1// Copyright 2011 Google Inc. All Rights Reserved.
2//
3// Use of this source code is governed by a BSD-style license
4// that can be found in the COPYING file in the root of the source
5// tree. An additional intellectual property rights grant can be found
6// in the file PATENTS. All contributing project authors may
7// be found in the AUTHORS file in the root of the source tree.
8// -----------------------------------------------------------------------------
9//
10// Multi-threaded worker
11//
12// Author: Skal (pascal.massimino@gmail.com)
13
14#ifndef WEBP_UTILS_THREAD_H_
15#define WEBP_UTILS_THREAD_H_
16
17#ifdef HAVE_CONFIG_H
18#include "../webp/config.h"
19#endif
20
21#include "../webp/types.h"
22
23#ifdef __cplusplus
24extern "C" {
25#endif
26
27// State of the worker thread object
28typedef enum {
29  NOT_OK = 0,   // object is unusable
30  OK,           // ready to work
31  WORK          // busy finishing the current task
32} WebPWorkerStatus;
33
34// Function to be called by the worker thread. Takes two opaque pointers as
35// arguments (data1 and data2), and should return false in case of error.
36typedef int (*WebPWorkerHook)(void*, void*);
37
38// Platform-dependent implementation details for the worker.
39typedef struct WebPWorkerImpl WebPWorkerImpl;
40
41// Synchronization object used to launch job in the worker thread
42typedef struct {
43  WebPWorkerImpl* impl_;
44  WebPWorkerStatus status_;
45  WebPWorkerHook hook;    // hook to call
46  void* data1;            // first argument passed to 'hook'
47  void* data2;            // second argument passed to 'hook'
48  int had_error;          // return value of the last call to 'hook'
49} WebPWorker;
50
51// The interface for all thread-worker related functions. All these functions
52// must be implemented.
53typedef struct {
54  // Must be called first, before any other method.
55  void (*Init)(WebPWorker* const worker);
56  // Must be called to initialize the object and spawn the thread. Re-entrant.
57  // Will potentially launch the thread. Returns false in case of error.
58  int (*Reset)(WebPWorker* const worker);
59  // Makes sure the previous work is finished. Returns true if worker->had_error
60  // was not set and no error condition was triggered by the working thread.
61  int (*Sync)(WebPWorker* const worker);
62  // Triggers the thread to call hook() with data1 and data2 arguments. These
63  // hook/data1/data2 values can be changed at any time before calling this
64  // function, but not be changed afterward until the next call to Sync().
65  void (*Launch)(WebPWorker* const worker);
66  // This function is similar to Launch() except that it calls the
67  // hook directly instead of using a thread. Convenient to bypass the thread
68  // mechanism while still using the WebPWorker structs. Sync() must
69  // still be called afterward (for error reporting).
70  void (*Execute)(WebPWorker* const worker);
71  // Kill the thread and terminate the object. To use the object again, one
72  // must call Reset() again.
73  void (*End)(WebPWorker* const worker);
74} WebPWorkerInterface;
75
76// Install a new set of threading functions, overriding the defaults. This
77// should be done before any workers are started, i.e., before any encoding or
78// decoding takes place. The contents of the interface struct are copied, it
79// is safe to free the corresponding memory after this call. This function is
80// not thread-safe. Return false in case of invalid pointer or methods.
81WEBP_EXTERN(int) WebPSetWorkerInterface(
82    const WebPWorkerInterface* const interface);
83
84// Retrieve the currently set thread worker interface.
85WEBP_EXTERN(const WebPWorkerInterface*) WebPGetWorkerInterface(void);
86
87//------------------------------------------------------------------------------
88
89#ifdef __cplusplus
90}    // extern "C"
91#endif
92
93#endif  /* WEBP_UTILS_THREAD_H_ */
94