erl_nif - API functions for an Erlang NIF library.
Please see following description for synopsis
erl_nif(3) C Library Functions erl_nif(3)
NAME
erl_nif - API functions for an Erlang NIF library.
DESCRIPTION
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. A NIF library
is built as a dynamically linked library file and loaded in runtime by
calling erlang:load_nif/2.
Warning:
Use this functionality with extreme care.
A native function is executed as a direct extension of the native code
of the VM. Execution is not made in a safe environment. The VM cannot
provide the same services as provided when executing Erlang code, such
as pre-emptive scheduling or memory protection. If the native function
does not behave well, the whole VM will misbehave.
* A native function that crashes will crash the whole VM.
* An erroneously implemented native function can cause a VM internal
state inconsistency, which can cause a crash of the VM, or miscel-
laneous misbehaviors of the VM at any point after the call to the
native function.
* A native function doing lengthy work before returning degrades
responsiveness of the VM, and can cause miscellaneous strange
behaviors. Such strange behaviors include, but are not limited to,
extreme memory usage, and bad load balancing between schedulers.
Strange behaviors that can occur because of lengthy work can also
vary between Erlang/OTP releases.
EXAMPLE
A minimal example of a NIF library can look as follows:
/* 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)
The Erlang module can look as follows:
-module(niftest).
-export([init/0, hello/0]).
-on_load(init/0).
init() ->
erlang:load_nif("./niftest", 0).
hello() ->
erlang:nif_error("NIF library not loaded").
Compile and test can look as follows (on Linux):
$> gcc -fPIC -shared -o niftest.so niftest.c -I $ERL_ROOT/usr/include/
$> erl
1> c(niftest).
{ok,niftest}
2> niftest:hello().
"Hello world!"
In the example above the on_load directive is used get function init
called automatically when the module is loaded. Function init in turn
calls erlang:load_nif/2 which loads the NIF library and replaces the
hello function with its native implementation in C. Once loaded, a NIF
library is persistent. It will not be unloaded until the module code
version that it belongs to is purged.
Each NIF must have an implementation in Erlang to be invoked if the
function is called before the NIF library is successfully loaded. A
typical such stub implementation is to call erlang:nif_error which will
raise an exception. The Erlang function can also be used as a fallback
implementation if the NIF library lacks implementation for some OS or
hardware architecture for example.
Note:
A NIF does not have to be exported, it can be local to the module. How-
ever, unused local stub functions will be optimized away by the com-
piler, causing loading of the NIF library to fail.
Warning:
There is a known limitation for Erlang fallback functions of NIFs.
Avoid functions involved in traversal of binaries by matching and
recursion. If a NIF is loaded over such function, binary arguments to
the NIF may get corrupted and cause VM crash or other misbehavior.
Example of such bad fallback function:
skip_until(Byte, <<Byte, Rest/binary>>) ->
Rest;
skip_until(Byte, <<_, Rest/binary>>) ->
skip_until(Byte, Rest).
FUNCTIONALITY
All interaction between NIF code and the Erlang runtime system is per-
formed by calling NIF API functions. Functions exist 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 function return values. The terms are of C-type
ERL_NIF_TERM and can only be read or written 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 is 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 lifetime of a term is controlled by the lifetime of
its environment object. All API functions that read or write terms
has the environment that the term belongs to as the first function
argument.
Binaries:
Terms of type binary are accessed with the help of struct type Erl-
NifBinary, which 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 are only to 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
operate on a binary 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. However, it does not have to occur 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 safe way to return pointers to
native data structures from a NIF. A resource object is only 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 opaque in nature. It can be stored and passed
between processes, but the only real end usage is to pass it back
as an argument to a NIF. The NIF can then call enif_get_resource
and get back a pointer to the memory block, which is guaranteed to
still be valid. A resource object is not deallocated until the last
handle term is garbage collected by the VM and the resource is
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 distin-
guishable. 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, which is automati-
cally 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.
The following is a template example of how to create and return a
resource object.
ERL_NIF_TERM term;
MyStruct* obj = enif_alloc_resource(my_resource_type, sizeof(MyStruct));
/* initialize struct ... */
term = enif_make_resource(env, obj);
if (keep_a_reference_of_our_own) {
/* store 'obj' in static variable, private data or other resource object */
}
else {
enif_release_resource(obj);
/* resource now only owned by "Erlang" */
}
return term;
Notice 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 immedi-
ately and rely only on the garbage collector to deallocate the
resource object eventually when it collects the term.
Another use of resource objects is to create binary terms with
user-defined memory management. enif_make_resource_binary creates a
binary term that is connected to a resource object. The destructor
of the resource is 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 take over an already existing resource type and by that
"inherit" all existing objects of that type. The destructor of the
new library is thereafter 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 unload-
ing of a library is postponed as long as there exist resource
objects with a destructor function in the library.
Module upgrade and static data:
A loaded NIF library is tied to the Erlang module instance that
loaded it. If the module is upgraded, the new module instance needs
to load its own NIF library (or maybe choose not to). The new mod-
ule instance can, however, choose to load the exact same NIF
library as the old code if it wants to. Sharing the dynamic library
means that static data defined by the library is shared as well. To
avoid unintentionally shared static data between module instances,
each Erlang module version can keep its own private data. This pri-
vate data can be set when the NIF library is loaded and later
retrieved by calling enif_priv_data.
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 argu-
ments. When you write to a shared state either through static vari-
ables or enif_priv_data, you need to supply your own explicit syn-
chronization. This includes terms in process independent environ-
ments that are shared between threads. Resource objects also
require synchronization if you treat them as mutable.
The library initialization callbacks load and upgrade are thread-
safe even for shared state data.
Version Management:
When a NIF library is built, information about the NIF API version
is compiled into the library. When a NIF library is loaded, the
runtime system verifies that the library is of a compatible ver-
sion. erl_nif.h defines the following:
ERL_NIF_MAJOR_VERSION:
Incremented when NIF library incompatible changes are made to the
Erlang runtime system. Normally it suffices to recompile the NIF
library when the ERL_NIF_MAJOR_VERSION has changed, but it can,
under rare circumstances, mean that NIF libraries must be
slightly modified. If so, this will of course be documented.
ERL_NIF_MINOR_VERSION:
Incremented when new features are added. The runtime system uses
the minor version to determine what features to use.
The runtime system normally refuses to load a NIF library if the
major versions differ, or if the major versions are equal and the
minor version used by the NIF library is greater than the one used
by the runtime system. Old NIF libraries with lower major versions
are, however, allowed after a bump of the major version during a
transition period of two major releases. Such old NIF libraries can
however fail if deprecated features are used.
Time Measurement:
Support for time measurement in NIF libraries:
* ErlNifTime
* ErlNifTimeUnit
* enif_monotonic_time()
* enif_time_offset()
* enif_convert_time_unit()
I/O Queues:
The Erlang nif library contains function for easily working with
I/O vectors as used by the unix system call writev. The I/O Queue
is not thread safe, so some other synchronization mechanism has to
be used.
* SysIOVec
* ErlNifIOVec
* enif_ioq_create()
* enif_ioq_destroy()
* enif_ioq_enq_binary()
* enif_ioq_enqv()
* enif_ioq_deq()
* enif_ioq_peek()
* enif_ioq_peek_head()
* enif_inspect_iovec()
* enif_free_iovec()
Typical usage when writing to a file descriptor looks like this:
int writeiovec(ErlNifEnv *env, ERL_NIF_TERM term, ERL_NIF_TERM *tail,
ErlNifIOQueue *q, int fd) {
ErlNifIOVec vec, *iovec = &vec;
SysIOVec *sysiovec;
int saved_errno;
int iovcnt, n;
if (!enif_inspect_iovec(env, 64, term, tail, &iovec))
return -2;
if (enif_ioq_size(q) > 0) {
/* If the I/O queue contains data we enqueue the iovec and
then peek the data to write out of the queue. */
if (!enif_ioq_enqv(q, iovec, 0))
return -3;
sysiovec = enif_ioq_peek(q, &iovcnt);
} else {
/* If the I/O queue is empty we skip the trip through it. */
iovcnt = iovec->iovcnt;
sysiovec = iovec->iov;
}
/* Attempt to write the data */
n = writev(fd, sysiovec, iovcnt);
saved_errno = errno;
if (enif_ioq_size(q) == 0) {
/* If the I/O queue was initially empty we enqueue any
remaining data into the queue for writing later. */
if (n >= 0 && !enif_ioq_enqv(q, iovec, n))
return -3;
} else {
/* Dequeue any data that was written from the queue. */
if (n > 0 && !enif_ioq_deq(q, n, NULL))
return -4;
}
/* return n, which is either number of bytes written or -1 if
some error happened */
errno = saved_errno;
return n;
}
Long-running NIFs:
As mentioned in the warning text at the beginning of this manual
page, it is of vital importance that a native function returns rel-
atively fast. It is difficult to give an exact maximum amount of
time that a native function is allowed to work, but usually a well-
behaving native function is to return to its caller within 1 mil-
lisecond. This can be achieved using different approaches. If you
have full control over the code to execute in the native function,
the best approach is to divide the work into multiple chunks of
work and call the native function multiple times. This is, however,
not always possible, for example when calling third-party
libraries.
