1 /* 2 * Copyright (C) 2015 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_LIBELFFILE_STREAM_ERROR_DELAYING_OUTPUT_STREAM_H_ 18 #define ART_LIBELFFILE_STREAM_ERROR_DELAYING_OUTPUT_STREAM_H_ 19 20 #include "output_stream.h" 21 22 #include <android-base/logging.h> 23 24 #include "base/macros.h" 25 26 namespace art { 27 28 // OutputStream wrapper that delays reporting an error until Flush(). 29 class ErrorDelayingOutputStream final : public OutputStream { 30 public: ErrorDelayingOutputStream(OutputStream * output)31 explicit ErrorDelayingOutputStream(OutputStream* output) 32 : OutputStream(output->GetLocation()), 33 output_(output), 34 output_good_(true), 35 output_offset_(0) { } 36 37 // This function always succeeds to simplify code. 38 // Use Good() to check the actual status of the output stream. WriteFully(const void * buffer,size_t byte_count)39 bool WriteFully(const void* buffer, size_t byte_count) override { 40 if (output_good_) { 41 if (!output_->WriteFully(buffer, byte_count)) { 42 PLOG(ERROR) << "Failed to write " << byte_count 43 << " bytes to " << GetLocation() << " at offset " << output_offset_; 44 output_good_ = false; 45 } 46 } 47 output_offset_ += byte_count; 48 return true; 49 } 50 51 // This function always succeeds to simplify code. 52 // Use Good() to check the actual status of the output stream. Seek(off_t offset,Whence whence)53 off_t Seek(off_t offset, Whence whence) override { 54 // We keep shadow copy of the offset so that we return 55 // the expected value even if the output stream failed. 56 off_t new_offset; 57 switch (whence) { 58 case kSeekSet: 59 new_offset = offset; 60 break; 61 case kSeekCurrent: 62 new_offset = output_offset_ + offset; 63 break; 64 default: 65 LOG(FATAL) << "Unsupported seek type: " << whence; 66 UNREACHABLE(); 67 } 68 if (output_good_) { 69 off_t actual_offset = output_->Seek(offset, whence); 70 if (actual_offset == static_cast<off_t>(-1)) { 71 PLOG(ERROR) << "Failed to seek in " << GetLocation() << ". Offset=" << offset 72 << " whence=" << whence << " new_offset=" << new_offset; 73 output_good_ = false; 74 } 75 DCHECK_EQ(actual_offset, new_offset); 76 } 77 output_offset_ = new_offset; 78 return new_offset; 79 } 80 81 // Flush the output and return whether all operations have succeeded. 82 // Do nothing if we already have a pending error. Flush()83 bool Flush() override { 84 if (output_good_) { 85 output_good_ = output_->Flush(); 86 } 87 return output_good_; 88 } 89 90 // Check (without flushing) whether all operations have succeeded so far. Good()91 bool Good() const { 92 return output_good_; 93 } 94 95 private: 96 OutputStream* output_; 97 bool output_good_; // True if all writes to output succeeded. 98 off_t output_offset_; // Keep track of the current position in the stream. 99 }; 100 101 } // namespace art 102 103 #endif // ART_LIBELFFILE_STREAM_ERROR_DELAYING_OUTPUT_STREAM_H_ 104