Create blobs from Disk Cache entries.

storage/browser/blob/blob_url_request_job.cc

 // Copyright (c) 2012 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 "storage/browser/blob/blob_url_request_job.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 #include <vector>
@@ skipping 333 matching lines @@
   }
 
   // Do the reading.
   const BlobDataItem& item = *items.at(current_item_index_);
   if (item.type() == DataElement::TYPE_BYTES)
     return ReadBytesItem(item, bytes_to_read);
   if (IsFileType(item.type())) {
     return ReadFileItem(GetFileStreamReader(current_item_index_),
                         bytes_to_read);
   }
+  if (item.type() == DataElement::TYPE_DISK_CACHE_ENTRY)
+    return ReadDiskCacheEntryItem(item, bytes_to_read);
   NOTREACHED();
   return false;
 }
 
 void BlobURLRequestJob::AdvanceItem() {
   // Close the file if the current item is a file.
   DeleteCurrentFileReader();
 
   // Advance to the next item.
   current_item_index_++;
@@ skipping 82 matching lines @@
 }
 
 void BlobURLRequestJob::DeleteCurrentFileReader() {
   IndexToReaderMap::iterator found = index_to_reader_.find(current_item_index_);
   if (found != index_to_reader_.end() && found->second) {
     delete found->second;
     index_to_reader_.erase(found);
   }
 }
 
+bool BlobURLRequestJob::ReadDiskCacheEntryItem(const BlobDataItem& item,
+                                               int bytes_to_read) {
+  DCHECK_GE(read_buf_->BytesRemaining(), bytes_to_read);
+
+  const int result = item.disk_cache_entry()->ReadData(
+      item.disk_cache_stream_index(), current_item_offset_, read_buf_.get(),
+      bytes_to_read, base::Bind(&BlobURLRequestJob::DidReadDiskCacheEntry,
+                                base::Unretained(this)));

[michaeln, 2015/06/12 22:35:09]

2 questions:

1) How is base::Unretained here safe? I don't think it is.

It's safe in ReadFileItem() because when this class is destructed the
FileStreamReader is deleted so that completion callback won't be called.

In this case, |item| is refcounted and outlives this job. And Entry's are
supposed to invoke the completion callback even after being closed.

WeakPtr?

2) Is it ok to have two ReadData calls pending against the same Entry instance.
Two different jobs could be running at the same time. Pretty sure its ok, but
just checking.

[gavinp, 2015/06/15 14:01:19]

I think you're right. jkarlin first raised this in his review, but I dismissed
it too easily, not seeing the real reason it was safe. WeakPtr.

Done.
Yes, this is OK.

+  DCHECK_LT(result, 0);
+  if (result == net::ERR_IO_PENDING)
+    SetStatus(net::URLRequestStatus(net::URLRequestStatus::IO_PENDING, 0));
+  else
+    NotifyFailure(result);
+  return false;
+}
+
+void BlobURLRequestJob::DidReadDiskCacheEntry(int result) {
+  if (result <= 0) {
+    NotifyFailure(net::ERR_FAILED);
+    return;
+  }
+  SetStatus(net::URLRequestStatus());
+
+  AdvanceBytesRead(result);
+
+  if (!read_buf_->BytesRemaining()) {
+    int bytes_read = BytesReadCompleted();
+    NotifyReadComplete(bytes_read);
+    return;
+  }
+
+  int bytes_read = 0;
+  if (ReadLoop(&bytes_read))
+    NotifyReadComplete(bytes_read);
+}
+
 int BlobURLRequestJob::BytesReadCompleted() {
   int bytes_read = read_buf_->BytesConsumed();
   read_buf_ = NULL;
   return bytes_read;
 }
 
 int BlobURLRequestJob::ComputeBytesToRead() const {
   int64 current_item_length = item_length_list_[current_item_index_];
 
   int64 item_remaining = current_item_length - current_item_offset_;
@@ skipping 148 matching lines @@
                    .release();
       break;
     default:
       NOTREACHED();
   }
   DCHECK(reader);
   index_to_reader_[index] = reader;
 }
 
 }  // namespace storage