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Linux 2.6 - man page for erl_nif (linux section 3erl)

erl_nif(3erl)			       C Library Functions			    erl_nif(3erl)

NAME
       erl_nif - API functions for an Erlang NIF library

DESCRIPTION
   Note:
       The  NIF  concept  is  officially supported from R14B. NIF source code written for earlier
       experimental versions might need adaption to run on R14B.

       No incompatible changes between R14B and R14A.

       Incompatible changes between R14A and R13B04:

	 * Environment	argument  removed  for	enif_alloc   ,	 enif_realloc	,   enif_free	,
	   enif_alloc_binary  , enif_realloc_binary , enif_release_binary , enif_alloc_resource ,
	   enif_release_resource , enif_is_identical and enif_compare .

	 * Character encoding argument added to enif_get_atom and enif_make_existing_atom .

	 * Module argument  added  to  enif_open_resource_type	while  changing  name  spaces  of
	   resource types from global to module local.

       Incompatible changes between R13B04 and R13B03:

	 * The	function  prototypes  of the NIFs have changed to expect argc and argv arguments.
	   The arity of a NIF is by that no longer limited to 3.

	 * enif_get_data renamed as enif_priv_data .

	 * enif_make_string got a third argument for character encoding.

       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 dif-
       ference 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.

       A minimal example of a NIF library can look like this:

       /* 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)

       and the Erlang module would have to look something like this:

       -module(niftest).

       -export([init/0, hello/0]).

       init() ->
	     erlang:load_nif("./niftest", 0).

       hello() ->
	     "NIF library not loaded".

       and compile and test something like this (on Linux):

       $> 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!"

       A  better  solution for a real module is to take advantage of the new directive on_load to
       automatically load the NIF library when the module is loaded.

   Note:
       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.

       A loaded NIF library is tied to the Erlang module code version that loaded it. If the mod-
       ule  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  unin-
       tentionally  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
       enif_priv_data .

       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 erlang:load_nif/2 from the same module code.

FUNCTIONALITY
       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:

	 Read and write Erlang terms :
	   Any Erlang terms can be passed to a NIF as function arguments and be returned as func-
	   tion return values. The terms are of C-type ERL_NIF_TERM and can only be read or writ-
	   ten	using  API  functions.	Most functions to read the content of a term are prefixed
	   enif_get_ and usually return true (or false) if the term was of the expected type  (or
	   not).  The functions to write terms are all prefixed enif_make_ and usually return the
	   created ERL_NIF_TERM . There are also some functions to query terms, like enif_is_atom
	   , enif_is_identical and enif_compare .

	   All	terms of type ERL_NIF_TERM belong to an environment of type ErlNifEnv . The life-
	   time of a term is controlled by the lifetime of its environment object. All API  func-
	   tions  that	read or write terms has the environment, that the term belongs to, as the
	   first function argument.

	 Binaries :
	   Terms of type binary are accessed with the help of the struct type  ErlNifBinary  that
	   contains a pointer ( data ) to the raw binary data and the length ( size ) of the data
	   in bytes. Both data and size are read-only and should only be written using	calls  to
	   API	functions.  Instances  of  ErlNifBinary  are however always allocated by the user
	   (usually as local variables).

	   The raw data pointed to by data is only mutable after a call to  enif_alloc_binary  or
	   enif_realloc_binary	.  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
	   enif_release_binary	or  made  read-only  by  transferring  it  to an Erlang term with
	   enif_make_binary . But it does not have to happen in  the  same  NIF  call.	Read-only
	   binaries do not have to be released.

	   enif_make_new_binary  can be used as a shortcut to allocate and return a binary in the
	   same NIF call.

	   Binaries are sequences of whole bytes. Bitstrings with an arbitrary bit length have no
	   support yet.

	 Resource objects :
	   The use of resource objects is 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
	   enif_alloc_resource	.  A  handle  ("safe  pointer")  to this memory block can then be
	   returned  to  Erlang  by  the  use  of  enif_make_resource  .  The  term  returned  by
	   enif_make_resource  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 argu-
	   ment  to  a NIF. The NIF can then call enif_get_resource and get back a pointer to the
	   memory block that is guaranteed to still be valid. A resource object will not be deal-
	   located  until  the	last  handle  term  has  been garbage collected by the VM and the
	   resource has been released with enif_release_resource (not necessarily in that order).

