// Copyright 2009 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 implements functions for the manipulation of byte slices. // It is analogous to the facilities of the [strings] package. package bytes import ( "internal/bytealg" "unicode" "unicode/utf8" ) // Equal reports whether a and b // are the same length and contain the same bytes. // A nil argument is equivalent to an empty slice. func Equal(a, b []byte) bool { // Neither cmd/compile nor gccgo allocates for these string conversions. return string(a) == string(b) } // Compare returns an integer comparing two byte slices lexicographically. // The result will be 0 if a == b, -1 if a < b, and +1 if a > b. // A nil argument is equivalent to an empty slice. func Compare(a, b []byte) int { return bytealg.Compare(a, b) } // explode splits s into a slice of UTF-8 sequences, one per Unicode code point (still slices of bytes), // up to a maximum of n byte slices. Invalid UTF-8 sequences are chopped into individual bytes. func explode(s []byte, n int) [][]byte { if n <= 0 || n > len(s) { n = len(s) } a := make([][]byte, n) var size int na := 0 for len(s) > 0 { if na+1 >= n { a[na] = s na++ break } _, size = utf8.DecodeRune(s) a[na] = s[0:size:size] s = s[size:] na++ } return a[0:na] } // 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 { // special case if len(sep) == 0 { return utf8.RuneCount(s) + 1 } if len(sep) == 1 { return bytealg.Count(s, sep[0]) } n := 0 for { i := Index(s, sep) if i == -1 { return n } n++ s = s[i+len(sep):] } } // Contains reports whether subslice is within b. func Contains(b, subslice []byte) bool { return Index(b, subslice) != -1 } // ContainsAny reports whether any of the UTF-8-encoded code points in chars are within b. func ContainsAny(b []byte, chars string) bool { return IndexAny(b, chars) >= 0 } // ContainsRune reports whether the rune is contained in the UTF-8-encoded byte slice b. func ContainsRune(b []byte, r rune) bool { return IndexRune(b, r) >= 0 } // ContainsFunc reports whether any of the UTF-8-encoded code points r within b satisfy f(r). func ContainsFunc(b []byte, f func(rune) bool) bool { return IndexFunc(b, f) >= 0 } // IndexByte returns the index of the first instance of c in b, or -1 if c is not present in b. func IndexByte(b []byte, c byte) int { return bytealg.IndexByte(b, c) } func indexBytePortable(s []byte, c byte) int { for i, b := range s { if b == c { return i } } return -1 } // LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s. func LastIndex(s, sep []byte) int { n := len(sep) switch { case n == 0: return len(s) case n == 1: return bytealg.LastIndexByte(s, sep[0]) case n == len(s): if Equal(s, sep) { return 0 } return -1 case n > len(s): return -1 } return bytealg.LastIndexRabinKarp(s, sep) } // LastIndexByte returns the index of the last instance of c in s, or -1 if c is not present in s. func LastIndexByte(s []byte, c byte) int { return bytealg.LastIndexByte(s, c) } // IndexRune interprets s as a sequence of UTF-8-encoded code points. // It returns the byte index of the first occurrence in s of the given rune. // It returns -1 if rune is not present in s. // If r is utf8.RuneError, it returns the first instance of any // invalid UTF-8 byte sequence. func IndexRune(s []byte, r rune) int { switch { case 0 <= r && r < utf8.RuneSelf: return IndexByte(s, byte(r)) case r == utf8.RuneError: for i := 0; i < len(s); { r1, n := utf8.DecodeRune(s[i:]) if r1 == utf8.RuneError { return i } i += n } return -1 case !utf8.ValidRune(r): return -1 default: var b [utf8.UTFMax]byte n := utf8.EncodeRune(b[:], r) return Index(s, b[:n]) } } // IndexAny interprets s as a sequence of UTF-8-encoded Unicode code points. // It returns the byte index of the first occurrence in s of any of the Unicode // code points in chars. It returns -1 if chars is empty or if there is no code // point in common. func IndexAny(s []byte, chars string) int { if chars == "" { // Avoid scanning all of s. return -1 } if len(s) == 1 { r := rune(s[0]) if r >= utf8.RuneSelf { // search utf8.RuneError. for _, r = range chars { if r == utf8.RuneError { return 0 } } return -1 } if bytealg.IndexByteString(chars, s[0]) >= 0 { return 0 } return -1 } if len(chars) == 1 { r := rune(chars[0]) if r >= utf8.RuneSelf { r = utf8.RuneError } return IndexRune(s, r) } if len(s) > 8 { if as, isASCII := makeASCIISet(chars); isASCII { for i, c := range s { if as.contains(c) { return i } } return -1 } } var width int for i := 0; i < len(s); i += width { r := rune(s[i]) if r < utf8.RuneSelf { if bytealg.IndexByteString(chars, s[i]) >= 0 { return i } width = 1 continue } r, width = utf8.DecodeRune(s[i:]) if r != utf8.RuneError { // r is 2 to 4 bytes if len(chars) == width { if chars == string(r) { return i } continue } // Use bytealg.IndexString for performance if available. if bytealg.MaxLen >= width { if bytealg.IndexString(chars, string(r)) >= 0 { return i } continue } } for _, ch := range chars { if r == ch { return i } } } return -1 } // LastIndexAny interprets s as a sequence of UTF-8-encoded Unicode code // points. It returns the byte index of the last occurrence in s of any of // the Unicode code points in chars. It returns -1 if chars is empty or if // there is no code point in common. func LastIndexAny(s []byte, chars string) int { if chars == "" { // Avoid scanning all of s. return -1 } if len(s) > 8 { if as, isASCII := makeASCIISet(chars); isASCII { for i := len(s) - 1; i >= 0; i-- { if as.contains(s[i]) { return i } } return -1 } } if len(s) == 1 { r := rune(s[0]) if r >= utf8.RuneSelf { for _, r = range chars { if r == utf8.RuneError { return 0 } } return -1 } if bytealg.IndexByteString(chars, s[0]) >= 0 { return 0 } return -1 } if len(chars) == 1 { cr := rune(chars[0]) if cr >= utf8.RuneSelf { cr = utf8.RuneError } for i := len(s); i > 0; { r, size := utf8.DecodeLastRune(s[:i]) i -= size if r == cr { return i } } return -1 } for i := len(s); i > 0; { r := rune(s[i-1]) if r < utf8.RuneSelf { if bytealg.IndexByteString(chars, s[i-1]) >= 0 { return i - 1 } i-- continue } r, size := utf8.DecodeLastRune(s[:i]) i -= size if r != utf8.RuneError { // r is 2 to 4 bytes if len(chars) == size { if chars == string(r) { return i } continue } // Use bytealg.IndexString for performance if available. if bytealg.MaxLen >= size { if bytealg.IndexString(chars, string(r)) >= 0 { return i } continue } } for _, ch := range chars { if r == ch { return i } } } return -1 } // Generic split: splits after each instance of sep, // including sepSave bytes of sep in the subslices. func genSplit(s, sep []byte, sepSave, n int) [][]byte { if n == 0 { return nil } if len(sep) == 0 { return explode(s, n) } if n < 0 { n = Count(s, sep) + 1 } if n > len(s)+1 { n = len(s) + 1 } a := make([][]byte, n) n-- i := 0 for i < n { m := Index(s, sep) if m < 0 { break } a[i] = s[: m+sepSave : m+sepSave] s = s[m+len(sep):] i++ } a[i] = s return a[:i+1] } // SplitN slices s into subslices separated by sep and returns a slice of // the subslices between those separators. // If sep is empty, SplitN splits after each UTF-8 sequence. // The count determines the number of subslices to return: // // n > 0: at most n subslices; the last subslice will be the unsplit remainder. // n == 0: the result is nil (zero subslices) // n < 0: all subslices // // To split around the first instance of a separator, see Cut. func SplitN(s, sep []byte, n int) [][]byte { return genSplit(s, sep, 0, n) } // SplitAfterN slices s into subslices after each instance of sep and // returns a slice of those subslices. // If sep is empty, SplitAfterN splits after each UTF-8 sequence. // The count determines the number of subslices to return: // // n > 0: at most n subslices; the last subslice will be the unsplit remainder. // n == 0: the result is nil (zero subslices) // n < 0: all subslices func SplitAfterN(s, sep []byte, n int) [][]byte { return genSplit(s, sep, len(sep), n) } // Split slices s into all subslices separated by sep and returns a slice of // the subslices between those separators. // If sep is empty, Split splits after each UTF-8 sequence. // It