Port optimized SHA256 SSE4 routines from KMD+BTC upstream

src/crypto/sha256.h

@@ -1,4 +1,4 @@
-// Copyright (c) 2014 The Bitcoin Core developers
+// Copyright (c) 2014-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -7,13 +7,19 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <string>
 
 /** A hasher class for SHA-256. */
 class CSHA256
 {
 public:
     static const size_t OUTPUT_SIZE = 32;
-
+private:
+    uint32_t s[8];
+    unsigned char buf[64];
+    size_t bytes;
+    void FinalizeNoPadding(unsigned char hash[OUTPUT_SIZE], bool enforce_compression);
+public:
     CSHA256();
     CSHA256& Write(const unsigned char* data, size_t len);
     void Finalize(unsigned char hash[OUTPUT_SIZE]);
@@ -21,12 +27,11 @@ public:
     	FinalizeNoPadding(hash, true);
     };
     CSHA256& Reset();
-
-private:
-    uint32_t s[8];
-    unsigned char buf[64];
-    size_t bytes;
-    void FinalizeNoPadding(unsigned char hash[OUTPUT_SIZE], bool enforce_compression);
 };
 
+/** Autodetect the best available SHA256 implementation.
+ *  Returns the name of the implementation.
+ */
+std::string SHA256AutoDetect();
+
 #endif // BITCOIN_CRYPTO_SHA256_H