Imported Upstream version 1.4upstream/1.4

1 files changed, 762 insertions, 0 deletions

diff --git a/src/strings/strings.go b/src/strings/strings.go
new file mode 100644
index 000000000..27d384983
--- /dev/null
+++ b/src/strings/strings.go
@@ -0,0 +1,762 @@
+// 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 strings implements simple functions to manipulate strings.
+package strings
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+// explode splits s into an array of UTF-8 sequences, one per Unicode character (still strings) up to a maximum of n (n < 0 means no limit).
+// Invalid UTF-8 sequences become correct encodings of U+FFF8.
+func explode(s string, n int) []string {
+	if n == 0 {
+		return nil
+	}
+	l := utf8.RuneCountInString(s)
+	if n <= 0 || n > l {
+		n = l
+	}
+	a := make([]string, n)
+	var size int
+	var ch rune
+	i, cur := 0, 0
+	for ; i+1 < n; i++ {
+		ch, size = utf8.DecodeRuneInString(s[cur:])
+		if ch == utf8.RuneError {
+			a[i] = string(utf8.RuneError)
+		} else {
+			a[i] = s[cur : cur+size]
+		}
+		cur += size
+	}
+	// add the rest, if there is any
+	if cur < len(s) {
+		a[i] = s[cur:]
+	}
+	return a
+}
+
+// primeRK is the prime base used in Rabin-Karp algorithm.
+const primeRK = 16777619
+
+// hashStr returns the hash and the appropriate multiplicative
+// factor for use in Rabin-Karp algorithm.
+func hashStr(sep string) (uint32, uint32) {
+	hash := uint32(0)
+	for i := 0; i < len(sep); i++ {
+		hash = hash*primeRK + uint32(sep[i])
+	}
+	var pow, sq uint32 = 1, primeRK
+	for i := len(sep); i > 0; i >>= 1 {
+		if i&1 != 0 {
+			pow *= sq
+		}
+		sq *= sq
+	}
+	return hash, pow
+}
+
+// hashStrRev returns the hash of the reverse of sep and the
+// appropriate multiplicative factor for use in Rabin-Karp algorithm.
+func hashStrRev(sep string) (uint32, uint32) {
+	hash := uint32(0)
+	for i := len(sep) - 1; i >= 0; i-- {
+		hash = hash*primeRK + uint32(sep[i])
+	}
+	var pow, sq uint32 = 1, primeRK
+	for i := len(sep); i > 0; i >>= 1 {
+		if i&1 != 0 {
+			pow *= sq
+		}
+		sq *= sq
+	}
+	return hash, pow
+}
+
+// Count counts the number of non-overlapping instances of sep in s.
+func Count(s, sep string) int {
+	n := 0
+	// special cases
+	switch {
+	case len(sep) == 0:
+		return utf8.RuneCountInString(s) + 1
+	case len(sep) == 1:
+		// special case worth making fast
+		c := sep[0]
+		for i := 0; i < len(s); i++ {
+			if s[i] == c {
+				n++
+			}
+		}
+		return n
+	case len(sep) > len(s):
+		return 0
+	case len(sep) == len(s):
+		if sep == s {
+			return 1
+		}
+		return 0
+	}
+	// Rabin-Karp search
+	hashsep, pow := hashStr(sep)
+	h := uint32(0)
+	for i := 0; i < len(sep); i++ {
+		h = h*primeRK + uint32(s[i])
+	}
+	lastmatch := 0
+	if h == hashsep && s[:len(sep)] == sep {
+		n++
+		lastmatch = len(sep)
+	}
+	for i := len(sep); i < len(s); {
+		h *= primeRK
+		h += uint32(s[i])
+		h -= pow * uint32(s[i-len(sep)])
+		i++
+		if h == hashsep && lastmatch <= i-len(sep) && s[i-len(sep):i] == sep {
+			n++
+			lastmatch = i
+		}
+	}
+	return n
+}
+
+// Contains returns true if substr is within s.
+func Contains(s, substr string) bool {
+	return Index(s, substr) >= 0
+}
+
+// ContainsAny returns true if any Unicode code points in chars are within s.