	   All resource objects are created as instances of  some  resource  type  .  This  makes
	   resources  from different modules to be distinguishable. A resource type is created by
	   calling enif_open_resource_type when a library is loaded.  Objects  of  that  resource
	   type  can  then later be allocated and enif_get_resource 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 enif_release_resource ). Resource types are  uniquely  identified
	   by a supplied name string and the name of the implementing module.

	   Here is a template example of how to create and return a resource object.

	     ERL_NIF_TERM term;
	     MyStruct* ptr = enif_alloc_resource(my_resource_type, sizeof(MyStruct));

	     /* initialize struct ... */

	     term = enif_make_resource(env, ptr);

	     if (keep_a_reference_of_our_own) {
		 /* store 'ptr' in static variable, private data or other resource object */
	     }
	     else {
		 enif_release_resource(obj);
		 /* resource now only owned by "Erlang" */
	     }
	     return term;

	   Note  that  once enif_make_resource 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 eventu-
	   ally deallocate the resource object when it collects the term.

	   Another usage of resource objects is to create binary terms with user  defined  memory
	   management. enif_make_resource_binary 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 mmap 'ed file. The destructor can  then
	   do munmap to release the memory region.

	   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.

	 Threads and concurrency :
	   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 enif_priv_data 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.

	   The library initialization callbacks load , reload and  upgrade  are  all  thread-safe
	   even for shared state data.

	   Avoid  doing  lengthy  work in NIF calls as that may degrade the responsiveness of the
	   VM. NIFs are called directly by the same scheduler thread that  executed  the  calling
	   Erlang  code.  The  calling	scheduler  will thus be blocked from doing any other work
	   until the NIF returns.

INITIALIZATION
	 ERL_NIF_INIT(MODULE, ErlNifFunc funcs[], load, reload, upgrade, unload) :
	   This is the magic macro to initialize a NIF library. It should be evaluated in  global
	   file scope.

	   MODULE is the name of the Erlang module as an identifier without string quotations. It
	   will be stringified by the macro.

	   funcs is a static array of function descriptors for all the implemented NIFs  in  this
	   library.

	   load  , reload , upgrade and unload are pointers to functions. One of load , reload or
	   upgrade will be called to initialize the library. unload  is  called  to  release  the
	   library. They are all described individually below.

	 int (*load)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info) :
	   load  is  called  when  the	NIF  library  is loaded and there is no previously loaded
	   library for this module.

	   *priv_data can be set to point to some private data that the library needs in order to
	   keep  a  state  between NIF calls. enif_priv_data will return this pointer. *priv_data
	   will be initialized to NULL when load is called.

	   load_info is the second argument to erlang:load_nif/2 .

	   The library will fail to load if load returns anything other than 0. load can be  NULL
	   in case no initialization is needed.

	 int (*reload)(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info) :
	   reload  is  called  when  the  NIF library is loaded and there is already a previously
	   loaded library for this module code.

	   Works the same as load . The only difference is that *priv_data already  contains  the
	   value set by the previous call to load or reload .

	   The	library will fail to load if reload returns anything other than 0 or if reload is
	   NULL.

	 int (*upgrade)(ErlNifEnv* env,  void**  priv_data,  void**  old_priv_data,  ERL_NIF_TERM
	 load_info) :
	   upgrade  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.

	   Works  the  same as load . The only difference is that *old_priv_data already contains
	   the value set by the last call to load or reload for the old module	code.  *priv_data
	   will  be  initialized  to  NULL when upgrade is called. It is allowed to write to both
	   *priv_data and *old_priv_data.

	   The library will fail to load if upgrade returns anything other than 0 or  if  upgrade
	   is NULL.

	 void (*unload)(ErlNifEnv* env, void* priv_data) :
	   unload  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 unload is not  called
	   for a replaced library as a consequence of reload .

DATA TYPES
	 ERL_NIF_TERM :
	   Variables  of  type	ERL_NIF_TERM 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 ERL_NIF_TERM 's belong to an environment ( ErlNifEnv ). A term
	   can not be destructed individually, it is valid until its environment is destructed.

