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Diffstat (limited to 'erts/doc/src/erl_nif.xml')
| -rw-r--r-- | erts/doc/src/erl_nif.xml | 448 |
1 files changed, 373 insertions, 75 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml index b5dc9037c4..5a69bed34c 100644 --- a/erts/doc/src/erl_nif.xml +++ b/erts/doc/src/erl_nif.xml @@ -4,7 +4,7 @@ <cref> <header> <copyright> - <year>2001</year><year>2016</year> + <year>2001</year><year>2017</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -80,7 +80,7 @@ <code type="none"> /* niftest.c */ -#include "erl_nif.h" +#include <erl_nif.h> static ERL_NIF_TERM hello(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[]) { @@ -123,7 +123,7 @@ ok "Hello world!"</code> <p>A better solution for a real module is to take advantage of the new - directive <c>on load</c> (see section + directive <c>on_load</c> (see section <seealso marker="doc/reference_manual:code_loading#on_load">Running a Function When a Module is Loaded</seealso> in the Erlang Reference Manual) to load the NIF library automatically when the module is @@ -135,27 +135,14 @@ ok away by the compiler, causing loading of the NIF library to fail.</p> </note> - <p>A loaded NIF library is tied to the Erlang module code version - that loaded it. If the module is upgraded with a new version, the - new Erlang code need to load its own NIF library (or maybe choose not - to). The new code version can, however, choose to load the - 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, each Erlang module code can keep its own private data. This - private data can be set when the NIF library is loaded and - then retrieved by calling <seealso marker="#enif_priv_data"> - <c>enif_priv_data</c></seealso>.</p> - - <p>A NIF library cannot be loaded explicitly. A library is - automatically unloaded when the module code that it belongs to is purged - by the code server.</p> + <p>Once loaded, a NIF library is persistent. It will not be unloaded + until the module code version that it belongs to is purged.</p> </description> <section> <title>Functionality</title> - <p>All functions that a NIF library needs to do with Erlang are - performed through the NIF API functions. Functions exist + <p>All interaction between NIF code and the Erlang runtime system is + performed by calling NIF API functions. Functions exist for the following functionality:</p> <taglist> @@ -286,6 +273,19 @@ return term;</code> library is postponed as long as there exist resource objects with a destructor function in the library.</p> </item> + <tag>Module upgrade and static data</tag> + <item> + <p>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 + module 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 private data can be + set when the NIF library is loaded and later retrieved by calling + <seealso marker="#enif_priv_data"><c>enif_priv_data</c></seealso>.</p> + </item> <tag>Threads and concurrency</tag> <item> <p>A NIF is thread-safe without any explicit synchronization as @@ -296,8 +296,8 @@ return term;</code> synchronization. This includes terms in process-independent environments that are shared between threads. Resource objects also require synchronization if you treat them as mutable.</p> - <p>The library initialization callbacks <c>load</c>, <c>reload</c>, and - <c>upgrade</c> are all thread-safe even for shared state data.</p> + <p>The library initialization callbacks <c>load</c> and + <c>upgrade</c> are thread-safe even for shared state data.</p> </item> <tag><marker id="version_management"/>Version Management</tag> <item> @@ -402,14 +402,14 @@ return term;</code> <tag><marker id="dirty_nifs"/>Dirty NIF</tag> <item> <note> - <p><em>The dirty NIF functionality described here - is experimental</em>. Dirty NIF support is available only when - the emulator is configured with dirty schedulers enabled. This - feature is disabled by default. The Erlang runtime - without SMP support does not support dirty schedulers even when - the dirty scheduler support is enabled. To check at runtime for - the presence of dirty scheduler threads, code can use the - <seealso marker="#enif_system_info"> + <p>Dirty NIF support is available only when the emulator is + configured with dirty scheduler support. As of ERTS version + 9.0, dirty scheduler support is enabled by default on the + runtime system with SMP support. The Erlang runtime without + SMP support does <em>not</em> support dirty schedulers even + when the dirty scheduler support is explicitly enabled. To + check at runtime for the presence of dirty scheduler threads, + code can use the <seealso marker="#enif_system_info"> <c>enif_system_info()</c></seealso> API function.