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Diffstat (limited to 'src/bytes/bytes.go')
-rw-r--r-- | src/bytes/bytes.go | 1381 |
1 files changed, 1381 insertions, 0 deletions
diff --git a/src/bytes/bytes.go b/src/bytes/bytes.go new file mode 100644 index 0000000..e2e5d5f --- /dev/null +++ b/src/bytes/bytes.go @@ -0,0 +1,1381 @@ +// 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 +} + +// 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 LastIndexByte(s, sep[0]) + case n == len(s): + if Equal(s, sep) { + return 0 + } + return -1 + case n > len(s): + return -1 + } + // Rabin-Karp search from the end of the string + hashss, pow := bytealg.HashStrRevBytes(sep) + last := len(s) - n + var h uint32 + for i := len(s) - 1; i >= last; i-- { + h = h*bytealg.PrimeRK + uint32(s[i]) + } + if h == hashss && Equal(s[last:], sep) { + return last + } + for i := last - 1; i >= 0; i-- { + h *= bytealg.PrimeRK + h += uint32(s[i]) + h -= pow * uint32(s[i+n]) + if h == hashss && Equal(s[i:i+n], sep) { + return i + } + } + return -1 +} + +// 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 { + for i := len(s) - 1; i >= 0; i-- { + if s[i] == c { + return i + } + } + return -1 +} + +// 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]...) + } + n := len(sep) * (len(s) - 1) + for _, v := range s { + n += len(v) + } + + b := make([]byte, n) + bp := copy(b, s[0]) + for _, v := range s[1:] { + bp += copy(b[bp:], sep) + bp += copy(b[bp:], v) + } + return b +} + +// 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. + 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") + } else if len(b)*count/count != len(b) { + panic("bytes: Repeat count causes overflow") + } + + if len(b) == 0 { + return []byte{} + } + + n := len(b) * count + + // 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 := make([]byte, n) + bp := copy(nb, b) + for bp < len(nb) { + 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 := 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 { + // 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.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 +} + +// 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 +} |