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// Copyright (c) 2011 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/memory/shared_memory.h"
#include <stddef.h>
#include <sys/mman.h>
#include "base/logging.h"
#include "third_party/ashmem/ashmem.h"
namespace base {
// For Android, we use ashmem to implement SharedMemory. ashmem_create_region
// will automatically pin the region. We never explicitly call pin/unpin. When
// all the file descriptors from different processes associated with the region
// are closed, the memory buffer will go away.
bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
DCHECK_EQ(-1, mapped_file_ );
if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
return false;
// "name" is just a label in ashmem. It is visible in /proc/pid/maps.
mapped_file_ = ashmem_create_region(
options.name_deprecated == NULL ? "" : options.name_deprecated->c_str(),
options.size);
if (-1 == mapped_file_) {
DLOG(ERROR) << "Shared memory creation failed";
return false;
}
int err = ashmem_set_prot_region(mapped_file_,
PROT_READ | PROT_WRITE | PROT_EXEC);
if (err < 0) {
DLOG(ERROR) << "Error " << err << " when setting protection of ashmem";
return false;
}
// Android doesn't appear to have a way to drop write access on an ashmem
// segment for a single descriptor. http://crbug.com/320865
readonly_mapped_file_ = dup(mapped_file_);
if (-1 == readonly_mapped_file_) {
DPLOG(ERROR) << "dup() failed";
return false;
}
requested_size_ = options.size;
return true;
}
bool SharedMemory::Delete(const std::string& name) {
// Like on Windows, this is intentionally returning true as ashmem will
// automatically releases the resource when all FDs on it are closed.
return true;
}
bool SharedMemory::Open(const std::string& name, bool read_only) {
// ashmem doesn't support name mapping
NOTIMPLEMENTED();
return false;
}
} // namespace base
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