[Blob] BlobReader class & tests, and removal of all redundant reading.

net/base/upload_disk_cache_entry_element_reader.h

-// Copyright 2015 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 NET_BASE_UPLOAD_DISK_CACHE_ENTRY_ELEMENT_READER_H_
-#define NET_BASE_UPLOAD_DISK_CACHE_ENTRY_ELEMENT_READER_H_
-
-#include "base/basictypes.h"
-#include "base/compiler_specific.h"
-#include "base/memory/weak_ptr.h"
-#include "net/base/completion_callback.h"
-#include "net/base/net_export.h"
-#include "net/base/upload_element_reader.h"
-
-namespace disk_cache {
-class Entry;
-}
-
-namespace net {
-
-// An UploadElementReader implementation for disk_cache::Entry objects. The
-// caller keeps ownership of |disk_cache_entry|, and is responsible for ensuring
-// it outlives the UploadDiskCacheEntryElementReader.
-class NET_EXPORT UploadDiskCacheEntryElementReader
-    : public UploadElementReader {
- public:
-  // Construct a new UploadDiskCacheEntryElementReader which reads from the disk
-  // cache entry |disk_cache_entry| with stream index |disk_cache_stream_index|.
-  // The new upload reader object will read |range_length| bytes, starting from
-  // |range_offset|. To read an whole cache entry give a 0 as |range_offset| and
-  // provide the length of the entry's stream as |range_length|.
-  UploadDiskCacheEntryElementReader(disk_cache::Entry* disk_cache_entry,
-                                    int disk_cache_stream_index,
-                                    int range_offset,
-                                    int range_length);
-  ~UploadDiskCacheEntryElementReader() override;
-
-  int range_offset_for_tests() const { return range_begin_offset_; }
-  int range_length_for_tests() const {
-    return range_end_offset_ - range_begin_offset_;
-  }
-
-  // UploadElementReader overrides:
-  const UploadDiskCacheEntryElementReader* AsDiskCacheEntryReaderForTests()
-      const override;
-  int Init(const CompletionCallback& callback) override;
-  uint64_t GetContentLength() const override;
-  uint64_t BytesRemaining() const override;
-  bool IsInMemory() const override;
-  int Read(IOBuffer* buf,
-           int buf_length,
-           const CompletionCallback& callback) override;
-
- private:
-  void OnReadCompleted(const CompletionCallback& callback, int result);
-
-  disk_cache::Entry* const disk_cache_entry_;
-  const int disk_cache_stream_index_;
-
-  const int range_begin_offset_;
-  const int range_end_offset_;
-
-  int current_read_offset_;
-
-  base::WeakPtrFactory<UploadDiskCacheEntryElementReader> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(UploadDiskCacheEntryElementReader);
-};
-
-}  // namespace net
-
-#endif  // NET_BASE_UPLOAD_DISK_CACHE_ENTRY_ELEMENT_READER_H_