[headless] Embed pak file into binary.

ui/base/resource/data_pack.h

 // 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.
 
 // DataPack represents a read-only view onto an on-disk file that contains
 // (key, value) pairs of data.  It's used to store static resources like
 // translation strings and images.
 
 #ifndef UI_BASE_RESOURCE_DATA_PACK_H_
 #define UI_BASE_RESOURCE_DATA_PACK_H_
@@ skipping 32 matching lines @@
   // Load a pack file from |path|, returning false on error.
   bool LoadFromPath(const base::FilePath& path);
 
   // Loads a pack file from |file|, returning false on error.
   bool LoadFromFile(base::File file);
 
   // Loads a pack file from |region| of |file|, returning false on error.
   bool LoadFromFileRegion(base::File file,
                           const base::MemoryMappedFile::Region& region);
 
+  // Loads a pack file from |buffer|, returning false on error.
+  bool LoadFromBuffer(base::StringPiece buffer);

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

bikeshed: Should this be InitializeFromBuffer?  Sami WDYT?

[altimin, 2016/05/12 18:07:53]

I don't think so — we already have LoadFromPath, LoadFromFile and
LoadFromFileRegion. For the sake of consistency I'd like it to be
LoadFromBuffer.

+
   // Writes a pack file containing |resources| to |path|. If there are any
   // text resources to be written, their encoding must already agree to the
   // |textEncodingType| specified. If no text resources are present, please
   // indicate BINARY.
   static bool WritePack(const base::FilePath& path,
                         const std::map<uint16_t, base::StringPiece>& resources,
                         TextEncodingType textEncodingType);
 
   // ResourceHandle implementation:
   bool HasResource(uint16_t resource_id) const override;
   bool GetStringPiece(uint16_t resource_id,
                       base::StringPiece* data) const override;
   base::RefCountedStaticMemory* GetStaticMemory(
       uint16_t resource_id) const override;
   TextEncodingType GetTextEncodingType() const override;
   ui::ScaleFactor GetScaleFactor() const override;
   bool HasOnlyMaterialDesignAssets() const override;
 
 #if DCHECK_IS_ON()
   // Checks to see if any resource in this DataPack already exists in the list
   // of resources.
   void CheckForDuplicateResources(const ScopedVector<ResourceHandle>& packs);
 #endif
 
  private:
-  // Does the actual loading of a pack file. Called by Load and LoadFromFile.
+  // Does the actual loading of a pack file.
+  // Called by Load and LoadFromFile and LoadFromBuffer.
   bool LoadImpl();
 
+  void Clear();
+
   // The memory-mapped data.

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

// The memory-mapped data.  Might be null if initialized from a memory buffer.

[altimin, 2016/05/12 18:07:53]

Acknowledged.

   std::unique_ptr<base::MemoryMappedFile> mmap_;

[alex clarke (OOO till 29th), 2016/05/12 17:31:04]

Not sure if this is overkill, but I would be tempted to add an inner class that
abstracts this, something like:

class DataSource {
  virtual size_t length() const = 0;
  virtual const uint8_t* data() const = 0;
};

Then have:

class MemoryMappedDataSource : public DataSource {
  size_t length() const override { return mmap_->length(); }
  const uint8_t* data() const override { return mmap_->data(); }

 private:
  std::unique_ptr<base::MemoryMappedFile> mmap_;
};

And the corresponding one for your in memory buffers.

This would amount to the same thing as your code, but I suspect it would be
easier to maintain, particularly if some third way of loading a file comes
along.

[altimin, 2016/05/12 18:07:53]

I thought about this and decided that's an overkill. But since you're thinking
about this too, we probably should do it.

+  size_t length_;
+  const uint8_t* data_;
 
   // Number of resources in the data.
   size_t resource_count_;
 
   // Type of encoding for text resources.
   TextEncodingType text_encoding_type_;
 
   // The scale of the image in this resource pack relative to images in the 1x
   // resource pak.
   ui::ScaleFactor scale_factor_;
 
   // Set to true if the only resources contained within this DataPack are
   // material design image assets.
   bool has_only_material_design_assets_;
 
   DISALLOW_COPY_AND_ASSIGN(DataPack);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_RESOURCE_DATA_PACK_H_