1276 lines
31 KiB
Go
1276 lines
31 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package bytes implements functions for the manipulation of byte slices.
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// It is analogous to the facilities of the strings package.
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package bytes
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import (
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"internal/bytealg"
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"unicode"
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"unicode/utf8"
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)
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// Equal reports whether a and b
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// are the same length and contain the same bytes.
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// A nil argument is equivalent to an empty slice.
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func Equal(a, b []byte) bool {
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// Neither cmd/compile nor gccgo allocates for these string conversions.
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return string(a) == string(b)
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}
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// Compare returns an integer comparing two byte slices lexicographically.
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// The result will be 0 if a == b, -1 if a < b, and +1 if a > b.
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// A nil argument is equivalent to an empty slice.
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func Compare(a, b []byte) int {
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return bytealg.Compare(a, b)
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}
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// explode splits s into a slice of UTF-8 sequences, one per Unicode code point (still slices of bytes),
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// up to a maximum of n byte slices. Invalid UTF-8 sequences are chopped into individual bytes.
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func explode(s []byte, n int) [][]byte {
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if n <= 0 {
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n = len(s)
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}
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a := make([][]byte, n)
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var size int
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na := 0
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for len(s) > 0 {
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if na+1 >= n {
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a[na] = s
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na++
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break
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}
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_, size = utf8.DecodeRune(s)
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a[na] = s[0:size:size]
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s = s[size:]
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na++
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}
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return a[0:na]
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}
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// Count counts the number of non-overlapping instances of sep in s.
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// If sep is an empty slice, Count returns 1 + the number of UTF-8-encoded code points in s.
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func Count(s, sep []byte) int {
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// special case
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if len(sep) == 0 {
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return utf8.RuneCount(s) + 1
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}
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if len(sep) == 1 {
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return bytealg.Count(s, sep[0])
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}
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n := 0
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for {
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i := Index(s, sep)
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if i == -1 {
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return n
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}
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n++
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s = s[i+len(sep):]
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}
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}
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// Contains reports whether subslice is within b.
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func Contains(b, subslice []byte) bool {
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return Index(b, subslice) != -1
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}
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// ContainsAny reports whether any of the UTF-8-encoded code points in chars are within b.
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func ContainsAny(b []byte, chars string) bool {
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return IndexAny(b, chars) >= 0
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}
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// ContainsRune reports whether the rune is contained in the UTF-8-encoded byte slice b.
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func ContainsRune(b []byte, r rune) bool {
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return IndexRune(b, r) >= 0
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}
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// IndexByte returns the index of the first instance of c in b, or -1 if c is not present in b.
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func IndexByte(b []byte, c byte) int {
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return bytealg.IndexByte(b, c)
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}
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func indexBytePortable(s []byte, c byte) int {
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for i, b := range s {
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if b == c {
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return i
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}
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}
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return -1
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}
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// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
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func LastIndex(s, sep []byte) int {
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n := len(sep)
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switch {
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case n == 0:
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return len(s)
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case n == 1:
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return LastIndexByte(s, sep[0])
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case n == len(s):
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if Equal(s, sep) {
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return 0
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}
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return -1
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case n > len(s):
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return -1
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}
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// Rabin-Karp search from the end of the string
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hashss, pow := bytealg.HashStrRevBytes(sep)
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last := len(s) - n
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var h uint32
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for i := len(s) - 1; i >= last; i-- {
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h = h*bytealg.PrimeRK + uint32(s[i])
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}
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if h == hashss && Equal(s[last:], sep) {
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return last
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}
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for i := last - 1; i >= 0; i-- {
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h *= bytealg.PrimeRK
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h += uint32(s[i])
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h -= pow * uint32(s[i+n])
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if h == hashss && Equal(s[i:i+n], sep) {
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return i
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}
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}
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return -1
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}
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// LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s.
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func LastIndexByte(s []byte, c byte) int {
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for i := len(s) - 1; i >= 0; i-- {
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if s[i] == c {
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return i
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}
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}
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return -1
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}
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// IndexRune interprets s as a sequence of UTF-8-encoded code points.
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// It returns the byte index of the first occurrence in s of the given rune.
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// It returns -1 if rune is not present in s.
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// If r is utf8.RuneError, it returns the first instance of any
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// invalid UTF-8 byte sequence.
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func IndexRune(s []byte, r rune) int {
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switch {
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case 0 <= r && r < utf8.RuneSelf:
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return IndexByte(s, byte(r))
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case r == utf8.RuneError:
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for i := 0; i < len(s); {
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r1, n := utf8.DecodeRune(s[i:])
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if r1 == utf8.RuneError {
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return i
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}
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i += n
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}
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return -1
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case !utf8.ValidRune(r):
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return -1
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default:
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var b [utf8.UTFMax]byte
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n := utf8.EncodeRune(b[:], r)
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return Index(s, b[:n])
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}
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}
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// IndexAny interprets s as a sequence of UTF-8-encoded Unicode code points.
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// It returns the byte index of the first occurrence in s of any of the Unicode
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// code points in chars. It returns -1 if chars is empty or if there is no code
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// point in common.