</p> </note> <p>A NIF that cannot be split and cannot execute in a millisecond @@ -498,7 +498,7 @@ return term;</code> <title>Initialization</title> <taglist> <tag><marker id="ERL_NIF_INIT"/><c>ERL_NIF_INIT(MODULE, - ErlNifFunc funcs[], load, reload, upgrade, unload)</c></tag> + ErlNifFunc funcs[], load, NULL, upgrade, unload)</c></tag> <item> <p>This is the magic macro to initialize a NIF library. It is to be evaluated in global file scope.</p> @@ -507,11 +507,14 @@ return term;</code> the macro.</p> <p><c>funcs</c> is a static array of function descriptors for all the implemented NIFs in this library.</p> - <p><c>load</c>, <c>reload</c>, <c>upgrade</c> and <c>unload</c> - are pointers to functions. One of <c>load</c>, <c>reload</c>, or + <p><c>load</c>, <c>upgrade</c> and <c>unload</c> + are pointers to functions. One of <c>load</c> or <c>upgrade</c> is called to initialize the library. <c>unload</c> is called to release the library. All are described individually below.</p> + <p>The fourth argument <c>NULL</c> is ignored. It + was earlier used for the deprectated <c>reload</c> callback + which is no longer supported since OTP 20.</p> <p>If compiling a NIF for static inclusion through <c>--enable-static-nifs</c>, you must define <c>STATIC_ERLANG_NIF</c> before the <c>ERL_NIF_INIT</c> declaration.</p> @@ -522,7 +525,7 @@ return term;</code> <p><c>load</c> is called when the NIF library is loaded and no previously loaded library exists for this module.</p> <p><c>*priv_data</c> can be set to point to some private data - that the library needs to keep a state between NIF + if the library needs to keep a state between NIF calls. <c>enif_priv_data</c> returns this pointer. <c>*priv_data</c> is initialized to <c>NULL</c> when <c>load</c> is called.</p> @@ -539,7 +542,7 @@ return term;</code> and there is old code of this module with a loaded NIF library.</p> <p>Works as <c>load</c>, except that <c>*old_priv_data</c> already contains the value set by the last call to <c>load</c> or - <c>reload</c> for the old module code. <c>*priv_data</c> is + <c>upgrade</c> for the old module code. <c>*priv_data</c> is initialized to <c>NULL</c> when <c>upgrade</c> is called. It is allowed to write to both <c>*priv_data</c> and <c>*old_priv_data.</c></p> @@ -551,27 +554,7 @@ return term;</code> <item> <p><c>unload</c> is called when the module code that the NIF library belongs to is purged as old. New code of the same - module may or may not exist. Notice that <c>unload</c> is not - called for a replaced library as a consequence of <c>reload</c>.</p> - </item> - <tag><marker id="reload"/><c>int (*reload)(ErlNifEnv* env, void** - priv_data, ERL_NIF_TERM load_info)</c></tag> - <item> - <note> - <p><em>The reload mechanism is deprecated.</em> It was only intended - as a development feature. Do not use it as an upgrade method for - live production systems. It can be removed in future releases. - Ensure to pass <c>reload</c> as <c>NULL</c> to - <seealso marker="#ERL_NIF_INIT"><c>ERL_NIF_INIT</c></seealso> - to disable it when not used.</p> - </note> - <p><c>reload</c> is called when the NIF library is loaded and a - previously loaded library already exists for this module code.</p> - <p>Works as <c>load</c>, except that - <c>*priv_data</c> already contains the value set by the - previous call to <c>load</c> or <c>reload</c>.</p> - <p>The library fails to load if <c>reload</c> returns - anything other than <c>0</c> or if <c>reload</c> is <c>NULL</c>.</p> + module may or may not exist.