	 ErlNifEnv :
	   ErlNifEnv represents an environment that can host Erlang terms. All terms in an  envi-
	   ronment are valid as long as the environment is valid. ErlNifEnv is an opaque type and
	   pointers to it can only be passed on to API functions. There are two types of environ-
	   ments; process bound and process independent.

	   A  process bound environment 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 envi-
	   ronment  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  environ-
	   ments between NIF calls.

	   A  process  independent  environment  is created by calling enif_alloc_env . It can be
	   used to store terms between NIF calls and to send terms with  enif_send  .  A  process
	   independent	environment  with all its terms is valid until you explicitly invalidates
	   it with enif_free_env or enif_send .

	   All elements of a list/tuple must belong to the same  environment  as  the  list/tuple
	   itself. Terms can be copied between environments with enif_make_copy .

	 ErlNifFunc :

	 typedef struct {
	     const char* name ;
	     unsigned arity ;
	     ERL_NIF_TERM (*fptr )(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
	 } ErlNifFunc;

	   Describes  a NIF by its name, arity and implementation. fptr is a pointer to the func-
	   tion that implements the NIF. The argument argv of a NIF  will  contain  the  function
	   arguments  passed  to  the  NIF and argc is the length of the array, i.e. the function
	   arity. argv[N-1] will thus denote the Nth argument to the  NIF.  Note  that	the  argc
	   argument  allows  for  the  same C function to implement several Erlang functions with
	   different arity (but same name probably).

	 ErlNifBinary :

	 typedef struct {
	     unsigned size ;
	     unsigned char* data ;
	 } ErlNifBinary;

	   ErlNifBinary contains transient information about an inspected binary term. data is	a
	   pointer to a buffer of size bytes with the raw content of the binary.

	   Note  that  ErlNifBinary is a semi-opaque type and you are only allowed to read fields
	   size and data .

	 ErlNifPid :
	   ErlNifPid is a process identifier (pid).  In  contrast  to  pid  terms  (instances  of
	   ERL_NIF_TERM  ),  ErlNifPid	's  are self contained and not bound to any environment .
	   ErlNifPid is an opaque type.

	 ErlNifResourceType :
	   Each instance of ErlNifResourceType 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.

	 ErlNifResourceDtor :

	 typedef void ErlNifResourceDtor(ErlNifEnv* env, void* obj);

	   The function prototype of a resource destructor function. A destructor function is not
	   allowed to call any term-making functions.

	 ErlNifCharEncoding :

	 typedef enum {
	     ERL_NIF_LATIN1
	 }ErlNifCharEncoding;

	   The	character encoding used in strings and atoms. The only supported encoding is cur-
	   rently ERL_NIF_LATIN1 for iso-latin-1 (8-bit ascii).

	 ErlNifSysInfo :
	   Used by enif_system_info to return information about the runtime system. Contains cur-
	   rently the exact same content as ErlDrvSysInfo .

	 ErlNifSInt64 :
	   A native signed 64-bit integer type.

	 ErlNifUInt64 :
	   A native unsigned 64-bit integer type.

EXPORTS
       void* enif_alloc(size_t size)

	      Allocate memory of size bytes. Return NULL if allocation failed.

       int enif_alloc_binary(size_t size, ErlNifBinary* bin)

	      Allocate	a  new	binary of size size bytes. Initialize the structure pointed to by
	      bin to refer to the allocated  binary.  The  binary  must  either  be  released  by
	      enif_release_binary   or	 ownership   transferred   to	an   Erlang   term   with
	      enif_make_binary . An allocated (and owned) ErlNifBinary can be  kept  between  NIF
	      calls.

	      Return true on success or false if allocation failed.

       ErlNifEnv* enif_alloc_env()

	      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 enif_make_copy or be sent to a process as a message with enif_send
	      .

	      Return pointer to the new environment.

       void* enif_alloc_resource(ErlNifResourceType* type, unsigned size)

	      Allocate a memory managed resource object of type type and size size bytes.

       void enif_clear_env(ErlNifEnv* env)

	      Free all terms in an environment and clear it for reuse. The environment must  have
	      been allocated with enif_alloc_env .

       int enif_compare(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)

	      Return  an  integer  less  than,	equal  to,  or greater than zero if lhs is found,
	      respectively, to be less than, equal, or greater than  rhs  .  Corresponds  to  the
	      Erlang operators == , /= , =< , < , >= and > (but not =:= or =/= ).

       void enif_cond_broadcast(ErlNifCond *cnd)

	      Same as erl_drv_cond_broadcast .