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func IndexAny(s []byte, chars string) int {
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if chars == "" {
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// Avoid scanning all of s.
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return -1
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}
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if len(s) == 1 {
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r := rune(s[0])
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if r >= utf8.RuneSelf {
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// search utf8.RuneError.
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for _, r = range chars {
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if r == utf8.RuneError {
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return 0
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}
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}
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return -1
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}
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if bytealg.IndexByteString(chars, s[0]) >= 0 {
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return 0
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}
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return -1
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}
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if len(chars) == 1 {
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r := rune(chars[0])
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if r >= utf8.RuneSelf {
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r = utf8.RuneError
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}
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return IndexRune(s, r)
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}
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if len(s) > 8 {
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if as, isASCII := makeASCIISet(chars); isASCII {
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for i, c := range s {
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if as.contains(c) {
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return i
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}
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}
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return -1
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}
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}
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var width int
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for i := 0; i < len(s); i += width {
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r := rune(s[i])
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if r < utf8.RuneSelf {
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if bytealg.IndexByteString(chars, s[i]) >= 0 {
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return i
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}
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width = 1
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continue
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}
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r, width = utf8.DecodeRune(s[i:])
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if r != utf8.RuneError {
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// r is 2 to 4 bytes
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if len(chars) == width {
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if chars == string(r) {
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return i
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}
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continue
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}
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// Use bytealg.IndexString for performance if available.
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if bytealg.MaxLen >= width {
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if bytealg.IndexString(chars, string(r)) >= 0 {
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return i
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}
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continue
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}
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}
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for _, ch := range chars {
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if r == ch {
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return i
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}
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}
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}
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return -1
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}
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// LastIndexAny interprets s as a sequence of UTF-8-encoded Unicode code
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// points. It returns the byte index of the last occurrence in s of any of
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// the Unicode code points in chars. It returns -1 if chars is empty or if
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// there is no code point in common.
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func LastIndexAny(s []byte, chars string) int {
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if chars == "" {
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// Avoid scanning all of s.
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return -1
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}
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if len(s) > 8 {
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if as, isASCII := makeASCIISet(chars); isASCII {
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for i := len(s) - 1; i >= 0; i-- {
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if as.contains(s[i]) {
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return i
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}
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}
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return -1
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}
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}
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if len(s) == 1 {
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r := rune(s[0])
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if r >= utf8.RuneSelf {
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for _, r = range chars {
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if r == utf8.RuneError {
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return 0
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}
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}
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return -1
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}
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if bytealg.IndexByteString(chars, s[0]) >= 0 {
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return 0
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}
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return -1
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}
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if len(chars) == 1 {
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cr := rune(chars[0])
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if cr >= utf8.RuneSelf {
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cr = utf8.RuneError
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}
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for i := len(s); i > 0; {
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r, size := utf8.DecodeLastRune(s[:i])
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i -= size
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if r == cr {
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return i
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}
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}
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return -1
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}
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for i := len(s); i > 0; {
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r := rune(s[i-1])
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if r < utf8.RuneSelf {
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if bytealg.IndexByteString(chars, s[i-1]) >= 0 {
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return i - 1
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}
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i--
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continue
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}
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r, size := utf8.DecodeLastRune(s[:i])
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i -= size
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if r != utf8.RuneError {
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// r is 2 to 4 bytes
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if len(chars) == size {
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if chars == string(r) {
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return i
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}
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continue
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}
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// Use bytealg.IndexString for performance if available.
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if bytealg.MaxLen >= size {
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if bytealg.IndexString(chars, string(r)) >= 0 {
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return i
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}
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continue
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}
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}
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for _, ch := range chars {
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if r == ch {
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return i
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}
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}
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}
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return -1
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}
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// Generic split: splits after each instance of sep,
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// including sepSave bytes of sep in the subslices.
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func genSplit(s, sep []byte, sepSave, n int) [][]byte {
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if n == 0 {
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return nil
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}
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if len(sep) == 0 {
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return explode(s, n)
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}
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if n < 0 {
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n = Count(s, sep) + 1
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}
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a := make([][]byte, n)
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n--
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i := 0
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for i < n {
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m := Index(s, sep)
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if m < 0 {
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break
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}
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a[i] = s[: m+sepSave : m+sepSave]
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s = s[m+len(sep):]
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i++
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}
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a[i] = s
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return a[:i+1]
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}
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// SplitN slices s into subslices separated by sep and returns a slice of
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// the subslices between those separators.
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// If sep is empty, SplitN splits after each UTF-8 sequence.
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// The count determines the number of subslices to return:
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// n > 0: at most n subslices; the last subslice will be the unsplit remainder.
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// n == 0: the result is nil (zero subslices)
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// n < 0: all subslices
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//
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// To split around the first instance of a separator, see Cut.
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func SplitN(s, sep []byte, n int) [][]byte { return genSplit(s, sep, 0, n) }
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// SplitAfterN slices s into subslices after each instance of sep and
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// returns a slice of those subslices.
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// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
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// The count determines the number of subslices to return:
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// n > 0: at most n subslices; the last subslice will be the unsplit remainder.
