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// Copyright 2015 Huan Du. All rights reserved.
// Licensed under the MIT license that can be found in the LICENSE file.
package xstrings
import (
"bytes"
"unicode"
"unicode/utf8"
)
type runeRangeMap struct {
FromLo rune // Lower bound of range map.
FromHi rune // An inclusive higher bound of range map.
ToLo rune
ToHi rune
}
type runeDict struct {
Dict [unicode.MaxASCII + 1]rune
}
type runeMap map[rune]rune
// Translator can translate string with pre-compiled from and to patterns.
// If a from/to pattern pair needs to be used more than once, it's recommended
// to create a Translator and reuse it.
type Translator struct {
quickDict *runeDict // A quick dictionary to look up rune by index. Only available for latin runes.
runeMap runeMap // Rune map for translation.
ranges []*runeRangeMap // Ranges of runes.
mappedRune rune // If mappedRune >= 0, all matched runes are translated to the mappedRune.
reverted bool // If to pattern is empty, all matched characters will be deleted.
hasPattern bool
}
// NewTranslator creates new Translator through a from/to pattern pair.
func NewTranslator(from, to string) *Translator {
tr := &Translator{}
if from == "" {
return tr
}
reverted := from[0] == '^'
deletion := len(to) == 0
if reverted {
from = from[1:]
}
var fromStart, fromEnd, fromRangeStep rune
var toStart, toEnd, toRangeStep rune
var fromRangeSize, toRangeSize rune
var singleRunes []rune
// Update the to rune range.
updateRange := func() {
// No more rune to read in the to rune pattern.
if toEnd == utf8.RuneError {
return
}
if toRangeStep == 0 {
to, toStart, toEnd, toRangeStep = nextRuneRange(to, toEnd)
return
}
// Current range is not empty. Consume 1 rune from start.
if toStart != toEnd {
toStart += toRangeStep
return
}
// No more rune. Repeat the last rune.
if to == "" {
toEnd = utf8.RuneError
return
}
// Both start and end are used. Read two more runes from the to pattern.
to, toStart, toEnd, toRangeStep = nextRuneRange(to, utf8.RuneError)
}
if deletion {
toStart = utf8.RuneError
toEnd = utf8.RuneError
} else {
// If from pattern is reverted, only the last rune in the to pattern will be used.
if reverted {
var size int
for len(to) > 0 {
toStart, size = utf8.DecodeRuneInString(to)
to = to[size:]
}
toEnd = utf8.RuneError
} else {
to, toStart, toEnd, toRangeStep = nextRuneRange(to, utf8.RuneError)
}
}
fromEnd = utf8.RuneError
for len(from) > 0 {
from, fromStart, fromEnd, fromRangeStep = nextRuneRange(from, fromEnd)
// fromStart is a single character. Just map it with a rune in the to pattern.
if fromRangeStep == 0 {
singleRunes = tr.addRune(fromStart, toStart, singleRunes)
updateRange()
continue
}
for toEnd != utf8.RuneError && fromStart != fromEnd {
// If mapped rune is a single character instead of a range, simply shift first
// rune in the range.
if toRangeStep == 0 {
singleRunes = tr.addRune(fromStart, toStart, singleRunes)
updateRange()
fromStart += fromRangeStep
continue
}
fromRangeSize = (fromEnd - fromStart) * fromRangeStep
toRangeSize = (toEnd - toStart) * toRangeStep
// Not enough runes in the to pattern. Need to read more.
if fromRangeSize > toRangeSize {
fromStart, toStart = tr.addRuneRange(fromStart, fromStart+toRangeSize*fromRangeStep, toStart, toEnd, singleRunes)
fromStart += fromRangeStep
updateRange()
// Edge case: If fromRangeSize == toRangeSize + 1, the last fromStart value needs be considered
// as a single rune.
if fromStart == fromEnd {
singleRunes = tr.addRune(fromStart, toStart, singleRunes)
updateRange()
}
continue
}
fromStart, toStart = tr.addRuneRange(fromStart, fromEnd, toStart, toStart+fromRangeSize*toRangeStep, singleRunes)
updateRange()
break
}
if fromStart == fromEnd {
fromEnd = utf8.RuneError
continue
}
fromStart, toStart = tr.addRuneRange(fromStart, fromEnd, toStart, toStart, singleRunes)
fromEnd = utf8.RuneError
}
if fromEnd != utf8.RuneError {
singleRunes = tr.addRune(fromEnd, toStart, singleRunes)
}
tr.reverted = reverted
tr.mappedRune = -1
tr.hasPattern = true
// Translate RuneError only if in deletion or reverted mode.