The enif_consume_timeslice() function can be used to inform the
runtime system about the length of the NIF call. It is typically
always to be used unless the NIF executes very fast.
If the NIF call is too lengthy, this must be handled in one of the
following ways to avoid degraded responsiveness, scheduler load
balancing problems, and other strange behaviors:
Yielding NIF:
If the functionality of a long-running NIF can be split so that
its work can be achieved through a series of shorter NIF calls,
the application has two options:
* Make that series of NIF calls from the Erlang level.
* Call a NIF that first performs a chunk of the work, then
invokes the enif_schedule_nif function to schedule another NIF
call to perform the next chunk. The final call scheduled in
this manner can then return the overall result.
Breaking up a long-running function in this manner enables the VM
to regain control between calls to the NIFs.
This approach is always preferred over the other alternatives
described below. This both from a performance perspective and a
system characteristics perspective.
Threaded NIF:
This is accomplished by dispatching the work to another thread
managed by the NIF library, return from the NIF, and wait for the
result. The thread can send the result back to the Erlang process
using enif_send. Information about thread primitives is provided
below.
Dirty NIF:
A NIF that cannot be split and cannot execute in a millisecond or
less is called a "dirty NIF", as it performs work that the ordi-
nary schedulers of the Erlang runtime system cannot handle
cleanly. Applications that make use of such functions must indi-
cate to the runtime that the functions are dirty so they can be
handled specially. This is handled by executing dirty jobs on a
separate set of schedulers called dirty schedulers. A dirty NIF
executing on a dirty scheduler does not have the same duration
restriction as a normal NIF.
It is important to classify the dirty job correct. An I/O bound
job should be classified as such, and a CPU bound job should be
classified as such. If you should classify CPU bound jobs as I/O
bound jobs, dirty I/O schedulers might starve ordinary sched-
ulers. I/O bound jobs are expected to either block waiting for
I/O, and/or spend a limited amount of time moving data.
To schedule a dirty NIF for execution, the application has two
options:
* Set the appropriate flags value for the dirty NIF in its Erl-
NifFunc entry.
* Call enif_schedule_nif, pass to it a pointer to the dirty NIF
to be executed, and indicate with argument flags whether it
expects the operation to be CPU-bound or I/O-bound.
A job that alternates between I/O bound and CPU bound can be
reclassified and rescheduled using enif_schedule_nif so that it
executes on the correct type of dirty scheduler at all times. For
more information see the documentation of the erl(1) command line
arguments +SDcpu, and +SDio.
While a process executes a dirty NIF, some operations that commu-
nicate with it can take a very long time to complete. Suspend or
garbage collection of a process executing a dirty NIF cannot be
done until the dirty NIF has returned. Thus, other processes
waiting for such operations to complete might have to wait for a
very long time. Blocking multi-scheduling, that is, calling
erlang:system_flag(multi_scheduling, block), can also take a very
long time to complete. This is because all ongoing dirty opera-
tions on all dirty schedulers must complete before the block
operation can complete.
Many operations communicating with a process executing a dirty
NIF can, however, complete while it executes the dirty NIF. For
example, retrieving information about it through process_info,
setting its group leader, register/unregister its name, and so
on.
Termination of a process executing a dirty NIF can only be com-
pleted up to a certain point while it executes the dirty NIF. All
Erlang resources, such as its registered name and its ETS tables,
are released. All links and monitors are triggered. The execution
of the NIF is, however, not stopped. The NIF can safely continue
execution, allocate heap memory, and so on, but it is of course
better to stop executing as soon as possible. The NIF can check
whether a current process is alive using enif_is_cur-
rent_process_alive. Communication using enif_send and
enif_port_command is also dropped when the sending process is not
alive. Deallocation of certain internal resources, such as
process heap and process control block, is delayed until the
dirty NIF has completed.
INITIALIZATION
ERL_NIF_INIT(MODULE, ErlNifFunc funcs[], load, NULL, upgrade,
unload):
This is the magic macro to initialize a NIF library. It is to be
evaluated in global file scope.
MODULE is the name of the Erlang module as an identifier without
string quotations. It is stringified by the macro.
funcs is a static array of function descriptors for all the imple-
mented NIFs in this library.
load, upgrade and unload are pointers to functions. One of load or
upgrade is called to initialize the library. unload is called to
release the library. All are described individually below.
The fourth argument NULL is ignored. It was earlier used for the
deprecated reload callback which is no longer supported since OTP
20.
If compiling a NIF for static inclusion through --enable-static-
nifs, you must define STATIC_ERLANG_NIF before the ERL_NIF_INIT
declaration.
int (*load)(ErlNifEnv* caller_env, void** priv_data, ERL_NIF_TERM
load_info):
load is called when the NIF library is loaded and no previously
loaded library exists for this module.
*priv_data can be set to point to some private data if the library
needs to keep a state between NIF calls. enif_priv_data returns
this pointer. *priv_data is initialized to NULL when load is
called.
load_info is the second argument to erlang:load_nif/2.
The library fails to load if load returns anything other than 0.
load can be NULL if initialization is not needed.
int (*upgrade)(ErlNifEnv* caller_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 old
code of this module with a loaded NIF library.
Works as load, except that *old_priv_data already contains the
value set by the last call to load or upgrade for the old module
code. *priv_data is initialized to NULL when upgrade is called. It
is allowed to write to both *priv_data and *old_priv_data.
The library fails to load if upgrade returns anything other than 0
or if upgrade is NULL.
void (*unload)(ErlNifEnv* caller_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.
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 argu-
ments to API functions or as return values from NIFs. All
ERL_NIF_TERMs belong to an environment (ErlNifEnv). A term cannot
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 environment are valid as long as the environment is
valid. ErlNifEnv is an opaque type; pointers to it can only be
passed on to API functions. Three types of environments exist:
Process bound environment:
Passed as the first argument to all NIFs. All function arguments
passed to a NIF belong to that environment. The return value from
a NIF must also be a term belonging to the same environment.
A process bound environment contains transient information about
the calling Erlang process. The environment is only valid in the
thread where it was supplied as argument until the NIF returns.
It is thus useless and dangerous to store pointers to process
bound environments between NIF calls.
Callback environment:
Passed as the first argument to all the non-NIF callback func-
tions (load, upgrade, unload, dtor, down, stop and dyncall).
Works like a process bound environment but with a temporary
pseudo process that "terminates" when the callback has returned.
Terms may be created in this environment but they will only be
accessible during the callback.
Process independent environment:
Created by calling enif_alloc_env. This environment 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 invalidate it with enif_free_env or
enif_send.
All contained terms of a list/tuple/map must belong to the same
environment as the list/tuple/map itself. Terms can be copied
between environments with enif_make_copy.
ErlNifFunc:
typedef struct {
const char* name;
unsigned arity;
ERL_NIF_TERM (*fptr)(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]);
unsigned flags;
} ErlNifFunc;
Describes a NIF by its name, arity, and implementation.
fptr:
A pointer to the function that implements the NIF.
argv:
Contains the function arguments passed to the NIF.
argc:
The array length, that is, the function arity. argv[N-1] thus
denotes the Nth argument to the NIF. Notice that the argument
argc allows for the same C function to implement several Erlang
functions with different arity (but probably with the same name).
flags:
Is 0 for a regular NIF (and so its value can be omitted for stat-
ically initialized ErlNifFunc instances).
flags can be used to indicate that the NIF is a dirty NIF that is
to be executed on a dirty scheduler thread.
If the dirty NIF is expected to be CPU-bound, its flags field is
to be set to ERL_NIF_DIRTY_JOB_CPU_BOUND or
ERL_NIF_DIRTY_JOB_IO_BOUND.
Note:
If one of the ERL_NIF_DIRTY_JOB_*_BOUND flags is set, and the run-
time system has no support for dirty schedulers, the runtime system
refuses to load the NIF library.
ErlNifBinary:
typedef struct {
size_t 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.
Notice that ErlNifBinary is a semi-opaque type and you are only
allowed to read fields size and data.
ErlNifBinaryToTerm:
An enumeration of the options that can be specified to
enif_binary_to_term. For default behavior, use value 0.
When receiving data from untrusted sources, use option
ERL_NIF_BIN2TERM_SAFE.
ErlNifMonitor:
This is an opaque data type that identifies a monitor.
The nif writer is to provide the memory for storing the monitor
when calling enif_monitor_process. The address of the data is not
stored by the runtime system, so ErlNifMonitor can be used as any
other data, it can be copied, moved in memory, forgotten, and so
on. To compare two monitors, enif_compare_monitors must be used.
ErlNifPid:
A process identifier (pid). In contrast to pid terms (instances of
ERL_NIF_TERM), ErlNifPids are self-contained and not bound to any
environment. ErlNifPid is an opaque type. It can be copied, moved
in memory, forgotten, and so on.