is equivalent to SplitN with a count of -1. // // To split around the first instance of a separator, see Cut. func Split(s, sep []byte) [][]byte { return genSplit(s, sep, 0, -1) } // SplitAfter slices s into all subslices after each instance of sep and // returns a slice of those subslices. // If sep is empty, SplitAfter splits after each UTF-8 sequence. // It is equivalent to SplitAfterN with a count of -1. func SplitAfter(s, sep []byte) [][]byte { return genSplit(s, sep, len(sep), -1) } var asciiSpace = [256]uint8{'\t': 1, '\n': 1, '\v': 1, '\f': 1, '\r': 1, ' ': 1} // Fields interprets s as a sequence of UTF-8-encoded code points. // It splits the slice s around each instance of one or more consecutive white space // characters, as defined by unicode.IsSpace, returning a slice of subslices of s or an // empty slice if s contains only white space. func Fields(s []byte) [][]byte { // First count the fields. // This is an exact count if s is ASCII, otherwise it is an approximation. n := 0 wasSpace := 1 // setBits is used to track which bits are set in the bytes of s. setBits := uint8(0) for i := 0; i < len(s); i++ { r := s[i] setBits |= r isSpace := int(asciiSpace[r]) n += wasSpace & ^isSpace wasSpace = isSpace } if setBits >= utf8.RuneSelf { // Some runes in the input slice are not ASCII. return FieldsFunc(s, unicode.IsSpace) } // ASCII fast path a := make([][]byte, n) na := 0 fieldStart := 0 i := 0 // Skip spaces in the front of the input. for i < len(s) && asciiSpace[s[i]] != 0 { i++ } fieldStart = i for i < len(s) { if asciiSpace[s[i]] == 0 { i++ continue } a[na] = s[fieldStart:i:i] na++ i++ // Skip spaces in between fields. for i < len(s) && asciiSpace[s[i]] != 0 { i++ } fieldStart = i } if fieldStart < len(s) { // Last field might end at EOF. a[na] = s[fieldStart:len(s):len(s)] } return a } // FieldsFunc interprets s as a sequence of UTF-8-encoded code points. // It splits the slice s at each run of code points c satisfying f(c) and // returns a slice of subslices of s. If all code points in s satisfy f(c), or // len(s) == 0, an empty slice is returned. // // FieldsFunc makes no guarantees about the order in which it calls f(c) // and assumes that f always returns the same value for a given c. func FieldsFunc(s []byte, f func(rune) bool) [][]byte { // A span is used to record a slice of s of the form s[start:end]. // The start index is inclusive and the end index is exclusive. type span struct { start int end int } spans := make([]span, 0, 32) // Find the field start and end indices. // Doing this in a separate pass (rather than slicing the string s // and collecting the result substrings right away) is significantly // more efficient, possibly due to cache effects. start := -1 // valid span start if >= 0 for i := 0; i < len(s); { size := 1 r := rune(s[i]) if r >= utf8.RuneSelf { r, size = utf8.DecodeRune(s[i:]) } if f(r) { if start >= 0 { spans = append(spans, span{start, i}) start = -1 } } else { if start < 0 { start = i } } i += size } // Last field might end at EOF. if start >= 0 { spans = append(spans, span{start, len(s)}) } // Create subslices from recorded field indices. a := make([][]byte, len(spans)) for i, span := range spans { a[i] = s[span.start:span.end:span.end] } return a } // Join concatenates the elements of s to create a new byte slice. The separator // sep is placed between elements in the resulting slice. func Join(s [][]byte, sep []byte) []byte { if len(s) == 0 { return []byte{} } if len(s) == 1 { // Just return a copy. return append([]byte(nil), s[0]...) } var n int if len(sep) > 0 { if len(sep) >= maxInt/(len(s)-1) { panic("bytes: Join output length overflow") } n += len(sep) * (len(s) - 1) } for _, v := range s { if len(v) > maxInt-n { panic("bytes: Join output length overflow") } n += len(v) } b := bytealg.MakeNoZero(n) bp := copy(b, s[0]) for _, v := range s[1:] { bp += copy(b[bp:], sep) bp += copy(b[bp:], v) } return b } // HasPrefix reports 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 reports 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. b := make([]byte, 0, len(s)) 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 { b = utf8.AppendRune(b, r) } i += wid } return b } // 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 golang.org/issue/16237. if count < 0 { panic("bytes: negative Repeat count") } if len(b) >= maxInt/count { panic("bytes: Repeat output length overflow") } n := len(b) * count if len(b) == 0 { return []byte{} } // Past a certain chunk size it is counterproductive to use // larger chunks as the source of the write, as when the source // is too large we are basically just thrashing the CPU D-cache. // So if the result length is larger than an empirically-found // limit (8KB), we stop growing the source string once the limit // is reached and keep reusing the same source string - that // should therefore be always resident in the L1 cache - until we // have completed the construction of the result. // This yields significant speedups (up to +100%) in cases where // the result length is large (roughly, over L2 cache size). const chunkLimit = 8 * 1024 chunkMax := n if chunkMax > chunkLimit { chunkMax = chunkLimit / len(b) * len(b) if chunkMax == 0 { chunkMax = len(b) } } nb := bytealg.MakeNoZero(n) bp := copy(nb, b) for bp < n { chunk := bp if chunk > chunkMax { chunk = chunkMax } bp += copy(nb[bp:], nb[:chunk]) } 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 := bytealg.MakeNoZero(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 := bytealg.MakeNoZero(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 { // This is what we've historically done. return nil } if 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 { // This is what we've historically done. return nil } if 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:] } if len(s) == 0 { // This is what we've historically done. return nil } return s } func trimLeftASCII(s []byte, as *asciiSet) []byte { for len(s) > 0 { if !as.contains(s[0]) { break } s = s[1:] } if len(s) == 0 { // This is what we've historically done. return nil } 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:] } if len(s) == 0 { // This is what we've historically done. return nil } 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 simple Unicode case-folding, which is a more general // form of case-insensitivity. func EqualFold(s, t []byte) bool { // ASCII fast path i := 0 for ; i < len(s) && i < len(t); i++ { sr := s[i] tr := t[i] if sr|tr >= utf8.RuneSelf { goto hasUnicode } // Easy case. if tr == sr { continue } // Make sr < tr to simplify what follows. if tr < sr { tr, sr = sr, tr } // ASCII only, sr/tr must be upper/lower case if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' { continue } return false } // Check if we've exhausted both strings. return len(s) == len(t) hasUnicode: s = s[i:] t = t[i:] 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.IndexRabinKarp(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 } // Clone returns a copy of b[:len(b)]. // The result may have additional unused capacity. // Clone(nil) returns nil. func Clone(b []byte) []byte { if b == nil { return nil } return append([]byte{}, b...) } // CutPrefix returns s without the provided leading prefix byte slice // and reports whether it found the prefix. // If s doesn't start with prefix, CutPrefix returns s, false. // If prefix is the empty byte slice, CutPrefix returns s, true. // // CutPrefix returns slices of the original slice s, not copies. func CutPrefix(s, prefix []byte) (after []byte, found bool) { if !HasPrefix(s, prefix) { return s, false } return s[len(prefix):], true } // CutSuffix returns s without the provided ending suffix byte slice // and reports whether it found the suffix. // If s doesn't end with suffix, CutSuffix returns s, false. // If suffix is the empty byte slice, CutSuffix returns s, true. // // CutSuffix returns slices of the original slice s, not copies. func CutSuffix(s, suffix []byte) (before []byte, found bool) { if !HasSuffix(s, suffix) { return s, false } return s[:len(s)-len(suffix)], true }