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// n == 0: the result is nil (zero subslices)
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// n < 0: all subslices
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func SplitAfterN(s, sep []byte, n int) [][]byte {
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return genSplit(s, sep, len(sep), n)
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}
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// Split slices s into all subslices separated by sep and returns a slice of
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// the subslices between those separators.
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// If sep is empty, Split splits after each UTF-8 sequence.
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// It is equivalent to SplitN with a count of -1.
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//
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// To split around the first instance of a separator, see Cut.
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func Split(s, sep []byte) [][]byte { return genSplit(s, sep, 0, -1) }
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// SplitAfter slices s into all subslices after each instance of sep and
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// returns a slice of those subslices.
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// If sep is empty, SplitAfter splits after each UTF-8 sequence.
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// It is equivalent to SplitAfterN with a count of -1.
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func SplitAfter(s, sep []byte) [][]byte {
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return genSplit(s, sep, len(sep), -1)
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}
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var asciiSpace = [256]uint8{'\t': 1, '\n': 1, '\v': 1, '\f': 1, '\r': 1, ' ': 1}
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// Fields interprets s as a sequence of UTF-8-encoded code points.
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// It splits the slice s around each instance of one or more consecutive white space
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// characters, as defined by unicode.IsSpace, returning a slice of subslices of s or an
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// empty slice if s contains only white space.
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func Fields(s []byte) [][]byte {
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// First count the fields.
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// This is an exact count if s is ASCII, otherwise it is an approximation.
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n := 0
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wasSpace := 1
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// setBits is used to track which bits are set in the bytes of s.
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setBits := uint8(0)
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for i := 0; i < len(s); i++ {
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r := s[i]
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setBits |= r
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isSpace := int(asciiSpace[r])
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n += wasSpace & ^isSpace
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wasSpace = isSpace
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}
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if setBits >= utf8.RuneSelf {
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// Some runes in the input slice are not ASCII.
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return FieldsFunc(s, unicode.IsSpace)
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}
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// ASCII fast path
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a := make([][]byte, n)
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na := 0
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fieldStart := 0
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i := 0
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// Skip spaces in the front of the input.
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for i < len(s) && asciiSpace[s[i]] != 0 {
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i++
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}
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fieldStart = i
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for i < len(s) {
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if asciiSpace[s[i]] == 0 {
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i++
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continue
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}
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a[na] = s[fieldStart:i:i]
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na++
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i++
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// Skip spaces in between fields.
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for i < len(s) && asciiSpace[s[i]] != 0 {
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i++
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}
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fieldStart = i
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}
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if fieldStart < len(s) { // Last field might end at EOF.
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a[na] = s[fieldStart:len(s):len(s)]
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}
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return a
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}
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// FieldsFunc interprets s as a sequence of UTF-8-encoded code points.
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// It splits the slice s at each run of code points c satisfying f(c) and
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// returns a slice of subslices of s. If all code points in s satisfy f(c), or
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// len(s) == 0, an empty slice is returned.
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//
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// FieldsFunc makes no guarantees about the order in which it calls f(c)
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// and assumes that f always returns the same value for a given c.
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func FieldsFunc(s []byte, f func(rune) bool) [][]byte {
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// A span is used to record a slice of s of the form s[start:end].
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// The start index is inclusive and the end index is exclusive.
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type span struct {
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start int
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end int
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}
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spans := make([]span, 0, 32)
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// Find the field start and end indices.
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// Doing this in a separate pass (rather than slicing the string s
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// and collecting the result substrings right away) is significantly
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// more efficient, possibly due to cache effects.
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start := -1 // valid span start if >= 0
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for i := 0; i < len(s); {
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size := 1
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r := rune(s[i])
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if r >= utf8.RuneSelf {
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r, size = utf8.DecodeRune(s[i:])
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}
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if f(r) {
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if start >= 0 {
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spans = append(spans, span{start, i})
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start = -1
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}
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} else {
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if start < 0 {
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start = i
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}
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}
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i += size
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}
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// Last field might end at EOF.
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if start >= 0 {
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spans = append(spans, span{start, len(s)})
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}
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// Create subslices from recorded field indices.
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a := make([][]byte, len(spans))
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for i, span := range spans {
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a[i] = s[span.start:span.end:span.end]
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}
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return a
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}
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// Join concatenates the elements of s to create a new byte slice. The separator
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// sep is placed between elements in the resulting slice.
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func Join(s [][]byte, sep []byte) []byte {
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if len(s) == 0 {
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return []byte{}
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}
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if len(s) == 1 {
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// Just return a copy.
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return append([]byte(nil), s[0]...)
