crypto: adapt sha256 multi-block transforms with intel avx2

-adapt sha256 to conditionally support multi-block transforms if USE_AVX2 is not defined

src/crypto/sha256.cpp

@@ -99,8 +99,13 @@ void inline Initialize(uint32_t* s)
     s[7] = 0x5be0cd19ul;
 }
 
+#ifndef USE_AVX2
 /** Perform a number of SHA-256 transformations, processing 64-byte chunks. */
 void Transform(uint32_t* s, const unsigned char* chunk, size_t blocks)
+#else
+/** Perform one SHA-256 transformation, processing a 64-byte chunk. */
+void Transform(uint32_t* s, const unsigned char* chunk)
+#endif
 {
 #if defined(USE_ARMV8) || defined(USE_ARMV82)
     // entire block is experimental
@@ -381,7 +386,7 @@ bool SelfTest(TransformType tr) {
     return true;
 }
 
-TransformType Transform = sha256::Transform;
+TransformType Transform = ::Transform;
 
 } // namespace
 
@@ -416,15 +421,29 @@ CSHA256& CSHA256::Write(const unsigned char* data, size_t len)
         memcpy(buf + bufsize, data, 64 - bufsize);
         bytes += 64 - bufsize;
         data += 64 - bufsize;
-        Transform(s, buf, 1);
+#ifndef USE_AVX2
+        sha256::Transform(s, buf, 1);
+#else
+        sha256::Transform(s, buf);
+#endif
         bufsize = 0;
     }
+
+#ifndef USE_AVX2
     if (end - data >= 64) {
         size_t blocks = (end - data) / 64;
         Transform(s, data, blocks);
         data += 64 * blocks;
         bytes += 64 * blocks;
     }
+#else
+    while (end >= data + 64) {
+        // Process full chunks directly from the source.
+        sha256::Transform(s, data);
+        bytes += 64;
+        data += 64;
+    }
+#endif
     if (end > data) {
         // Fill the buffer with what remains.
         memcpy(buf + bufsize, data, end - data);