+func ContainsAny(s, chars string) bool {
+	return IndexAny(s, chars) >= 0
+}
+
+// ContainsRune returns true if the Unicode code point r is within s.
+func ContainsRune(s string, r rune) bool {
+	return IndexRune(s, r) >= 0
+}
+
+// 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 string) int {
+	n := len(sep)
+	switch {
+	case n == 0:
+		return 0
+	case n == 1:
+		return IndexByte(s, sep[0])
+	case n == len(s):
+		if sep == s {
+			return 0
+		}
+		return -1
+	case n > len(s):
+		return -1
+	}
+	// Rabin-Karp search
+	hashsep, pow := hashStr(sep)
+	var h uint32
+	for i := 0; i < n; i++ {
+		h = h*primeRK + uint32(s[i])
+	}
+	if h == hashsep && s[:n] == sep {
+		return 0
+	}
+	for i := n; i < len(s); {
+		h *= primeRK
+		h += uint32(s[i])
+		h -= pow * uint32(s[i-n])
+		i++
+		if h == hashsep && s[i-n:i] == sep {
+			return i - n
+		}
+	}
+	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 string) int {
+	n := len(sep)
+	switch {
+	case n == 0:
+		return len(s)
+	case n == 1:
+		// special case worth making fast
+		c := sep[0]
+		for i := len(s) - 1; i >= 0; i-- {
+			if s[i] == c {
+				return i
+			}
+		}
+		return -1
+	case n == len(s):
+		if sep == s {
+			return 0
+		}
+		return -1
+	case n > len(s):
+		return -1
+	}
+	// Rabin-Karp search from the end of the string
+	hashsep, pow := hashStrRev(sep)
+	last := len(s) - n
+	var h uint32
+	for i := len(s) - 1; i >= last; i-- {
+		h = h*primeRK + uint32(s[i])
+	}
+	if h == hashsep && s[last:] == sep {
+		return last
+	}
+	for i := last - 1; i >= 0; i-- {
+		h *= primeRK
+		h += uint32(s[i])
+		h -= pow * uint32(s[i+n])
+		if h == hashsep && s[i:i+n] == sep {
+			return i
+		}
+	}
+	return -1
+}
+
+// IndexRune returns the index of the first instance of the Unicode code point
+// r, or -1 if rune is not present in s.
+func IndexRune(s string, r rune) int {
+	switch {
+	case r < utf8.RuneSelf:
+		return IndexByte(s, byte(r))
+	default:
+		for i, c := range s {
+			if c == r {
+				return i
+			}
+		}
+	}
+	return -1
+}
+
+// IndexAny returns the index of the first instance of any Unicode code point
+// from chars in s, or -1 if no Unicode code point from chars is present in s.
+func IndexAny(s, chars string) int {
+	if len(chars) > 0 {
+		for i, c := range s {
+			for _, m := range chars {
+				if c == m {
+					return i
+				}
+			}
+		}
+	}
+	return -1
+}
+
+// LastIndexAny returns the index of the last instance of any Unicode code
+// point from chars in s, or -1 if no Unicode code point from chars is
+// present in s.
+func LastIndexAny(s, chars string) int {
+	if len(chars) > 0 {
+		for i := len(s); i > 0; {
+			rune, size := utf8.DecodeLastRuneInString(s[0:i])
+			i -= size
+			for _, m := range chars {
+				if rune == m {
+					return i
+				}
+			}
+		}
+	}
+	return -1
+}
+
+// Generic split: splits after each instance of sep,
+// including sepSave bytes of sep in the subarrays.
+func genSplit(s, sep string, sepSave, n int) []string {
+	if n == 0 {
+		return nil
+	}
+	if sep == "" {
+		return explode(s, n)
+	}
+	if n < 0 {
+		n = Count(s, sep) + 1
+	}
+	c := sep[0]
+	start := 0
+	a := make([]string, n)
+	na := 0
+	for i := 0; i+len(sep) <= len(s) && na+1 < n; i++ {
+		if s[i] == c && (len(sep) == 1 || s[i:i+len(sep)] == sep) {
+			a[na] = s[start : i+sepSave]
+			na++
+			start = i + len(sep)
+			i += len(sep) - 1
+		}
+	}
+	a[na] = s[start:]
+	return a[0 : na+1]
+}
+
+// SplitN slices s into substrings separated by sep and returns a slice of
+// the substrings between those separators.
