444 lines
11 KiB
Go
444 lines
11 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package strconv
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import (
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"unicode/utf8"
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)
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const lowerhex = "0123456789abcdef"
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func quoteWith(s string, quote byte, ASCIIonly bool) string {
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var runeTmp [utf8.UTFMax]byte
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buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
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buf = append(buf, quote)
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for width := 0; len(s) > 0; s = s[width:] {
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r := rune(s[0])
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width = 1
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if r >= utf8.RuneSelf {
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r, width = utf8.DecodeRuneInString(s)
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}
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if width == 1 && r == utf8.RuneError {
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buf = append(buf, `\x`...)
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buf = append(buf, lowerhex[s[0]>>4])
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buf = append(buf, lowerhex[s[0]&0xF])
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continue
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}
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if r == rune(quote) || r == '\\' { // always backslashed
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buf = append(buf, '\\')
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buf = append(buf, byte(r))
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continue
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}
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if ASCIIonly {
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if r < utf8.RuneSelf && IsPrint(r) {
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buf = append(buf, byte(r))
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continue
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}
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} else if IsPrint(r) {
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n := utf8.EncodeRune(runeTmp[:], r)
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buf = append(buf, runeTmp[:n]...)
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continue
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}
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switch r {
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case '\a':
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buf = append(buf, `\a`...)
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case '\b':
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buf = append(buf, `\b`...)
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case '\f':
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buf = append(buf, `\f`...)
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case '\n':
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buf = append(buf, `\n`...)
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case '\r':
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buf = append(buf, `\r`...)
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case '\t':
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buf = append(buf, `\t`...)
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case '\v':
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buf = append(buf, `\v`...)
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default:
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switch {
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case r < ' ':
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buf = append(buf, `\x`...)
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buf = append(buf, lowerhex[s[0]>>4])
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buf = append(buf, lowerhex[s[0]&0xF])
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case r > utf8.MaxRune:
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r = 0xFFFD
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fallthrough
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case r < 0x10000:
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buf = append(buf, `\u`...)
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for s := 12; s >= 0; s -= 4 {
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buf = append(buf, lowerhex[r>>uint(s)&0xF])
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}
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default:
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buf = append(buf, `\U`...)
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for s := 28; s >= 0; s -= 4 {
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buf = append(buf, lowerhex[r>>uint(s)&0xF])
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}
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}
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}
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}
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buf = append(buf, quote)
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return string(buf)
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}
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// Quote returns a double-quoted Go string literal representing s. The
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// returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
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// control characters and non-printable characters as defined by
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// IsPrint.
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func Quote(s string) string {
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return quoteWith(s, '"', false)
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}
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// AppendQuote appends a double-quoted Go string literal representing s,
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// as generated by Quote, to dst and returns the extended buffer.
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func AppendQuote(dst []byte, s string) []byte {
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return append(dst, Quote(s)...)
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}
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// QuoteToASCII returns a double-quoted Go string literal representing s.
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// The returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
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// non-ASCII characters and non-printable characters as defined by IsPrint.
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func QuoteToASCII(s string) string {
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return quoteWith(s, '"', true)
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}
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// AppendQuoteToASCII appends a double-quoted Go string literal representing s,
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// as generated by QuoteToASCII, to dst and returns the extended buffer.
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func AppendQuoteToASCII(dst []byte, s string) []byte {
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return append(dst, QuoteToASCII(s)...)
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}
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// QuoteRune returns a single-quoted Go character literal representing the
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// rune. The returned string uses Go escape sequences (\t, \n, \xFF, \u0100)
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// for control characters and non-printable characters as defined by IsPrint.
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func QuoteRune(r rune) string {
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// TODO: avoid the allocation here.
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return quoteWith(string(r), '\'', false)
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}
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// AppendQuoteRune appends a single-quoted Go character literal representing the rune,
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// as generated by QuoteRune, to dst and returns the extended buffer.
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func AppendQuoteRune(dst []byte, r rune) []byte {
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return append(dst, QuoteRune(r)...)
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}
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// QuoteRuneToASCII returns a single-quoted Go character literal representing
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// the rune. The returned string uses Go escape sequences (\t, \n, \xFF,
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// \u0100) for non-ASCII characters and non-printable characters as defined
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// by IsPrint.
