Separate the key setting code in the constructor of HMAC class into the Init...

base/hmac_mac.cc

 // Copyright (c) 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.
 
 #include "base/hmac.h"
 
 #include <CommonCrypto/CommonHMAC.h>
 
 #include "base/logging.h"
 
 namespace base {
 
 struct HMACPlatformData {
   std::string key_;
 };
 
-HMAC::HMAC(HashAlgorithm hash_alg, const unsigned char* key, int key_length)
+HMAC::HMAC(HashAlgorithm hash_alg)
     : hash_alg_(hash_alg), plat_(new HMACPlatformData()) {
+  // Only SHA-1 digest is supported now.
+  DCHECK(hash_alg_ == SHA1);
+}
+
+bool HMAC::Init(const unsigned char *key, int key_length) {
+  if (!plat_->key_.empty()) {
+    // Init must not be called more than once on the same HMAC object.
+    NOTREACHED();
+    return false;
+  }
+
   plat_->key_.assign(reinterpret_cast<const char*>(key), key_length);
+
+  return true;
 }
 
 HMAC::~HMAC() {
   // Zero out key copy.
   plat_->key_.assign(plat_->key_.length(), std::string::value_type());
   plat_->key_.clear();
   plat_->key_.reserve(0);
 }
 
 bool HMAC::Sign(const std::string& data,
@@ skipping 17 matching lines @@
   }
 
   CCHmac(algorithm,
          plat_->key_.data(), plat_->key_.length(), data.data(), data.length(),
          digest);
 
   return true;
 }
 
 }  // namespace base