ErlNifPort:
A port identifier. In contrast to port ID terms (instances of
ERL_NIF_TERM), ErlNifPorts are self-contained and not bound to any
environment. ErlNifPort is an opaque type. It can be copied, moved
in memory, forgotten, and so on.
ErlNifResourceType:
Each instance of ErlNifResourceType represents 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.
ErlNifResourceTypeInit:
typedef struct {
ErlNifResourceDtor* dtor; // #1 Destructor
ErlNifResourceStop* stop; // #2 Select stop
ErlNifResourceDown* down; // #3 Monitor down
int members;
ErlNifResourceDynCall* dyncall; // #4 Dynamic call
} ErlNifResourceTypeInit;
Initialization structure read by enif_open_resource_type_x
enif_init_resource_type.
ErlNifResourceDtor:
typedef void ErlNifResourceDtor(ErlNifEnv* caller_env, void* obj);
The function prototype of a resource destructor function.
The obj argument is a pointer to the resource. The only allowed use
for the resource in the destructor is to access its user data one
final time. The destructor is guaranteed to be the last callback
before the resource is deallocated.
ErlNifResourceDown:
typedef void ErlNifResourceDown(ErlNifEnv* caller_env, void* obj, ErlNifPid* pid, ErlNifMonitor* mon);
The function prototype of a resource down function, called on the
behalf of enif_monitor_process. obj is the resource, pid is the
identity of the monitored process that is exiting, and mon is the
identity of the monitor.
ErlNifResourceStop:
typedef void ErlNifResourceStop(ErlNifEnv* caller_env, void* obj, ErlNifEvent event, int is_direct_call);
The function prototype of a resource stop function, called on the
behalf of enif_select. obj is the resource, event is OS event,
is_direct_call is true if the call is made directly from
enif_select or false if it is a scheduled call (potentially from
another thread).
ErlNifResourceDynCall:
typedef void ErlNifResourceDynCall(ErlNifEnv* caller_env, void* obj, void* call_data);
The function prototype of a dynamic resource call function, called
by enif_dynamic_resource_call. Argument obj is the resource object
and call_data is the last argument to enif_dynamic_resource_call
passed through.
ErlNifCharEncoding:
typedef enum {
ERL_NIF_LATIN1
}ErlNifCharEncoding;
The character encoding used in strings and atoms. The only sup-
ported encoding is ERL_NIF_LATIN1 for ISO Latin-1 (8-bit ASCII).
ErlNifSysInfo:
Used by enif_system_info to return information about the runtime
system. Contains the same content as ErlDrvSysInfo.
ErlNifSInt64:
A native signed 64-bit integer type.
ErlNifUInt64:
A native unsigned 64-bit integer type.
ErlNifTime:
A signed 64-bit integer type for representation of time.
ErlNifTimeUnit:
An enumeration of time units supported by the NIF API:
ERL_NIF_SEC:
Seconds
ERL_NIF_MSEC:
Milliseconds
ERL_NIF_USEC:
Microseconds
ERL_NIF_NSEC:
Nanoseconds
ErlNifUniqueInteger:
An enumeration of the properties that can be requested from
enif_make_unique_integer. For default properties, use value 0.
ERL_NIF_UNIQUE_POSITIVE:
Return only positive integers.
ERL_NIF_UNIQUE_MONOTONIC:
Return only strictly monotonically increasing integer corre-
sponding to creation time.
ErlNifHash:
An enumeration of the supported hash types that can be generated
using enif_hash.
ERL_NIF_INTERNAL_HASH:
Non-portable hash function that only guarantees the same hash for
the same term within one Erlang VM instance.
It takes 32-bit salt values and generates hashes within
0..2^32-1.
ERL_NIF_PHASH2:
Portable hash function that gives the same hash for the same
Erlang term regardless of machine architecture and ERTS version.
It ignores salt values and generates hashes within 0..2^27-1.
Slower than ERL_NIF_INTERNAL_HASH. It corresponds to
erlang:phash2/1.
SysIOVec:
A system I/O vector, as used by writev on Unix and WSASend on
Win32. It is used in ErlNifIOVec and by enif_ioq_peek.
ErlNifIOVec:
typedef struct {
int iovcnt;
size_t size;
SysIOVec* iov;
} ErlNifIOVec;
An I/O vector containing iovcnt SysIOVecs pointing to the data. It
is used by enif_inspect_iovec and enif_ioq_enqv.
ErlNifIOQueueOpts:
Options to configure a ErlNifIOQueue.
ERL_NIF_IOQ_NORMAL:
Create a normal I/O Queue
EXPORTS
void *enif_alloc(size_t size)
Allocates memory of size bytes.
Returns NULL if the allocation fails.
The returned pointer is suitably aligned for any built-in type
that fit in the allocated memory.
int enif_alloc_binary(size_t size, ErlNifBinary* bin)
Allocates a new binary of size size bytes. Initializes 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.
If you do not need to reallocate or keep the data alive across
NIF calls, consider using enif_make_new_binary instead as it
will allocate small binaries on the process heap when possible.
Returns true on success, or false if allocation fails.
ErlNifEnv *enif_alloc_env()
Allocates a new process independent environment. The environment
can be used to hold terms that are 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.
Returns pointer to the new environment.
void *enif_alloc_resource(ErlNifResourceType*
type, unsigned size)
Allocates a memory-managed resource object of type type and size
size bytes.
size_t enif_binary_to_term(ErlNifEnv *env,
const unsigned char* data, size_t size, ERL_NIF_TERM *term,
ErlNifBinaryToTerm opts)
Creates a term that is the result of decoding the binary data at
data, which must be encoded according to the Erlang external
term format. No more than size bytes are read from data. Argu-
ment opts corresponds to the second argument to
erlang:binary_to_term/2 and must be either 0 or
ERL_NIF_BIN2TERM_SAFE.
On success, stores the resulting term at *term and returns the
number of bytes read. Returns 0 if decoding fails or if opts is
invalid.
See also ErlNifBinaryToTerm, erlang:binary_to_term/2, and
enif_term_to_binary.
void enif_clear_env(ErlNifEnv* env)
Frees all terms in an environment and clears it for reuse. The
environment must have been allocated with enif_alloc_env.
int enif_compare(ERL_NIF_TERM lhs, ERL_NIF_TERM rhs)
Returns an integer < 0 if lhs < rhs, 0 if lhs = rhs, and > 0 if
lhs > rhs. Corresponds to the Erlang operators ==, /=, =<, <,
>=, and > (but not =:= or =/=).
int enif_compare_monitors(const ErlNifMonitor
*monitor1, const ErlNifMonitor *monitor2)
Compares two ErlNifMonitors. Can also be used to imply some
artificial order on monitors, for whatever reason.
Returns 0 if monitor1 and monitor2 are equal, < 0 if monitor1 <
monitor2, and > 0 if monitor1 > monitor2.
int enif_compare_pids(const ErlNifPid *pid1, const ErlNifPid *pid2)
Compares two ErlNifPids according to term order.
Returns 0 if pid1 and pid2 are equal, < 0 if pid1 < pid2, and >
0 if pid1 > pid2.
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.
char*enif_cond_name(ErlNifCond* cnd)
Same as erl_drv_cond_name.
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_consume_timeslice(ErlNifEnv *env, int percent)
Gives the runtime system a hint about how much CPU time the cur-
rent NIF call has consumed since the last hint, or since the
start of the NIF if no previous hint has been specified. The
time is specified as a percent of the timeslice that a process
is allowed to execute Erlang code until it can be suspended to
give time for other runnable processes. The scheduling timeslice
is not an exact entity, but can usually be approximated to about
1 millisecond.
Notice that it is up to the runtime system to determine if and
how to use this information. Implementations on some platforms
can use other means to determine consumed CPU time. Lengthy NIFs
should regardless of this frequently call enif_consume_timeslice
to determine if it is allowed to continue execution.
Argument percent must be an integer between 1 and 100. This
function must only be called from a NIF-calling thread, and
argument env must be the environment of the calling process.
Returns 1 if the timeslice is exhausted, otherwise 0. If 1 is
returned, the NIF is to return as soon as possible in order for
the process to yield.
This function is provided to better support co-operative sched-
uling, improve system responsiveness, and make it easier to pre-
vent misbehaviors of the VM because of a NIF monopolizing a
scheduler thread. It can be used to divide length work into a
number of repeated NIF calls without the need to create threads.
See also the warning text at the beginning of this manual page.
ErlNifTime enif_convert_time_unit(ErlNifTime
val, ErlNifTimeUnit from, ErlNifTimeUnit to)
Converts the val value of time unit from to the corresponding
value of time unit to. The result is rounded using the floor
function.
val:
Value to convert time unit for.
from:
Time unit of val.
to:
Time unit of returned value.
Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
argument.
See also ErlNifTime and ErlNifTimeUnit.
ERL_NIF_TERM enif_cpu_time(ErlNifEnv *)
Returns the CPU time in the same format as erlang:timestamp().
The CPU time is the time the current logical CPU has spent exe-
cuting since some arbitrary point in the past. If the OS does
not support fetching this value, enif_cpu_time invokes
enif_make_badarg.
int enif_demonitor_process(ErlNifEnv* caller_env,
void* obj, const ErlNifMonitor* mon)
Cancels a monitor created earlier with enif_monitor_process.
