Abstracts SHA256 context for NSS / OpenSSL.

base/sha2.h

 // 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.
 
 #ifndef BASE_SHA2_H_
 #define BASE_SHA2_H_
 #pragma once
 
 #include <string>
 
+#include "base/basictypes.h"
+
 namespace base {
 
 // These functions perform SHA-256 operations.
 //
 // Functions for SHA-384 and SHA-512 can be added when the need arises.
 
 enum {
   SHA256_LENGTH = 32  // length in bytes of a SHA-256 hash
 };
 
 // Computes the SHA-256 hash of the input string 'str' and stores the first
 // 'len' bytes of the hash in the output buffer 'output'.  If 'len' > 32,
 // only 32 bytes (the full hash) are stored in the 'output' buffer.
 void SHA256HashString(const std::string& str, void* output, size_t len);
 
 // Convenience version of the above that returns the result in a 32-byte
 // string.
 std::string SHA256HashString(const std::string& str);
 
+// A wrapper for calculating SHA256 when the full string is not known in
+// advance.
+class SHA256Context {

[wtc, 2011/01/21 22:48:51]

Please name this class SHA256Hash or SHA256.  (I am worried
that SHA256 may conflict with an existing enum or macro in
a system crypto library.)

Ideally, we should create a Hash or SecureHash class,
whose Create method takes an algorithm enum as input.
Then we can use the class to compute an MD5, SHA-1, or
SHA-256 hash.

[bulach, 2011/01/24 20:54:33]

I liked this idea, seems more flexible.
I extracted this into a SecureHash class and moved things accordingly.

+ public:
+  virtual ~SHA256Context() {}
+
+  static SHA256Context* Create();
+
+  virtual void Update(const std::string& str) = 0;
+  virtual void Finish(void* output, size_t len) = 0;

[wtc, 2011/01/21 22:48:51]

This method should be named Final.

[bulach, 2011/01/24 20:54:33]

done, in the new files.

+
+ protected:
+  SHA256Context() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SHA256Context);
+};
+
 }  // namespace base
 
 #endif  // BASE_SHA2_H_