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func QuoteRuneToASCII(r rune) string {
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// TODO: avoid the allocation here.
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return quoteWith(string(r), '\'', true)
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}
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// AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
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// as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
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func AppendQuoteRuneToASCII(dst []byte, r rune) []byte {
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return append(dst, QuoteRuneToASCII(r)...)
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}
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// CanBackquote reports whether the string s can be represented
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// unchanged as a single-line backquoted string without control
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// characters other than space and tab.
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func CanBackquote(s string) bool {
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for i := 0; i < len(s); i++ {
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c := s[i]
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if (c < ' ' && c != '\t') || c == '`' || c == '\u007F' {
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return false
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}
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}
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return true
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}
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func unhex(b byte) (v rune, ok bool) {
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c := rune(b)
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switch {
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case '0' <= c && c <= '9':
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return c - '0', true
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case 'a' <= c && c <= 'f':
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return c - 'a' + 10, true
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case 'A' <= c && c <= 'F':
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return c - 'A' + 10, true
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}
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return
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}
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// UnquoteChar decodes the first character or byte in the escaped string
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// or character literal represented by the string s.
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// It returns four values:
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//
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// 1) value, the decoded Unicode code point or byte value;
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// 2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
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// 3) tail, the remainder of the string after the character; and
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// 4) an error that will be nil if the character is syntactically valid.
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//
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// The second argument, quote, specifies the type of literal being parsed
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// and therefore which escaped quote character is permitted.
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// If set to a single quote, it permits the sequence \' and disallows unescaped '.
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// If set to a double quote, it permits \" and disallows unescaped ".
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// If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
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func UnquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
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// easy cases
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switch c := s[0]; {
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case c == quote && (quote == '\'' || quote == '"'):
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err = ErrSyntax
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return
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case c >= utf8.RuneSelf:
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r, size := utf8.DecodeRuneInString(s)
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return r, true, s[size:], nil
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case c != '\\':
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return rune(s[0]), false, s[1:], nil
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}
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// hard case: c is backslash
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if len(s) <= 1 {
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err = ErrSyntax
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return
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}
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c := s[1]
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s = s[2:]
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switch c {
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case 'a':
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value = '\a'
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case 'b':
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value = '\b'
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case 'f':
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value = '\f'
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case 'n':
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value = '\n'
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case 'r':
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value = '\r'
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case 't':
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value = '\t'
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case 'v':
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value = '\v'
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case 'x', 'u', 'U':
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n := 0
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switch c {
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case 'x':
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n = 2
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case 'u':
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n = 4
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case 'U':
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n = 8
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}
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var v rune
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if len(s) < n {
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err = ErrSyntax
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return
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}
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for j := 0; j < n; j++ {
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x, ok := unhex(s[j])
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if !ok {
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err = ErrSyntax
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return
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}
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v = v<<4 | x
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}
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s = s[n:]
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if c == 'x' {
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// single-byte string, possibly not UTF-8
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value = v
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break
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}
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if v > utf8.MaxRune {
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err = ErrSyntax
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return
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}
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value = v
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multibyte = true
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case '0', '1', '2', '3', '4', '5', '6', '7':
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v := rune(c) - '0'
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if len(s) < 2 {
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err = ErrSyntax
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return
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}
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for j := 0; j < 2; j++ { // one digit already; two more
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x := rune(s[j]) - '0'
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if x < 0 || x > 7 {
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err = ErrSyntax
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return
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}
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v = (v << 3) | x
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}
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s = s[2:]
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if v > 255 {
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err = ErrSyntax
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return
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}
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value = v
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case '\\':
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value = '\\'
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case '\'', '"':
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if c != quote {
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err = ErrSyntax
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return
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}
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value = rune(c)
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default:
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err = ErrSyntax
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return
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}
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tail = s
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return
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}
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// Unquote interprets s as a single-quoted, double-quoted,
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// or backquoted Go string literal, returning the string value
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// that s quotes. (If s is single-quoted, it would be a Go
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// character literal; Unquote returns the corresponding
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// one-character string.)