Argument obj is a pointer to the resource holding the monitor
and *mon identifies the monitor.
Argument caller_env is the environment of the calling thread
(process bound or callback environment) or NULL if calling from
a custom thread not spawned by ERTS.
Returns 0 if the monitor was successfully identified and
removed. Returns a non-zero value if the monitor could not be
identified, which means it was either
* never created for this resource
* already cancelled
* already triggered
* just about to be triggered by a concurrent thread
This function is thread-safe.
int enif_dynamic_resource_call(ErlNifEnv* caller_env, ERL_NIF_MOD-
ULE rt_module, ERL_NIF_MODULE rt_name, ERL_NIF_TERM resource,
void* call_data)
Call code of a resource type implemented by another NIF module.
The atoms rt_module and rt_name identifies the resource type to
be called. Argument resource identifies a resource object of
that type.
The callback dyncall of the identified resource type will be
called with a pointer to the resource objects obj and the argu-
ment call_data passed through. The call_data argument is typi-
cally a pointer to a struct used to passed both arguments to the
dyncall function as well as results back to the caller.
Returns 0 if the dyncall callback function was called. Returns a
non-zero value if no call was made, which happens if rt_module
and rt_name did not identify a resource type with a dyncall
callback or if resource was not a resource object of that type.
int enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)
Same as erl_drv_equal_tids.
int enif_fprintf(FILE *stream, const char *format, ...)
Similar to fprintf but this format string also accepts "%T",
which formats Erlang terms of type ERL_NIF_TERM.
This function is primarily intended for debugging purpose. It is
not recommended to print very large terms with %T. The function
may change errno, even if successful.
void enif_free(void* ptr)
Frees memory allocated by enif_alloc.
void enif_free_env(ErlNifEnv* env)
Frees an environment allocated with enif_alloc_env. All terms
created in the environment are freed as well.
void enif_free_iovec(ErlNifIOVec* iov)
Frees an io vector returned from enif_inspect_iovec. This is
needed only if a NULL environment is passed to
enif_inspect_iovec.
ErlNifIOVec *iovec = NULL;
size_t max_elements = 128;
ERL_NIF_TERM tail;
if (!enif_inspect_iovec(NULL, max_elements, term, &tail, &iovec))
return 0;
// Do things with the iovec
/* Free the iovector, possibly in another thread or nif function call */
enif_free_iovec(iovec);
int enif_get_atom(ErlNifEnv* env, ERL_NIF_TERM
term, char* buf, unsigned size, ErlNifCharEncoding encode)
Writes a NULL-terminated string in the buffer pointed to by buf
of size size, consisting of the string representation of the
atom term with encoding encode.
Returns 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, ErlNifCharEncoding encode)
Sets *len to the length (number of bytes excluding terminating
NULL character) of the atom term with encoding encode.
Returns true on success, or false if term is not an atom.
int enif_get_double(ErlNifEnv* env,
ERL_NIF_TERM term, double* dp)
Sets *dp to the floating-point value of term.
Returns true on success, or false if term is not a float.
int enif_get_int(ErlNifEnv* env, ERL_NIF_TERM
term, int* ip)
Sets *ip to the integer value of term.
Returns 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)
Sets *ip to the integer value of term.
Returns 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, this function ini-
tializes the pid variable *pid from it and returns true. Other-
wise returns false. No check is done to see if the process is
alive.
Note:
enif_get_local_pid will return false if argument term is the
atom undefined.
int enif_get_local_port(ErlNifEnv* env,
ERL_NIF_TERM term, ErlNifPort* port_id)
If term identifies a node local port, this function initializes
the port variable *port_id from it and returns true. Otherwise
returns false. No check is done to see if the port is alive.
int enif_get_list_cell(ErlNifEnv* env,
ERL_NIF_TERM list, ERL_NIF_TERM* head, ERL_NIF_TERM* tail)
Sets *head and *tail from list list.
Returns true on success, or false if it is not a list or the
list is empty.
int enif_get_list_length(ErlNifEnv* env,
ERL_NIF_TERM term, unsigned* len)
Sets *len to the length of list term.
Returns true on success, or false if term is not a proper list.
int enif_get_long(ErlNifEnv* env, ERL_NIF_TERM
term, long int* ip)
Sets *ip to the long integer value of term.
Returns true on success, or false if term is not an integer or
is outside the bounds of type long int.
int enif_get_map_size(ErlNifEnv* env,
ERL_NIF_TERM term, size_t *size)
Sets *size to the number of key-value pairs in the map term.
Returns true on success, or false if term is not a map.
int enif_get_map_value(ErlNifEnv* env,
ERL_NIF_TERM map, ERL_NIF_TERM key, ERL_NIF_TERM* value)
Sets *value to the value associated with key in the map map.
Returns true on success, or false if map is not a map or if map
does not contain key.
int enif_get_resource(ErlNifEnv* env,
ERL_NIF_TERM term, ErlNifResourceType* type, void** objp)
Sets *objp to point to the resource object referred to by term.
Returns true on success, or false if term is not a handle to a
resource object of type type.
enif_get_resource does not add a reference to the resource
object. However, the pointer received in *objp is guaranteed to
be valid at least as long as the resource handle term is valid.
int enif_get_string(ErlNifEnv* env,
ERL_NIF_TERM list, char* buf, unsigned size,
ErlNifCharEncoding encode)
Writes 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.
Returns one of the following:
* The number of bytes written (including terminating NULL
character)
* -size if the string was truncated because of buffer space
* 0 if list is not a string that can be encoded with encode or
if size was < 1.
The written string is always NULL-terminated, unless buffer size
is < 1.
int enif_get_tuple(ErlNifEnv* env, ERL_NIF_TERM
term, int* arity, const ERL_NIF_TERM** array)
If term is a tuple, this function sets *array to point to an
array containing the elements of the tuple, and sets *arity to
the number of elements. Notice that the array is read-only and
(*array)[N-1] is the Nth element of the tuple. *array is unde-
fined if the arity of the tuple is zero.
Returns true on success, or false if term is not a tuple.
int enif_get_uint(ErlNifEnv* env, ERL_NIF_TERM
term, unsigned int* ip)
Sets *ip to the unsigned integer value of term.
Returns true on success, or 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)
Sets *ip to the unsigned integer value of term.
Returns true on success, or 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)
Sets *ip to the unsigned long integer value of term.
Returns true on success, or false if term is not an unsigned
integer or is outside the bounds of type unsigned long.
int enif_getenv(const char* key, char* value,
size_t *value_size)
Same as erl_drv_getenv.
int enif_has_pending_exception(ErlNifEnv* env,
ERL_NIF_TERM* reason)
Returns true if a pending exception is associated with the envi-
ronment env. If reason is a NULL pointer, ignore it. Otherwise,
if a pending exception associated with env exists, set *reason
to the value of the exception term. For example, if
enif_make_badarg is called to set a pending badarg exception, a
later call to enif_has_pending_exception(env, &reason) sets
*reason to the atom badarg, then return true.
See also enif_make_badarg and enif_raise_exception.
ErlNifUInt64 enif_hash(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64
salt)
Hashes term according to the specified ErlNifHash type.
Ranges of taken salt (if any) and returned value depend on the
hash type.
int enif_inspect_binary(ErlNifEnv* env,
ERL_NIF_TERM bin_term, ErlNifBinary* bin)
Initializes the structure pointed to by bin with information
about binary term bin_term.
Returns 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)
Initializes the structure pointed to by bin with a 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.
Returns true on success, or false if iolist is not an iolist.
int enif_inspect_iovec(ErlNifEnv*
env, size_t max_elements, ERL_NIF_TERM iovec_term,
ERL_NIF_TERM* tail,
ErlNifIOVec** iovec)
Fills iovec with the list of binaries provided in iovec_term.
The number of elements handled in the call is limited to
max_elements, and tail is set to the remainder of the list. Note
that the output may be longer than max_elements on some plat-
forms.
To create a list of binaries from an arbitrary iolist, use
erlang:iolist_to_iovec/1.
When calling this function, iovec should contain a pointer to
NULL or a ErlNifIOVec structure that should be used if possible.
e.g.
/* Don't use a pre-allocated structure */
ErlNifIOVec *iovec = NULL;
enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
/* Use a stack-allocated vector as an optimization for vectors with few elements */
ErlNifIOVec vec, *iovec = &vec;
enif_inspect_iovec(env, max_elements, term, &tail, &iovec);
The contents of the iovec is valid until the called nif function
returns. If the iovec should be valid after the nif call
returns, it is possible to call this function with a NULL envi-
ronment. If no environment is given the iovec owns the data in
the vector and it has to be explicitly freed using
enif_free_iovec.
Returns true on success, or false if iovec_term not an iovec.
ErlNifIOQueue *enif_ioq_create(ErlNifIOQueueOpts opts)
Create a new I/O Queue that can be used to store data. opts has
to be set to ERL_NIF_IOQ_NORMAL.
void enif_ioq_destroy(ErlNifIOQueue *q)
Destroy the I/O queue and free all of it's contents
int enif_ioq_deq(ErlNifIOQueue *q, size_t count, size_t *size)
Dequeue count bytes from the I/O queue. If size is not NULL, the
new size of the queue is placed there.
