Blob Consolidation & Registry Hookup

content/child/blob_storage/blob_consolidation.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 CONTENT_CHILD_BLOB_STORAGE_BLOB_CONSOLIDATION_H_
+#define CONTENT_CHILD_BLOB_STORAGE_BLOB_CONSOLIDATION_H_
+
+#include <string>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/common/content_export.h"
+#include "storage/common/data_element.h"
+#include "third_party/WebKit/public/platform/WebThreadSafeData.h"
+
+namespace content {
+
+// This class facilitates the consolidation of memory items in blobs. No memory
+// is copied to store items in this object. Instead, the memory is copied into
+// the external char* array given to the ReadMemory method.
+// Features:
+// * Add_Item methods for building the blob.
+// * consolidated_items for getting the consolidated items. This is
+//   used to describe the blob to the browser.
+// * total_memory to get the total memory size of the blob.
+// * ReadMemory for reading arbitrary memory from any consolidated item.
+//
+// NOTE: this class does not do memory accounting or garbage collecting. The
+// memory for the blob sticks around until this class is destructed.
+class CONTENT_EXPORT BlobConsolidation {
+ public:
+  enum class ReadStatus {
+    ERROR = 0,
+    ERROR_WRONG_TYPE,
+    ERROR_OUT_OF_BOUNDS,
+    DONE

[kinuko, 2015/06/25 05:04:19]

nit: DONE -> OK maybe if DONE means no-error?

nit: I feel putting DONE (or OK) first and the generic ERROR one last is more
common, but it'd be super trivial & subjective

[dmurph, 2015/06/25 23:38:54]

I don't put the SUCCESS case first because it could mean that an uninitialized
ReadStatus (which often defaults to 0) would erroneously be SUCCESS, which could
hide bugs.  I think there was a cpp-tip about this at some point.

+  };
+  struct ConsolidatedItem {
+    ConsolidatedItem();
+    ConsolidatedItem(storage::DataElement::Type type, uint64_t offset,
+                     uint64_t length);
+    ~ConsolidatedItem();
+
+    storage::DataElement::Type type;
+    uint64_t offset;
+    uint64_t length;
+
+    base::FilePath path;                // For TYPE_FILE.
+    GURL filesystem_url;                // For TYPE_FILE_FILESYSTEM.
+    double expected_modification_time;  // For TYPE_FILE, TYPE_FILE_FILESYSTEM.
+    std::string blob_uuid;              // For TYPE_BLOB.
+    // Only populated if len(items) > 1.  Used for binary search.
+    // Since the offset of the first item is always 0, we exclude this.
+    std::vector<size_t> offsets;                 // For TYPE_BYTES.
+    std::vector<blink::WebThreadSafeData> data;  // For TYPE_BYTES.
+  };
+
+  BlobConsolidation();
+  ~BlobConsolidation();
+
+  void AddDataItem(const blink::WebThreadSafeData& data);
+  void AddFileItem(const base::FilePath& path,
+                   uint64_t offset,
+                   uint64_t length,
+                   double expected_modification_time);
+  void AddBlobItem(const std::string& uuid,
+                   uint64_t offset,
+                   uint64_t length);
+  void AddFileSystemItem(const GURL& url,
+                         uint64_t offset,
+                         uint64_t length,
+                         double expected_modification_time);
+
+  // This gets the consolidated items constructed from the WebBlobData. This

[kinuko, 2015/06/25 05:04:19]

nit: The comment's a bit stale? Any of methods don't seem to take WebBlobData

[dmurph, 2015/06/25 23:38:55]

Done.

+  // is used to describe the blob to the browser.
+  const std::vector<ConsolidatedItem>& consolidated_items() const {
+    return consolidated_items_;
+  }
+
+  size_t total_memory() const { return total_memory_; }
+
+  // Reads memory from the given item into the given buffer. Returns:
+  // * ReadStatus::ERROR if the state or arguments are invalid (see error log),
+  // * ReadStatus::ERROR_WRONG_TYPE if the item at the index isn't memory,
+  // * ReadStatus::ERROR_OUT_OF_BOUNDS if index, offset, or size are invalid,
+  // * ReadStatus::DONE if the memory has been successfully read.
+  // Precondition: memory_out must be a valid pointer to memory with a size of
+  //               at least consolidated_size.
+  ReadStatus ReadMemory(size_t consolidated_item_index,
+                        size_t consolidated_offset, size_t consolidated_size,
+                        void* memory_out);
+
+ private:
+  size_t total_memory_;
+  std::vector<ConsolidatedItem> consolidated_items_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobConsolidation);
+};
+
+}  // namespace content
+#endif  // CONTENT_CHILD_BLOB_STORAGE_BLOB_CONSOLIDATION_H_