Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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
+}