Returns true on success, or false if the I/O does not contain
count bytes. On failure the queue is left un-altered.
int enif_ioq_enq_binary(ErlNifIOQueue *q, ErlNifBinary *bin, size_t
skip)
Enqueue the bin into q skipping the first skip bytes.
Returns true on success, or false if skip is greater than the
size of bin. Any ownership of the binary data is transferred to
the queue and bin is to be considered read-only for the rest of
the NIF call and then as released.
int enif_ioq_enqv(ErlNifIOQueue *q, ErlNifIOVec *iovec, size_t skip)
Enqueue the iovec into q skipping the first skip bytes.
Returns true on success, or false if skip is greater than the
size of iovec.
SysIOVec *enif_ioq_peek(ErlNifIOQueue *q, int *iovlen)
Get the I/O queue as a pointer to an array of SysIOVecs. It also
returns the number of elements in iovlen.
Nothing is removed from the queue by this function, that must be
done with enif_ioq_deq.
The returned array is suitable to use with the Unix system call
writev.
int enif_ioq_peek_head(ErlNifEnv *env, ErlNifIOQueue *q, size_t *size,
ERL_NIF_TERM *bin_term)
Get the head of the IO Queue as a binary term.
If size is not NULL, the size of the head is placed there.
Nothing is removed from the queue by this function, that must be
done with enif_ioq_deq.
Returns true on success, or false if the queue is empty.
size_t enif_ioq_size(ErlNifIOQueue *q)
Get the size of q.
int enif_is_atom(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is an atom.
int enif_is_binary(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a binary.
int enif_is_current_process_alive(ErlNifEnv* env)
Returns true if the currently executing process is currently
alive, otherwise false.
This function can only be used from a NIF-calling thread, and
with an environment corresponding to currently executing pro-
cesses.
int enif_is_empty_list(ErlNifEnv* env,
ERL_NIF_TERM term)
Returns true if term is an empty list.
int enif_is_exception(ErlNifEnv* env,
ERL_NIF_TERM term)
Return true if term is an exception.
int enif_is_fun(ErlNifEnv* env, ERL_NIF_TERM
term)
Returns true if term is a fun.
int enif_is_identical(ERL_NIF_TERM lhs,
ERL_NIF_TERM rhs)
Returns true if the two terms are identical. Corresponds to the
Erlang operators =:= and =/=.
int enif_is_list(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a list.
int enif_is_map(ErlNifEnv* env, ERL_NIF_TERM
term)
Returns true if term is a map, otherwise false.
int enif_is_number(ErlNifEnv* env, ERL_NIF_TERM
term)
Returns true if term is a number.
int enif_is_pid(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a pid.
int enif_is_pid_undefined(const ErlNifPid* pid)
Returns true if pid has been set as undefined by
enif_set_pid_undefined.
int enif_is_port(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a port.
int enif_is_port_alive(ErlNifEnv* env,
ErlNifPort *port_id)
Returns true if port_id is alive.
This function is thread-safe.
int enif_is_process_alive(ErlNifEnv* env,
ErlNifPid *pid)
Returns true if pid is alive.
This function is thread-safe.
int enif_is_ref(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a reference.
int enif_is_tuple(ErlNifEnv* env, ERL_NIF_TERM term)
Returns true if term is a tuple.
int enif_keep_resource(void* obj)
Adds 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 is destructed.
ERL_NIF_TERM enif_make_atom(ErlNifEnv* env, const char* name)
Creates an atom term from the NULL-terminated C-string name with
ISO Latin-1 encoding. If the length of name exceeds the maximum
length allowed for an atom (255 characters), enif_make_atom
invokes enif_make_badarg.
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. If len exceeds
the maximum length allowed for an atom (255 characters),
enif_make_atom invokes enif_make_badarg.
ERL_NIF_TERM enif_make_badarg(ErlNifEnv* env)
Makes a badarg exception to be returned from a NIF, and asso-
ciates it with environment env. Once a NIF or any function it
calls invokes enif_make_badarg, the runtime ensures that a
badarg exception is raised when the NIF returns, even if the NIF
attempts to return a non-exception term instead.
The return value from enif_make_badarg can be used only as the
return value from the NIF that invoked it (directly or indi-
rectly) or be passed to enif_is_exception, but not to any other
NIF API function.
See also enif_has_pending_exception and enif_raise_exception.
Note:
Before ERTS 7.0 (Erlang/OTP 18), the return value from
enif_make_badarg had to be returned from the NIF. This require-
ment is now lifted as the return value from the NIF is ignored
if enif_make_badarg has been invoked.
ERL_NIF_TERM enif_make_binary(ErlNifEnv* env, ErlNifBinary* bin)
Makes a binary term from bin. Any ownership of the binary data
is transferred to the created term and bin is to 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)
Makes a copy of term src_term. The copy is created in environ-
ment dst_env. The source term can be located in any environment.
ERL_NIF_TERM enif_make_double(ErlNifEnv* env, double d)
Creates a floating-point term from a double. If argument double
is not finite or is NaN, enif_make_double invokes
enif_make_badarg.
int enif_make_existing_atom(ErlNifEnv* env,
const char* name, ERL_NIF_TERM* atom, ErlNifCharEncoding
encode)
Tries to create the term of an already existing atom from the
NULL-terminated C-string name with encoding encode.
If the atom already exists, this function stores the term in
*atom and returns true, otherwise false. Also returns false if
the length of name exceeds the maximum length allowed for an
atom (255 characters).
int enif_make_existing_atom_len(ErlNifEnv* env,
const char* name, size_t len, ERL_NIF_TERM* atom, ErlNifCharEn-
coding
encoding)
Tries 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, this function stores the term in
*atom and returns true, otherwise false. Also returns false if
len exceeds the maximum length allowed for an atom (255 charac-
ters).
ERL_NIF_TERM enif_make_int(ErlNifEnv* env, int i)
Creates an integer term.
ERL_NIF_TERM enif_make_int64(ErlNifEnv* env, ErlNifSInt64 i)
Creates an integer term from a signed 64-bit integer.
ERL_NIF_TERM enif_make_list(ErlNifEnv* env, unsigned cnt, ...)
Creates 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.
Returns an empty list 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)
Creates an ordinary list term with length indicated by the func-
tion 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)
Creates a list cell [head | tail].
ERL_NIF_TERM enif_make_list_from_array(ErlNifEnv* env, const
ERL_NIF_TERM
arr[], unsigned cnt)
Creates an ordinary list containing the elements of array arr of
length cnt.
Returns an empty list if cnt is 0.
ERL_NIF_TERM enif_make_long(ErlNifEnv* env, long int i)
Creates an integer term from a long int.
int enif_make_map_put(ErlNifEnv* env,
ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM value,
ERL_NIF_TERM* map_out)
Makes a copy of map map_in and inserts key with value. If key
already exists in map_in, the old associated value is replaced
by value.
If successful, this function sets *map_out to the new map and
returns true. Returns false if map_in is not a map.
The map_in term must belong to environment env.
int enif_make_map_remove(ErlNifEnv* env,
ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM* map_out)
If map map_in contains key, this function makes a copy of map_in
in *map_out, and removes key and the associated value. If map
map_in does not contain key, *map_out is set to map_in.
Returns true on success, or false if map_in is not a map.
The map_in term must belong to environment env.
int enif_make_map_update(ErlNifEnv* env,
ERL_NIF_TERM map_in, ERL_NIF_TERM key, ERL_NIF_TERM new_value,
ERL_NIF_TERM* map_out)
Makes a copy of map map_in and replace the old associated value
for key with new_value.
If successful, this function sets *map_out to the new map and
returns true. Returns false if map_in is not a map or if it does
not contain key.
The map_in term must belong to environment env.
int enif_make_map_from_arrays(ErlNifEnv* env, ERL_NIF_TERM keys[],
ERL_NIF_TERM values[], size_t cnt, ERL_NIF_TERM *map_out)
Makes a map term from the given keys and values.
If successful, this function sets *map_out to the new map and
returns true. Returns false there are any duplicate keys.
All keys and values must belong to env.
ERL_NIF_TERM enif_make_monitor_term(ErlNifEnv* env, const ErlNifMoni-
tor* mon)
Creates a term identifying the given monitor received from
enif_monitor_process.
This function is primarily intended for debugging purpose.
unsigned char *enif_make_new_binary(ErlNifEnv*
env, size_t size, ERL_NIF_TERM* termp)
Allocates a binary of size size bytes and creates 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 cannot be kept
between NIF calls and it cannot be reallocated.
Returns a pointer to the raw binary data and sets *termp to the
binary term.
ERL_NIF_TERM enif_make_new_map(ErlNifEnv* env)
Makes an empty map term.
ERL_NIF_TERM enif_make_pid(ErlNifEnv* env, const ErlNifPid* pid)
Makes a pid term or the atom undefined from *pid.
