c>name</c>. Unlike other terms, atom
terms may be saved and used between NIF calls.</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.</p></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_double(ErlNifEnv* env, double d)</nametext></name>
<fsummary>Create an floating-point term</fsummary>
<desc><p>Create an floating-point term from a <c>double</c>.</p></desc>
</func>
<func><name><ret>int</ret><nametext>enif_make_existing_atom(ErlNifEnv* env, const char* name, ERL_NIF_TERM* atom)</nametext></name>
<fsummary>Create an existing atom term</fsummary>
<desc><p>Try to create the term of an already existing atom from
the C-string <c>name</c>. If the atom already exist store the
term in <c>*atom</c> and return true, otherwise return
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_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. Prefere these functions (macros) over the variadic
<c>enif_make_list</c> to get 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>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="erl_nif#enif_alloc_resource">enif_alloc_resource</seealso>.
No ownership transfer is done, the resource object still needs to be released by
<seealso marker="erl_nif#enif_release_resource">enif_release_resource</seealso>.</p>
<p>Note that the only defined behaviour when using of 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_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 <c>encoding</c>.</p></desc>
</func>
<func><name><ret>ERL_NIF_TERM</ret><nametext>enif_make_sub_binary(ErlNifEnv*
env, ERL_NIF_TERM bin_term, unsigned pos, unsigned 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. Prefere these functions (macros) over the variadic
<c>enif_make_tuple</c> to get 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_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>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>ErlNifResourceType*</ret><nametext>enif_open_resource_type(ErlNifEnv* env, 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 <c>dtor</c>.
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. To avoid unintentionally
name clashes a good practice is to include the module name as part of the
type <c>name</c>. 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="erl_nif#load">load</seealso>, <seealso marker="erl_nif#reload">reload</seealso>
and <seealso marker="erl_nif#upgrade">upgrade</seealso>.</p>
</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>void</ret><nametext>enif_release_binary(ErlNifEnv* env, 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(ErlNifEnv* env, void* obj)</nametext></name>
<fsummary>Release a resource object.</fsummary>
<desc><p>Release a resource objects obtained from <c>enif_alloc_resource</c>.
The object may still be alive if it is referred to by Erlang terms. Each call to
<c>enif_release_resource</c> must correspond to a previous call to <c>enif_alloc_resource</c>.
References made by <c>enif_make_resource</c> can only be released 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>unsigned</ret><nametext>enif_sizeof_resource(ErlNifEnv* env, 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
<c>enif_alloc_resource</c>.</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_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>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">load_nif(3)</seealso></p>
</section>
</cref>
