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 // Copyright (c) 2006-2008 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.

 // Utility class for calculating the HMAC for a given message. We currently

 // only support SHA1 for the hash algorithm, but this can be extended easily.

 #ifndef BASE_HMAC_H_

 #define BASE_HMAC_H_

 #include <string>

 #include "base/basictypes.h"

 #include "base/scoped_ptr.h"

 namespace base {

 // Simplify the interface and reduce includes by abstracting out the internals.

 struct HMACPlatformData;

 class HMAC {

  public:

   // The set of supported hash functions. Extend as required.

   enum HashAlgorithm {

     SHA1

   };

   explicit HMAC(HashAlgorithm hash_alg);

   ~HMAC();

   // Initializes this instance using |key| of the length |key_length|. Call Init

   // only once. It returns false on the second or later calls.

   bool Init(const unsigned char* key, int key_length);

   // Initializes this instance using |key|. Call Init only once. It returns

   // false on the second or later calls.

   bool Init(const std::string& key) {

     return Init(reinterpret_cast<const unsigned char*>(key.data()),

                 static_cast<int>(key.size()));

   }

   // Calculates the HMAC for the message in |data| using the algorithm supplied

   // to the constructor and the key supplied to the Init method. The HMAC is

   // returned in |digest|, which has |digest_length| bytes of storage available.

   bool Sign(const std::string& data, unsigned char* digest, int digest_length);

  private:

   HashAlgorithm hash_alg_;

   scoped_ptr<HMACPlatformData> plat_;

   DISALLOW_COPY_AND_ASSIGN(HMAC);

 };

 }  // namespace base

 #endif  // BASE_HMAC_H_