1 /* 2 * Copyright (C) 2016 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 #pragma once 18 19 #include <string> 20 #include "android-base/off64_t.h" 21 22 namespace android { 23 24 // InputStream interface that mimics protobuf's ZeroCopyInputStream, 25 // with added error handling methods to better report issues. 26 class InputStream { 27 public: 28 virtual ~InputStream() = default; 29 30 // Returns a chunk of data for reading. data and size must not be nullptr. 31 // Returns true so long as there is more data to read, returns false if an error occurred 32 // or no data remains. If an error occurred, check HadError(). 33 // The stream owns the buffer returned from this method and the buffer is invalidated 34 // anytime another mutable method is called. 35 virtual bool Next(const void** data, size_t* size) = 0; 36 37 // Backup count bytes, where count is smaller or equal to the size of the last buffer returned 38 // from Next(). 39 // Useful when the last block returned from Next() wasn't fully read. 40 virtual void BackUp(size_t count) = 0; 41 42 // Returns true if this InputStream can rewind. If so, Rewind() can be called. CanRewind()43 virtual bool CanRewind() const { 44 return false; 45 }; 46 47 // Rewinds the stream to the beginning so it can be read again. 48 // Returns true if the rewind succeeded. 49 // This does nothing if CanRewind() returns false. Rewind()50 virtual bool Rewind() { 51 return false; 52 } 53 54 // Returns the number of bytes that have been read from the stream. 55 virtual size_t ByteCount() const = 0; 56 57 // Returns an error message if HadError() returned true. GetError()58 virtual std::string GetError() const { 59 return {}; 60 } 61 62 // Returns true if an error occurred. Errors are permanent. 63 virtual bool HadError() const = 0; 64 ReadFullyAtOffset(void * data,size_t byte_count,off64_t offset)65 virtual bool ReadFullyAtOffset(void* data, size_t byte_count, off64_t offset) { 66 (void)data; 67 (void)byte_count; 68 (void)offset; 69 return false; 70 } 71 }; 72 73 // A sub-InputStream interface that knows the total size of its stream. 74 class KnownSizeInputStream : public InputStream { 75 public: 76 virtual size_t TotalSize() const = 0; 77 }; 78 79 // OutputStream interface that mimics protobuf's ZeroCopyOutputStream, 80 // with added error handling methods to better report issues. 81 class OutputStream { 82 public: 83 virtual ~OutputStream() = default; 84 85 // Returns a buffer to which data can be written to. The data written to this buffer will 86 // eventually be written to the stream. Call BackUp() if the data written doesn't occupy the 87 // entire buffer. 88 // Return false if there was an error. 89 // The stream owns the buffer returned from this method and the buffer is invalidated 90 // anytime another mutable method is called. 91 virtual bool Next(void** data, size_t* size) = 0; 92 93 // Backup count bytes, where count is smaller or equal to the size of the last buffer returned 94 // from Next(). 95 // Useful for when the last block returned from Next() wasn't fully written to. 96 virtual void BackUp(size_t count) = 0; 97 98 // Returns the number of bytes that have been written to the stream. 99 virtual size_t ByteCount() const = 0; 100 101 // Returns an error message if HadError() returned true. GetError()102 virtual std::string GetError() const { 103 return {}; 104 } 105 106 // Returns true if an error occurred. Errors are permanent. 107 virtual bool HadError() const = 0; 108 }; 109 110 } // namespace android