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//= llvm/Support/Win32/Mutex.inc - Win32 Reader/Writer Mutual Exclusion Lock =//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the Win32 specific (non-pthread) RWMutex class.
//
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
//=== WARNING: Implementation here must contain only generic Win32 code that
//=== is guaranteed to work on *all* Win32 variants.
//===----------------------------------------------------------------------===//
#include "WindowsSupport.h"
namespace llvm {
// Windows has slim read-writer lock support on Vista and higher, so we
// will attempt to load the APIs. If they exist, we will use them, and
// if not, we will fall back on critical sections. When we drop support
// for XP, we can stop lazy-loading these APIs and just use them directly.
#if defined(__MINGW32__)
// Taken from WinNT.h
typedef struct _RTL_SRWLOCK {
PVOID Ptr;
} RTL_SRWLOCK, *PRTL_SRWLOCK;
// Taken from WinBase.h
typedef RTL_SRWLOCK SRWLOCK, *PSRWLOCK;
#endif
static VOID (WINAPI *fpInitializeSRWLock)(PSRWLOCK lock) = NULL;
static VOID (WINAPI *fpAcquireSRWLockExclusive)(PSRWLOCK lock) = NULL;
static VOID (WINAPI *fpAcquireSRWLockShared)(PSRWLOCK lock) = NULL;
static VOID (WINAPI *fpReleaseSRWLockExclusive)(PSRWLOCK lock) = NULL;
static VOID (WINAPI *fpReleaseSRWLockShared)(PSRWLOCK lock) = NULL;
static bool sHasSRW = false;
static bool loadSRW() {
static bool sChecked = false;
if (!sChecked) {
sChecked = true;
if (HMODULE hLib = ::GetModuleHandleW(L"Kernel32.dll")) {
fpInitializeSRWLock =
(VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
"InitializeSRWLock");
fpAcquireSRWLockExclusive =
(VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
"AcquireSRWLockExclusive");
fpAcquireSRWLockShared =
(VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
"AcquireSRWLockShared");
fpReleaseSRWLockExclusive =
(VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
"ReleaseSRWLockExclusive");
fpReleaseSRWLockShared =
(VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
"ReleaseSRWLockShared");
if (fpInitializeSRWLock != NULL) {
sHasSRW = true;
}
}
}
return sHasSRW;
}
sys::RWMutexImpl::RWMutexImpl() {
if (loadSRW()) {
data_ = safe_calloc(1, sizeof(SRWLOCK));
fpInitializeSRWLock(static_cast<PSRWLOCK>(data_));
} else {
data_ = safe_calloc(1, sizeof(CRITICAL_SECTION));
InitializeCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
}
}
sys::RWMutexImpl::~RWMutexImpl() {
if (!sHasSRW)
DeleteCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
// Nothing to do in the case of slim reader/writers except free the memory.
free(data_);
}
bool sys::RWMutexImpl::reader_acquire() {
if (sHasSRW) {
fpAcquireSRWLockShared(static_cast<PSRWLOCK>(data_));
} else {
EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
}
return true;
}
bool sys::RWMutexImpl::reader_release() {
if (sHasSRW) {
fpReleaseSRWLockShared(static_cast<PSRWLOCK>(data_));
} else {
LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
}
return true;
}
bool sys::RWMutexImpl::writer_acquire() {
if (sHasSRW) {
fpAcquireSRWLockExclusive(static_cast<PSRWLOCK>(data_));
} else {
EnterCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
}
return true;
}
bool sys::RWMutexImpl::writer_release() {
if (sHasSRW) {
fpReleaseSRWLockExclusive(static_cast<PSRWLOCK>(data_));
} else {
LeaveCriticalSection(static_cast<LPCRITICAL_SECTION>(data_));
}
return true;
}
}
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