Revert "reland of Improve linearized pdf load/show time."

pdf/chunk_stream.cc

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "pdf/chunk_stream.h"
+
+#include <stddef.h>
+#include <string.h>
+
+#define __STDC_LIMIT_MACROS
+#ifdef _WIN32
+#include <limits.h>
+#else
+#include <stdint.h>
+#endif
+
+#include <algorithm>
+
+namespace chrome_pdf {
+
+ChunkStream::ChunkStream() : stream_size_(0) {
+}
+
+ChunkStream::~ChunkStream() {
+}
+
+void ChunkStream::Clear() {
+  chunks_.clear();
+  data_.clear();
+  stream_size_ = 0;
+}
+
+void ChunkStream::Preallocate(size_t stream_size) {
+  data_.reserve(stream_size);
+  stream_size_ = stream_size;
+}
+
+size_t ChunkStream::GetSize() const {
+  return data_.size();
+}
+
+bool ChunkStream::WriteData(size_t offset, void* buffer, size_t size) {
+  if (SIZE_MAX - size < offset)
+    return false;
+
+  if (data_.size() < offset + size)
+    data_.resize(offset + size);
+
+  memcpy(&data_[offset], buffer, size);
+
+  if (chunks_.empty()) {
+    chunks_[offset] = size;
+    return true;
+  }
+
+  std::map<size_t, size_t>::iterator start = chunks_.upper_bound(offset);
+  if (start != chunks_.begin())
+    --start;  // start now points to the key equal or lower than offset.
+  if (start->first + start->second < offset)
+    ++start;  // start element is entirely before current chunk, skip it.
+
+  std::map<size_t, size_t>::iterator end = chunks_.upper_bound(offset + size);
+  if (start == end) {  // No chunks to merge.
+    chunks_[offset] = size;
+    return true;
+  }
+
+  --end;
+
+  size_t new_offset = std::min<size_t>(start->first, offset);
+  size_t new_size =
+      std::max<size_t>(end->first + end->second, offset + size) - new_offset;
+
+  chunks_.erase(start, ++end);
+
+  chunks_[new_offset] = new_size;
+
+  return true;
+}
+
+bool ChunkStream::ReadData(size_t offset, size_t size, void* buffer) const {
+  if (!IsRangeAvailable(offset, size))
+    return false;
+
+  memcpy(buffer, &data_[offset], size);
+  return true;
+}
+
+bool ChunkStream::GetMissedRanges(
+    size_t offset, size_t size,
+    std::vector<std::pair<size_t, size_t> >* ranges) const {
+  if (IsRangeAvailable(offset, size))
+    return false;
+
+  ranges->clear();
+  if (chunks_.empty()) {
+    ranges->push_back(std::pair<size_t, size_t>(offset, size));
+    return true;
+  }
+
+  std::map<size_t, size_t>::const_iterator start = chunks_.upper_bound(offset);
+  if (start != chunks_.begin())
+    --start;  // start now points to the key equal or lower than offset.
+  if (start->first + start->second < offset)
+    ++start;  // start element is entirely before current chunk, skip it.
+
+  std::map<size_t, size_t>::const_iterator end =
+      chunks_.upper_bound(offset + size);
+  if (start == end) {  // No data in the current range available.
+    ranges->push_back(std::pair<size_t, size_t>(offset, size));
+    return true;
+  }
+
+  size_t cur_offset = offset;
+  std::map<size_t, size_t>::const_iterator it;
+  for (it = start; it != end; ++it) {
+    if (cur_offset < it->first) {
+      size_t new_size = it->first - cur_offset;
+      ranges->push_back(std::pair<size_t, size_t>(cur_offset, new_size));
+      cur_offset = it->first + it->second;
+    } else if (cur_offset < it->first + it->second) {
+      cur_offset = it->first + it->second;
+    }
+  }
+
+  // Add last chunk.
+  if (cur_offset < offset + size)
+    ranges->push_back(std::pair<size_t, size_t>(cur_offset,
+        offset + size - cur_offset));
+
+  return true;
+}
+
+bool ChunkStream::IsRangeAvailable(size_t offset, size_t size) const {
+  if (chunks_.empty())
+    return false;
+
+  if (SIZE_MAX - size < offset)
+    return false;
+
+  std::map<size_t, size_t>::const_iterator it = chunks_.upper_bound(offset);
+  if (it == chunks_.begin())
+    return false;  // No chunks includes offset byte.
+
+  --it;  // Now it starts equal or before offset.
+  return (it->first + it->second) >= (offset + size);
+}
+
+size_t ChunkStream::GetFirstMissingByte() const {
+  if (chunks_.empty())
+    return 0;
+  std::map<size_t, size_t>::const_iterator begin = chunks_.begin();
+  return begin->first > 0 ? 0 : begin->second;
+}
+
+size_t ChunkStream::GetFirstMissingByteInInterval(size_t offset) const {
+  if (chunks_.empty())
+    return 0;
+  std::map<size_t, size_t>::const_iterator it = chunks_.upper_bound(offset);
+  if (it == chunks_.begin())
+    return 0;
+  --it;
+  return it->first + it->second;
+}
+
+size_t ChunkStream::GetLastMissingByteInInterval(size_t offset) const {
+  if (chunks_.empty())
+    return stream_size_ - 1;
+  std::map<size_t, size_t>::const_iterator it = chunks_.upper_bound(offset);
+  if (it == chunks_.end())
+    return stream_size_ - 1;
+  return it->first - 1;
+}
+
+}  // namespace chrome_pdf