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// Copyright 2011 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
// Author: Skal (
#include "../webp/config.h"
#include "../webp/types.h"
#ifdef __cplusplus
extern "C" {
// State of the worker thread object
typedef enum {
NOT_OK = 0, // object is unusable
OK, // ready to work
WORK // busy finishing the current task
} WebPWorkerStatus;
// 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 (*WebPWorkerHook)(void*, void*);
// Platform-dependent implementation details for the worker.
typedef struct WebPWorkerImpl WebPWorkerImpl;
// Synchronization object used to launch job in the worker thread
typedef struct {
WebPWorkerImpl* impl_;
WebPWorkerStatus status_;
WebPWorkerHook 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'
} WebPWorker;
// 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)(WebPWorker* 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)(WebPWorker* 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)(WebPWorker* 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)(WebPWorker* 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 WebPWorker structs. Sync() must
// still be called afterward (for error reporting).
void (*Execute)(WebPWorker* const worker);
// Kill the thread and terminate the object. To use the object again, one
// must call Reset() again.
void (*End)(WebPWorker* const worker);
} WebPWorkerInterface;
// 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.
WEBP_EXTERN(int) WebPSetWorkerInterface(
const WebPWorkerInterface* const winterface);
// Retrieve the currently set thread worker interface.
WEBP_EXTERN(const WebPWorkerInterface*) WebPGetWorkerInterface(void);
#ifdef __cplusplus
} // extern "C"
#endif /* WEBP_UTILS_THREAD_H_ */