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}
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n := len(sep) * (len(s) - 1)
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for _, v := range s {
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n += len(v)
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}
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b := make([]byte, n)
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bp := copy(b, s[0])
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for _, v := range s[1:] {
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bp += copy(b[bp:], sep)
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bp += copy(b[bp:], v)
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}
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return b
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}
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|
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// HasPrefix tests whether the byte slice s begins with prefix.
|
|
func HasPrefix(s, prefix []byte) bool {
|
|
return len(s) >= len(prefix) && Equal(s[0:len(prefix)], prefix)
|
|
}
|
|
|
|
// HasSuffix tests whether the byte slice s ends with suffix.
|
|
func HasSuffix(s, suffix []byte) bool {
|
|
return len(s) >= len(suffix) && Equal(s[len(s)-len(suffix):], suffix)
|
|
}
|
|
|
|
// Map returns a copy of the byte slice s with all its characters modified
|
|
// according to the mapping function. If mapping returns a negative value, the character is
|
|
// dropped from the byte slice with no replacement. The characters in s and the
|
|
// output are interpreted as UTF-8-encoded code points.
|
|
func Map(mapping func(r rune) rune, s []byte) []byte {
|
|
// In the worst case, the slice can grow when mapped, making
|
|
// things unpleasant. But it's so rare we barge in assuming it's
|
|
// fine. It could also shrink but that falls out naturally.
|
|
maxbytes := len(s) // length of b
|
|
nbytes := 0 // number of bytes encoded in b
|
|
b := make([]byte, maxbytes)
|
|
for i := 0; i < len(s); {
|
|
wid := 1
|
|
r := rune(s[i])
|
|
if r >= utf8.RuneSelf {
|
|
r, wid = utf8.DecodeRune(s[i:])
|
|
}
|
|
r = mapping(r)
|
|
if r >= 0 {
|
|
rl := utf8.RuneLen(r)
|
|
if rl < 0 {
|
|
rl = len(string(utf8.RuneError))
|
|
}
|
|
if nbytes+rl > maxbytes {
|
|
// Grow the buffer.
|
|
maxbytes = maxbytes*2 + utf8.UTFMax
|
|
nb := make([]byte, maxbytes)
|
|
copy(nb, b[0:nbytes])
|
|
b = nb
|
|
}
|
|
nbytes += utf8.EncodeRune(b[nbytes:maxbytes], r)
|
|
}
|
|
i += wid
|
|
}
|
|
return b[0:nbytes]
|
|
}
|
|
|
|
// Repeat returns a new byte slice consisting of count copies of b.
|
|
//
|
|
// It panics if count is negative or if
|
|
// the result of (len(b) * count) overflows.
|
|
func Repeat(b []byte, count int) []byte {
|
|
if count == 0 {
|
|
return []byte{}
|
|
}
|
|
// Since we cannot return an error on overflow,
|
|
// we should panic if the repeat will generate
|
|
// an overflow.
|
|
// See Issue golang.org/issue/16237.
|
|
if count < 0 {
|
|
panic("bytes: negative Repeat count")
|
|
} else if len(b)*count/count != len(b) {
|
|
panic("bytes: Repeat count causes overflow")
|
|
}
|
|
|
|
nb := make([]byte, len(b)*count)
|
|
bp := copy(nb, b)
|
|
for bp < len(nb) {
|
|
copy(nb[bp:], nb[:bp])
|
|
bp *= 2
|
|
}
|
|
return nb
|
|
}
|
|
|
|
// ToUpper returns a copy of the byte slice s with all Unicode letters mapped to
|
|
// their upper case.
|
|
func ToUpper(s []byte) []byte {
|
|
isASCII, hasLower := true, false
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if c >= utf8.RuneSelf {
|
|
isASCII = false
|
|
break
|
|
}
|
|
hasLower = hasLower || ('a' <= c && c <= 'z')
|
|
}
|
|
|
|
if isASCII { // optimize for ASCII-only byte slices.
|
|
if !hasLower {
|
|
// Just return a copy.
|
|
return append([]byte(""), s...)
|
|
}
|
|
b := make([]byte, len(s))
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if 'a' <= c && c <= 'z' {
|
|
c -= 'a' - 'A'
|
|
}
|
|
b[i] = c
|
|
}
|
|
return b
|
|
}
|
|
return Map(unicode.ToUpper, s)
|
|
}
|
|
|
|
// ToLower returns a copy of the byte slice s with all Unicode letters mapped to
|
|
// their lower case.
|
|
func ToLower(s []byte) []byte {
|
|
isASCII, hasUpper := true, false
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if c >= utf8.RuneSelf {
|
|
isASCII = false
|
|
break
|
|
}
|
|
hasUpper = hasUpper || ('A' <= c && c <= 'Z')
|
|
}
|
|
|
|
if isASCII { // optimize for ASCII-only byte slices.
|
|
if !hasUpper {
|
|
return append([]byte(""), s...)
|
|
}
|
|
b := make([]byte, len(s))
|
|
for i := 0; i < len(s); i++ {
|
|
c := s[i]
|
|
if 'A' <= c && c <= 'Z' {
|
|
c += 'a' - 'A'
|
|
}
|
|
b[i] = c
|
|
}
|
|
return b
|
|
}
|
|
return Map(unicode.ToLower, s)
|
|
}
|
|
|
|
// ToTitle treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their title case.
|
|
func ToTitle(s []byte) []byte { return Map(unicode.ToTitle, s) }
|
|
|
|
// ToUpperSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
|
|
// upper case, giving priority to the special casing rules.
|
|
func ToUpperSpecial(c unicode.SpecialCase, s []byte) []byte {
|
|
return Map(c.ToUpper, s)
|
|
}
|
|
|
|
// ToLowerSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
|
|
// lower case, giving priority to the special casing rules.