       ErlNifCond* enif_cond_create(char *name)

	      Same as erl_drv_cond_create .

       void enif_cond_destroy(ErlNifCond *cnd)

	      Same as erl_drv_cond_destroy .

       void enif_cond_signal(ErlNifCond *cnd)

	      Same as erl_drv_cond_signal .

       void enif_cond_wait(ErlNifCond *cnd, ErlNifMutex *mtx)

	      Same as erl_drv_cond_wait .

       int enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)

	      Same as erl_drv_equal_tids .

       void enif_free(void* ptr)

	      Free memory allocated by enif_alloc .

       void enif_free_env(ErlNifEnv* env)

	      Free  an environment allocated with enif_alloc_env . All terms created in the envi-
	      ronment will be freed as well.

       int enif_get_atom(ErlNifEnv* env,  ERL_NIF_TERM	term,  char*  buf,  unsigned  size,  Erl-
       NifCharEncoding encode)

	      Write a null-terminated string, in the buffer pointed to by buf of size size , con-
	      sisting of the string representation of the atom term with encoding encode . Return
	      the  number of bytes written (including terminating null character) or 0 if term is
	      not an atom with maximum length of size-1 .

       int enif_get_atom_length(ErlNifEnv* env, ERL_NIF_TERM term, unsigned*  len,  ErlNifCharEn-
       coding encode)

	      Set  *len  to  the length (number of bytes excluding terminating null character) of
	      the atom term with encoding encode . Return true on success or false if term is not
	      an atom.

       int enif_get_double(ErlNifEnv* env, ERL_NIF_TERM term, double* dp)

	      Set  *dp	to  the floating point value of term . Return true on success or false if
	      term is not a float.

       int enif_get_int(ErlNifEnv* env, ERL_NIF_TERM term, int* ip)

	      Set *ip to the integer value of term . Return true on success or false if  term  is
	      not an integer or is outside the bounds of type int .

       int enif_get_int64(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifSInt64* ip)

	      Set  *ip	to the integer value of term . Return true on success or false if term is
	      not an integer or is outside the bounds of a signed 64-bit integer.

       int enif_get_local_pid(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifPid* pid)

	      If term is the pid of a node local process, initialize the pid variable  *pid  from
	      it  and  return  true.  Otherwise return false. No check if the process is alive is
	      done.

       int   enif_get_list_cell(ErlNifEnv*   env,   ERL_NIF_TERM   list,   ERL_NIF_TERM*    head,
       ERL_NIF_TERM* tail)

	      Set  *head  and  *tail  from list and return true, or return false if list is not a
	      non-empty list.

       int enif_get_list_length(ErlNifEnv* env, ERL_NIF_TERM term, unsigned* len)

	      Set *len to the length of list term and return true, or return false if term is not
	      a list.

       int enif_get_long(ErlNifEnv* env, ERL_NIF_TERM term, long int* ip)

	      Set  *ip to the long integer value of term and return true, or return false if term
	      is not an integer or is outside the bounds of type long int .

       int enif_get_resource(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifResourceType* type,  void**
       objp)

	      Set *objp to point to the resource object referred to by term .

	      Return  true  on	success  or false if term is not a handle to a resource object of
	      type type .

       int enif_get_string(ErlNifEnv* env, ERL_NIF_TERM list,  char*  buf,  unsigned  size,  Erl-
       NifCharEncoding encode)

	      Write  a	null-terminated  string, in the buffer pointed to by buf with size size ,
	      consisting of the characters in the string list . The characters are written  using
	      encoding	encode	.  Return the number of bytes written (including terminating null
	      character), or -size if the string was truncated due to buffer space, or 0 if  list
	      is  not  a  string  that can be encoded with encode or if size was less than 1. The
	      written string is always null-terminated unless buffer size is less than 1.

       int enif_get_tuple(ErlNifEnv* env, ERL_NIF_TERM term,  int*  arity,  const  ERL_NIF_TERM**
       array)

	      If  term is a tuple, set *array to point to an array containing the elements of the
	      tuple and set *arity to the number of elements. Note that the  array  is	read-only
	      and  (*array)[N-1] will be the Nth element of the tuple. *array is undefined if the
	      arity of the tuple is zero.

