mirror of
https://github.com/ergochat/ergo.git
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c972a92e51
Resolves CVE-2021-42836, which probably didn't affect us, but we might as well upgrade.
238 lines
5.4 KiB
Go
238 lines
5.4 KiB
Go
// Package match provides a simple pattern matcher with unicode support.
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package match
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import (
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"unicode/utf8"
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)
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// Match returns true if str matches pattern. This is a very
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// simple wildcard match where '*' matches on any number characters
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// and '?' matches on any one character.
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//
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// pattern:
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// { term }
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// term:
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// '*' matches any sequence of non-Separator characters
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// '?' matches any single non-Separator character
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// c matches character c (c != '*', '?', '\\')
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// '\\' c matches character c
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//
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func Match(str, pattern string) bool {
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if pattern == "*" {
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return true
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}
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return match(str, pattern, 0, nil, -1) == rMatch
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}
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// MatchLimit is the same as Match but will limit the complexity of the match
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// operation. This is to avoid long running matches, specifically to avoid ReDos
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// attacks from arbritary inputs.
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//
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// How it works:
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// The underlying match routine is recursive and may call itself when it
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// encounters a sandwiched wildcard pattern, such as: `user:*:name`.
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// Everytime it calls itself a counter is incremented.
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// The operation is stopped when counter > maxcomp*len(str).
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func MatchLimit(str, pattern string, maxcomp int) (matched, stopped bool) {
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if pattern == "*" {
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return true, false
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}
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counter := 0
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r := match(str, pattern, len(str), &counter, maxcomp)
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if r == rStop {
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return false, true
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}
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return r == rMatch, false
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}
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type result int
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const (
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rNoMatch result = iota
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rMatch
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rStop
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)
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func match(str, pat string, slen int, counter *int, maxcomp int) result {
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// check complexity limit
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if maxcomp > -1 {
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if *counter > slen*maxcomp {
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return rStop
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}
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*counter++
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}
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for len(pat) > 0 {
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var wild bool
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pc, ps := rune(pat[0]), 1
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if pc > 0x7f {
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pc, ps = utf8.DecodeRuneInString(pat)
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}
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var sc rune
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var ss int
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if len(str) > 0 {
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sc, ss = rune(str[0]), 1
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if sc > 0x7f {
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sc, ss = utf8.DecodeRuneInString(str)
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}
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}
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switch pc {
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case '?':
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if ss == 0 {
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return rNoMatch
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}
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case '*':
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// Ignore repeating stars.
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for len(pat) > 1 && pat[1] == '*' {
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pat = pat[1:]
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}
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// If this star is the last character then it must be a match.
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if len(pat) == 1 {
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return rMatch
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}
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// Match and trim any non-wildcard suffix characters.
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var ok bool
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str, pat, ok = matchTrimSuffix(str, pat)
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if !ok {
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return rNoMatch
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}
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// Check for single star again.
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if len(pat) == 1 {
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return rMatch
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}
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// Perform recursive wildcard search.
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r := match(str, pat[1:], slen, counter, maxcomp)
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if r != rNoMatch {
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return r
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}
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if len(str) == 0 {
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return rNoMatch
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}
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wild = true
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default:
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if ss == 0 {
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return rNoMatch
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}
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if pc == '\\' {
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pat = pat[ps:]
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pc, ps = utf8.DecodeRuneInString(pat)
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if ps == 0 {
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return rNoMatch
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}
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}
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if sc != pc {
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return rNoMatch
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}
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}
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str = str[ss:]
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if !wild {
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pat = pat[ps:]
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}
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}
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if len(str) == 0 {
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return rMatch
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}
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return rNoMatch
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}
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// matchTrimSuffix matches and trims any non-wildcard suffix characters.
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// Returns the trimed string and pattern.
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//
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// This is called because the pattern contains extra data after the wildcard
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// star. Here we compare any suffix characters in the pattern to the suffix of
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// the target string. Basically a reverse match that stops when a wildcard
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// character is reached. This is a little trickier than a forward match because
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// we need to evaluate an escaped character in reverse.
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//
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// Any matched characters will be trimmed from both the target
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// string and the pattern.
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func matchTrimSuffix(str, pat string) (string, string, bool) {
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// It's expected that the pattern has at least two bytes and the first byte
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// is a wildcard star '*'
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match := true
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for len(str) > 0 && len(pat) > 1 {
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pc, ps := utf8.DecodeLastRuneInString(pat)
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var esc bool
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for i := 0; ; i++ {
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if pat[len(pat)-ps-i-1] != '\\' {
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if i&1 == 1 {
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esc = true
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ps++
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}
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break
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}
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}
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if pc == '*' && !esc {
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match = true
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break
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}
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sc, ss := utf8.DecodeLastRuneInString(str)
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if !((pc == '?' && !esc) || pc == sc) {
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match = false
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break
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}
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str = str[:len(str)-ss]
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pat = pat[:len(pat)-ps]
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}
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return str, pat, match
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}
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var maxRuneBytes = [...]byte{244, 143, 191, 191}
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// Allowable parses the pattern and determines the minimum and maximum allowable
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// values that the pattern can represent.
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// When the max cannot be determined, 'true' will be returned
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// for infinite.
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func Allowable(pattern string) (min, max string) {
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if pattern == "" || pattern[0] == '*' {
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return "", ""
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}
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minb := make([]byte, 0, len(pattern))
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maxb := make([]byte, 0, len(pattern))
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var wild bool
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for i := 0; i < len(pattern); i++ {
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if pattern[i] == '*' {
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wild = true
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break
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}
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if pattern[i] == '?' {
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minb = append(minb, 0)
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maxb = append(maxb, maxRuneBytes[:]...)
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} else {
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minb = append(minb, pattern[i])
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maxb = append(maxb, pattern[i])
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}
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}
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if wild {
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r, n := utf8.DecodeLastRune(maxb)
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if r != utf8.RuneError {
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if r < utf8.MaxRune {
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r++
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if r > 0x7f {
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b := make([]byte, 4)
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nn := utf8.EncodeRune(b, r)
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maxb = append(maxb[:len(maxb)-n], b[:nn]...)
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} else {
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maxb = append(maxb[:len(maxb)-n], byte(r))
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}
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}
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}
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}
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return string(minb), string(maxb)
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}
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// IsPattern returns true if the string is a pattern.
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func IsPattern(str string) bool {
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for i := 0; i < len(str); i++ {
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if str[i] == '*' || str[i] == '?' {
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return true
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}
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}
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return false
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}
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