1 /* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_ 18 #define ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_ 19 20 #include <stdint.h> 21 22 namespace unix_file { 23 24 // A file interface supporting random-access reading and writing of content, 25 // along with the ability to set the length of a file (smaller or greater than 26 // its current extent). 27 // 28 // This interface does not support a stream position (i.e. every read or write 29 // must specify an offset). This interface does not imply any buffering policy. 30 // 31 // All operations return >= 0 on success or -errno on failure. 32 // 33 // Implementations never return EINTR; callers are spared the need to manually 34 // retry interrupted operations. 35 // 36 // Any concurrent access to files should be externally synchronized. 37 class RandomAccessFile { 38 public: 39 virtual ~RandomAccessFile() { } 40 41 virtual int Close() = 0; 42 43 // Reads 'byte_count' bytes into 'buf' starting at offset 'offset' in the 44 // file. Returns the number of bytes actually read. 45 virtual int64_t Read(char* buf, int64_t byte_count, int64_t offset) const = 0; 46 47 // Sets the length of the file to 'new_length'. If this is smaller than the 48 // file's current extent, data is discarded. If this is greater than the 49 // file's current extent, it is as if a write of the relevant number of zero 50 // bytes occurred. Returns 0 on success. 51 virtual int SetLength(int64_t new_length) = 0; 52 53 // Returns the current size of this file. 54 virtual int64_t GetLength() const = 0; 55 56 // Writes 'byte_count' bytes from 'buf' starting at offset 'offset' in the 57 // file. Zero-byte writes are acceptable, and writes past the end are as if 58 // a write of the relevant number of zero bytes also occurred. Returns the 59 // number of bytes actually written. 60 virtual int64_t Write(const char* buf, int64_t byte_count, int64_t offset) = 0; 61 62 // Flushes file data. 63 virtual int Flush() = 0; 64 }; 65 66 } // namespace unix_file 67 68 #endif // ART_LIBARTBASE_BASE_UNIX_FILE_RANDOM_ACCESS_FILE_H_ 69