|
|
func ToLowerSpecial(c unicode.SpecialCase, s []byte) []byte {
|
|
return Map(c.ToLower, s)
|
|
}
|
|
|
|
// ToTitleSpecial treats s as UTF-8-encoded bytes and returns a copy with all the Unicode letters mapped to their
|
|
// title case, giving priority to the special casing rules.
|
|
func ToTitleSpecial(c unicode.SpecialCase, s []byte) []byte {
|
|
return Map(c.ToTitle, s)
|
|
}
|
|
|
|
// ToValidUTF8 treats s as UTF-8-encoded bytes and returns a copy with each run of bytes
|
|
// representing invalid UTF-8 replaced with the bytes in replacement, which may be empty.
|
|
func ToValidUTF8(s, replacement []byte) []byte {
|
|
b := make([]byte, 0, len(s)+len(replacement))
|
|
invalid := false // previous byte was from an invalid UTF-8 sequence
|
|
for i := 0; i < len(s); {
|
|
c := s[i]
|
|
if c < utf8.RuneSelf {
|
|
i++
|
|
invalid = false
|
|
b = append(b, c)
|
|
continue
|
|
}
|
|
_, wid := utf8.DecodeRune(s[i:])
|
|
if wid == 1 {
|
|
i++
|
|
if !invalid {
|
|
invalid = true
|
|
b = append(b, replacement...)
|
|
}
|
|
continue
|
|
}
|
|
invalid = false
|
|
b = append(b, s[i:i+wid]...)
|
|
i += wid
|
|
}
|
|
return b
|
|
}
|
|
|
|
// isSeparator reports whether the rune could mark a word boundary.
|
|
// TODO: update when package unicode captures more of the properties.
|
|
func isSeparator(r rune) bool {
|
|
// ASCII alphanumerics and underscore are not separators
|
|
if r <= 0x7F {
|
|
switch {
|
|
case '0' <= r && r <= '9':
|
|
return false
|
|
case 'a' <= r && r <= 'z':
|
|
return false
|
|
case 'A' <= r && r <= 'Z':
|
|
return false
|
|
case r == '_':
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
// Letters and digits are not separators
|
|
if unicode.IsLetter(r) || unicode.IsDigit(r) {
|
|
return false
|
|
}
|
|
// Otherwise, all we can do for now is treat spaces as separators.
|
|
return unicode.IsSpace(r)
|
|
}
|
|
|
|
// Title treats s as UTF-8-encoded bytes and returns a copy with all Unicode letters that begin
|
|
// words mapped to their title case.
|
|
//
|
|
// Deprecated: The rule Title uses for word boundaries does not handle Unicode
|
|
// punctuation properly. Use golang.org/x/text/cases instead.
|
|
func Title(s []byte) []byte {
|
|
// Use a closure here to remember state.
|
|
// Hackish but effective. Depends on Map scanning in order and calling
|
|
// the closure once per rune.
|
|
prev := ' '
|
|
return Map(
|
|
func(r rune) rune {
|
|
if isSeparator(prev) {
|
|
prev = r
|
|
return unicode.ToTitle(r)
|
|
}
|
|
prev = r
|
|
return r
|
|
},
|
|
s)
|
|
}
|
|
|
|
// TrimLeftFunc treats s as UTF-8-encoded bytes and returns a subslice of s by slicing off
|
|
// all leading UTF-8-encoded code points c that satisfy f(c).
|
|
func TrimLeftFunc(s []byte, f func(r rune) bool) []byte {
|
|
i := indexFunc(s, f, false)
|
|
if i == -1 {
|
|
return nil
|
|
}
|
|
return s[i:]
|
|
}
|
|
|
|
// TrimRightFunc returns a subslice of s by slicing off all trailing
|
|
// UTF-8-encoded code points c that satisfy f(c).
|
|
func TrimRightFunc(s []byte, f func(r rune) bool) []byte {
|
|
i := lastIndexFunc(s, f, false)
|
|
if i >= 0 && s[i] >= utf8.RuneSelf {
|
|
_, wid := utf8.DecodeRune(s[i:])
|
|
i += wid
|
|
} else {
|
|
i++
|
|
}
|
|
return s[0:i]
|
|
}
|
|
|
|
// TrimFunc returns a subslice of s by slicing off all leading and trailing
|
|
// UTF-8-encoded code points c that satisfy f(c).
|
|
func TrimFunc(s []byte, f func(r rune) bool) []byte {
|
|
return TrimRightFunc(TrimLeftFunc(s, f), f)
|
|
}
|
|
|
|
// TrimPrefix returns s without the provided leading prefix string.
|
|
// If s doesn't start with prefix, s is returned unchanged.
|
|
func TrimPrefix(s, prefix []byte) []byte {
|
|
if HasPrefix(s, prefix) {
|
|
return s[len(prefix):]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// TrimSuffix returns s without the provided trailing suffix string.
|
|
// If s doesn't end with suffix, s is returned unchanged.