if deletion || reverted {
tr.mappedRune = toStart
}
return tr
}
func (tr *Translator) addRune(from, to rune, singleRunes []rune) []rune {
if from <= unicode.MaxASCII {
if tr.quickDict == nil {
tr.quickDict = &runeDict{}
}
tr.quickDict.Dict[from] = to
} else {
if tr.runeMap == nil {
tr.runeMap = make(runeMap)
}
tr.runeMap[from] = to
}
singleRunes = append(singleRunes, from)
return singleRunes
}
func (tr *Translator) addRuneRange(fromLo, fromHi, toLo, toHi rune, singleRunes []rune) (rune, rune) {
var r rune
var rrm *runeRangeMap
if fromLo < fromHi {
rrm = &runeRangeMap{
FromLo: fromLo,
FromHi: fromHi,
ToLo: toLo,
ToHi: toHi,
}
} else {
rrm = &runeRangeMap{
FromLo: fromHi,
FromHi: fromLo,
ToLo: toHi,
ToHi: toLo,
}
}
// If there is any single rune conflicts with this rune range, clear single rune record.
for _, r = range singleRunes {
if rrm.FromLo <= r && r <= rrm.FromHi {
if r <= unicode.MaxASCII {
tr.quickDict.Dict[r] = 0
} else {
delete(tr.runeMap, r)
}
}
}
tr.ranges = append(tr.ranges, rrm)
return fromHi, toHi
}
func nextRuneRange(str string, last rune) (remaining string, start, end rune, rangeStep rune) {
var r rune
var size int
remaining = str
escaping := false
isRange := false
for len(remaining) > 0 {
r, size = utf8.DecodeRuneInString(remaining)
remaining = remaining[size:]
// Parse special characters.
if !escaping {
if r == '\\' {
escaping = true
continue
}
if r == '-' {
// Ignore slash at beginning of string.
if last == utf8.RuneError {
continue
}
start = last
isRange = true
continue
}
}
escaping = false
if last != utf8.RuneError {
// This is a range which start and end are the same.
// Considier it as a normal character.
if isRange && last == r {
isRange = false
continue
}
start = last
end = r
if isRange {
if start < end {
rangeStep = 1
} else {
rangeStep = -1
}
}
return
}
last = r
}
start = last
end = utf8.RuneError
return
}
// Translate str with a from/to pattern pair.
//
// See comment in Translate function for usage and samples.
func (tr *Translator) Translate(str string) string {
if !tr.hasPattern || str == "" {
return str
}
var r rune
var size int
var needTr bool
orig := str
var output *bytes.Buffer
for len(str) > 0 {
r, size = utf8.DecodeRuneInString(str)
r, needTr = tr.TranslateRune(r)
if needTr && output == nil {
output = allocBuffer(orig, str)
}
if r != utf8.RuneError && output != nil {
output.WriteRune(r)
}
str = str[size:]
}
// No character is translated.
if output == nil {
return orig
}
return output.String()
}
// TranslateRune return translated rune and true if r matches the from pattern.
// If r doesn't match the pattern, original r is returned and translated is false.
func (tr *Translator) TranslateRune(r rune) (result rune, translated bool) {
switch {
case tr.quickDict != nil:
if r <= unicode.MaxASCII {
result = tr.quickDict.Dict[r]
if result != 0 {
translated = true
if tr.mappedRune >= 0 {
result = tr.mappedRune
}
break
}
}
fallthrough
case tr.runeMap != nil:
var ok bool
if result, ok = tr.runeMap[r]; ok {
translated = true
if tr.mappedRune >= 0 {
result = tr.mappedRune
}
break
}
fallthrough
default:
var rrm *runeRangeMap
ranges := tr.ranges
for i := len(ranges) - 1; i >= 0; i-- {
rrm = ranges[i]
if rrm.FromLo <= r && r <= rrm.FromHi {
translated = true
if tr.mappedRune >= 0 {
result = tr.mappedRune
break
}
if rrm.ToLo < rrm.ToHi {
result = rrm.ToLo + r - rrm.FromLo
} else if rrm.ToLo > rrm.ToHi {
// ToHi can be smaller than ToLo if range is from higher to lower.
