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      1 /*
      2  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #include "webrtc/system_wrappers/source/rw_lock_win.h"
     12 
     13 #include "webrtc/system_wrappers/include/trace.h"
     14 
     15 namespace webrtc {
     16 
     17 static bool native_rw_locks_supported = false;
     18 static bool module_load_attempted = false;
     19 static HMODULE library = NULL;
     20 
     21 typedef void (WINAPI* InitializeSRWLock)(PSRWLOCK);
     22 
     23 typedef void (WINAPI* AcquireSRWLockExclusive)(PSRWLOCK);
     24 typedef void (WINAPI* ReleaseSRWLockExclusive)(PSRWLOCK);
     25 
     26 typedef void (WINAPI* AcquireSRWLockShared)(PSRWLOCK);
     27 typedef void (WINAPI* ReleaseSRWLockShared)(PSRWLOCK);
     28 
     29 InitializeSRWLock       initialize_srw_lock;
     30 AcquireSRWLockExclusive acquire_srw_lock_exclusive;
     31 AcquireSRWLockShared    acquire_srw_lock_shared;
     32 ReleaseSRWLockShared    release_srw_lock_shared;
     33 ReleaseSRWLockExclusive release_srw_lock_exclusive;
     34 
     35 RWLockWin::RWLockWin() {
     36   initialize_srw_lock(&lock_);
     37 }
     38 
     39 RWLockWin* RWLockWin::Create() {
     40   if (!LoadModule()) {
     41     return NULL;
     42   }
     43   return new RWLockWin();
     44 }
     45 
     46 void RWLockWin::AcquireLockExclusive() {
     47   acquire_srw_lock_exclusive(&lock_);
     48 }
     49 
     50 void RWLockWin::ReleaseLockExclusive() {
     51   release_srw_lock_exclusive(&lock_);
     52 }
     53 
     54 void RWLockWin::AcquireLockShared() {
     55   acquire_srw_lock_shared(&lock_);
     56 }
     57 
     58 void RWLockWin::ReleaseLockShared() {
     59   release_srw_lock_shared(&lock_);
     60 }
     61 
     62 bool RWLockWin::LoadModule() {
     63   if (module_load_attempted) {
     64     return native_rw_locks_supported;
     65   }
     66   module_load_attempted = true;
     67   // Use native implementation if supported (i.e Vista+)
     68   library = LoadLibrary(TEXT("Kernel32.dll"));
     69   if (!library) {
     70     return false;
     71   }
     72   WEBRTC_TRACE(kTraceStateInfo, kTraceUtility, -1, "Loaded Kernel.dll");
     73 
     74   initialize_srw_lock =
     75     (InitializeSRWLock)GetProcAddress(library, "InitializeSRWLock");
     76 
     77   acquire_srw_lock_exclusive =
     78     (AcquireSRWLockExclusive)GetProcAddress(library,
     79                                             "AcquireSRWLockExclusive");
     80   release_srw_lock_exclusive =
     81     (ReleaseSRWLockExclusive)GetProcAddress(library,
     82                                             "ReleaseSRWLockExclusive");
     83   acquire_srw_lock_shared =
     84     (AcquireSRWLockShared)GetProcAddress(library, "AcquireSRWLockShared");
     85   release_srw_lock_shared =
     86     (ReleaseSRWLockShared)GetProcAddress(library, "ReleaseSRWLockShared");
     87 
     88   if (initialize_srw_lock && acquire_srw_lock_exclusive &&
     89       release_srw_lock_exclusive && acquire_srw_lock_shared &&
     90       release_srw_lock_shared) {
     91     WEBRTC_TRACE(kTraceStateInfo, kTraceUtility, -1, "Loaded Native RW Lock");
     92     native_rw_locks_supported = true;
     93   }
     94   return native_rw_locks_supported;
     95 }
     96 
     97 }  // namespace webrtc
     98