|
|
func TrimSuffix(s, suffix []byte) []byte {
|
|
if HasSuffix(s, suffix) {
|
|
return s[:len(s)-len(suffix)]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// IndexFunc interprets s as a sequence of UTF-8-encoded code points.
|
|
// It returns the byte index in s of the first Unicode
|
|
// code point satisfying f(c), or -1 if none do.
|
|
func IndexFunc(s []byte, f func(r rune) bool) int {
|
|
return indexFunc(s, f, true)
|
|
}
|
|
|
|
// LastIndexFunc interprets s as a sequence of UTF-8-encoded code points.
|
|
// It returns the byte index in s of the last Unicode
|
|
// code point satisfying f(c), or -1 if none do.
|
|
func LastIndexFunc(s []byte, f func(r rune) bool) int {
|
|
return lastIndexFunc(s, f, true)
|
|
}
|
|
|
|
// indexFunc is the same as IndexFunc except that if
|
|
// truth==false, the sense of the predicate function is
|
|
// inverted.
|
|
func indexFunc(s []byte, f func(r rune) bool, truth bool) int {
|
|
start := 0
|
|
for start < len(s) {
|
|
wid := 1
|
|
r := rune(s[start])
|
|
if r >= utf8.RuneSelf {
|
|
r, wid = utf8.DecodeRune(s[start:])
|
|
}
|
|
if f(r) == truth {
|
|
return start
|
|
}
|
|
start += wid
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// lastIndexFunc is the same as LastIndexFunc except that if
|
|
// truth==false, the sense of the predicate function is
|
|
// inverted.
|
|
func lastIndexFunc(s []byte, f func(r rune) bool, truth bool) int {
|
|
for i := len(s); i > 0; {
|
|
r, size := rune(s[i-1]), 1
|
|
if r >= utf8.RuneSelf {
|
|
r, size = utf8.DecodeLastRune(s[0:i])
|
|
}
|
|
i -= size
|
|
if f(r) == truth {
|
|
return i
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// asciiSet is a 32-byte value, where each bit represents the presence of a
|
|
// given ASCII character in the set. The 128-bits of the lower 16 bytes,
|
|
// starting with the least-significant bit of the lowest word to the
|
|
// most-significant bit of the highest word, map to the full range of all
|
|
// 128 ASCII characters. The 128-bits of the upper 16 bytes will be zeroed,
|
|
// ensuring that any non-ASCII character will be reported as not in the set.
|
|
// This allocates a total of 32 bytes even though the upper half
|
|
// is unused to avoid bounds checks in asciiSet.contains.
|
|
type asciiSet [8]uint32
|
|
|
|
// makeASCIISet creates a set of ASCII characters and reports whether all
|
|
// characters in chars are ASCII.
|
|
func makeASCIISet(chars string) (as asciiSet, ok bool) {
|
|
for i := 0; i < len(chars); i++ {
|
|
c := chars[i]
|
|
if c >= utf8.RuneSelf {
|
|
return as, false
|
|
}
|
|
as[c/32] |= 1 << (c % 32)
|
|
}
|
|
return as, true
|
|
}
|
|
|
|
// contains reports whether c is inside the set.
|
|
func (as *asciiSet) contains(c byte) bool {
|
|
return (as[c/32] & (1 << (c % 32))) != 0
|
|
}
|
|
|
|
// containsRune is a simplified version of strings.ContainsRune
|
|
// to avoid importing the strings package.
|
|
// We avoid bytes.ContainsRune to avoid allocating a temporary copy of s.
|
|
func containsRune(s string, r rune) bool {
|
|
for _, c := range s {
|
|
if c == r {
|
|
return true
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
// Trim returns a subslice of s by slicing off all leading and
|
|
// trailing UTF-8-encoded code points contained in cutset.
|
|
func Trim(s []byte, cutset string) []byte {
|
|
if len(s) == 0 || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimLeftByte(trimRightByte(s, cutset[0]), cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimLeftASCII(trimRightASCII(s, &as), &as)
|
|
}
|
|
return trimLeftUnicode(trimRightUnicode(s, cutset), cutset)
|
|
}
|
|
|
|
// TrimLeft returns a subslice of s by slicing off all leading
|
|
// UTF-8-encoded code points contained in cutset.
|
|
func TrimLeft(s []byte, cutset string) []byte {
|
|
if len(s) == 0 || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimLeftByte(s, cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimLeftASCII(s, &as)
|
|
}
|
|
return trimLeftUnicode(s, cutset)
|
|
}
|
|
|
|
func trimLeftByte(s []byte, c byte) []byte {
|
|
for len(s) > 0 && s[0] == c {
|
|
s = s[1:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimLeftASCII(s []byte, as *asciiSet) []byte {
|
|
for len(s) > 0 {
|
|
if !as.contains(s[0]) {
|
|
break
|
|
}
|
|
s = s[1:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimLeftUnicode(s []byte, cutset string) []byte {
|
|
for len(s) > 0 {
|
|
r, n := rune(s[0]), 1
|
|
if r >= utf8.RuneSelf {
|
|
r, n = utf8.DecodeRune(s)
|
|
}
|
|
if !containsRune(cutset, r) {
|
|
break
|
|
}
|
|
s = s[n:]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// TrimRight returns a subslice of s by slicing off all trailing
|
|
// UTF-8-encoded code points that are contained in cutset.
