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// Copyright 2010 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 html provides functions for escaping and unescaping HTML text.
package html
 
import (
        "bytes"
        "strings"
        "unicode/utf8"
)
 
type writer interface {
        WriteString(string) (int, error)
}
 
// These replacements permit compatibility with old numeric entities that
// assumed Windows-1252 encoding.
// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#consume-a-character-reference
var replacementTable = [...]rune{
        '\u20AC', // First entry is what 0x80 should be replaced with.
        '\u0081',
        '\u201A',
        '\u0192',
        '\u201E',
        '\u2026',
        '\u2020',
        '\u2021',
        '\u02C6',
        '\u2030',
        '\u0160',
        '\u2039',
        '\u0152',
        '\u008D',
        '\u017D',
        '\u008F',
        '\u0090',
        '\u2018',
        '\u2019',
        '\u201C',
        '\u201D',
        '\u2022',
        '\u2013',
        '\u2014',
        '\u02DC',
        '\u2122',
        '\u0161',
        '\u203A',
        '\u0153',
        '\u009D',
        '\u017E',
        '\u0178', // Last entry is 0x9F.
        // 0x00->'\uFFFD' is handled programmatically.
        // 0x0D->'\u000D' is a no-op.
}
 
// unescapeEntity reads an entity like "<" from b[src:] and writes the
// corresponding "<" to b[dst:], returning the incremented dst and src cursors.
// Precondition: b[src] == '&' && dst <= src.
// attribute should be true if parsing an attribute value.
func unescapeEntity(b []byte, dst, src int, attribute bool) (dst1, src1 int) {
        // http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#consume-a-character-reference
 
        // i starts at 1 because we already know that s[0] == '&'.
        i, s := 1, b[src:]
 
        if len(s) <= 1 {
                b[dst] = b[src]
                return dst + 1, src + 1
        }
 
        if s[i] == '#' {
                if len(s) <= 3 { // We need to have at least "&#.".
                        b[dst] = b[src]
                        return dst + 1, src + 1
                }
                i++
                c := s[i]
                hex := false
                if c == 'x' || c == 'X' {
                        hex = true
                        i++
                }
 
                x := '\x00'
                for i < len(s) {
                        c = s[i]
                        i++
                        if hex {
                                if '0' <= c && c <= '9' {
                                        x = 16*x + rune(c) - '0'
                                        continue
                                } else if 'a' <= c && c <= 'f' {
                                        x = 16*x + rune(c) - 'a' + 10
                                        continue
                                } else if 'A' <= c && c <= 'F' {
                                        x = 16*x + rune(c) - 'A' + 10
                                        continue
                                }
                        } else if '0' <= c && c <= '9' {
                                x = 10*x + rune(c) - '0'
                                continue
                        }
                        if c != ';' {
                                i--
                        }
                        break
                }
 
                if i <= 3 { // No characters matched.
                        b[dst] = b[src]
                        return dst + 1, src + 1
                }
 
                if 0x80 <= x && x <= 0x9F {
                        // Replace characters from Windows-1252 with UTF-8 equivalents.
                        x = replacementTable[x-0x80]
                } else if x == 0 || (0xD800 <= x && x <= 0xDFFF) || x > 0x10FFFF {
                        // Replace invalid characters with the replacement character.
                        x = '\uFFFD'
                }
 
                return dst + utf8.EncodeRune(b[dst:], x), src + i
        }
 
        // Consume the maximum number of characters possible, with the
        // consumed characters matching one of the named references.
 
        for i < len(s) {
                c := s[i]
                i++
                // Lower-cased characters are more common in entities, so we check for them first.
                if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9' {
                        continue
                }
                if c != ';' {
                        i--
                }
                break
        }
 
        entityName := string(s[1:i])
        if entityName == "" {
                // No-op.
        } else if attribute && entityName[len(entityName)-1] != ';' && len(s) > i && s[i] == '=' {
                // No-op.
        } else if x := entity[entityName]; x != 0 {
                return dst + utf8.EncodeRune(b[dst:], x), src + i
        } else if x := entity2[entityName]; x[0] != 0 {
                dst1 := dst + utf8.EncodeRune(b[dst:], x[0])
                return dst1 + utf8.EncodeRune(b[dst1:], x[1]), src + i
        } else if !attribute {
                maxLen := len(entityName) - 1
                if maxLen > longestEntityWithoutSemicolon {
                        maxLen = longestEntityWithoutSemicolon
                }
                for j := maxLen; j > 1; j-- {
                        if x := entity[entityName[:j]]; x != 0 {
                                return dst + utf8.EncodeRune(b[dst:], x), src + j + 1
                        }
                }
        }
 
        dst1, src1 = dst+i, src+i
        copy(b[dst:dst1], b[src:src1])
        return dst1, src1
}
 
