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// Copyright 2020 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include "base/EintrWrapper.h"
#include "base/SharedMemory.h"
#include "base/PathUtils.h"
#ifndef _MSC_VER
#include <unistd.h>
#endif
namespace android {
namespace base {
SharedMemory::SharedMemory(const std::string& name, size_t size) : mSize(size) {
const std::string& kFileUri = "file://";
if (name.find(kFileUri, 0) == 0) {
mShareType = ShareType::FILE_BACKED;
auto path = name.substr(kFileUri.size());
mName = PathUtils::recompose(PathUtils::decompose(std::move(path)));
} else {
mShareType = ShareType::SHARED_MEMORY;
mName = name;
}
}
int SharedMemory::create(mode_t mode) {
return openInternal(O_CREAT | O_RDWR, mode);
}
int SharedMemory::createNoMapping(mode_t mode) {
return openInternal(O_CREAT | O_RDWR, mode, false /* no mapping */);
}
int SharedMemory::open(AccessMode access) {
int oflag = O_RDONLY;
int mode = 0400;
if (access == AccessMode::READ_WRITE) {
oflag = O_RDWR;
mode = 0600;
}
return openInternal(oflag, mode);
}
void SharedMemory::close(bool forceDestroy) {
if (mAddr != unmappedMemory()) {
munmap(mAddr, mSize);
mAddr = unmappedMemory();
}
if (mFd) {
::close(mFd);
mFd = invalidHandle();
}
assert(!isOpen());
if (forceDestroy || mCreate) {
if (mShareType == ShareType::FILE_BACKED) {
remove(mName.c_str());
} else {
shm_unlink(mName.c_str());
}
}
}
bool SharedMemory::isOpen() const {
return mFd != invalidHandle();
}
int SharedMemory::openInternal(int oflag, int mode, bool doMapping) {
if (isOpen()) {
return EEXIST;
}
int err = 0;
struct stat sb;
if (mShareType == ShareType::SHARED_MEMORY) {
mFd = shm_open(mName.c_str(), oflag, mode);
} else {
mFd = ::open(mName.c_str(), oflag, mode);
// Make sure the file can hold at least mSize bytes..
struct stat stat;
if (!fstat(mFd, &stat) && stat.st_size < mSize) {
ftruncate(mFd, mSize);
}
}
if (mFd == -1) {
err = -errno;
close();
return err;
}
if (oflag & O_CREAT) {
if (HANDLE_EINTR(fstat(mFd, &sb)) == -1) {
err = -errno;
close();
return err;
}
// Only increase size, as we don't want to yank away memory
// from another process.
if (mSize > sb.st_size && HANDLE_EINTR(ftruncate(mFd, mSize)) == -1) {
err = -errno;
close();
return err;
}
}
if (doMapping) {
int mapFlags = PROT_READ;
if (oflag & O_RDWR || oflag & O_CREAT) {
mapFlags |= PROT_WRITE;
}
mAddr = mmap(nullptr, mSize, mapFlags, MAP_SHARED, mFd, 0);
if (mAddr == unmappedMemory()) {
err = -errno;
close();
return err;
}
}
mCreate |= (oflag & O_CREAT);
assert(isOpen());
return 0;
}
} // namespace base
} // namespace android
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