| /* |
| * Copyright (C) 2017 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 "common/mmap.h" |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <stdint.h> |
| #include <string.h> |
| #include <sys/mman.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| #include "util/base/logging.h" |
| #include "util/base/macros.h" |
| |
| namespace libtextclassifier { |
| namespace nlp_core { |
| |
| namespace { |
| inline std::string GetLastSystemError() { |
| return std::string(strerror(errno)); |
| } |
| |
| inline MmapHandle GetErrorMmapHandle() { |
| return MmapHandle(nullptr, 0); |
| } |
| |
| class FileCloser { |
| public: |
| explicit FileCloser(int fd) : fd_(fd) {} |
| ~FileCloser() { |
| int result = close(fd_); |
| if (result != 0) { |
| const std::string last_error = GetLastSystemError(); |
| TC_LOG(ERROR) << "Error closing file descriptor: " << last_error; |
| } |
| } |
| private: |
| const int fd_; |
| |
| TC_DISALLOW_COPY_AND_ASSIGN(FileCloser); |
| }; |
| } // namespace |
| |
| MmapHandle MmapFile(const std::string &filename) { |
| int fd = open(filename.c_str(), O_RDONLY); |
| |
| if (fd < 0) { |
| const std::string last_error = GetLastSystemError(); |
| TC_LOG(ERROR) << "Error opening " << filename << ": " << last_error; |
| return GetErrorMmapHandle(); |
| } |
| |
| // Make sure we close fd no matter how we exit this function. As the man page |
| // for mmap clearly states: "closing the file descriptor does not unmap the |
| // region." Hence, we can close fd as soon as we return from here. |
| FileCloser file_closer(fd); |
| |
| return MmapFile(fd); |
| } |
| |
| MmapHandle MmapFile(int fd) { |
| // Get file stats to obtain file size. |
| struct stat sb; |
| if (fstat(fd, &sb) != 0) { |
| const std::string last_error = GetLastSystemError(); |
| TC_LOG(ERROR) << "Unable to stat fd: " << last_error; |
| return GetErrorMmapHandle(); |
| } |
| size_t file_size_in_bytes = static_cast<size_t>(sb.st_size); |
| |
| // Perform actual mmap. |
| void *mmap_addr = mmap( |
| |
| // Let system pick address for mmapp-ed data. |
| nullptr, |
| |
| // Mmap all bytes from the file. |
| file_size_in_bytes, |
| |
| // One can read / write the mapped data (but see MAP_PRIVATE below). |
| // Normally, we expect only to read it, but in the future, we may want to |
| // write it, to fix e.g., endianness differences. |
| PROT_READ | PROT_WRITE, |
| |
| // Updates to mmaped data are *not* propagated to actual file. |
| // AFAIK(salcianu) that's anyway not possible on Android. |
| MAP_PRIVATE, |
| |
| // Descriptor of file to mmap. |
| fd, |
| |
| // Map bytes right from the beginning of the file. This, and |
| // file_size_in_bytes (2nd argument) means we map all bytes from the file. |
| 0); |
| if (mmap_addr == MAP_FAILED) { |
| const std::string last_error = GetLastSystemError(); |
| TC_LOG(ERROR) << "Error while mmaping: " << last_error; |
| return GetErrorMmapHandle(); |
| } |
| |
| return MmapHandle(mmap_addr, file_size_in_bytes); |
| } |
| |
| bool Unmap(MmapHandle mmap_handle) { |
| if (!mmap_handle.ok()) { |
| // Unmapping something that hasn't been mapped is trivially successful. |
| return true; |
| } |
| if (munmap(mmap_handle.start(), mmap_handle.num_bytes()) != 0) { |
| const std::string last_error = GetLastSystemError(); |
| TC_LOG(ERROR) << "Error during Unmap / munmap: " << last_error; |
| return false; |
| } |
| return true; |
| } |
| |
| } // namespace nlp_core |
| } // namespace libtextclassifier |