</p> </item> </taglist> </section> @@ -659,9 +642,6 @@ typedef struct { <p><c>flags</c> can be used to indicate that the NIF is a <seealso marker="#dirty_nifs">dirty NIF</seealso> that is to be executed on a dirty scheduler thread.</p> - <p><em>The dirty NIF functionality described here is - experimental.</em> You have to enable support for dirty - schedulers when building OTP to try out the functionality.</p> <p>If the dirty NIF is expected to be CPU-bound, its <c>flags</c> field is to be set to <c>ERL_NIF_DIRTY_JOB_CPU_BOUND</c> or <c>ERL_NIF_DIRTY_JOB_IO_BOUND</c>.</p> @@ -695,6 +675,18 @@ typedef struct { <p>When receiving data from untrusted sources, use option <c>ERL_NIF_BIN2TERM_SAFE</c>.</p> </item> + <tag><marker id="ErlNifMonitor"/><c>ErlNifMonitor</c></tag> + <item> + <p>This is an opaque data type that identifies a monitor.</p> + <p>The nif writer is to provide the memory for storing the + monitor when calling <seealso marker="#enif_monitor_process"> + <c>enif_monitor_process</c></seealso>. The + address of the data is not stored by the runtime system, so + <c>ErlNifMonitor</c> can be used as any other data, it + can be copied, moved in memory, forgotten, and so on. + To compare two monitors, <seealso marker="#enif_compare_monitors"> + <c>enif_compare_monitors</c></seealso> must be used.</p> + </item> <tag><marker id="ErlNifPid"/><c>ErlNifPid</c></tag> <item> <p>A process identifier (pid). In contrast to pid terms (instances of @@ -716,11 +708,47 @@ typedef struct { Each resource type has a unique name and a destructor function that is called when objects of its type are released.</p> </item> + <tag><marker id="ErlNifResourceTypeInit"/><c>ErlNifResourceTypeInit</c></tag> + <item> + <code type="none"> +typedef struct { + ErlNifResourceDtor* dtor; + ErlNifResourceStop* stop; + ErlNifResourceDown* down; +} ErlNifResourceTypeInit;</code> + <p>Initialization structure read by <seealso marker="#enif_open_resource_type_x"> + enif_open_resource_type_x</seealso>.</p> + </item> <tag><marker id="ErlNifResourceDtor"/><c>ErlNifResourceDtor</c></tag> <item> <code type="none"> typedef void ErlNifResourceDtor(ErlNifEnv* env, void* obj);</code> <p>The function prototype of a resource destructor function.</p> + <p>The <c>obj</c> 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.</p> + </item> + <tag><marker id="ErlNifResourceDown"/><c>ErlNifResourceDown</c></tag> + <item> + <code type="none"> +typedef void ErlNifResourceDown(ErlNifEnv* env, void* obj, const ErlNifPid* pid, const ErlNifMonitor* mon);</code> + <p>The function prototype of a resource down function, + called on the behalf of <seealso marker="#enif_monitor_process"> + enif_monitor_process</seealso>. <c>obj</c> is the resource, <c>pid</c> + is the identity of the monitored process that is exiting, and <c>mon</c> + is the identity of the monitor. + </p> + </item> + <tag><marker id="ErlNifResourceStop"/><c>ErlNifResourceStop</c></tag> + <item> + <code type="none"> +typedef void ErlNifResourceStop(ErlNifEnv* env, void* obj, ErlNifEvent event, int is_direct_call);</code> + <p>The function prototype of a resource stop function, + called on the behalf of <seealso marker="#enif_select"> + enif_select</seealso>. <c>obj</c> is the resource, <c>event</c> is OS event, + <c>is_direct_call</c> is true if the call is made directly from <c>enif_select</c> + or false if it is a scheduled call (potentially from another thread).</p> </item> <tag><marker id="ErlNifCharEncoding"/><c>ErlNifCharEncoding</c></tag> <item> @@ -786,6 +814,29 @@ typedef enum { </item> </taglist> </item> + <tag><marker id="ErlNifHash"/><c>ErlNifHash</c></tag> + <item> + <p>An enumeration of the supported hash types that can be generated + using <seealso marker="#enif_hash"><c>enif_hash</c></seealso>. + </p> + <taglist> + <tag><c>ERL_NIF_INTERNAL_HASH</c></tag> + <item> + <p>Non-portable hash function that only guarantees the same hash + for the same term within one Erlang VM instance.</p> + <p>It takes 32-bit salt values and generates hashes within <c>0..2^32-1</c>.</p> + </item> + <tag><c>ERL_NIF_PHASH2</c></tag> + <item> + <p>Portable hash function that gives the same hash for the + same Erlang term regardless of machine architecture and ERTS version.