	      Return true on success or false if term is not a tuple.

       int enif_get_uint(ErlNifEnv* env, ERL_NIF_TERM term, unsigned int* ip)

	      Set *ip to the unsigned integer value of term and return true, or return	false  if
	      term is not an unsigned integer or is outside the bounds of type unsigned int .

       int enif_get_uint64(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifUInt64* ip)

	      Set  *ip	to the unsigned integer value of term and return true, or return false if
	      term is not an unsigned integer or is outside the  bounds  of  an  unsigned  64-bit
	      integer.

       int enif_get_ulong(ErlNifEnv* env, ERL_NIF_TERM term, unsigned long* ip)

	      Set *ip to the unsigned long integer value of term and return true, or return false
	      if term is not an unsigned integer or is outside the bounds of type unsigned long .

       int enif_inspect_binary(ErlNifEnv* env, ERL_NIF_TERM bin_term, ErlNifBinary* bin)

	      Initialize the structure pointed to by bin with information about the  binary  term
	      bin_term . Return true on success or false if bin_term is not a binary.

       int enif_inspect_iolist_as_binary(ErlNifEnv* env, ERL_NIF_TERM term, ErlNifBinary* bin)

	      Initialize the structure pointed to by bin with one continuous buffer with the same
	      byte content as iolist . As with inspect_binary, the data  pointed  to  by  bin  is
	      transient  and  does  not  need  to be released. Return true on success or false if
	      iolist is not an iolist.

       int enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is an atom.

       int enif_is_binary(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a binary

       int enif_is_empty_list(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is an empty list.

       int enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a fun.

       int enif_is_identical(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)

	      Return true if the two terms are identical. Corresponds to the Erlang operators =:=
	      and =/= .

       int enif_is_pid(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a pid.

       int enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a port.

       int enif_is_ref(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a reference.

       int enif_is_tuple(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a tuple.

       int enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term)

	      Return true if term is a list.

       int enif_keep_resource(void* obj)

	      Add  a  reference  to  resource object obj obtained from enif_alloc_resource . Each
	      call  to	enif_keep_resource  for  an  object  must  be  balanced  by  a	call   to
	      enif_release_resource before the object will be destructed.

       ERL_NIF_TERM enif_make_atom(ErlNifEnv* env, const char* name)

	      Create  an atom term from the null-terminated C-string name with iso-latin-1 encod-
	      ing.

       ERL_NIF_TERM enif_make_atom_len(ErlNifEnv* env, const char* name, size_t len)

	      Create an atom term from the string name with  length  len  .  Null-characters  are
	      treated as any other characters.

       ERL_NIF_TERM enif_make_badarg(ErlNifEnv* env)

	      Make a badarg exception to be returned from a NIF.

       ERL_NIF_TERM enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)

	      Make  a binary term from bin . Any ownership of the binary data will be transferred
	      to the created term and bin should be considered read-only for the rest of the  NIF
	      call and then as released.

       ERL_NIF_TERM enif_make_copy(ErlNifEnv* dst_env, ERL_NIF_TERM src_term)

	      Make  a  copy  of term src_term . The copy will be created in environment dst_env .
	      The source term may be located in any environment.

       ERL_NIF_TERM enif_make_double(ErlNifEnv* env, double d)

	      Create a floating-point term from a double .

       int enif_make_existing_atom(ErlNifEnv* env, const char*	name,  ERL_NIF_TERM*  atom,  Erl-
       NifCharEncoding encode)

	      Try  to  create  the  term  of an already existing atom from the null-terminated C-
	      string name with encoding encode . If the atom already exists  store  the  term  in
	      *atom and return true, otherwise return false.

       int   enif_make_existing_atom_len(ErlNifEnv*   env,   const   char*   name,   size_t  len,
       ERL_NIF_TERM* atom, ErlNifCharEncoding encoding)

	      Try to create the term of an already existing atom from the string name with length
	      len  and	encoding encode . Null-characters are treated as any other characters. If
	      the atom already exists store the term in *atom and return true,	otherwise  return
	      false.

