[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_flattener.cc

+// TODO: Insert description here. (generated by dmurph)
+
+#include "storage/browser/blob/blob_flattener.h"
+
+#include <limits>
+#include <set>
+#include <utility>
+
+#include "storage/browser/blob/blob_async_transport_request_builder.h"
+#include "storage/browser/blob/blob_data_builder.h"
+#include "storage/browser/blob/blob_storage_context.h"
+#include "storage/browser/blob/blob_storage_registry.h"
+#include "storage/browser/blob/shareable_blob_data_item.h"
+
+namespace storage {
+namespace {
+using ItemCopyEntry = BlobStorageRegistry::ItemCopyEntry;
+using BlobEntry = BlobStorageRegistry::Entry;
+
+bool IsBytes(DataElement::Type type) {
+  return type == DataElement::TYPE_BYTES ||
+         type == DataElement::TYPE_BYTES_DESCRIPTION;
+}
+
+}  // namespace
+
+// static
+BlobFlattener::BlobFlattener(const BlobDataBuilder& transportation_result,
+                             InternalBlobData* output_blob,
+                             BlobStorageRegistry* registry) {
+  const std::vector<scoped_refptr<BlobDataItem>>& transport_items =
+      transportation_result.items_;
+  const std::string& uuid = transportation_result.uuid_;
+
+  std::set<std::string> dependent_blob_uuids;
+  for (size_t transport_item_index = 0;
+       transport_item_index < transport_items.size(); transport_item_index++) {
+    scoped_refptr<BlobDataItem> transport_item =
+        transport_items[transport_item_index];
+
+    DataElement::Type type = transport_item->type();
+    contains_pending_content |= type == DataElement::TYPE_BYTES_DESCRIPTION;
+
+    if (IsBytes(type)) {
+      memory_needed += transport_item->length();
+      total_size += transport_item->length();
+      output_blob->AppendSharedBlobItem(
+          uuid, new ShareableBlobDataItem(std::move(transport_item)));
+    } else if (type == DataElement::TYPE_BLOB) {
+      BlobEntry* ref_entry = registry->GetEntry(transport_item->blob_uuid());
+
+      if (!ref_entry || BlobStatusIsError(ref_entry->status) ||
+          transport_item->blob_uuid() == uuid) {
+        contains_broken_references = true;
+        return;
+      }
+
+      if (dependent_blob_uuids.find(transport_item->blob_uuid()) ==
+          dependent_blob_uuids.end()) {
+        dependent_blobs.push_back(
+            std::make_pair(transport_item->blob_uuid(), ref_entry));
+        dependent_blob_uuids.insert(transport_item->blob_uuid());
+      }
+
+      uint64_t length =
+          transport_item->length() == std::numeric_limits<uint64_t>::max()

[Marijn Kruisselbrink, 2016/07/12 21:33:06]

if ::max() is a magic number for the length of a transport item, maybe define a
constant somewhere to make it clearer what max is used for?

[dmurph, 2016/07/14 01:04:31]

Yes, that sounds good.

+              ? ref_entry->data.total_size()
+              : transport_item->length();
+
+      total_size += length;
+
+      // If we're referencing the whole blob, then we don't need to slice.
+      if (transport_item->offset() == 0 &&
+          length == ref_entry->data.total_size()) {
+        for (const auto& shareable_item : ref_entry->data.items()) {
+          output_blob->AppendSharedBlobItem(uuid, shareable_item);
+        }
+        continue;
+      }
+
+      BlobSlice slice(ref_entry->data, transport_item->offset(),
+                      transport_item->length());
+
+      if (slice.has_sliced_first_memory_item) {
+        copies.push_back(ItemCopyEntry(slice.first_source_item,
+                                       slice.first_item_slice_offset,
+                                       slice.dest_items.front()));
+      }
+
+      memory_needed += slice.copying_memory_size;
+      for (auto& shareable_item : slice.dest_items) {
+        output_blob->AppendSharedBlobItem(uuid, std::move(shareable_item));
+      }
+
+      if (slice.has_sliced_last_memory_item) {
+        copies.push_back(
+            ItemCopyEntry(slice.last_source_item, 0, slice.dest_items.back()));

[Marijn Kruisselbrink, 2016/07/12 21:33:06]

Does this work? Above you've moved all the items in slice.dest_items away, so at
this point slice.dest_items.back() should be a moved-from scoped_refptr (so
probably null?).

[dmurph, 2016/07/14 01:04:31]

Yep, nice bug catch.

+      }
+    } else {
+      if (type == DataElement::TYPE_FILE) {
+        contains_pending_content =
+            transport_item->path().value() ==
+            BlobDataBuilder::kAppendFutureFileTemporaryFileName;
+      }
+      total_size += transport_item->length();
+      output_blob->AppendSharedBlobItem(
+          uuid, new ShareableBlobDataItem(std::move(transport_item)));
+    }
+  }
+}
+
+BlobFlattener::~BlobFlattener() {}
+
+}  // namespace storage