ERL_NIF_TERM enif_make_ref(ErlNifEnv* env)
Creates a reference like erlang:make_ref/0.
ERL_NIF_TERM enif_make_resource(ErlNifEnv* env, void* obj)
Creates 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. However, notice that the call to
enif_release_resource can occur immediately after obtaining the
term from enif_make_resource, in which case the resource object
is deallocated when the term is garbage collected. For more
details, see the example of creating and returning a resource
object in the User's Guide.
Note:
Since ERTS 9.0 (OTP-20.0), resource terms have a defined behav-
ior when compared and serialized through term_to_binary or
passed between nodes.
* Two resource terms will compare equal if and only if they
would yield the same resource object pointer when passed to
enif_get_resource.
* A resource term can be serialized with term_to_binary and
later be fully recreated if the resource object is still
alive when binary_to_term is called. A stale resource term
will be returned from binary_to_term if the resource object
has been deallocated. enif_get_resource will return false
for stale resource terms.
The same principles of serialization apply when passing
resource terms in messages to remote nodes and back again. A
resource term will act stale on all nodes except the node
where its resource object is still alive in memory.
Before ERTS 9.0 (OTP-20.0), all resource terms did compare equal
to each other and to empty binaries (<<>>). If serialized, they
would be recreated as plain empty binaries.
ERL_NIF_TERM enif_make_resource_binary(ErlNifEnv* env, void* obj, const
void* data, size_t size)
Creates a binary term that is memory-managed by a resource
object obj obtained by enif_alloc_resource. The returned binary
term consists 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 can be stored external
to the resource object, in which case the destructor is respon-
sible for releasing the data.
Several binary terms can be managed by the same resource object.
The destructor is not called until the last binary is garbage
collected. This can be useful 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.
int enif_make_reverse_list(ErlNifEnv* env, ERL_NIF_TERM list_in,
ERL_NIF_TERM *list_out)
Sets *list_out to the reverse list of the list list_in and
returns true, or returns false if list_in is not a list.
This function is only to be used on short lists, as a copy is
created of the list, which is not released until after the NIF
returns.
The list_in term must belong to environment env.
ERL_NIF_TERM enif_make_string(ErlNifEnv* env,
const char* string, ErlNifCharEncoding encoding)
Creates 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, ErlNifCharEncoding
encoding)
Creates 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)
Makes 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. pos+size must be less or equal to the num-
ber of whole bytes in bin_term.
ERL_NIF_TERM enif_make_tuple(ErlNifEnv* env,
unsigned cnt, ...)
Creates a tuple term of arity cnt. Expects cnt number of argu-
ments (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)
Creates a tuple term with length indicated by the function name.
Prefer these functions (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)
Creates a tuple containing the elements of array arr of length
cnt.
ERL_NIF_TERM enif_make_uint(ErlNifEnv* env, unsigned int i)
Creates an integer term from an unsigned int.
ERL_NIF_TERM enif_make_uint64(ErlNifEnv* env, ErlNifUInt64 i)
Creates an integer term from an unsigned 64-bit integer.
ERL_NIF_TERM enif_make_ulong(ErlNifEnv* env, unsigned long i)
Creates an integer term from an unsigned long int.
ERL_NIF_TERM enif_make_unique_integer(ErlNifEnv
*env, ErlNifUniqueInteger properties)
Returns a unique integer with the same properties as specified
by erlang:unique_integer/1.
env is the environment to create the integer in.
ERL_NIF_UNIQUE_POSITIVE and ERL_NIF_UNIQUE_MONOTONIC can be
passed as the second argument to change the properties of the
integer returned. They can be combined by OR:ing the two values
together.
See also ErlNifUniqueInteger.
int enif_map_iterator_create(ErlNifEnv *env,
ERL_NIF_TERM map, ErlNifMapIterator *iter, ErlNifMapIteratorEn-
try
entry)
Creates an iterator for the map map by initializing the struc-
ture pointed to by iter. Argument entry determines the start
position of the iterator: ERL_NIF_MAP_ITERATOR_FIRST or
ERL_NIF_MAP_ITERATOR_LAST.
Returns true on success, or false if map is not a map.
A map iterator is only useful during the lifetime of environment
env that the map belongs to. The iterator must be destroyed by
calling enif_map_iterator_destroy:
ERL_NIF_TERM key, value;
ErlNifMapIterator iter;
enif_map_iterator_create(env, my_map, &iter, ERL_NIF_MAP_ITERATOR_FIRST);
while (enif_map_iterator_get_pair(env, &iter, &key, &value)) {
do_something(key,value);
enif_map_iterator_next(env, &iter);
}
enif_map_iterator_destroy(env, &iter);
Note:
The key-value pairs of a map have no defined iteration order.
The only guarantee is that the iteration order of a single map
instance is preserved during the lifetime of the environment
that the map belongs to.
void enif_map_iterator_destroy(ErlNifEnv *env,
ErlNifMapIterator *iter)
Destroys a map iterator created by enif_map_iterator_create.
int enif_map_iterator_get_pair(ErlNifEnv *env,
ErlNifMapIterator *iter, ERL_NIF_TERM *key, ERL_NIF_TERM
*value)
Gets key and value terms at the current map iterator position.
On success, sets *key and *value and returns true. Returns false
if the iterator is positioned at head (before first entry) or
tail (beyond last entry).
int enif_map_iterator_is_head(ErlNifEnv *env,
ErlNifMapIterator *iter)
Returns true if map iterator iter is positioned before the first
entry.
int enif_map_iterator_is_tail(ErlNifEnv *env,
ErlNifMapIterator *iter)
Returns true if map iterator iter is positioned after the last
entry.
int enif_map_iterator_next(ErlNifEnv *env,
ErlNifMapIterator *iter)
Increments map iterator to point to the next key-value entry.
Returns true if the iterator is now positioned at a valid key-
value entry, or false if the iterator is positioned at the tail
(beyond the last entry).
int enif_map_iterator_prev(ErlNifEnv *env,
ErlNifMapIterator *iter)
Decrements map iterator to point to the previous key-value
entry.
Returns true if the iterator is now positioned at a valid key-
value entry, or false if the iterator is positioned at the head
(before the first entry).
int enif_monitor_process(ErlNifEnv* caller_env,
void* obj, const ErlNifPid* target_pid, ErlNifMonitor* mon)
Starts monitoring a process from a resource. When a process is
monitored, a process exit results in a call to the provided down
callback associated with the resource type.
Argument obj is pointer to the resource to hold the monitor and
*target_pid identifies the local process to be monitored.
If mon is not NULL, a successful call stores the identity of the
monitor in the ErlNifMonitor struct pointed to by mon. This
identifier is used to refer to the monitor for later removal
with enif_demonitor_process or compare with enif_compare_moni-
tors. A monitor is automatically removed when it triggers or
when the resource is deallocated.
Argument caller_env is the environment of the calling thread
(process bound or callback environment) or NULL if calling from
a custom thread not spawned by ERTS.
Returns 0 on success, < 0 if no down callback is provided, and >
0 if the process is no longer alive or if target_pid is unde-
fined.
This function is thread-safe.
ErlNifTime enif_monotonic_time(ErlNifTimeUnit time_unit)
Returns the current Erlang monotonic time. Notice that it is
not uncommon with negative values.
time_unit is the time unit of the returned value.
Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
argument, or if called from a thread that is not a scheduler
thread.
See also ErlNifTime and ErlNifTimeUnit.
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.
char*enif_mutex_name(ErlNifMutex* mtx)
Same as erl_drv_mutex_name.
int enif_mutex_trylock(ErlNifMutex *mtx)
Same as erl_drv_mutex_trylock.
void enif_mutex_unlock(ErlNifMutex *mtx)
Same as erl_drv_mutex_unlock.
ERL_NIF_TERM enif_now_time(ErlNifEnv *env)
Returns an erlang:now() time stamp.
This function is deprecated.
ErlNifResourceType *enif_open_resource_type(ErlNifEnv* env, const char*
module_str, const char* name, ErlNifResourceDtor* dtor,
ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
Creates or takes over a resource type identified by the string
name and gives it the destructor function pointed to by dtor.
Argument flags can have the following values:
ERL_NIF_RT_CREATE:
Creates a new resource type that does not already exist.
ERL_NIF_RT_TAKEOVER:
Opens an existing resource type and takes over ownership of
all its instances. The supplied destructor dtor is called
both for existing instances and new instances not yet cre-
ated by the calling NIF library.
The two flag values can be combined with bitwise OR. The
resource type name is local to the calling module. Argument mod-
ule_str is not (yet) used and must be NULL. dtor can be NULL if
no destructor is needed.
On success, the function returns a pointer to the resource type
and *tried is set to either ERL_NIF_RT_CREATE or
ERL_NIF_RT_TAKEOVER to indicate what was done. On failure,
returns NULL and sets *tried to flags. It is allowed to set
tried to NULL.
Notice that enif_open_resource_type is only allowed to be called
in the two callbacks load and upgrade.
See also enif_open_resource_type_x.
