// Copyright 2016 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package bytes //go:noescape // indexShortStr returns the index of the first instance of sep in s, // or -1 if sep is not present in s. // indexShortStr requires 2 <= len(sep) <= shortStringLen func indexShortStr(s, c []byte) int // ../runtime/asm_s390x.s // supportsVX reports whether the vector facility is available. // indexShortStr must not be called if the vector facility is not // available. func supportsVX() bool // ../runtime/asm_s390x.s var shortStringLen = -1 func init() { if supportsVX() { shortStringLen = 64 } } // Index returns the index of the first instance of sep in s, or -1 if sep is not present in s. func Index(s, sep []byte) int { n := len(sep) switch { case n == 0: return 0 case n == 1: return IndexByte(s, sep[0]) case n == len(s): if Equal(sep, s) { return 0 } return -1 case n > len(s): return -1 case n <= shortStringLen: // Use brute force when s and sep both are small if len(s) <= 64 { return indexShortStr(s, sep) } c := sep[0] i := 0 t := s[:len(s)-n+1] fails := 0 for i < len(t) { if t[i] != c { // IndexByte skips 16/32 bytes per iteration, // so it's faster than indexShortStr. o := IndexByte(t[i:], c) if o < 0 { return -1 } i += o } if Equal(s[i:i+n], sep) { return i } fails++ i++ // Switch to indexShortStr when IndexByte produces too many false positives. // Too many means more that 1 error per 8 characters. // Allow some errors in the beginning. if fails > (i+16)/8 { r := indexShortStr(s[i:], sep) if r >= 0 { return r + i } return -1 } } return -1 } return indexRabinKarp(s, sep) } // Count counts the number of non-overlapping instances of sep in s. // If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s. func Count(s, sep []byte) int { return countGeneric(s, sep) }