81 lines
1.6 KiB
Go
81 lines
1.6 KiB
Go
// Copyright 2015 The 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 mdurl
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import (
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"bytes"
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"unicode/utf8"
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)
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func advance(s string, pos int) (byte, int) {
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if pos >= len(s) {
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return 0, len(s) + 1
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}
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if s[pos] != '%' {
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return s[pos], pos + 1
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}
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if pos+2 < len(s) &&
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hexDigit(s[pos+1]) &&
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hexDigit(s[pos+2]) {
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return unhex(s[pos+1])<<4 | unhex(s[pos+2]), pos + 3
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}
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return '%', pos + 1
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}
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// Decode decodes a percent-encoded URL.
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// Invalid percent-encoded sequences are left as is.
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// Invalid UTF-8 sequences are replaced with U+FFFD.
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func Decode(rawurl string) string {
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var buf bytes.Buffer
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i := 0
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const replacement = "\xEF\xBF\xBD"
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outer:
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for i < len(rawurl) {
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r, rlen := utf8.DecodeRuneInString(rawurl[i:])
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if r == '%' && i+2 < len(rawurl) &&
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hexDigit(rawurl[i+1]) &&
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hexDigit(rawurl[i+2]) {
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b := unhex(rawurl[i+1])<<4 | unhex(rawurl[i+2])
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if b < 0x80 {
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buf.WriteByte(b)
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i += 3
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continue
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}
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var n int
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if b&0xe0 == 0xc0 {
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n = 1
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} else if b&0xf0 == 0xe0 {
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n = 2
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} else if b&0xf8 == 0xf0 {
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n = 3
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}
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if n == 0 {
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buf.WriteString(replacement)
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i += 3
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continue
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}
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rb := make([]byte, n+1)
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rb[0] = b
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j := i + 3
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for k := 0; k < n; k++ {
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b, j = advance(rawurl, j)
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if j > len(rawurl) || b&0xc0 != 0x80 {
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buf.WriteString(replacement)
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i += 3
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continue outer
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}
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rb[k+1] = b
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}
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r, _ := utf8.DecodeRune(rb)
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buf.WriteRune(r)
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i = j
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continue
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}
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buf.WriteRune(r)
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i += rlen
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}
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return buf.String()
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}
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