+// If sep is empty, SplitN splits after each UTF-8 sequence.
+// The count determines the number of substrings to return:
+//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
+//   n == 0: the result is nil (zero substrings)
+//   n < 0: all substrings
+func SplitN(s, sep string, n int) []string { return genSplit(s, sep, 0, n) }
+
+// SplitAfterN slices s into substrings after each instance of sep and
+// returns a slice of those substrings.
+// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
+// The count determines the number of substrings to return:
+//   n > 0: at most n substrings; the last substring will be the unsplit remainder.
+//   n == 0: the result is nil (zero substrings)
+//   n < 0: all substrings
+func SplitAfterN(s, sep string, n int) []string {
+	return genSplit(s, sep, len(sep), n)
+}
+
+// Split slices s into all substrings separated by sep and returns a slice of
+// the substrings between those separators.
+// If sep is empty, Split splits after each UTF-8 sequence.
+// It is equivalent to SplitN with a count of -1.
+func Split(s, sep string) []string { return genSplit(s, sep, 0, -1) }
+
+// SplitAfter slices s into all substrings after each instance of sep and
+// returns a slice of those substrings.
+// 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 string) []string {
+	return genSplit(s, sep, len(sep), -1)
+}
+
+// Fields splits the string s around each instance of one or more consecutive white space
+// characters, as defined by unicode.IsSpace, returning an array of substrings of s or an
+// empty list if s contains only white space.
+func Fields(s string) []string {
+	return FieldsFunc(s, unicode.IsSpace)
+}
+
+// FieldsFunc splits the string s at each run of Unicode code points c satisfying f(c)
+// and returns an array of slices of s. If all code points in s satisfy f(c) or the
+// string is empty, an empty slice is returned.
+// FieldsFunc makes no guarantees about the order in which it calls f(c).
+// If f does not return consistent results for a given c, FieldsFunc may crash.
+func FieldsFunc(s string, f func(rune) bool) []string {
+	// First count the fields.
+	n := 0
+	inField := false
+	for _, rune := range s {
+		wasInField := inField
+		inField = !f(rune)
+		if inField && !wasInField {
+			n++
+		}
+	}
+
+	// Now create them.
+	a := make([]string, n)
+	na := 0
+	fieldStart := -1 // Set to -1 when looking for start of field.
+	for i, rune := range s {
+		if f(rune) {
+			if fieldStart >= 0 {
+				a[na] = s[fieldStart:i]
+				na++
+				fieldStart = -1
+			}
+		} else if fieldStart == -1 {
+			fieldStart = i
+		}
+	}
+	if fieldStart >= 0 { // Last field might end at EOF.
+		a[na] = s[fieldStart:]
+	}
+	return a
+}
+
+// Join concatenates the elements of a to create a single string.   The separator string
+// sep is placed between elements in the resulting string.
+func Join(a []string, sep string) string {
+	if len(a) == 0 {
+		return ""
+	}
+	if len(a) == 1 {
+		return a[0]
+	}
+	n := len(sep) * (len(a) - 1)
+	for i := 0; i < len(a); i++ {
+		n += len(a[i])
+	}
+
+	b := make([]byte, n)
+	bp := copy(b, a[0])
+	for _, s := range a[1:] {
+		bp += copy(b[bp:], sep)
+		bp += copy(b[bp:], s)
+	}
+	return string(b)
+}
+
+// HasPrefix tests whether the string s begins with prefix.
+func HasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[0:len(prefix)] == prefix
+}
+
+// HasSuffix tests whether the string s ends with suffix.
+func HasSuffix(s, suffix string) bool {
+	return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
+}
+
+// Map returns a copy of the string s with all its characters modified
+// according to the mapping function. If mapping returns a negative value, the character is
+// dropped from the string with no replacement.
