1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  //
  15    :  // Internal implementation details for msf_file_stream.h. Not meant to be
  16    :  // included directly.
  17    :  
  18    :  #ifndef SYZYGY_MSF_MSF_FILE_STREAM_IMPL_H_
  19    :  #define SYZYGY_MSF_MSF_FILE_STREAM_IMPL_H_
  20    :  
  21    :  #include <algorithm>
  22    :  #include <cstdio>
  23    :  
  24    :  #include "base/logging.h"
  25    :  #include "syzygy/msf/msf_decl.h"
  26    :  
  27    :  namespace msf {
  28    :  namespace detail {
  29    :  
  30    :  template <MsfFileType T>
  31    :  MsfFileStreamImpl<T>::MsfFileStreamImpl(RefCountedFILE* file,
  32    :                                          size_t length,
  33    :                                          const uint32* pages,
  34    :                                          size_t page_size)
  35  E :      : MsfStreamImpl(length), file_(file), page_size_(page_size) {
  36  E :    size_t num_pages = (length + page_size - 1) / page_size;
  37  E :    pages_.assign(pages, pages + num_pages);
  38  E :  }
  39    :  
  40    :  template <MsfFileType T>
  41  E :  MsfFileStreamImpl<T>::~MsfFileStreamImpl() {
  42  E :  }
  43    :  
  44    :  template <MsfFileType T>
  45    :  bool MsfFileStreamImpl<T>::ReadBytes(void* dest,
  46    :                                       size_t count,
  47  E :                                       size_t* bytes_read) {
  48  E :    DCHECK(dest != NULL);
  49  E :    DCHECK(bytes_read != NULL);
  50    :  
  51    :    // Return 0 once we've reached the end of the stream.
  52  E :    if (pos() == length()) {
  53  i :      *bytes_read = 0;
  54  i :      return true;
  55    :    }
  56    :  
  57    :    // Don't read beyond the end of the known stream length.
  58  E :    count = std::min(count, length() - pos());
  59  E :    *bytes_read = count;
  60    :  
  61    :    // Read the stream.
  62  E :    while (count > 0) {
  63  E :      size_t page_index = pos() / page_size_;
  64  E :      size_t offset = pos() % page_size_;
  65  E :      size_t chunk_size = std::min(count, page_size_ - (pos() % page_size_));
  66  E :      if (!ReadFromPage(dest, pages_[page_index], offset, chunk_size))
  67  i :        return false;
  68    :  
  69  E :      count -= chunk_size;
  70  E :      Seek(pos() + chunk_size);
  71  E :      dest = reinterpret_cast<uint8*>(dest) + chunk_size;
  72  E :    }
  73    :  
  74  E :    return true;
  75  E :  }
  76    :  
  77    :  template <MsfFileType T>
  78    :  bool MsfFileStreamImpl<T>::ReadFromPage(void* dest,
  79    :                                          uint32 page_num,
  80    :                                          size_t offset,
  81  E :                                          size_t count) {
  82  E :    DCHECK(dest != NULL);
  83  E :    DCHECK(offset + count <= page_size_);
  84    :  
  85  E :    size_t page_offset = page_size_ * page_num;
  86  E :    if (fseek(file_->file(), page_offset + offset, SEEK_SET) != 0) {
  87  i :      LOG(ERROR) << "Page seek failed";
  88  i :      return false;
  89    :    }
  90    :  
  91  E :    if (fread(dest, 1, count, file_->file()) != static_cast<size_t>(count)) {
  92  i :      LOG(ERROR) << "Page read failed";
  93  i :      return false;
  94    :    }
  95    :  
  96  E :    return true;
  97  E :  }
  98    :  
  99    :  }  // namespace detail
 100    :  }  // namespace msf
 101    :  
 102    :  #endif  // SYZYGY_MSF_MSF_FILE_STREAM_IMPL_H_