</p> + <p><em>It ignores salt values</em> and generates hashes within <c>0..2^27-1</c>.</p> + <p>Slower than <c>ERL_NIF_INTERNAL_HASH.</c> + It corresponds to <seealso marker="erlang#phash2-1"><c>erlang:phash2/1</c></seealso>. + </p> + </item> + </taglist> + </item> </taglist> </section> @@ -895,6 +946,21 @@ typedef enum { </func> <func> + <name><ret>int</ret><nametext>enif_compare_monitors(const ErlNifMonitor + *monitor1, const ErlNifMonitor *monitor2)</nametext></name> + <fsummary>Compare two monitors.</fsummary> + <desc> + <marker id="enif_compare_monitors"></marker> + <p>Compares two <seealso marker="#ErlNifMonitor"><c>ErlNifMonitor</c></seealso>s. + Can also be used to imply some artificial order on monitors, + for whatever reason.</p> + <p>Returns <c>0</c> if <c>monitor1</c> and <c>monitor2</c> are equal, + < <c>0</c> if <c>monitor1</c> < <c>monitor2</c>, and + > <c>0</c> if <c>monitor1</c> > <c>monitor2</c>.</p> + </desc> + </func> + + <func> <name><ret>void</ret> <nametext>enif_cond_broadcast(ErlNifCond *cnd)</nametext></name> <fsummary></fsummary> @@ -1022,6 +1088,30 @@ typedef enum { </func> <func> + <name><ret>int</ret><nametext>enif_demonitor_process(ErlNifEnv* env, void* obj, + const ErlNifMonitor* mon)</nametext></name> + <fsummary>Cancel a process monitor.</fsummary> + <desc> + <marker id="enif_demonitor_process"></marker> + <p>Cancels a monitor created earlier with <seealso marker="#enif_monitor_process"> + <c>enif_monitor_process</c></seealso>. Argument <c>obj</c> is a pointer + to the resource holding the monitor and <c>*mon</c> identifies the monitor.</p> + <p>Returns <c>0</c> 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</p> + <list type="bulleted"> + <item>never created for this resource</item> + <item>already cancelled</item> + <item>already triggered</item> + <item>just about to be triggered by a concurrent thread</item> + </list> + <p>This function is only thread-safe when the emulator with SMP support + is used. It can only be used in a non-SMP emulator from a NIF-calling + thread.</p> + </desc> + </func> + + <func> <name><ret>int</ret> <nametext>enif_equal_tids(ErlNifTid tid1, ErlNifTid tid2)</nametext> </name> @@ -1306,13 +1396,12 @@ typedef enum { <p>Returns <c>true</c> if a pending exception is associated with the environment <c>env</c>. If <c>reason</c> is a <c>NULL</c> pointer, ignore it. Otherwise, if a pending exception associated with - <c>env</c> exists, set <c>ERL_NIF_TERM</c> to which <c>reason</c> - points to the value of the exception's term. For example, if - <seealso marker="#enif_make_badarg"> + <c>env</c> exists, set <c>*reason</c> to the value of the exception + term. For example, if <seealso marker="#enif_make_badarg"> <c>enif_make_badarg</c></seealso> is called to set a pending <c>badarg</c> exception, a later call to <c>enif_has_pending_exception(env, &reason)</c> sets - <c>reason</c> to the atom <c>badarg</c>, then return <c>true</c>.</p> + <c>*reason</c> to the atom <c>badarg</c>, then return <c>true</c>.</p> <p>See also <seealso marker="#enif_make_badarg"> <c>enif_make_badarg</c></seealso> and <seealso marker="#enif_raise_exception"> @@ -1321,6 +1410,19 @@ typedef enum { </func> <func> + <name> + <ret>ErlNifUInt64</ret> + <nametext>enif_hash(ErlNifHash type, ERL_NIF_TERM term, ErlNifUInt64 salt)</nametext> + </name> + <fsummary>Hash terms.</fsummary> + <desc> + <p>Hashes <c>term</c> according to the specified + <seealso marker="#ErlNifHash"><c>ErlNifHash</c></seealso> <c>type</c>.</p> + <p>Ranges of taken salt (if any) and returned value depend on the hash type.</p> + </desc> + </func> + + <func> <name><ret>int</ret><nametext>enif_inspect_binary(ErlNifEnv* env, ERL_NIF_TERM bin_term, ErlNifBinary* bin)</nametext></name> <fsummary>Inspect the content of a binary.</fsummary> @@ -2137,6 +2239,36 @@ enif_map_iterator_destroy(env, &iter);</code> </func> <func> + <name><ret>int</ret><nametext>enif_monitor_process(ErlNifEnv* env, void* obj, + const ErlNifPid* target_pid, ErlNifMonitor* mon)</nametext></name> + <fsummary>Monitor a process from a resource.