       ERL_NIF_TERM enif_make_int(ErlNifEnv* env, int i)

	      Create an integer term.

       ERL_NIF_TERM enif_make_int64(ErlNifEnv* env, ErlNifSInt64 i)

	      Create an integer term from a signed 64-bit integer.

       ERL_NIF_TERM enif_make_list(ErlNifEnv* env, unsigned cnt, ...)

	      Create an ordinary list term of length cnt . Expects cnt number of arguments (after
	      cnt ) of type ERL_NIF_TERM as the elements of the list. An empty list  is  returned
	      if cnt is 0.

       ERL_NIF_TERM enif_make_list1(ErlNifEnv* env, ERL_NIF_TERM e1)
       ERL_NIF_TERM enif_make_list2(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2)
       ERL_NIF_TERM   enif_make_list3(ErlNifEnv*   env,   ERL_NIF_TERM	 e1,   ERL_NIF_TERM   e2,
       ERL_NIF_TERM e3)
       ERL_NIF_TERM enif_make_list4(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
       ERL_NIF_TERM enif_make_list5(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
       ERL_NIF_TERM enif_make_list6(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
       ERL_NIF_TERM enif_make_list7(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
       ERL_NIF_TERM enif_make_list8(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
       ERL_NIF_TERM enif_make_list9(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)

	      Create an ordinary list term with length indicated by  the  function  name.  Prefer
	      these  functions	(macros)  over	the variadic enif_make_list to get a compile time
	      error if the number of arguments does not match.

       ERL_NIF_TERM enif_make_list_cell(ErlNifEnv* env, ERL_NIF_TERM head, ERL_NIF_TERM tail)

	      Create a list cell [head | tail] .

       ERL_NIF_TERM enif_make_list_from_array(ErlNifEnv* env, const ERL_NIF_TERM arr[],  unsigned
       cnt)

	      Create  an  ordinary  list  containing the elements of array arr of length cnt . An
	      empty list is returned if cnt is 0.

       ERL_NIF_TERM enif_make_long(ErlNifEnv* env, long int i)

	      Create an integer term from a long int .

       unsigned char* enif_make_new_binary(ErlNifEnv* env, size_t size, ERL_NIF_TERM* termp)

	      Allocate a binary of size size 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 ErlNifBinary . The drawbacks are that the binary can  not  be
	      kept between NIF calls and it can not be reallocated.

	      Return a pointer to the raw binary data and set *termp to the binary term.

       ERL_NIF_TERM enif_make_pid(ErlNifEnv* env, const ErlNifPid* pid)

	      Make a pid term from *pid .

       ERL_NIF_TERM enif_make_ref(ErlNifEnv* env)

	      Create a reference like erlang:make_ref/0 .

       ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)

	      Create   an  opaque  handle  to  a  memory  managed  resource  object  obtained  by
	      enif_alloc_resource . No ownership transfer is done, as the resource  object  still
	      needs  to  be  released  by  enif_release_resource  ,  but  note	that  the call to
	      enif_release_resource  can  occur  immediately  after  obtaining	the   term   from
	      enif_make_resource , in which case the resource object will be deallocated when the
	      term is garbage collected. See the example of creating  and  returning  a  resource
	      object for more details.

	      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 term_to_binary will have unpredictable (but harmless) results.

       ERL_NIF_TERM enif_make_resource_binary(ErlNifEnv* env, void* obj, const void* data, size_t
       size)

	      Create a binary term that is memory managed by a resource object	obj  obtained  by
	      enif_alloc_resource  .  The returned binary term will consist of size bytes pointed
	      to by data . 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.

	      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.

	      As  with	enif_make_resource  ,  no  ownership transfer is done. The resource still
	      needs to be released with enif_release_resource .

       ERL_NIF_TERM  enif_make_string(ErlNifEnv*  env,	const  char*  string,  ErlNifCharEncoding
       encoding)

	      Create  a  list containing the characters of the null-terminated string string with
	      encoding encoding .

       ERL_NIF_TERM enif_make_string_len(ErlNifEnv* env, const char*  string,  size_t  len,  Erl-
       NifCharEncoding encoding)

	      Create  a  list  containing the characters of the string string with length len and
	      encoding encoding . Null-characters are treated as any other characters.

