Revert of [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