+func Map(mapping func(rune) rune, s string) string {
+	// In the worst case, the string can grow when mapped, making
+	// things unpleasant.  But it's so rare we barge in assuming it's
+	// fine.  It could also shrink but that falls out naturally.
+	maxbytes := len(s) // length of b
+	nbytes := 0        // number of bytes encoded in b
+	// The output buffer b is initialized on demand, the first
+	// time a character differs.
+	var b []byte
+
+	for i, c := range s {
+		r := mapping(c)
+		if b == nil {
+			if r == c {
+				continue
+			}
+			b = make([]byte, maxbytes)
+			nbytes = copy(b, s[:i])
+		}
+		if r >= 0 {
+			wid := 1
+			if r >= utf8.RuneSelf {
+				wid = utf8.RuneLen(r)
+			}
+			if nbytes+wid > maxbytes {
+				// Grow the buffer.
+				maxbytes = maxbytes*2 + utf8.UTFMax
+				nb := make([]byte, maxbytes)
+				copy(nb, b[0:nbytes])
+				b = nb
+			}
+			nbytes += utf8.EncodeRune(b[nbytes:maxbytes], r)
+		}
+	}
+	if b == nil {
+		return s
+	}
+	return string(b[0:nbytes])
+}
+
+// Repeat returns a new string consisting of count copies of the string s.
+func Repeat(s string, count int) string {
+	b := make([]byte, len(s)*count)
+	bp := copy(b, s)
+	for bp < len(b) {
+		copy(b[bp:], b[:bp])
+		bp *= 2
+	}
+	return string(b)
+}
+
+// ToUpper returns a copy of the string s with all Unicode letters mapped to their upper case.
+func ToUpper(s string) string { return Map(unicode.ToUpper, s) }
+
+// ToLower returns a copy of the string s with all Unicode letters mapped to their lower case.
+func ToLower(s string) string { return Map(unicode.ToLower, s) }
+
+// ToTitle returns a copy of the string s with all Unicode letters mapped to their title case.
+func ToTitle(s string) string { return Map(unicode.ToTitle, s) }
+
+// ToUpperSpecial returns a copy of the string s with all Unicode letters mapped to their
+// upper case, giving priority to the special casing rules.
+func ToUpperSpecial(_case unicode.SpecialCase, s string) string {
+	return Map(func(r rune) rune { return _case.ToUpper(r) }, s)
+}
+
+// ToLowerSpecial returns a copy of the string s with all Unicode letters mapped to their
+// lower case, giving priority to the special casing rules.
+func ToLowerSpecial(_case unicode.SpecialCase, s string) string {
+	return Map(func(r rune) rune { return _case.ToLower(r) }, s)
+}
+
+// ToTitleSpecial returns a copy of the string s with all Unicode letters mapped to their
+// title case, giving priority to the special casing rules.
+func ToTitleSpecial(_case unicode.SpecialCase, s string) string {
+	return Map(func(r rune) rune { return _case.ToTitle(r) }, s)
+}
+
+// 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 returns a copy of the string s with all Unicode letters that begin words
+// mapped to their title case.
+//
+// BUG: The rule Title uses for word boundaries does not handle Unicode punctuation properly.
+func Title(s string) string {
+	// 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 returns a slice of the string s with all leading
+// Unicode code points c satisfying f(c) removed.
+func TrimLeftFunc(s string, f func(rune) bool) string {
+	i := indexFunc(s, f, false)
+	if i == -1 {
+		return ""
+	}
+	return s[i:]
+}
+
+// TrimRightFunc returns a slice of the string s with all trailing
+// Unicode code points c satisfying f(c) removed.
+func TrimRightFunc(s string, f func(rune) bool) string {
+	i := lastIndexFunc(s, f, false)
+	if i >= 0 && s[i] >= utf8.RuneSelf {
+		_, wid := utf8.DecodeRuneInString(s[i:])
+		i += wid
+	} else {
+		i++
+	}
+	return s[0:i]
+}
+
+// TrimFunc returns a slice of the string s with all leading
+// and trailing Unicode code points c satisfying f(c) removed.
