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authorSverker Eriksson <[email protected]>2009-12-09 11:04:51 +0000
committerErlang/OTP <[email protected]>2009-12-09 11:04:51 +0000
commitf7c1ea4ff481a8dd7bd8c79ae540342fd8213434 (patch)
tree1db7ad6096eadfbca1d1c60330ab4392be6db690 /erts/doc/src/erl_nif.xml
parent8fbc15b2502bb6d8c808f4d0c8077c39a1f828e8 (diff)
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OTP-8304 Incompatible changes in the experimental NIF feature. Changed the
NIF function prototypes in order to allow more than 3 function arguments. Also an incompatible change in the return value of erlang:load_nif/2. Added support for references, floats and term comparison in NIFs. Read more in the documentation of erl_nif and erlang:load_nif/2.
Diffstat (limited to 'erts/doc/src/erl_nif.xml')
-rw-r--r--erts/doc/src/erl_nif.xml196
1 files changed, 124 insertions, 72 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index c636d65ef3..2033ba8a66 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -34,12 +34,14 @@
<lib>erl_nif</lib>
<libsummary>API functions for an Erlang NIF library</libsummary>
<description>
- <warning><p>The NIF concept is introduced in R13B03 as an
+ <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 introduced in this release is very
- sparse and contains only the most basic functions to read and
- write Erlang terms.
- </p></warning>
+ 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></warning>
<p>A NIF library contains native implementation of some functions
of an erlang module. The native implemented functions (NIFs) are
@@ -56,7 +58,7 @@
/* niftest.c */
#include "erl_nif.h"
-static ERL_NIF_TERM hello(ErlNifEnv* env)
+static ERL_NIF_TERM hello(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
{
return enif_make_string(env, "Hello world!");
}
@@ -100,8 +102,9 @@ ok
</code>
<p>A better solution for a real module is to take advantage of
- the new attribute <c>on_load</c> to automatically load the NIF
- library when the module is loaded.</p>
+ 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
@@ -190,7 +193,7 @@ ok
<title>DATA TYPES</title>
<taglist>
- <tag><marker id="ErlDrvEnv"/>ErlDrvEnv</tag>
+ <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
@@ -205,31 +208,28 @@ ok
<p/>
<code type="none">
typedef struct {
- const char* name;
- unsigned arity;
- ERL_NIF_TERM (*fptr)(ErlNifEnv* env, ...);
+ 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 number of arguments must match the arity. A NIF of
- arity 2 will thus look like:</p>
- <p/>
- <code type="none">
-ERL_NIF_TERM my_nif(ErlNifEnv* env, ERL_NIF_TERM arg1, ERL_NIF_TERM arg2)
-{
- /* ... */
-}
-</code>
- <p>The maximum allowed arity for a NIF is 3 in current implementation.</p>
+ 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 size;
- unsigned char* data;
+ unsigned <em>size</em>;
+ unsigned char* <em>data</em>;
} ErlNifBinary;
</code>
<p><c>ErlNifBinary</c> contains transient information about an
@@ -249,37 +249,36 @@ typedef struct {
</section>
<funcs>
- <func><name><ret>void*</ret><nametext>enif_get_data(ErlNifEnv* env)</nametext></name>
- <fsummary>Get the private data of a NIF library</fsummary>
- <desc><p>Returns the pointer to the private data that was set by <c>load</c>, <c>reload</c> or <c>upgrade</c>.</p></desc>
- </func>
<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.</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_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_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
- transient information about the binary term
- <c>bin_term</c>. Return false if <c>bin_term</c> is not a binary.</p></desc>
+ <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.</p></desc>
+ refer to the allocated binary. Return false if allocation failed.</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> or <c>enif_inspect_binary</c>.</p></desc>
+ <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>=&lt;</c>, <c>&lt;</c>,
+ <c>&gt;=</c> and <c>&gt;</c> (but <em>not</em> <c>=:=</c> or <c>=/=</c>).</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>void*</ret><nametext>enif_get_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></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>
@@ -287,45 +286,80 @@ typedef struct {
<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_ulong(ErlNifEnv* env, ERL_NIF_TERM term, unsigned long* ip)</nametext></name>
- <fsummary>Read an unsigned long integer</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_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>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>. Will also release
- the binary.</p></desc>
+ <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 an <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>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><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>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><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
+ transient 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>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><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_identical(ErlNifEnv* env, ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)</nametext></name>
+ <fsummary>Erlang operator =:=</fsummary>
+ <desc><p>Return true if and only 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_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>. Atom
terms may be saved and used between NIF calls.</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><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>. Will also release
+ the binary.</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>
@@ -337,11 +371,29 @@ typedef struct {
<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_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_string(ErlNifEnv* env, const char* string)</nametext></name>
<fsummary>Create a string.</fsummary>
- <desc><p>Creates a list containing the characters of the
+ <desc><p>Create a list containing the characters of the
C-string <c>string</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_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>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> or <c>enif_inspect_binary</c>.</p></desc>
+ </func>
</funcs>
<section>
<title>SEE ALSO</title>