github.com/euank/go@v0.0.0-20160829210321-495514729181/src/crypto/sha1/sha1block_amd64.go (about)

     1  // Copyright 2016 The Go Authors.  All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package sha1
     6  
     7  //go:noescape
     8  
     9  func blockAVX2(dig *digest, p []byte)
    10  
    11  //go:noescape
    12  func blockAMD64(dig *digest, p []byte)
    13  func checkAVX2() bool
    14  
    15  var hasAVX2 = checkAVX2()
    16  
    17  func block(dig *digest, p []byte) {
    18  	if hasAVX2 && len(p) >= 256 {
    19  		// blockAVX2 calculates sha1 for 2 block per iteration
    20  		// it also interleaves precalculation for next block.
    21  		// So it may read up-to 192 bytes past end of p
    22  		// We may add checks inside blockAVX2, but this will
    23  		// just turn it into a copy of blockAMD64,
    24  		// so call it directly, instead.
    25  		safeLen := len(p) - 128
    26  		if safeLen%128 != 0 {
    27  			safeLen -= 64
    28  		}
    29  		blockAVX2(dig, p[:safeLen])
    30  		blockAMD64(dig, p[safeLen:])
    31  	} else {
    32  		blockAMD64(dig, p)
    33  	}
    34  }