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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/memory/platform_shared_memory_mapper.h"
#include <aclapi.h>
#include "base/compiler_specific.h"
#include "base/logging.h"
#include "partition_alloc/page_allocator.h"
namespace base {
namespace {
// Returns the length of the memory section starting at the supplied address.
size_t GetMemorySectionSize(void* address) {
MEMORY_BASIC_INFORMATION memory_info;
if (!::VirtualQuery(address, &memory_info, sizeof(memory_info))) {
return 0;
}
return memory_info.RegionSize -
static_cast<size_t>(static_cast<char*>(address) -
static_cast<char*>(memory_info.AllocationBase));
}
} // namespace
std::optional<span<uint8_t>> PlatformSharedMemoryMapper::Map(
subtle::PlatformSharedMemoryHandle handle,
bool write_allowed,
uint64_t offset,
size_t size) {
// Try to map the shared memory. On the first failure, release any reserved
// address space for a single retry.
void* address;
for (int i = 0; i < 2; ++i) {
address = MapViewOfFile(
handle, FILE_MAP_READ | (write_allowed ? FILE_MAP_WRITE : 0),
static_cast<DWORD>(offset >> 32), static_cast<DWORD>(offset), size);
if (address) {
break;
}
partition_alloc::ReleaseReservation();
}
if (!address) {
DPLOG(ERROR) << "Failed executing MapViewOfFile";
return std::nullopt;
}
return UNSAFE_TODO(
span(static_cast<uint8_t*>(address), GetMemorySectionSize(address)));
}
void PlatformSharedMemoryMapper::Unmap(span<uint8_t> mapping) {
if (!UnmapViewOfFile(mapping.data())) {
DPLOG(ERROR) << "UnmapViewOfFile";
}
}
} // namespace base
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