ref: 66de2b710fb65ef51bdc9569f037f6d674e60a2f
dir: /vpx_util/vpx_thread.h/
// Copyright 2013 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Multi-threaded worker
//
// Original source:
// http://git.chromium.org/webm/libwebp.git
// 100644 blob 7bd451b124ae3b81596abfbcc823e3cb129d3a38 src/utils/thread.h
#ifndef VPX_THREAD_H_
#define VPX_THREAD_H_
#include "./vpx_config.h"
#ifdef __cplusplus
extern "C" {
#endif
// Set maximum decode threads to be 8 due to the limit of frame buffers
// and not enough semaphores in the emulation layer on windows.
#define MAX_DECODE_THREADS 8
#if CONFIG_MULTITHREAD
#if defined(_WIN32) && !HAVE_PTHREAD_H
#include <errno.h> // NOLINT
#include <process.h> // NOLINT
#include <windows.h> // NOLINT
typedef HANDLE pthread_t;
typedef CRITICAL_SECTION pthread_mutex_t;
typedef struct {
HANDLE waiting_sem_;
HANDLE received_sem_;
HANDLE signal_event_;
} pthread_cond_t;
//------------------------------------------------------------------------------
// simplistic pthread emulation layer
// _beginthreadex requires __stdcall
#define THREADFN unsigned int __stdcall
#define THREAD_RETURN(val) (unsigned int)((DWORD_PTR)val)
static INLINE int pthread_create(pthread_t* const thread, const void* attr,
unsigned int (__stdcall *start)(void*),
void* arg) {
(void)attr;
*thread = (pthread_t)_beginthreadex(NULL, /* void *security */
0, /* unsigned stack_size */
start,
arg,
0, /* unsigned initflag */
NULL); /* unsigned *thrdaddr */
if (*thread == NULL) return 1;
SetThreadPriority(*thread, THREAD_PRIORITY_ABOVE_NORMAL);
return 0;
}
static INLINE int pthread_join(pthread_t thread, void** value_ptr) {
(void)value_ptr;
return (WaitForSingleObject(thread, INFINITE) != WAIT_OBJECT_0 ||
CloseHandle(thread) == 0);
}
// Mutex
static INLINE int pthread_mutex_init(pthread_mutex_t *const mutex,
void* mutexattr) {
(void)mutexattr;
InitializeCriticalSection(mutex);
return 0;
}
static INLINE int pthread_mutex_trylock(pthread_mutex_t *const mutex) {
return TryEnterCriticalSection(mutex) ? 0 : EBUSY;
}
static INLINE int pthread_mutex_lock(pthread_mutex_t *const mutex) {
EnterCriticalSection(mutex);
return 0;
}
static INLINE int pthread_mutex_unlock(pthread_mutex_t *const mutex) {
LeaveCriticalSection(mutex);
return 0;
}
static INLINE int pthread_mutex_destroy(pthread_mutex_t *const mutex) {
DeleteCriticalSection(mutex);
return 0;
}
// Condition
static INLINE int pthread_cond_destroy(pthread_cond_t *const condition) {
int ok = 1;
ok &= (CloseHandle(condition->waiting_sem_) != 0);
ok &= (CloseHandle(condition->received_sem_) != 0);
ok &= (CloseHandle(condition->signal_event_) != 0);
return !ok;
}
static INLINE int pthread_cond_init(pthread_cond_t *const condition,
void* cond_attr) {
(void)cond_attr;
condition->waiting_sem_ = CreateSemaphore(NULL, 0, MAX_DECODE_THREADS, NULL);
condition->received_sem_ = CreateSemaphore(NULL, 0, MAX_DECODE_THREADS, NULL);
condition->signal_event_ = CreateEvent(NULL, FALSE, FALSE, NULL);
if (condition->waiting_sem_ == NULL ||
condition->received_sem_ == NULL ||
condition->signal_event_ == NULL) {
pthread_cond_destroy(condition);
return 1;
}
return 0;
}
static INLINE int pthread_cond_signal(pthread_cond_t *const condition) {
int ok = 1;
if (WaitForSingleObject(condition->waiting_sem_, 0) == WAIT_OBJECT_0) {
// a thread is waiting in pthread_cond_wait: allow it to be notified
ok = SetEvent(condition->signal_event_);
// wait until the event is consumed so the signaler cannot consume
// the event via its own pthread_cond_wait.
