/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "utils/memory/mmap.h"
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#include <errno.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "utils/base/logging.h"
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#include "utils/base/macros.h"
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namespace libtextclassifier3 {
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namespace {
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inline std::string GetLastSystemError() { return std::string(strerror(errno)); }
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inline MmapHandle GetErrorMmapHandle() { return MmapHandle(nullptr, 0); }
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class FileCloser {
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public:
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explicit FileCloser(int fd) : fd_(fd) {}
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~FileCloser() {
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int result = close(fd_);
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if (result != 0) {
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const std::string last_error = GetLastSystemError();
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TC3_LOG(ERROR) << "Error closing file descriptor: " << last_error;
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}
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}
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private:
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const int fd_;
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TC3_DISALLOW_COPY_AND_ASSIGN(FileCloser);
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};
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} // namespace
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MmapHandle MmapFile(const std::string &filename) {
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int fd = open(filename.c_str(), O_RDONLY);
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if (fd < 0) {
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const std::string last_error = GetLastSystemError();
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TC3_LOG(ERROR) << "Error opening " << filename << ": " << last_error;
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return GetErrorMmapHandle();
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}
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// Make sure we close fd no matter how we exit this function. As the man page
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// for mmap clearly states: "closing the file descriptor does not unmap the
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// region." Hence, we can close fd as soon as we return from here.
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FileCloser file_closer(fd);
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return MmapFile(fd);
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}
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MmapHandle MmapFile(int fd) {
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// Get file stats to obtain file size.
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struct stat sb;
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if (fstat(fd, &sb) != 0) {
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const std::string last_error = GetLastSystemError();
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TC3_LOG(ERROR) << "Unable to stat fd: " << last_error;
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return GetErrorMmapHandle();
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}
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return MmapFile(fd, /*segment_offset=*/0, /*segment_size=*/sb.st_size);
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}
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MmapHandle MmapFile(int fd, int64 segment_offset, int64 segment_size) {
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static const int64 kPageSize = sysconf(_SC_PAGE_SIZE);
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const int64 aligned_offset = (segment_offset / kPageSize) * kPageSize;
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const int64 alignment_shift = segment_offset - aligned_offset;
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const int64 aligned_length = segment_size + alignment_shift;
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// Perform actual mmap.
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void *mmap_addr = mmap(
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// Let system pick address for mmapp-ed data.
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nullptr,
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aligned_length,
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// One can read / write the mapped data (but see MAP_PRIVATE below).
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// Normally, we expect only to read it, but in the future, we may want to
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// write it, to fix e.g., endianness differences.
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PROT_READ | PROT_WRITE,
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// Updates to mmaped data are *not* propagated to actual file.
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// AFAIK(salcianu) that's anyway not possible on Android.
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MAP_PRIVATE,
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// Descriptor of file to mmap.
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fd,
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aligned_offset);
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if (mmap_addr == MAP_FAILED) {
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const std::string last_error = GetLastSystemError();
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TC3_LOG(ERROR) << "Error while mmapping: " << last_error;
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return GetErrorMmapHandle();
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}
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return MmapHandle(static_cast<char *>(mmap_addr) + alignment_shift,
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segment_size, /*unmap_addr=*/mmap_addr);
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}
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bool Unmap(MmapHandle mmap_handle) {
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if (!mmap_handle.ok()) {
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// Unmapping something that hasn't been mapped is trivially successful.
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return true;
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}
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if (munmap(mmap_handle.unmap_addr(), mmap_handle.num_bytes()) != 0) {
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const std::string last_error = GetLastSystemError();
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TC3_LOG(ERROR) << "Error during Unmap / munmap: " << last_error;
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return false;
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}
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return true;
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}
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} // namespace libtextclassifier3
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