|
|
func TrimRight(s []byte, cutset string) []byte {
|
|
if len(s) == 0 || cutset == "" {
|
|
return s
|
|
}
|
|
if len(cutset) == 1 && cutset[0] < utf8.RuneSelf {
|
|
return trimRightByte(s, cutset[0])
|
|
}
|
|
if as, ok := makeASCIISet(cutset); ok {
|
|
return trimRightASCII(s, &as)
|
|
}
|
|
return trimRightUnicode(s, cutset)
|
|
}
|
|
|
|
func trimRightByte(s []byte, c byte) []byte {
|
|
for len(s) > 0 && s[len(s)-1] == c {
|
|
s = s[:len(s)-1]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimRightASCII(s []byte, as *asciiSet) []byte {
|
|
for len(s) > 0 {
|
|
if !as.contains(s[len(s)-1]) {
|
|
break
|
|
}
|
|
s = s[:len(s)-1]
|
|
}
|
|
return s
|
|
}
|
|
|
|
func trimRightUnicode(s []byte, cutset string) []byte {
|
|
for len(s) > 0 {
|
|
r, n := rune(s[len(s)-1]), 1
|
|
if r >= utf8.RuneSelf {
|
|
r, n = utf8.DecodeLastRune(s)
|
|
}
|
|
if !containsRune(cutset, r) {
|
|
break
|
|
}
|
|
s = s[:len(s)-n]
|
|
}
|
|
return s
|
|
}
|
|
|
|
// TrimSpace returns a subslice of s by slicing off all leading and
|
|
// trailing white space, as defined by Unicode.
|
|
func TrimSpace(s []byte) []byte {
|
|
// Fast path for ASCII: look for the first ASCII non-space byte
|
|
start := 0
|
|
for ; start < len(s); start++ {
|
|
c := s[start]
|
|
if c >= utf8.RuneSelf {
|
|
// If we run into a non-ASCII byte, fall back to the
|
|
// slower unicode-aware method on the remaining bytes
|
|
return TrimFunc(s[start:], unicode.IsSpace)
|
|
}
|
|
if asciiSpace[c] == 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
// Now look for the first ASCII non-space byte from the end
|
|
stop := len(s)
|
|
for ; stop > start; stop-- {
|
|
c := s[stop-1]
|
|
if c >= utf8.RuneSelf {
|
|
return TrimFunc(s[start:stop], unicode.IsSpace)
|
|
}
|
|
if asciiSpace[c] == 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
// At this point s[start:stop] starts and ends with an ASCII
|
|
// non-space bytes, so we're done. Non-ASCII cases have already
|
|
// been handled above.
|
|
if start == stop {
|
|
// Special case to preserve previous TrimLeftFunc behavior,
|
|
// returning nil instead of empty slice if all spaces.
|
|
return nil
|
|
}
|
|
return s[start:stop]
|
|
}
|
|
|
|
// Runes interprets s as a sequence of UTF-8-encoded code points.
|
|
// It returns a slice of runes (Unicode code points) equivalent to s.
|
|
func Runes(s []byte) []rune {
|
|
t := make([]rune, utf8.RuneCount(s))
|
|
i := 0
|
|
for len(s) > 0 {
|
|
r, l := utf8.DecodeRune(s)
|
|
t[i] = r
|
|
i++
|
|
s = s[l:]
|
|
}
|
|
return t
|
|
}
|
|
|
|
// Replace returns a copy of the slice s with the first n
|
|
// non-overlapping instances of old replaced by new.
|
|
// If old is empty, it matches at the beginning of the slice
|
|
// and after each UTF-8 sequence, yielding up to k+1 replacements
|
|
// for a k-rune slice.
|
|
// If n < 0, there is no limit on the number of replacements.
|
|
func Replace(s, old, new []byte, n int) []byte {
|
|
m := 0
|
|
if n != 0 {
|
|
// Compute number of replacements.
|
|
m = Count(s, old)
|
|
}
|
|
if m == 0 {
|
|
// Just return a copy.
|
|
return append([]byte(nil), s...)
|
|
}
|
|
if n < 0 || m < n {
|
|
n = m
|
|
}
|
|
|
|
// Apply replacements to buffer.
|
|
t := make([]byte, len(s)+n*(len(new)-len(old)))
|
|
w := 0
|
|
start := 0
|
|
for i := 0; i < n; i++ {
|
|
j := start
|
|
if len(old) == 0 {
|
|
if i > 0 {
|
|
_, wid := utf8.DecodeRune(s[start:])
|
|
j += wid
|
|
}
|
|
} else {
|
|
j += Index(s[start:], old)
|
|
}
|
|
w += copy(t[w:], s[start:j])
|
|
w += copy(t[w:], new)
|
|
start = j + len(old)
|
|
}
|
|
w += copy(t[w:], s[start:])
|
|
return t[0:w]
|
|
}
|
|
|
|
// ReplaceAll returns a copy of the slice s with all
|
|
// non-overlapping instances of old replaced by new.