+func TrimFunc(s string, f func(rune) bool) string {
+	return TrimRightFunc(TrimLeftFunc(s, f), f)
+}
+
+// IndexFunc returns the index into s of the first Unicode
+// code point satisfying f(c), or -1 if none do.
+func IndexFunc(s string, f func(rune) bool) int {
+	return indexFunc(s, f, true)
+}
+
+// LastIndexFunc returns the index into s of the last
+// Unicode code point satisfying f(c), or -1 if none do.
+func LastIndexFunc(s string, f func(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 string, f func(rune) bool, truth bool) int {
+	start := 0
+	for start < len(s) {
+		wid := 1
+		r := rune(s[start])
+		if r >= utf8.RuneSelf {
+			r, wid = utf8.DecodeRuneInString(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 string, f func(rune) bool, truth bool) int {
+	for i := len(s); i > 0; {
+		r, size := utf8.DecodeLastRuneInString(s[0:i])
+		i -= size
+		if f(r) == truth {
+			return i
+		}
+	}
+	return -1
+}
+
+func makeCutsetFunc(cutset string) func(rune) bool {
+	return func(r rune) bool { return IndexRune(cutset, r) >= 0 }
+}
+
+// Trim returns a slice of the string s with all leading and
+// trailing Unicode code points contained in cutset removed.
+func Trim(s string, cutset string) string {
+	if s == "" || cutset == "" {
+		return s
+	}
+	return TrimFunc(s, makeCutsetFunc(cutset))
+}
+
+// TrimLeft returns a slice of the string s with all leading
+// Unicode code points contained in cutset removed.
+func TrimLeft(s string, cutset string) string {
+	if s == "" || cutset == "" {
+		return s
+	}
+	return TrimLeftFunc(s, makeCutsetFunc(cutset))
+}
+
+// TrimRight returns a slice of the string s, with all trailing
+// Unicode code points contained in cutset removed.
+func TrimRight(s string, cutset string) string {
+	if s == "" || cutset == "" {
+		return s
+	}
+	return TrimRightFunc(s, makeCutsetFunc(cutset))
+}
+
+// TrimSpace returns a slice of the string s, with all leading
+// and trailing white space removed, as defined by Unicode.
+func TrimSpace(s string) string {
+	return TrimFunc(s, unicode.IsSpace)
+}
+
+// TrimPrefix returns s without the provided leading prefix string.
+// If s doesn't start with prefix, s is returned unchanged.
+func TrimPrefix(s, prefix string) string {
+	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 string) string {
+	if HasSuffix(s, suffix) {
+		return s[:len(s)-len(suffix)]
+	}
+	return s
+}
+
+// Replace returns a copy of the string s with the first n
+// non-overlapping instances of old replaced by new.
+// If old is empty, it matches at the beginning of the string
+// and after each UTF-8 sequence, yielding up to k+1 replacements
+// for a k-rune string.
+// If n < 0, there is no limit on the number of replacements.
+func Replace(s, old, new string, n int) string {
+	if old == new || n == 0 {
+		return s // avoid allocation
+	}
+
+	// Compute number of replacements.
+	if m := Count(s, old); m == 0 {
+		return s // avoid allocation
+	} else 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.DecodeRuneInString(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 string(t[0:w])
+}
+
+// EqualFold reports whether s and t, interpreted as UTF-8 strings,
+// are equal under Unicode case-folding.
+func EqualFold(s, t string) bool {
+	for s != "" && t != "" {
+		// Extract first rune from each string.
+		var sr, tr rune
+		if s[0] < utf8.RuneSelf {
+			sr, s = rune(s[0]), s[1:]
+		} else {
+			r, size := utf8.DecodeRuneInString(s)
+			sr, s = r, s[size:]
+		}
+		if t[0] < utf8.RuneSelf {
+			tr, t = rune(t[0]), t[1:]
+		} else {
+			r, size := utf8.DecodeRuneInString(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 && 'A' <= sr && sr <= 'Z' {
+			// ASCII, and sr is upper case.  tr must be lower case.
+			if 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 s == t
+}