</fsummary> + <desc> + <marker id="enif_monitor_process"></marker> + <p>Starts monitoring a process from a resource. When a process is + monitored, a process exit results in a call to the provided + <seealso marker="#ErlNifResourceDown"> + <c>down</c></seealso> callback associated with the resource type.</p> + <p>Argument <c>obj</c> is pointer to the resource to hold the monitor and + <c>*target_pid</c> identifies the local process to be monitored.</p> + <p>If <c>mon</c> is not <c>NULL</c>, a successful call stores the + identity of the monitor in the + <seealso marker="#ErlNifMonitor"><c>ErlNifMonitor</c></seealso> + struct pointed to by <c>mon</c>. This identifier is used to refer to the + monitor for later removal with + <seealso marker="#enif_demonitor_process"><c>enif_demonitor_process</c></seealso> + or compare with + <seealso marker="#enif_compare_monitors"><c>enif_compare_monitors</c></seealso>. + A monitor is automatically removed when it triggers or when + the resource is deallocated.</p> + <p>Returns <c>0</c> on success, < 0 if no <c>down</c> callback is + provided, and > 0 if the process is no longer alive.</p> + <p>This function is only thread-safe when the emulator with SMP support + is used. It can only be used in a non-SMP emulator from a NIF-calling + thread.</p> + </desc> + </func> + + <func> <name><ret>ErlNifTime</ret> <nametext>enif_monotonic_time(ErlNifTimeUnit time_unit)</nametext> </name> @@ -2249,10 +2381,30 @@ enif_map_iterator_destroy(env, &iter);</code> returns <c>NULL</c> and sets <c>*tried</c> to <c>flags</c>. It is allowed to set <c>tried</c> to <c>NULL</c>.</p> <p>Notice that <c>enif_open_resource_type</c> is only allowed to be - called in the three callbacks - <seealso marker="#load"><c>load</c></seealso>, - <seealso marker="#reload"><c>reload</c></seealso>, and + called in the two callbacks + <seealso marker="#load"><c>load</c></seealso> and <seealso marker="#upgrade"><c>upgrade</c></seealso>.</p> + <p>See also <seealso marker="#enif_open_resource_type_x"> + <c>enif_open_resource_type_x</c></seealso>.</p> + </desc> + </func> + + <func> + <name><ret>ErlNifResourceType *</ret> + <nametext>enif_open_resource_type_x(ErlNifEnv* env, const char* name, + const ErlNifResourceTypeInit* init, + ErlNifResourceFlags flags, ErlNifResourceFlags* tried)</nametext> + </name> + <fsummary>Create or takeover a resource type.</fsummary> + <desc> + <p>Same as <seealso marker="#enif_open_resource_type"><c>enif_open_resource_type</c></seealso> + except it accepts additional callback functions for resource types that are + used together with <seealso marker="#enif_select"><c>enif_select</c></seealso> + and <seealso marker="#enif_monitor_process"><c>enif_monitor_process</c></seealso>.</p> + <p>Argument <c>init</c> is a pointer to an + <seealso marker="#ErlNifResourceTypeInit"><c>ErlNifResourceTypeInit</c></seealso> + structure that contains the function pointers for destructor, down and stop callbacks + for the resource type.</p> </desc> </func> @@ -2305,10 +2457,8 @@ enif_map_iterator_destroy(env, &iter);</code> <fsummary>Get the private data of a NIF library.</fsummary> <desc> <p>Returns the pointer to the private data that was set by - <seealso marker="#load"><c>load</c></seealso>, - <seealso marker="#reload"><c>reload</c></seealso>, or + <seealso marker="#load"><c>load</c></seealso> or <seealso marker="#upgrade"><c>upgrade</c></seealso>.</p> - <p>Was previously named <c>enif_get_data</c>.</p> </desc> </func> @@ -2365,7 +2515,7 @@ enif_map_iterator_destroy(env, &iter);</code> <nametext>enif_release_resource(void* obj)</nametext></name> <fsummary>Release a resource object.</fsummary> <desc> - <p>Removes a reference to resource object <c>obj</c>obtained from + <p>Removes a reference to resource object <c>obj</c> obtained from <seealso marker="#enif_alloc_resource"> <c>enif_alloc_resource</c></seealso>. The resource object is destructed when the last reference is removed. @@ -2470,9 +2620,6 @@ enif_map_iterator_destroy(env, &iter);</code> application to break up long-running work into multiple regular NIF calls or to schedule a <seealso marker="#dirty_nifs"> dirty NIF</seealso> to execute on a dirty scheduler thread.