ErlNifResourceType *enif_open_resource_type_x(ErlNifEnv* env, const
char* name, const ErlNifResourceTypeInit* init,
ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
Same as enif_open_resource_type except it accepts additional
callback functions for resource types that are used together
with enif_select and enif_monitor_process.
Argument init is a pointer to an ErlNifResourceTypeInit struc-
ture that contains the function pointers for destructor, down
and stop callbacks for the resource type.
Note:
Only members dtor, down and stop in ErlNifResourceTypeInit are
read by enif_open_resource_type_x. To implement the new dyncall
callback use enif_init_resource_type.
ErlNifResourceType *enif_init_resource_type(ErlNifEnv* env, const char*
name, const ErlNifResourceTypeInit* init,
ErlNifResourceFlags flags, ErlNifResourceFlags* tried)
Same as enif_open_resource_type_x except it accepts an addi-
tional callback function for resource types that are used
together with enif_dynamic_resource_call.
Argument init is a pointer to an ErlNifResourceTypeInit struc-
ture that contains the callback function pointers dtor, down,
stop and the new dyncall. The struct also contains the field
members that must be set to the number of initialized callbacks
counted from the top of the struct. For example, to initialize
all callbacks including dyncall, members should be set to 4. All
callbacks are optional and may be set to NULL.
int enif_port_command(ErlNifEnv* env, const
ErlNifPort* to_port, ErlNifEnv *msg_env, ERL_NIF_TERM msg)
Works as erlang:port_command/2, except that it is always com-
pletely asynchronous.
env:
The environment of the calling process. Must not be NULL.
*to_port:
The port ID of the receiving port. The port ID is to refer
to a port on the local node.
msg_env:
The environment of the message term. Can be a process inde-
pendent environment allocated with enif_alloc_env or NULL.
msg:
The message term to send. The same limitations apply as on
the payload to erlang:port_command/2.
Using a msg_env of NULL is an optimization, which groups
together calls to enif_alloc_env, enif_make_copy, enif_port_com-
mand, and enif_free_env into one call. This optimization is only
useful when a majority of the terms are to be copied from env to
msg_env.
Returns true if the command is successfully sent. Returns false
if the command fails, for example:
* *to_port does not refer to a local port.
* The currently executing process (that is, the sender) is not
alive.
* msg is invalid.
See also enif_get_local_port.
void *enif_priv_data(ErlNifEnv* env)
Returns the pointer to the private data that was set by load or
upgrade.
ERL_NIF_TERM enif_raise_exception(ErlNifEnv*
env, ERL_NIF_TERM reason)
Creates an error exception with the term reason to be returned
from a NIF, and associates it with environment env. Once a NIF
or any function it calls invokes enif_raise_exception, the run-
time ensures that the exception it creates is raised when the
NIF returns, even if the NIF attempts to return a non-exception
term instead.
The return value from enif_raise_exception can only be used as
the return value from the NIF that invoked it (directly or indi-
rectly) or be passed to enif_is_exception, but not to any other
NIF API function.
See also enif_has_pending_exception and enif_make_badarg.
void *enif_realloc(void* ptr, size_t size)
Reallocates memory allocated by enif_alloc to size bytes.
Returns NULL if the reallocation fails.
The returned pointer is suitably aligned for any built-in type
that fit in the allocated memory.
int enif_realloc_binary(ErlNifBinary* bin, size_t size)
Changes the size of a binary bin. The source binary can be read-
only, in which case it is left untouched and a mutable copy is
allocated and assigned to *bin.
Returns true on success, or false if memory allocation failed.
void enif_release_binary(ErlNifBinary* bin)
Releases a binary obtained from enif_alloc_binary.
void enif_release_resource(void* obj)
Removes a reference to resource object obj obtained from
enif_alloc_resource. The resource object is 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.
There are no guarantees exactly when the destructor of an unref-
erenced resource is called. It could be called directly by
enif_release_resource but it could also be scheduled to be
called at a later time possibly by another thread.
ErlNifRWLock *enif_rwlock_create(char *name)
Same as erl_drv_rwlock_create.
void enif_rwlock_destroy(ErlNifRWLock *rwlck)
Same as erl_drv_rwlock_destroy.
char*enif_rwlock_name(ErlNifRWLock* rwlck)
Same as erl_drv_rwlock_name.
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.
ERL_NIF_TERM enif_schedule_nif(
ErlNifEnv* caller_env, const char* fun_name, int flags,
ERL_NIF_TERM (*fp)(ErlNifEnv* env, int argc, const ERL_NIF_TERM
argv[]), int argc, const ERL_NIF_TERM argv[])
Schedules NIF fp to execute. This function allows an application
to break up long-running work into multiple regular NIF calls or
to schedule a dirty NIF to execute on a dirty scheduler thread.
caller_env:
Must be process bound environment of the calling NIF.
fun_name:
Provides a name for the NIF that is scheduled for execution.
If it cannot be converted to an atom, enif_schedule_nif
returns a badarg exception.
flags:
Must be set to 0 for a regular NIF. If the emulator was
built with dirty scheduler support enabled, flags can be set
to either ERL_NIF_DIRTY_JOB_CPU_BOUND if the job is expected
to be CPU-bound, or ERL_NIF_DIRTY_JOB_IO_BOUND for jobs that
will be I/O-bound. If dirty scheduler threads are not avail-
able in the emulator, an attempt to schedule such a job
results in a notsup exception.
argc and argv:
Can either be the originals passed into the calling NIF, or
can be values created by the calling NIF.
The calling NIF must use the return value of enif_schedule_nif
as its own return value.
Be aware that enif_schedule_nif, as its name implies, only
schedules the NIF for future execution. The calling NIF does not
block waiting for the scheduled NIF to execute and return. This
means that the calling NIF cannot expect to receive the sched-
uled NIF return value and use it for further operations.
int enif_select(ErlNifEnv* env, ErlNifEvent event, enum ErlNifSelect-
Flags mode, void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref)
This function can be used to receive asynchronous notifications
when OS-specific event objects become ready for either read or
write operations.
Argument event identifies the event object. On Unix systems, the
functions select/poll are used. The event object must be a
socket, pipe or other file descriptor object that select/poll
can use.
Argument mode describes the type of events to wait for. It can
be ERL_NIF_SELECT_READ, ERL_NIF_SELECT_WRITE or a bitwise OR
combination to wait for both. It can also be ERL_NIF_SELECT_STOP
or ERL_NIF_SELECT_CANCEL which are described further below. When
a read or write event is triggered, a notification message like
this is sent to the process identified by pid:
{select, Obj, Ref, ready_input | ready_output}
ready_input or ready_output indicates if the event object is
ready for reading or writing.
Note:
For complete control over the message format use the newer func-
tions enif_select_read or enif_select_write introduced in
erts-11.0 (OTP-22.0).
Argument pid may be NULL to indicate the calling process. It
must not be set as undefined.
Argument obj is a resource object obtained from
enif_alloc_resource. The purpose of the resource objects is as a
container of the event object to manage its state and lifetime.
A handle to the resource is received in the notification message
as Obj.
Argument ref must be either a reference obtained from
erlang:make_ref/0 or the atom undefined. It will be passed as
Ref in the notifications. If a selective receive statement is
used to wait for the notification then a reference created just
before the receive will exploit a runtime optimization that
bypasses all earlier received messages in the queue.
The notifications are one-shot only. To receive further notifi-
cations of the same type (read or write), repeated calls to
enif_select must be made after receiving each notification.
ERL_NIF_SELECT_CANCEL can be used to cancel previously selected
events. It must be used in a bitwise OR combination with
ERL_NIF_SELECT_READ and/or ERL_NIF_SELECT_WRITE to indicate
which type of event to cancel. Arguments pid and ref are ignored
when ERL_NIF_SELECT_CANCEL is specified. The return value will
tell if the event was actualy cancelled or if a notification may
already have been sent.
Use ERL_NIF_SELECT_STOP as mode in order to safely close an
event object that has been passed to enif_select. The stop call-
back of the resource obj will be called when it is safe to close
the event object. This safe way of closing event objects must be
used even if all notifications have been received (or cancelled)
and no further calls to enif_select have been made.
ERL_NIF_SELECT_STOP will first cancel any selected events before
it calls or schedules the stop callback. Arguments pid and ref
are ignored when ERL_NIF_SELECT_STOP is specified.
The first call to enif_select for a specific OS event will
establish a relation between the event object and the containing
resource. All subsequent calls for an event must pass its con-
taining resource as argument obj. The relation is dissolved when
enif_select has been called with mode as ERL_NIF_SELECT_STOP and
the corresponding stop callback has returned. A resource can
contain several event objects but one event object can only be
contained within one resource. A resource will not be destructed
until all its contained relations have been dissolved.
Note:
Use enif_monitor_process together with enif_select to detect
failing Erlang processes and prevent them from causing permanent
leakage of resources and their contained OS event objects.
Returns a non-negative value on success where the following bits
can be set:
ERL_NIF_SELECT_STOP_CALLED:
The stop callback was called directly by enif_select.
ERL_NIF_SELECT_STOP_SCHEDULED:
The stop callback was scheduled to run on some other thread
or later by this thread.