// unescape unescapes b's entities in-place, so that "a<b" becomes "a
func unescape(b []byte) []byte {
        for i, c := range b {
                if c == '&' {
                        dst, src := unescapeEntity(b, i, i, false)
                        for src < len(b) {
                                c := b[src]
                                if c == '&' {
                                        dst, src = unescapeEntity(b, dst, src, false)
                                } else {
                                        b[dst] = c
                                        dst, src = dst+1, src+1
                                }
                        }
                        return b[0:dst]
                }
        }
        return b
}
 
// lower lower-cases the A-Z bytes in b in-place, so that "aBc" becomes "abc".
func lower(b []byte) []byte {
        for i, c := range b {
                if 'A' <= c && c <= 'Z' {
                        b[i] = c + 'a' - 'A'
                }
        }
        return b
}
 
const escapedChars = `&'<>"`
 
func escape(w writer, s string) error {
        i := strings.IndexAny(s, escapedChars)
        for i != -1 {
                if _, err := w.WriteString(s[:i]); err != nil {
                        return err
                }
                var esc string
                switch s[i] {
                case '&':
                        esc = "&"
                case '\'':
                        esc = "'"
                case '<':
                        esc = "<"
                case '>':
                        esc = ">"
                case '"':
                        esc = """
                default:
                        panic("unrecognized escape character")
                }
                s = s[i+1:]
                if _, err := w.WriteString(esc); err != nil {
                        return err
                }
                i = strings.IndexAny(s, escapedChars)
        }
        _, err := w.WriteString(s)
        return err
}
 
// EscapeString escapes special characters like "<" to become "<". It
// escapes only five such characters: amp, apos, lt, gt and quot.
// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't
// always true.
func EscapeString(s string) string {
        if strings.IndexAny(s, escapedChars) == -1 {
                return s
        }
        var buf bytes.Buffer
        escape(&buf, s)
        return buf.String()
}
 
// UnescapeString unescapes entities like "<" to become "<". It unescapes a
// larger range of entities than EscapeString escapes. For example, "á"
// unescapes to "á", as does "á" and "&xE1;".
// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't
// always true.
func UnescapeString(s string) string {
        for _, c := range s {
                if c == '&' {
                        return string(unescape([]byte(s)))
                }
        }
        return s
}

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Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [go/] [html/] [escape.go] - Blame information for rev 747

