github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/src/hash/crc32/crc32_amd64p32.go (about)

     1  // Copyright 2011 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 crc32
     6  
     7  // This file contains the code to call the SSE 4.2 version of the Castagnoli
     8  // CRC.
     9  
    10  // haveSSE42 is defined in crc_amd64p32.s and uses CPUID to test for SSE 4.2
    11  // support.
    12  func haveSSE42() bool
    13  
    14  // castagnoliSSE42 is defined in crc_amd64.s and uses the SSE4.2 CRC32
    15  // instruction.
    16  //go:noescape
    17  func castagnoliSSE42(crc uint32, p []byte) uint32
    18  
    19  var sse42 = haveSSE42()
    20  
    21  func updateCastagnoli(crc uint32, p []byte) uint32 {
    22  	if sse42 {
    23  		return castagnoliSSE42(crc, p)
    24  	}
    25  	// Use slicing-by-8 on larger inputs.
    26  	if len(p) >= sliceBy8Cutoff {
    27  		return updateSlicingBy8(crc, castagnoliTable8, p)
    28  	}
    29  	return update(crc, castagnoliTable, p)
    30  }
    31  
    32  func updateIEEE(crc uint32, p []byte) uint32 {
    33  	// Use slicing-by-8 on larger inputs.
    34  	if len(p) >= sliceBy8Cutoff {
    35  		ieeeTable8Once.Do(func() {
    36  			ieeeTable8 = makeTable8(IEEE)
    37  		})
    38  		return updateSlicingBy8(crc, ieeeTable8, p)
    39  	}
    40  
    41  	return update(crc, IEEETable, p)
    42  }