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_t* 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  E :  bool MsfFileStreamImpl<T>::ReadBytesAt(size_t pos, size_t count, void* dest) {
  46  E :    DCHECK(dest != NULL);
  47    :  
  48    :    // Don't read beyond the end of the known stream length.
  49  E :    if (count > length() - pos)
  50  E :      return false;
  51    :  
  52    :    // Read the stream.
  53  E :    while (count > 0) {
  54  E :      size_t page_index = pos / page_size_;
  55  E :      size_t offset = pos % page_size_;
  56  E :      size_t chunk_size = std::min(count, page_size_ - (pos % page_size_));
  57  E :      if (!ReadFromPage(dest, pages_[page_index], offset, chunk_size))
  58  i :        return false;
  59    :  
  60  E :      count -= chunk_size;
  61  E :      pos += chunk_size;
  62  E :      dest = reinterpret_cast<uint8_t*>(dest) + chunk_size;
  63  E :    }
  64    :  
  65  E :    return true;
  66  E :  }
  67    :  
  68    :  template <MsfFileType T>
  69    :  bool MsfFileStreamImpl<T>::ReadFromPage(void* dest,
  70    :                                          uint32_t page_num,
  71    :                                          size_t offset,
  72  E :                                          size_t count) {
  73  E :    DCHECK(dest != NULL);
  74  E :    DCHECK(offset + count <= page_size_);
  75    :  
  76  E :    size_t page_offset = page_size_ * page_num;
  77    :    if (fseek(file_->file(),
  78    :              static_cast<long>(page_offset + offset),
  79  E :              SEEK_SET) != 0) {
  80  i :      LOG(ERROR) << "Page seek failed";
  81  i :      return false;
  82    :    }
  83    :  
  84  E :    if (fread(dest, 1, count, file_->file()) != static_cast<size_t>(count)) {
  85  i :      LOG(ERROR) << "Page read failed";
  86  i :      return false;
  87    :    }
  88    :  
  89  E :    return true;
  90  E :  }
  91    :  
  92    :  }  // namespace detail
  93    :  }  // namespace msf
  94    :  
  95    :  #endif  // SYZYGY_MSF_MSF_FILE_STREAM_IMPL_H_