Improve linearized pdf load/show time.

pdf/chunk_stream.h

 // 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.
 
 #ifndef PDF_CHUNK_STREAM_H_
 #define PDF_CHUNK_STREAM_H_
 
 #include <stddef.h>
+#include <string.h>
 
-#include <map>
-#include <utility>
+#include <algorithm>
+#include <array>
+#include <memory>
 #include <vector>
 
+#include "pdf/range_set.h"
+
 namespace chrome_pdf {
 
 // This class collects a chunks of data into one data stream. Client can check
 // if data in certain range is available, and get missing chunks of data.
+template <size_t N>
 class ChunkStream {
  public:
-  ChunkStream();
-  ~ChunkStream();
+  static const int kChunkSize = N;
+  typedef typename std::array<unsigned char, N> ChunkData;
 
-  void Clear();
+  ChunkStream() {}
+  ~ChunkStream() {}
 
-  void Preallocate(size_t stream_size);
-  size_t GetSize() const;
+  void SetChunkData(int chunk_index, std::unique_ptr<ChunkData> data) {
+    if (!data)
+      return;
+    if (chunk_index >= static_cast<int>(data_.size())) {
+      data_.resize(chunk_index + 1);
+    }
+    if (!data_[chunk_index]) {
+      ++filled_chunks_count_;
+    }
+    data_[chunk_index] = std::move(data);
+    filled_chunks_.Union(gfx::Range(chunk_index, chunk_index + 1));
+  }
 
-  bool WriteData(size_t offset, void* buffer, size_t size);
-  bool ReadData(size_t offset, size_t size, void* buffer) const;
+  bool ReadData(const gfx::Range& range, void* buffer) const {
+    if (!IsRangeAvailable(range)) {
+      return false;
+    }
+    unsigned char* data_buffer = static_cast<unsigned char*>(buffer);
+    uint32_t start = range.start();
+    while (start != range.end()) {
+      const uint32_t chunk_index = GetChunkIndex(start);
+      const uint32_t chunk_start = start % kChunkSize;
+      const uint32_t len =
+          std::min(kChunkSize - chunk_start, range.end() - start);
+      memcpy(data_buffer, data_[chunk_index]->data() + chunk_start, len);
+      data_buffer += len;
+      start += len;
+    }
+    return true;
+  }
 
-  // Returns vector of pairs where first is an offset, second is a size.
-  bool GetMissedRanges(size_t offset, size_t size,
-      std::vector<std::pair<size_t, size_t> >* ranges) const;
-  bool IsRangeAvailable(size_t offset, size_t size) const;
-  size_t GetFirstMissingByte() const;
+  uint32_t GetChunkIndex(uint32_t offset) const { return offset / kChunkSize; }
 
-  // Finds the first byte of the missing byte interval that offset belongs to.
-  size_t GetFirstMissingByteInInterval(size_t offset) const;
-  // Returns the last byte of the missing byte interval that offset belongs to.
-  size_t GetLastMissingByteInInterval(size_t offset) const;
+  gfx::Range GetChunksRange(uint32_t offset, uint32_t size) const {
+    return gfx::Range(GetChunkIndex(offset),
+                      GetChunkIndex(offset + size + kChunkSize - 1));
+  }
+
+  bool IsRangeAvailable(const gfx::Range& range) const {
+    if (!range.IsValid() || range.is_reversed() ||
+        (eof_pos_ && eof_pos_ < range.end()))

[spelchat, 2016/10/12 00:35:31]

I may be wrong (other reviewers, please correct me), but I think the preferred
style is eof_pos_ != 0 (i.e. don't use the implicit conversion from integer
types to bool).

[snake, 2016/10/14 11:31:17]

Done

+      return false;
+    if (range.is_empty())
+      return true;
+    const gfx::Range chunks_range(GetChunkIndex(range.start()),
+                                  GetChunkIndex(range.end() + kChunkSize - 1));
+    return filled_chunks_.Contains(chunks_range);
+  }
+
+  void set_eof_pos(uint32_t eof_pos) { eof_pos_ = eof_pos; }
+  uint32_t eof_pos() const { return eof_pos_; }
+
+  const RangeSet& filled_chunks() const { return filled_chunks_; }
+
+  bool IsComplete() const {
+    return eof_pos_ > 0 && IsRangeAvailable(gfx::Range(0, eof_pos_));
+  }
+
+  void Clear() {
+    data_.clear();
+    eof_pos_ = 0;
+    filled_chunks_.Clear();
+    filled_chunks_count_ = 0;
+  }
+
+  uint32_t filled_chunks_count() const { return filled_chunks_count_; }
+  uint32_t total_chunks_count() const {
+    return GetChunkIndex(eof_pos_ + kChunkSize - 1);
+  }
 
  private:
-  std::vector<unsigned char> data_;
-
-  // Pair, first - begining of the chunk, second - size of the chunk.
-  std::map<size_t, size_t> chunks_;
-
-  size_t stream_size_;
+  std::vector<std::unique_ptr<ChunkData>> data_;
+  uint32_t eof_pos_ = 0;
+  RangeSet filled_chunks_;
+  uint32_t filled_chunks_count_ = 0;
 };
 
 };  // namespace chrome_pdf
 
 #endif  // PDF_CHUNK_STREAM_H_