|
|
// If old is empty, it matches at the beginning of the slice
|
|
// and after each UTF-8 sequence, yielding up to k+1 replacements
|
|
// for a k-rune slice.
|
|
func ReplaceAll(s, old, new []byte) []byte {
|
|
return Replace(s, old, new, -1)
|
|
}
|
|
|
|
// EqualFold reports whether s and t, interpreted as UTF-8 strings,
|
|
// are equal under Unicode case-folding, which is a more general
|
|
// form of case-insensitivity.
|
|
func EqualFold(s, t []byte) bool {
|
|
for len(s) != 0 && len(t) != 0 {
|
|
// Extract first rune from each.
|
|
var sr, tr rune
|
|
if s[0] < utf8.RuneSelf {
|
|
sr, s = rune(s[0]), s[1:]
|
|
} else {
|
|
r, size := utf8.DecodeRune(s)
|
|
sr, s = r, s[size:]
|
|
}
|
|
if t[0] < utf8.RuneSelf {
|
|
tr, t = rune(t[0]), t[1:]
|
|
} else {
|
|
r, size := utf8.DecodeRune(t)
|
|
tr, t = r, t[size:]
|
|
}
|
|
|
|
// If they match, keep going; if not, return false.
|
|
|
|
// Easy case.
|
|
if tr == sr {
|
|
continue
|
|
}
|
|
|
|
// Make sr < tr to simplify what follows.
|
|
if tr < sr {
|
|
tr, sr = sr, tr
|
|
}
|
|
// Fast check for ASCII.
|
|
if tr < utf8.RuneSelf {
|
|
// ASCII only, sr/tr must be upper/lower case
|
|
if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' {
|
|
continue
|
|
}
|
|
return false
|
|
}
|
|
|
|
// General case. SimpleFold(x) returns the next equivalent rune > x
|
|
// or wraps around to smaller values.
|
|
r := unicode.SimpleFold(sr)
|
|
for r != sr && r < tr {
|
|
r = unicode.SimpleFold(r)
|
|
}
|
|
if r == tr {
|
|
continue
|
|
}
|
|
return false
|
|
}
|
|
|
|
// One string is empty. Are both?
|
|
return len(s) == len(t)
|
|
}
|
|
|
|
// 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 <= bytealg.MaxLen:
|
|
// Use brute force when s and sep both are small
|
|
if len(s) <= bytealg.MaxBruteForce {
|
|
return bytealg.Index(s, sep)
|
|
}
|
|
c0 := sep[0]
|
|
c1 := sep[1]
|
|
i := 0
|
|
t := len(s) - n + 1
|
|
fails := 0
|
|
for i < t {
|
|
if s[i] != c0 {
|
|
// IndexByte is faster than bytealg.Index, so use it as long as
|
|
// we're not getting lots of false positives.
|
|
o := IndexByte(s[i+1:t], c0)
|
|
if o < 0 {
|
|
return -1
|
|
}
|
|
i += o + 1
|
|
}
|
|
if s[i+1] == c1 && Equal(s[i:i+n], sep) {
|
|
return i
|
|
}
|
|
fails++
|
|
i++
|
|
// Switch to bytealg.Index when IndexByte produces too many false positives.
|
|
if fails > bytealg.Cutover(i) {
|
|
r := bytealg.Index(s[i:], sep)
|
|
if r >= 0 {
|
|
return r + i
|
|
}
|
|
return -1
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
c0 := sep[0]
|
|
c1 := sep[1]
|
|
i := 0
|
|
fails := 0
|
|
t := len(s) - n + 1
|
|
for i < t {
|
|
if s[i] != c0 {
|
|
o := IndexByte(s[i+1:t], c0)
|
|
if o < 0 {
|
|
break
|
|
}
|
|
i += o + 1
|
|
}
|
|
if s[i+1] == c1 && Equal(s[i:i+n], sep) {
|
|
return i
|
|
}
|
|
i++
|
|
fails++
|
|
if fails >= 4+i>>4 && i < t {
|
|
// Give up on IndexByte, it isn't skipping ahead
|
|
// far enough to be better than Rabin-Karp.
|
|
// Experiments (using IndexPeriodic) suggest
|
|
// the cutover is about 16 byte skips.
|
|
// TODO: if large prefixes of sep are matching
|
|
// we should cutover at even larger average skips,
|
|
// because Equal becomes that much more expensive.
|
|
// This code does not take that effect into account.
|
|
j := bytealg.IndexRabinKarpBytes(s[i:], sep)
|
|
if j < 0 {
|
|
return -1
|
|
}
|
|
return i + j
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
// Cut slices s around the first instance of sep,
|
|
// returning the text before and after sep.
|
|
// The found result reports whether sep appears in s.
|
|
// If sep does not appear in s, cut returns s, nil, false.
|
|
//
|
|
// Cut returns slices of the original slice s, not copies.
|
|
func Cut(s, sep []byte) (before, after []byte, found bool) {
|
|
if i := Index(s, sep); i >= 0 {
|
|
return s[:i], s[i+len(sep):], true
|
|
}
|
|
return s, nil, false
|
|
}
|