result = rrm.ToLo - r + rrm.FromLo
} else {
result = rrm.ToLo
}
break
}
}
}
if tr.reverted {
if !translated {
result = tr.mappedRune
}
translated = !translated
}
if !translated {
result = r
}
return
}
// HasPattern returns true if Translator has one pattern at least.
func (tr *Translator) HasPattern() bool {
return tr.hasPattern
}
// Translate str with the characters defined in from replaced by characters defined in to.
//
// From and to are patterns representing a set of characters. Pattern is defined as following.
//
// * Special characters
// * '-' means a range of runes, e.g.
// * "a-z" means all characters from 'a' to 'z' inclusive;
// * "z-a" means all characters from 'z' to 'a' inclusive.
// * '^' as first character means a set of all runes excepted listed, e.g.
// * "^a-z" means all characters except 'a' to 'z' inclusive.
// * '\' escapes special characters.
// * Normal character represents itself, e.g. "abc" is a set including 'a', 'b' and 'c'.
//
// Translate will try to find a 1:1 mapping from from to to.
// If to is smaller than from, last rune in to will be used to map "out of range" characters in from.
//
// Note that '^' only works in the from pattern. It will be considered as a normal character in the to pattern.
//
// If the to pattern is an empty string, Translate works exactly the same as Delete.
//
// Samples:
// Translate("hello", "aeiou", "12345") => "h2ll4"
// Translate("hello", "a-z", "A-Z") => "HELLO"
// Translate("hello", "z-a", "a-z") => "svool"
// Translate("hello", "aeiou", "*") => "h*ll*"
// Translate("hello", "^l", "*") => "**ll*"
// Translate("hello ^ world", `\^lo`, "*") => "he*** * w*r*d"
func Translate(str, from, to string) string {
tr := NewTranslator(from, to)
return tr.Translate(str)
}
// Delete runes in str matching the pattern.
// Pattern is defined in Translate function.
//
// Samples:
// Delete("hello", "aeiou") => "hll"
// Delete("hello", "a-k") => "llo"
// Delete("hello", "^a-k") => "he"
func Delete(str, pattern string) string {
tr := NewTranslator(pattern, "")
return tr.Translate(str)
}
// Count how many runes in str match the pattern.
// Pattern is defined in Translate function.
//
// Samples:
// Count("hello", "aeiou") => 3
// Count("hello", "a-k") => 3
// Count("hello", "^a-k") => 2
func Count(str, pattern string) int {
if pattern == "" || str == "" {
return 0
}
var r rune
var size int
var matched bool
tr := NewTranslator(pattern, "")
cnt := 0
for len(str) > 0 {
r, size = utf8.DecodeRuneInString(str)
str = str[size:]
if _, matched = tr.TranslateRune(r); matched {
cnt++
}
}
return cnt
}
// Squeeze deletes adjacent repeated runes in str.
// If pattern is not empty, only runes matching the pattern will be squeezed.
//
// Samples:
// Squeeze("hello", "") => "helo"
// Squeeze("hello", "m-z") => "hello"
// Squeeze("hello world", " ") => "hello world"
func Squeeze(str, pattern string) string {
var last, r rune
var size int
var skipSqueeze, matched bool
var tr *Translator
var output *bytes.Buffer
orig := str
last = -1
if len(pattern) > 0 {
tr = NewTranslator(pattern, "")
}
for len(str) > 0 {
r, size = utf8.DecodeRuneInString(str)
// Need to squeeze the str.
if last == r && !skipSqueeze {
if tr != nil {
if _, matched = tr.TranslateRune(r); !matched {
skipSqueeze = true
}
}
if output == nil {
output = allocBuffer(orig, str)
}
if skipSqueeze {
output.WriteRune(r)
}
} else {
if output != nil {
output.WriteRune(r)
}
last = r
skipSqueeze = false
}
str = str[size:]
}
if output == nil {
return orig
}
return output.String()
}
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