More implementation details of extension content verification

extensions/browser/content_hash_reader.h

+// Copyright 2014 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 EXTENSIONS_BROWSER_CONTENT_HASH_READER_H_
+#define EXTENSIONS_BROWSER_CONTENT_HASH_READER_H_
+
+#include <string>
+
+#include "base/files/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/version.h"
+#include "extensions/browser/content_verifier_delegate.h"
+
+namespace extensions {
+
+// This class creates an object that will read expected hashes that may have
+// been fetched/calculated by the ContentHashFetcher, and vends them out for
+// use in ContentVerifyJob's.
+class ContentHashReader : public base::RefCountedThreadSafe<ContentHashReader> {
+ public:
+  // Create one of these to get expected hashes for the file at |relative_path|
+  // within an extension.
+  ContentHashReader(const std::string& extension_id,
+                    const base::Version& extension_version,
+                    const base::FilePath& extension_root,
+                    const base::FilePath& relative_path,
+                    const ContentVerifierKey& key);
+
+  const std::string& extension_id() const { return extension_id_; }
+  const base::FilePath& relative_path() const { return relative_path_; }
+
+  // This should be called to initialize this object (reads the expected hashes
+  // from storage, etc.). Must be called on a thread that is allowed to do file
+  // I/O. Returns a boolean indicating success/failure. On failure, this object
+  // should likely be discarded.
+  bool Init();
+
+  // Return the number of blocks and block size, respectively. Only valid after
+  // calling Init().
+  int block_count() const;
+  int block_size() const;
+
+  // Returns a pointer to the expected sha256 hash value for the block at the
+  // given index. Only valid after calling Init().
+  bool GetHashForBlock(int block_index, const std::string** result) const;
+
+ private:
+  friend class base::RefCountedThreadSafe<ContentHashReader>;
+  virtual ~ContentHashReader();
+
+  bool ReadHashes(const base::FilePath& hashes_file);
+
+  std::string extension_id_;
+  base::Version extension_version_;
+  base::FilePath extension_root_;
+  base::FilePath relative_path_;
+  ContentVerifierKey key_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContentHashReader);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_BROWSER_CONTENT_HASH_READER_H_