       ERL_NIF_TERM  enif_make_sub_binary(ErlNifEnv*  env,  ERL_NIF_TERM  bin_term,  size_t  pos,
       size_t size)

	      Make  a  subbinary  of binary bin_term , starting at zero-based position pos with a
	      length of size bytes. bin_term must be a binary or bitstring and pos+size  must  be
	      less or equal to the number of whole bytes in bin_term .

       ERL_NIF_TERM enif_make_tuple(ErlNifEnv* env, unsigned cnt, ...)

	      Create  a tuple term of arity cnt . Expects cnt number of arguments (after cnt ) of
	      type ERL_NIF_TERM as the elements of the tuple.

       ERL_NIF_TERM enif_make_tuple1(ErlNifEnv* env, ERL_NIF_TERM e1)
       ERL_NIF_TERM enif_make_tuple2(ErlNifEnv* env, ERL_NIF_TERM e1, ERL_NIF_TERM e2)
       ERL_NIF_TERM  enif_make_tuple3(ErlNifEnv*   env,   ERL_NIF_TERM	 e1,   ERL_NIF_TERM   e2,
       ERL_NIF_TERM e3)
       ERL_NIF_TERM enif_make_tuple4(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e4)
       ERL_NIF_TERM enif_make_tuple5(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e5)
       ERL_NIF_TERM enif_make_tuple6(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e6)
       ERL_NIF_TERM enif_make_tuple7(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e7)
       ERL_NIF_TERM enif_make_tuple8(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e8)
       ERL_NIF_TERM enif_make_tuple9(ErlNifEnv* env, ERL_NIF_TERM e1, ..., ERL_NIF_TERM e9)

	      Create  a tuple term with length indicated by the function name. Prefer these func-
	      tions (macros) over the variadic enif_make_tuple to get a compile time error if the
	      number of arguments does not match.

       ERL_NIF_TERM enif_make_tuple_from_array(ErlNifEnv* env, const ERL_NIF_TERM arr[], unsigned
       cnt)

	      Create a tuple containing the elements of array arr of length cnt .

       ERL_NIF_TERM enif_make_uint(ErlNifEnv* env, unsigned int i)

	      Create an integer term from an unsigned int .

       ERL_NIF_TERM enif_make_uint64(ErlNifEnv* env, ErlNifUInt64 i)

	      Create an integer term from an unsigned 64-bit integer.

       ERL_NIF_TERM enif_make_ulong(ErlNifEnv* env, unsigned long i)

	      Create an integer term from an unsigned long int .

       ErlNifMutex* enif_mutex_create(char *name)

	      Same as erl_drv_mutex_create .

       void enif_mutex_destroy(ErlNifMutex *mtx)

	      Same as erl_drv_mutex_destroy .

       void enif_mutex_lock(ErlNifMutex *mtx)

	      Same as erl_drv_mutex_lock .

       int enif_mutex_trylock(ErlNifMutex *mtx)

	      Same as erl_drv_mutex_trylock .

       void enif_mutex_unlock(ErlNifMutex *mtx)

	      Same as erl_drv_mutex_unlock .

       ErlNifResourceType* enif_open_resource_type(ErlNifEnv* env, const char* module_str,  const
       char*  name,  ErlNifResourceDtor*  dtor,  ErlNifResourceFlags  flags, ErlNifResourceFlags*
       tried)

	      Create or takeover a resource type identified by the string name and  give  it  the
	      destructor function pointed to by dtor . Argument flags can have the following val-
	      ues:

		ERL_NIF_RT_CREATE :
		  Create a new resource type that does not already exist.

		ERL_NIF_RT_TAKEOVER :
		  Open an existing resource type and take over ownership of  all  its  instances.
		  The supplied destructor dtor will be called both for existing instances as well
		  as new instances not yet created by the calling NIF library.

	      The two flag values can be combined with bitwise-or. The name of the resource  type
	      is  local  to the calling module. Argument module_str is not (yet) used and must be
	      NULL. The dtor may be NULL in case no destructor is needed.

	      On success, return a pointer to the resource type and *tried will be set to  either
	      ERL_NIF_RT_CREATE  or  ERL_NIF_RT_TAKEOVER  to  indicate what was actually done. On
	      failure, return NULL and set *tried to flags . It is allowed to set tried to NULL .

