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shared_memory_win.cc

// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/shared_memory.h"

#include "base/logging.h"
#include "base/win_util.h"

namespace base {

SharedMemory::SharedMemory()
    : mapped_file_(NULL),
      memory_(NULL),
      read_only_(false),
      max_size_(0),
      lock_(NULL) {
}

SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only)
    : mapped_file_(handle),
      memory_(NULL),
      read_only_(read_only),
      max_size_(0),
      lock_(NULL) {
}

SharedMemory::SharedMemory(SharedMemoryHandle handle, bool read_only,
                           ProcessHandle process)
    : mapped_file_(NULL),
      memory_(NULL),
      read_only_(read_only),
      max_size_(0),
      lock_(NULL) {
  ::DuplicateHandle(process, handle,
                    GetCurrentProcess(), &mapped_file_,
                    STANDARD_RIGHTS_REQUIRED |
                    (read_only_ ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS),
                    FALSE, 0);
}

SharedMemory::~SharedMemory() {
  Close();
  if (lock_ != NULL)
    CloseHandle(lock_);
}

// static
bool SharedMemory::IsHandleValid(const SharedMemoryHandle& handle) {
  return handle != NULL;
}

// static
SharedMemoryHandle SharedMemory::NULLHandle() {
  return NULL;
}

// static
void SharedMemory::CloseHandle(const SharedMemoryHandle& handle) {
  DCHECK(handle != NULL);
  ::CloseHandle(handle);
}

bool SharedMemory::Create(const std::wstring &name, bool read_only,
                          bool open_existing, uint32 size) {
  DCHECK(mapped_file_ == NULL);

  // NaCl's memory allocator requires 0mod64K alignment and size for
  // shared memory objects.  To allow passing shared memory to NaCl,
  // therefore we round the size actually created to the nearest 64K unit.
  // To avoid client impact, we continue to retain the size as the
  // actual requested size.
  uint32 rounded_size = (size + 0xffff) & ~0xffff;
  name_ = name;
  read_only_ = read_only;
  mapped_file_ = CreateFileMapping(INVALID_HANDLE_VALUE, NULL,
      read_only_ ? PAGE_READONLY : PAGE_READWRITE, 0,
      static_cast<DWORD>(rounded_size),
      name.empty() ? NULL : name.c_str());
  if (!mapped_file_)
    return false;

  // Check if the shared memory pre-exists.
  if (GetLastError() == ERROR_ALREADY_EXISTS && !open_existing) {
    Close();
    return false;
  }
  max_size_ = size;
  return true;
}

bool SharedMemory::Delete(const std::wstring& name) {
  // intentionally empty -- there is nothing for us to do on Windows.
  return true;
}

bool SharedMemory::Open(const std::wstring &name, bool read_only) {
  DCHECK(mapped_file_ == NULL);

  name_ = name;
  read_only_ = read_only;
  mapped_file_ = OpenFileMapping(
      read_only_ ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS, false,
      name.empty() ? NULL : name.c_str());
  if (mapped_file_ != NULL) {
    // Note: size_ is not set in this case.
    return true;
  }
  return false;
}

bool SharedMemory::Map(uint32 bytes) {
  if (mapped_file_ == NULL)
    return false;

  memory_ = MapViewOfFile(mapped_file_,
      read_only_ ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS, 0, 0, bytes);
  if (memory_ != NULL) {
    return true;
  }
  return false;
}

bool SharedMemory::Unmap() {
  if (memory_ == NULL)
    return false;

  UnmapViewOfFile(memory_);
  memory_ = NULL;
  return true;
}

bool SharedMemory::ShareToProcessCommon(ProcessHandle process,
                                        SharedMemoryHandle *new_handle,
                                        bool close_self) {
  *new_handle = 0;
  DWORD access = STANDARD_RIGHTS_REQUIRED | FILE_MAP_READ;
  DWORD options = 0;
  HANDLE mapped_file = mapped_file_;
  HANDLE result;
  if (!read_only_)
    access |= FILE_MAP_WRITE;
  if (close_self) {
    // DUPLICATE_CLOSE_SOURCE causes DuplicateHandle to close mapped_file.
    options = DUPLICATE_CLOSE_SOURCE;
    mapped_file_ = NULL;
    Unmap();
  }

  if (process == GetCurrentProcess() && close_self) {
    *new_handle = mapped_file;
    return true;
  }

  if (!DuplicateHandle(GetCurrentProcess(), mapped_file, process,
      &result, access, FALSE, options))
    return false;
  *new_handle = result;
  return true;
}


void SharedMemory::Close() {
  if (memory_ != NULL) {
    UnmapViewOfFile(memory_);
    memory_ = NULL;
  }

  if (mapped_file_ != NULL) {
    CloseHandle(mapped_file_);
    mapped_file_ = NULL;
  }
}

void SharedMemory::Lock() {
  if (lock_ == NULL) {
    std::wstring name = name_;
    name.append(L"lock");
    lock_ = CreateMutex(NULL, FALSE, name.c_str());
    DCHECK(lock_ != NULL);
    if (lock_ == NULL) {
      DLOG(ERROR) << "Could not create mutex" << GetLastError();
      return;  // there is nothing good we can do here.
    }
  }
  WaitForSingleObject(lock_, INFINITE);
}

void SharedMemory::Unlock() {
  DCHECK(lock_ != NULL);
  ReleaseMutex(lock_);
}

SharedMemoryHandle SharedMemory::handle() const {
  return mapped_file_;
}

}  // namespace base

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