</p> - <p><em>The dirty NIF functionality described here is - experimental.</em> You have to enable support for dirty - schedulers when building OTP to try out the functionality.</p> <taglist> <tag><c>fun_name</c></tag> <item> @@ -2483,13 +2630,13 @@ enif_map_iterator_destroy(env, &iter);</code> <tag><c>flags</c></tag> <item> <p>Must be set to <c>0</c> for a regular NIF. If the emulator was - built with the experimental dirty scheduler support enabled, + built with dirty scheduler support enabled, <c>flags</c> can be set to either <c>ERL_NIF_DIRTY_JOB_CPU_BOUND</c> if the job is expected to be CPU-bound, or <c>ERL_NIF_DIRTY_JOB_IO_BOUND</c> for jobs that will be I/O-bound. If dirty scheduler threads are not available in the emulator, an attempt to schedule such a job - results in a <c>badarg</c> exception.</p> + results in a <c>notsup</c> exception.</p> </item> <tag><c>argc</c> and <c>argv</c></tag> <item> @@ -2508,6 +2655,100 @@ enif_map_iterator_destroy(env, &iter);</code> </func> <func> + <name><ret>int</ret> + <nametext>enif_select(ErlNifEnv* env, ErlNifEvent event, enum ErlNifSelectFlags mode, + void* obj, const ErlNifPid* pid, ERL_NIF_TERM ref)</nametext> + </name> + <fsummary>Manage subscription on IO event.</fsummary> + <desc> + <p>This function can be used to receive asynchronous notifications + when OS-specific event objects become ready for either read or write operations.</p> + <p>Argument <c>event</c> identifies the event object. On Unix + systems, the functions <c>select</c>/<c>poll</c> are used. The event + object must be a socket, pipe or other file descriptor object that + <c>select</c>/<c>poll</c> can use.</p> + <p>Argument <c>mode</c> describes the type of events to wait for. It can be + <c>ERL_NIF_SELECT_READ</c>, <c>ERL_NIF_SELECT_WRITE</c> or a bitwise + OR combination to wait for both. It can also be <c>ERL_NIF_SELECT_STOP</c> + which is described further below. When a read or write event is triggerred, + a notification message like this is sent to the process identified by + <c>pid</c>:</p> + <code type="none">{select, Obj, Ref, ready_input | ready_output}</code> + <p><c>ready_input</c> or <c>ready_output</c> indicates if the event object + is ready for reading or writing.</p> + <p>Argument <c>pid</c> may be <c>NULL</c> to indicate the calling process.</p> + <p>Argument <c>obj</c> is a resource object obtained from + <seealso marker="#enif_alloc_resource"><c>enif_alloc_resource</c></seealso>. + 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 <c>Obj</c>.</p> + <p>Argument <c>ref</c> must be either a reference obtained from + <seealso marker="erlang#make_ref-0"><c>erlang:make_ref/0</c></seealso> + or the atom <c>undefined</c>. It will be passed as <c>Ref</c> in the notifications. + If a selective <c>receive</c> statement is used to wait for the notification + then a reference created just before the <c>receive</c> will exploit a runtime + optimization that bypasses all earlier received messages in the queue.</p> + <p>The notifications are one-shot only. To receive further notifications of the same + type (read or write), repeated calls to <c>enif_select</c> must be made + after receiving each notification.</p> + <p>Use <c>ERL_NIF_SELECT_STOP</c> as <c>mode</c> in order to safely + close an event object that has been passed to <c>enif_select</c>. The + <seealso marker="#ErlNifResourceStop"><c>stop</c></seealso> callback + of the resource <c>obj</c> 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 and no further calls to + <c>enif_select</c> have been made.</p> + <p>The first call to <c>enif_select</c> for a specific OS <c>event</c> will establish + a relation between the event object and the containing resource. All subsequent calls + for an <c>event</c> must pass its containing resource as argument + <c>obj</c>. The relation is dissolved when <c>enif_select</c> has + been called with <c>mode</c> as <c>ERL_NIF_SELECT_STOP</c> and the + corresponding <c>stop</c> 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.