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