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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_UTILS_H_
15 #define WEBP_UTILS_THREAD_UTILS_H_
16 
17 #ifdef HAVE_CONFIG_H
18 #include "src/webp/config.h"
19 #endif
20 
21 #include "src/webp/types.h"
22 
23 #ifdef __cplusplus
24 extern "C" {
25 #endif
26 
27 // State of the worker thread object
28 typedef 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.
36 typedef int (*WebPWorkerHook)(void*, void*);
37 
38 // Synchronization object used to launch job in the worker thread
39 typedef struct {
40   void* impl_;            // platform-dependent implementation worker details
41   WebPWorkerStatus status_;
42   WebPWorkerHook hook;    // hook to call
43   void* data1;            // first argument passed to 'hook'
44   void* data2;            // second argument passed to 'hook'
45   int had_error;          // return value of the last call to 'hook'
46 } WebPWorker;
47 
48 // The interface for all thread-worker related functions. All these functions
49 // must be implemented.
50 typedef struct {
51   // Must be called first, before any other method.
52   void (*Init)(WebPWorker* const worker);
53   // Must be called to initialize the object and spawn the thread. Re-entrant.
54   // Will potentially launch the thread. Returns false in case of error.
55   int (*Reset)(WebPWorker* const worker);
56   // Makes sure the previous work is finished. Returns true if worker->had_error
57   // was not set and no error condition was triggered by the working thread.
58   int (*Sync)(WebPWorker* const worker);
59   // Triggers the thread to call hook() with data1 and data2 arguments. These
60   // hook/data1/data2 values can be changed at any time before calling this
61   // function, but not be changed afterward until the next call to Sync().
62   void (*Launch)(WebPWorker* const worker);
63   // This function is similar to Launch() except that it calls the
64   // hook directly instead of using a thread. Convenient to bypass the thread
65   // mechanism while still using the WebPWorker structs. Sync() must
66   // still be called afterward (for error reporting).
67   void (*Execute)(WebPWorker* const worker);
68   // Kill the thread and terminate the object. To use the object again, one
69   // must call Reset() again.
70   void (*End)(WebPWorker* const worker);
71 } WebPWorkerInterface;
72 
73 // Install a new set of threading functions, overriding the defaults. This
74 // should be done before any workers are started, i.e., before any encoding or
75 // decoding takes place. The contents of the interface struct are copied, it
76 // is safe to free the corresponding memory after this call. This function is
77 // not thread-safe. Return false in case of invalid pointer or methods.
78 WEBP_EXTERN int WebPSetWorkerInterface(
79     const WebPWorkerInterface* const winterface);
80 
81 // Retrieve the currently set thread worker interface.
82 WEBP_EXTERN const WebPWorkerInterface* WebPGetWorkerInterface(void);
83 
84 //------------------------------------------------------------------------------
85 
86 #ifdef __cplusplus
87 }    // extern "C"
88 #endif
89 
90 #endif  // WEBP_UTILS_THREAD_UTILS_H_
91