ok &= (WaitForSingleObject(condition->received_sem_, INFINITE) !=
WAIT_OBJECT_0);
}
return !ok;
}
static INLINE int pthread_cond_wait(pthread_cond_t *const condition,
pthread_mutex_t *const mutex) {
int ok;
// note that there is a consumer available so the signal isn't dropped in
// pthread_cond_signal
if (!ReleaseSemaphore(condition->waiting_sem_, 1, NULL))
return 1;
// now unlock the mutex so pthread_cond_signal may be issued
pthread_mutex_unlock(mutex);
ok = (WaitForSingleObject(condition->signal_event_, INFINITE) ==
WAIT_OBJECT_0);
ok &= ReleaseSemaphore(condition->received_sem_, 1, NULL);
pthread_mutex_lock(mutex);
return !ok;
}
#else // _WIN32
#include <pthread.h> // NOLINT
# define THREADFN void*
# define THREAD_RETURN(val) val
#endif
#endif // CONFIG_MULTITHREAD
// State of the worker thread object
typedef enum {
NOT_OK = 0, // object is unusable
OK, // ready to work
WORK // busy finishing the current task
} VPxWorkerStatus;
// Function to be called by the worker thread. Takes two opaque pointers as
// arguments (data1 and data2), and should return false in case of error.
typedef int (*VPxWorkerHook)(void*, void*);
// Platform-dependent implementation details for the worker.
typedef struct VPxWorkerImpl VPxWorkerImpl;
// Synchronization object used to launch job in the worker thread
typedef struct {
VPxWorkerImpl *impl_;
VPxWorkerStatus status_;
VPxWorkerHook hook; // hook to call
void *data1; // first argument passed to 'hook'
void *data2; // second argument passed to 'hook'
int had_error; // return value of the last call to 'hook'
} VPxWorker;
// The interface for all thread-worker related functions. All these functions
// must be implemented.
typedef struct {
// Must be called first, before any other method.
void (*init)(VPxWorker *const worker);
// Must be called to initialize the object and spawn the thread. Re-entrant.
// Will potentially launch the thread. Returns false in case of error.
int (*reset)(VPxWorker *const worker);
// Makes sure the previous work is finished. Returns true if worker->had_error
// was not set and no error condition was triggered by the working thread.
int (*sync)(VPxWorker *const worker);
// Triggers the thread to call hook() with data1 and data2 arguments. These
// hook/data1/data2 values can be changed at any time before calling this
// function, but not be changed afterward until the next call to Sync().
void (*launch)(VPxWorker *const worker);
// This function is similar to launch() except that it calls the
// hook directly instead of using a thread. Convenient to bypass the thread
// mechanism while still using the VPxWorker structs. sync() must
// still be called afterward (for error reporting).
void (*execute)(VPxWorker *const worker);
// Kill the thread and terminate the object. To use the object again, one
// must call reset() again.
void (*end)(VPxWorker *const worker);
} VPxWorkerInterface;
// Install a new set of threading functions, overriding the defaults. This
// should be done before any workers are started, i.e., before any encoding or
// decoding takes place. The contents of the interface struct are copied, it
// is safe to free the corresponding memory after this call. This function is
// not thread-safe. Return false in case of invalid pointer or methods.
int vpx_set_worker_interface(const VPxWorkerInterface *const winterface);
// Retrieve the currently set thread worker interface.
const VPxWorkerInterface *vpx_get_worker_interface(void);
//------------------------------------------------------------------------------
#ifdef __cplusplus
} // extern "C"
#endif
#endif // VPX_THREAD_H_