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func Unquote(s string) (t string, err error) {
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n := len(s)
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if n < 2 {
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return "", ErrSyntax
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}
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quote := s[0]
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if quote != s[n-1] {
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return "", ErrSyntax
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}
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s = s[1 : n-1]
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if quote == '`' {
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if contains(s, '`') {
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return "", ErrSyntax
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}
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return s, nil
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}
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if quote != '"' && quote != '\'' {
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return "", ErrSyntax
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}
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if contains(s, '\n') {
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return "", ErrSyntax
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}
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// Is it trivial? Avoid allocation.
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if !contains(s, '\\') && !contains(s, quote) {
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switch quote {
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case '"':
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return s, nil
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case '\'':
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r, size := utf8.DecodeRuneInString(s)
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if size == len(s) && (r != utf8.RuneError || size != 1) {
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return s, nil
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}
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}
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}
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var runeTmp [utf8.UTFMax]byte
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buf := make([]byte, 0, 3*len(s)/2) // Try to avoid more allocations.
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for len(s) > 0 {
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c, multibyte, ss, err := UnquoteChar(s, quote)
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if err != nil {
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return "", err
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}
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s = ss
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if c < utf8.RuneSelf || !multibyte {
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buf = append(buf, byte(c))
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} else {
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n := utf8.EncodeRune(runeTmp[:], c)
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buf = append(buf, runeTmp[:n]...)
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}
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if quote == '\'' && len(s) != 0 {
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// single-quoted must be single character
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return "", ErrSyntax
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}
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}
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return string(buf), nil
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}
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// contains reports whether the string contains the byte c.
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func contains(s string, c byte) bool {
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for i := 0; i < len(s); i++ {
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if s[i] == c {
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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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// bsearch16 returns the smallest i such that a[i] >= x.
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// If there is no such i, bsearch16 returns len(a).
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func bsearch16(a []uint16, x uint16) int {
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i, j := 0, len(a)
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for i < j {
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h := i + (j-i)/2
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if a[h] < x {
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i = h + 1
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} else {
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j = h
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}
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}
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return i
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}
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// bsearch32 returns the smallest i such that a[i] >= x.
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// If there is no such i, bsearch32 returns len(a).
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func bsearch32(a []uint32, x uint32) int {
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i, j := 0, len(a)
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for i < j {
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h := i + (j-i)/2
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if a[h] < x {
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i = h + 1
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} else {
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j = h
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}
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}
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return i
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}
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// TODO: IsPrint is a local implementation of unicode.IsPrint, verified by the tests
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// to give the same answer. It allows this package not to depend on unicode,
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// and therefore not pull in all the Unicode tables. If the linker were better
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// at tossing unused tables, we could get rid of this implementation.
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// That would be nice.
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// IsPrint reports whether the rune is defined as printable by Go, with
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// the same definition as unicode.IsPrint: letters, numbers, punctuation,
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// symbols and ASCII space.
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func IsPrint(r rune) bool {
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// Fast check for Latin-1
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if r <= 0xFF {
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if 0x20 <= r && r <= 0x7E {
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// All the ASCII is printable from space through DEL-1.
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return true
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}
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if 0xA1 <= r && r <= 0xFF {
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// Similarly for ¡ through ÿ...
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return r != 0xAD // ...except for the bizarre soft hyphen.
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}
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return false
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}
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// Same algorithm, either on uint16 or uint32 value.
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// First, find first i such that isPrint[i] >= x.
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// This is the index of either the start or end of a pair that might span x.
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// The start is even (isPrint[i&^1]) and the end is odd (isPrint[i|1]).
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// If we find x in a range, make sure x is not in isNotPrint list.
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if 0 <= r && r < 1<<16 {
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rr, isPrint, isNotPrint := uint16(r), isPrint16, isNotPrint16
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i := bsearch16(isPrint, rr)
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if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
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return false
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}
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j := bsearch16(isNotPrint, rr)
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return j >= len(isNotPrint) || isNotPrint[j] != rr
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}
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rr, isPrint, isNotPrint := uint32(r), isPrint32, isNotPrint32
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i := bsearch32(isPrint, rr)
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if i >= len(isPrint) || rr < isPrint[i&^1] || isPrint[i|1] < rr {
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return false
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}
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if r >= 0x20000 {
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return true
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}
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r -= 0x10000
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j := bsearch16(isNotPrint, uint16(r))
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return j >= len(isNotPrint) || isNotPrint[j] != uint16(r)
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}
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