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

net/base/upload_disk_cache_entry_element_reader.cc

-// 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.
-
-#include "net/base/upload_disk_cache_entry_element_reader.h"
-
-#include <algorithm>
-
-#include "base/bind.h"
-#include "base/logging.h"
-#include "net/base/io_buffer.h"
-#include "net/base/net_errors.h"
-#include "net/disk_cache/disk_cache.h"
-
-namespace net {
-
-UploadDiskCacheEntryElementReader::UploadDiskCacheEntryElementReader(
-    disk_cache::Entry* disk_cache_entry,
-    int disk_cache_stream_index,
-    int range_offset,
-    int range_length)
-    : disk_cache_entry_(disk_cache_entry),
-      disk_cache_stream_index_(disk_cache_stream_index),
-      range_begin_offset_(range_offset),
-      range_end_offset_(range_offset + range_length),
-      current_read_offset_(range_offset),
-      weak_factory_(this) {
-  DCHECK_LE(0, range_offset);
-  DCHECK_LT(0, range_length);
-  DCHECK_LE(range_offset + range_length,
-            disk_cache_entry_->GetDataSize(disk_cache_stream_index_));
-}
-
-UploadDiskCacheEntryElementReader::~UploadDiskCacheEntryElementReader() {
-}
-
-const UploadDiskCacheEntryElementReader*
-UploadDiskCacheEntryElementReader::AsDiskCacheEntryReaderForTests() const {
-  return this;
-}
-
-int UploadDiskCacheEntryElementReader::Init(
-    const CompletionCallback& callback) {
-  weak_factory_.InvalidateWeakPtrs();
-  current_read_offset_ = range_begin_offset_;
-  return OK;
-}
-
-uint64_t UploadDiskCacheEntryElementReader::GetContentLength() const {
-  return range_end_offset_ - range_begin_offset_;
-}
-
-uint64_t UploadDiskCacheEntryElementReader::BytesRemaining() const {
-  return range_end_offset_ - current_read_offset_;
-}
-
-bool UploadDiskCacheEntryElementReader::IsInMemory() const {
-  return false;
-}
-
-int UploadDiskCacheEntryElementReader::Read(
-    IOBuffer* buf,
-    int buf_length,
-    const CompletionCallback& callback) {
-  DCHECK(!callback.is_null());
-  int bytes_to_read = std::min(buf_length, static_cast<int>(BytesRemaining()));
-
-  CompletionCallback new_callback =
-      base::Bind(&UploadDiskCacheEntryElementReader::OnReadCompleted,
-                 weak_factory_.GetWeakPtr(), callback);
-
-  int result = disk_cache_entry_->ReadData(disk_cache_stream_index_,
-                                           current_read_offset_, buf,
-                                           bytes_to_read, new_callback);
-  if (result == ERR_IO_PENDING)
-    return ERR_IO_PENDING;
-  if (result > 0)
-    current_read_offset_ += result;
-  return result;
-}
-
-void UploadDiskCacheEntryElementReader::OnReadCompleted(
-    const CompletionCallback& callback,
-    int result) {
-  if (result > 0)
-    current_read_offset_ += result;
-  callback.Run(result);
-}
-
-}  // namespace net