ERL_NIF_SELECT_READ_CANCELLED:
A read event was cancelled by ERL_NIF_SELECT_CANCEL or
ERL_NIF_SELECT_STOP and is guaranteed not to generate a
ready_input notification message.
ERL_NIF_SELECT_WRITE_CANCELLED:
A write event was cancelled by ERL_NIF_SELECT_CANCEL or
ERL_NIF_SELECT_STOP and is guaranteed not to generate a
ready_output notification message.
Returns a negative value if the call failed where the following
bits can be set:
ERL_NIF_SELECT_INVALID_EVENT:
Argument event is not a valid OS event object.
ERL_NIF_SELECT_FAILED:
The system call failed to add the event object to the poll
set.
Note:
Use bitwise AND to test for specific bits in the return value.
New significant bits may be added in future releases to give
more detailed information for both failed and successful calls.
Do NOT use equality tests like ==, as that may cause your appli-
cation to stop working.
Example:
retval = enif_select(env, fd, ERL_NIF_SELECT_STOP, resource, ref);
if (retval < 0) {
/* handle error */
}
/* Success! */
if (retval & ERL_NIF_SELECT_STOP_CALLED) {
/* ... */
}
Note:
The mode flag ERL_NIF_SELECT_CANCEL and the return flags
ERL_NIF_SELECT_READ_CANCELLED and ERL_NIF_SELECT_WRITE_CANCELLED
were introduced in erts-11.0 (OTP-22.0).
int enif_select_read(ErlNifEnv* env, ErlNifEvent event, void* obj,
const ErlNifPid* pid, ERL_NIF_TERM msg, ErlNifEnv* msg_env)
int enif_select_write(ErlNifEnv* env, ErlNifEvent event, void* obj,
const ErlNifPid* pid, ERL_NIF_TERM msg, ErlNifEnv* msg_env)
These are variants of enif_select where you can supply your own
message term msg that will be sent to the process instead of the
predefined tuple {select,_,_,_}.
Argument msg_env must either be NULL or the environment of msg
allocated with enif_alloc_env. If argument msg_env is NULL the
term msg will be copied, otherwise both msg and msg_env will be
invalidated by a successful call to enif_select_read or
enif_select_write. The environment is then to either be freed
with enif_free_env or cleared for reuse with enif_clear_env. An
unsuccessful call will leave msg and msg_env still valid.
Apart from the message format enif_select_read and
enif_select_write behaves exactly the same as enif_select with
argument mode as either ERL_NIF_SELECT_READ or
ERL_NIF_SELECT_WRITE. To cancel or close events use enif_select.
ErlNifPid *enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)
Initializes the ErlNifPid variable at *pid to represent the
calling process.
Returns pid if successful, or NULL if caller_env is not a
process bound environment.
int enif_send(ErlNifEnv* caller_env,
ErlNifPid* to_pid, ErlNifEnv* msg_env, ERL_NIF_TERM msg)
Sends a message to a process.
caller_env:
The environment of the calling thread (process bound or
callback environment) or NULL if calling from a custom
thread not spawned by ERTS.
*to_pid:
The pid of the receiving process. The pid is to refer to a
process on the local node.
msg_env:
The environment of the message term. Must be a process inde-
pendent environment allocated with enif_alloc_env or NULL.
msg:
The message term to send.
Returns true if the message is successfully sent. Returns false
if the send operation fails, that is:
* *to_pid does not refer to an alive local process.
* The currently executing process (that is, the sender) is not
alive.
The message environment msg_env with all its terms (including
msg) is invalidated by a successful call to enif_send. The envi-
ronment is to either be freed with enif_free_env or cleared for
reuse with enif_clear_env. An unsuccessful call will leave msg
and msg_env still valid.
If msg_env is set to NULL, the msg term is copied and the origi-
nal term and its environment is still valid after the call.
This function is thread-safe.
Note:
Passing msg_env as NULL is only supported as from ERTS 8.0
(Erlang/OTP 19).
void enif_set_pid_undefined(ErlNifPid* pid)
Sets an ErlNifPid variable as undefined. See enif_is_pid_unde-
fined.
unsigned enif_sizeof_resource(void* obj)
Gets the byte size of resource object obj obtained by
enif_alloc_resource.
int enif_snprintf(char *str, size_t size, const
char *format, ...)
Similar to snprintf but this format string also accepts "%T",
which formats Erlang terms of type ERL_NIF_TERM.
This function is primarily intended for debugging purpose. It is
not recommended to print very large terms with %T. The function
may change errno, even if successful.
void enif_system_info(ErlNifSysInfo
*sys_info_ptr, size_t size)
Same as driver_system_info.
int enif_term_to_binary(ErlNifEnv *env,
ERL_NIF_TERM term, ErlNifBinary *bin)
Allocates a new binary with enif_alloc_binary and stores the
result of encoding term according to the Erlang external term
format.
Returns true on success, or false if the allocation fails.
See also erlang:term_to_binary/1 and enif_binary_to_term.
ErlNifTermType enif_term_type(ErlNifEnv *env, ERL_NIF_TERM term)
Determines the type of the given term. The term must be an ordi-
nary Erlang term and not one of the special terms returned by
enif_raise_exception, enif_schedule_nif, or similar.
The following types are defined at the moment:
ERL_NIF_TERM_TYPE_ATOM:
ERL_NIF_TERM_TYPE_BITSTRING:
A bitstring or binary
ERL_NIF_TERM_TYPE_FLOAT:
ERL_NIF_TERM_TYPE_FUN:
ERL_NIF_TERM_TYPE_INTEGER:
ERL_NIF_TERM_TYPE_LIST:
A list, empty or not
ERL_NIF_TERM_TYPE_MAP:
ERL_NIF_TERM_TYPE_PID:
ERL_NIF_TERM_TYPE_PORT:
ERL_NIF_TERM_TYPE_REFERENCE:
ERL_NIF_TERM_TYPE_TUPLE:
Note that new types may be added in the future, so the caller
must be prepared to handle unknown types.
int enif_thread_create(char *name,ErlNifTid
*tid,void * (*func)(void *),void *args,ErlNifThreadOpts
*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.
char*enif_thread_name(ErlNifTid tid)
Same as erl_drv_thread_name.
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_thread_type(void)
Determine the type of currently executing thread. A positive
value indicates a scheduler thread while a negative value or
zero indicates another type of thread. Currently the following
specific types exist (which may be extended in the future):
ERL_NIF_THR_UNDEFINED:
Undefined thread that is not a scheduler thread.
ERL_NIF_THR_NORMAL_SCHEDULER:
A normal scheduler thread.
ERL_NIF_THR_DIRTY_CPU_SCHEDULER:
A dirty CPU scheduler thread.
ERL_NIF_THR_DIRTY_IO_SCHEDULER:
A dirty I/O scheduler thread.
ErlNifTime enif_time_offset(ErlNifTimeUnit time_unit)
Returns the current time offset between Erlang monotonic time
and Erlang system time converted into the time_unit passed as
argument.
time_unit is the time unit of the returned value.
Returns ERL_NIF_TIME_ERROR if called with an invalid time unit
argument or if called from a thread that is not a scheduler
thread.
See also ErlNifTime and ErlNifTimeUnit.
void *enif_tsd_get(ErlNifTSDKey key)
Same as erl_drv_tsd_get.
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_set(ErlNifTSDKey key, void *data)
Same as erl_drv_tsd_set.
int enif_vfprintf(FILE *stream, const char *format, va_list ap)
Equivalent to enif_fprintf except that its called with a va_list
instead of a variable number of arguments.
int enif_vsnprintf(char *str, size_t size, const char *format, va_list
ap)
Equivalent to enif_snprintf except that its called with a
va_list instead of a variable number of arguments.
int enif_whereis_pid(ErlNifEnv *caller_env,
ERL_NIF_TERM name, ErlNifPid *pid)
Looks up a process by its registered name.
caller_env:
The environment of the calling thread (process bound or
callback environment) or NULL if calling from a custom
thread not spawned by ERTS.
name:
The name of a registered process, as an atom.
*pid:
The ErlNifPid in which the resolved process id is stored.
On success, sets *pid to the local process registered with name
and returns true. If name is not a registered process, or is not
an atom, false is returned and *pid is unchanged.
Works as erlang:whereis/1, but restricted to processes. See
enif_whereis_port to resolve registered ports.
int enif_whereis_port(ErlNifEnv *caller_env,
ERL_NIF_TERM name, ErlNifPort *port)
Looks up a port by its registered name.
caller_env:
The environment of the calling thread (process bound or
callback environment) or NULL if calling from a custom
thread not spawned by ERTS.
name:
The name of a registered port, as an atom.
*port:
The ErlNifPort in which the resolved port id is stored.
On success, sets *port to the port registered with name and
returns true. If name is not a registered port, or is not an
atom, false is returned and *port is unchanged.
Works as erlang:whereis/1, but restricted to ports. See
enif_whereis_pid to resolve registered processes.
SEE ALSO
erlang:load_nif/2
Ericsson AB erts 12.2 erl_nif(3)