</p> + <note> + <p>Use <seealso marker="#enif_monitor_process"><c>enif_monitor_process</c></seealso> + together with <c>enif_select</c> to detect failing Erlang + processes and prevent them from causing permanent leakage of resources + and their contained OS event objects.</p> + </note> + <p>Returns a non-negative value on success where the following bits can be set:</p> + <taglist> + <tag><c>ERL_NIF_SELECT_STOP_CALLED</c></tag> + <item>The stop callback was called directly by <c>enif_select</c>.</item> + <tag><c>ERL_NIF_SELECT_STOP_SCHEDULED</c></tag> + <item>The stop callback was scheduled to run on some other thread + or later by this thread.</item> + </taglist> + <p>Returns a negative value if the call failed where the follwing bits can be set:</p> + <taglist> + <tag><c>ERL_NIF_SELECT_INVALID_EVENT</c></tag> + <item>Argument <c>event</c> is not a valid OS event object.</item> + <tag><c>ERL_NIF_SELECT_FAILED</c></tag> + <item>The system call failed to add the event object to the poll set.</item> + </taglist> + <note> + <p>Use bitwise AND to test for specific bits in the return vaue. + New significant bits may be added in future releases to give more detailed + information for both failed and successful calls. Do NOT use equallity tests + like <c>==</c>, as that may cause your application to stop working.</p> + <p>Example:</p> + <code type="none"> +retval = enif_select(env, fd, ERL_NIF_SELECT_STOP, resource, ref); +if (retval < 0) { + /* handle error */ +} +/* Success! */ +if (retval & ERL_NIF_SELECT_STOP_CALLED) { + /* ... */ +} +</code> + </note> + </desc> + </func> + + <func> <name><ret>ErlNifPid *</ret> <nametext>enif_self(ErlNifEnv* caller_env, ErlNifPid* pid)</nametext> </name> @@ -2761,6 +3002,63 @@ enif_map_iterator_destroy(env, &iter);</code> <c>erl_drv_tsd_set</c></seealso>.</p> </desc> </func> + + <func> + <name><ret>int</ret> + <nametext>enif_whereis_pid(ErlNifEnv *env, + ERL_NIF_TERM name, ErlNifPid *pid)</nametext></name> + <fsummary>Looks up a process by its registered name.</fsummary> + <desc> + <p>Looks up a process by its registered name.</p> + <taglist> + <tag><c>env</c></tag> + <item>The environment of the calling process. Must be <c>NULL</c> + only if calling from a created thread.</item> + <tag><c>name</c></tag> + <item>The name of a registered process, as an atom.</item> + <tag><c>*pid</c></tag> + <item>The <seealso marker="#ErlNifPid"><c>ErlNifPid</c></seealso> + in which the resolved process id is stored.</item> + </taglist> + <p>On success, sets <c>*pid</c> to the local process registered with + <c>name</c> and returns <c>true</c>. If <c>name</c> is not a + registered process, or is not an atom, <c>false</c> is returned and + <c>*pid</c> is unchanged.</p> + <p>Works as <seealso marker="erlang#whereis-1"> + <c>erlang:whereis/1</c></seealso>, but restricted to processes. See + <seealso marker="#enif_whereis_port"><c>enif_whereis_port</c></seealso> + to resolve registered ports.</p> + </desc> + </func> + + <func> + <name><ret>int</ret> + <nametext>enif_whereis_port(ErlNifEnv *env, + ERL_NIF_TERM name, ErlNifPort *port)</nametext></name> + <fsummary>Looks up a port by its registered name.</fsummary> + <desc> + <p>Looks up a port by its registered name.</p> + <taglist> + <tag><c>env</c></tag> + <item>The environment of the calling process. Must be <c>NULL</c> + only if calling from a created thread.</item> + <tag><c>name</c></tag> + <item>The name of a registered port, as an atom.</item> + <tag><c>*port</c></tag> + <item>The <seealso marker="#ErlNifPort"><c>ErlNifPort</c></seealso> + in which the resolved port id is stored.</item> + </taglist> + <p>On success, sets <c>*port</c> to the port registered with + <c>name</c> and returns <c>true</c>. If <c>name</c> is not a + registered port, or is not an atom, <c>false</c> is returned and + <c>*port</c> is unchanged.</p> + <p>Works as <seealso marker="erlang#whereis-1"> + <c>erlang:whereis/1</c></seealso>, but restricted to ports. See + <seealso marker="#enif_whereis_pid"><c>enif_whereis_pid</c></seealso> + to resolve registered processes.</p> + </desc> + </func> + </funcs> <section> |