	      Note that enif_open_resource_type is only allowed to be called in the  three  call-
	      backs load , reload and upgrade .

       void* enif_priv_data(ErlNifEnv* env)

	      Return the pointer to the private data that was set by load , reload or upgrade .

	      Was previously named enif_get_data .

       int enif_realloc_binary(ErlNifBinary* bin, size_t size)

	      Change the size of a binary bin . The source binary may be read-only, in which case
	      it will be left untouched and a mutable copy is allocated and assigned  to  *bin	.
	      Return true on success, false if memory allocation failed.

       void enif_release_binary(ErlNifBinary* bin)

	      Release a binary obtained from enif_alloc_binary .

       void enif_release_resource(void* obj)

	      Remove  a  reference to resource object obj obtained from enif_alloc_resource . The
	      resource object will be destructed when the last reference is removed. Each call to
	      enif_release_resource  must correspond to a previous call to enif_alloc_resource or
	      enif_keep_resource . References made by enif_make_resource can only be  removed  by
	      the garbage collector.

       ErlNifRWLock* enif_rwlock_create(char *name)

	      Same as erl_drv_rwlock_create .

       void enif_rwlock_destroy(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_destroy .

       void enif_rwlock_rlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_rlock .

       void enif_rwlock_runlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_runlock .

       void enif_rwlock_rwlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_rwlock .

       void enif_rwlock_rwunlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_rwunlock .

       int enif_rwlock_tryrlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_tryrlock .

       int enif_rwlock_tryrwlock(ErlNifRWLock *rwlck)

	      Same as erl_drv_rwlock_tryrwlock .

       ErlNifPid* enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)

	      Initialize the pid variable *pid to represent the calling process. Return pid .

       int enif_send(ErlNifEnv* env, ErlNifPid* to_pid, ErlNifEnv* msg_env, ERL_NIF_TERM msg)

	      Send a message to a process.

		env :
		  The  environment  of	the  calling process. Must be NULL if and only if calling
		  from a created thread.

		*to_pid :
		  The pid of the receiving process. The pid should refer  to  a  process  on  the
		  local node.

		msg_env :
		  The  environment of the message term. Must be a process independent environment
		  allocated with enif_alloc_env .

		msg :
		  The message term to send.

	      Return true on success, or false if *to_pid  does  not  refer  to  an  alive  local
	      process.

	      The message environment msg_env with all its terms (including msg ) will be invali-
	      dated by a successful call to enif_send . The environment should	either	be  freed
	      with enif_free_env of cleared for reuse with enif_clear_env .

	      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.

       unsigned enif_sizeof_resource(void* obj)

	      Get the byte size of a resource object obj obtained by enif_alloc_resource .

       void enif_system_info(ErlNifSysInfo *sys_info_ptr, size_t size)

	      Same as driver_system_info .

       int enif_thread_create(char *name,ErlNifTid *tid,void *	(*func)(void  *),void  *args,Erl-
       NifThreadOpts *opts)

	      Same as erl_drv_thread_create .

       void enif_thread_exit(void *resp)

	      Same as erl_drv_thread_exit .

       int enif_thread_join(ErlNifTid, void **respp)

	      Same as erl_drv_thread_join .

       ErlNifThreadOpts* enif_thread_opts_create(char *name)

	      Same as erl_drv_thread_opts_create .

       void enif_thread_opts_destroy(ErlNifThreadOpts *opts)

	      Same as erl_drv_thread_opts_destroy .

       ErlNifTid enif_thread_self(void)

	      Same as erl_drv_thread_self .

       int enif_tsd_key_create(char *name, ErlNifTSDKey *key)

	      Same as erl_drv_tsd_key_create .

       void enif_tsd_key_destroy(ErlNifTSDKey key)

	      Same as erl_drv_tsd_key_destroy .

       void* enif_tsd_get(ErlNifTSDKey key)

	      Same as erl_drv_tsd_get .

       void enif_tsd_set(ErlNifTSDKey key, void *data)

	      Same as erl_drv_tsd_set .

SEE ALSO
       erlang:load_nif/2

Ericsson AB				    erts 5.8.3				    erl_nif(3erl)


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