Line No.	Rev	Author	Line
1	747	jeremybenn	`// Copyright 2010 The Go Authors. All rights reserved.`
2			`// Use of this source code is governed by a BSD-style`
3			`// license that can be found in the LICENSE file.`
4
5			`// Package html provides functions for escaping and unescaping HTML text.`
6			`package html`
7
8			`import (`
9			`"bytes"`
10			`"strings"`
11			`"unicode/utf8"`
12			`)`
13
14			`type writer interface {`
15			`WriteString(string) (int, error)`
16			`}`
17
18			`// These replacements permit compatibility with old numeric entities that`
19			`// assumed Windows-1252 encoding.`
20			`// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#consume-a-character-reference`
21			`var replacementTable = [...]rune{`
22			`'\u20AC', // First entry is what 0x80 should be replaced with.`
23			`'\u0081',`
24			`'\u201A',`
25			`'\u0192',`
26			`'\u201E',`
27			`'\u2026',`
28			`'\u2020',`
29			`'\u2021',`
30			`'\u02C6',`
31			`'\u2030',`
32			`'\u0160',`
33			`'\u2039',`
34			`'\u0152',`
35			`'\u008D',`
36			`'\u017D',`
37			`'\u008F',`
38			`'\u0090',`
39			`'\u2018',`
40			`'\u2019',`
41			`'\u201C',`
42			`'\u201D',`
43			`'\u2022',`
44			`'\u2013',`
45			`'\u2014',`
46			`'\u02DC',`
47			`'\u2122',`
48			`'\u0161',`
49			`'\u203A',`
50			`'\u0153',`
51			`'\u009D',`
52			`'\u017E',`
53			`'\u0178', // Last entry is 0x9F.`
54			`// 0x00->'\uFFFD' is handled programmatically.`
55			`// 0x0D->'\u000D' is a no-op.`
56			`}`
57
58			`// unescapeEntity reads an entity like "<" from b[src:] and writes the`
59			`// corresponding "<" to b[dst:], returning the incremented dst and src cursors.`
60			`// Precondition: b[src] == '&' && dst <= src.`
61			`// attribute should be true if parsing an attribute value.`
62			`func unescapeEntity(b []byte, dst, src int, attribute bool) (dst1, src1 int) {`
63			`// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#consume-a-character-reference`
64
65			`// i starts at 1 because we already know that s[0] == '&'.`
66			`i, s := 1, b[src:]`
67
68			`if len(s) <= 1 {`
69			`b[dst] = b[src]`
70			`return dst + 1, src + 1`
71			`}`
72
73			`if s[i] == '#' {`
74			`if len(s) <= 3 { // We need to have at least "&#.".`
75			`b[dst] = b[src]`
76			`return dst + 1, src + 1`
77			`}`
78			`i++`
79			`c := s[i]`
80			`hex := false`
81			`if c == 'x' \|\| c == 'X' {`
82			`hex = true`
83			`i++`
84			`}`
85
86			`x := '\x00'`
87			`for i < len(s) {`
88			`c = s[i]`
89			`i++`
90			`if hex {`
91			`if '0' <= c && c <= '9' {`
92			`x = 16*x + rune(c) - '0'`
93			`continue`
94			`} else if 'a' <= c && c <= 'f' {`
95			`x = 16*x + rune(c) - 'a' + 10`
96			`continue`
97			`} else if 'A' <= c && c <= 'F' {`
98			`x = 16*x + rune(c) - 'A' + 10`
99			`continue`
100			`}`
101			`} else if '0' <= c && c <= '9' {`
102			`x = 10*x + rune(c) - '0'`
103			`continue`
104			`}`
105			`if c != ';' {`
106			`i--`
107			`}`
108			`break`
109			`}`
110
111			`if i <= 3 { // No characters matched.`
112			`b[dst] = b[src]`
113			`return dst + 1, src + 1`
114			`}`
115
116			`if 0x80 <= x && x <= 0x9F {`
117			`// Replace characters from Windows-1252 with UTF-8 equivalents.`
118			`x = replacementTable[x-0x80]`
119			`} else if x == 0 \|\| (0xD800 <= x && x <= 0xDFFF) \|\| x > 0x10FFFF {`
120			`// Replace invalid characters with the replacement character.`
121			`x = '\uFFFD'`
122			`}`
123
124			`return dst + utf8.EncodeRune(b[dst:], x), src + i`
125			`}`
126
127			`// Consume the maximum number of characters possible, with the`
128			`// consumed characters matching one of the named references.`
129
130			`for i < len(s) {`
131			`c := s[i]`
132			`i++`
133			`// Lower-cased characters are more common in entities, so we check for them first.`
134			`if 'a' <= c && c <= 'z' \|\| 'A' <= c && c <= 'Z' \|\| '0' <= c && c <= '9' {`
135			`continue`
136			`}`
137			`if c != ';' {`
138			`i--`
139			`}`
140			`break`
141			`}`
142
143			`entityName := string(s[1:i])`
144			`if entityName == "" {`
145			`// No-op.`
146			`} else if attribute && entityName[len(entityName)-1] != ';' && len(s) > i && s[i] == '=' {`
147			`// No-op.`
148			`} else if x := entity[entityName]; x != 0 {`
149			`return dst + utf8.EncodeRune(b[dst:], x), src + i`
150			`} else if x := entity2[entityName]; x[0] != 0 {`
151			`dst1 := dst + utf8.EncodeRune(b[dst:], x[0])`
152			`return dst1 + utf8.EncodeRune(b[dst1:], x[1]), src + i`
153			`} else if !attribute {`
154			`maxLen := len(entityName) - 1`
155			`if maxLen > longestEntityWithoutSemicolon {`
156			`maxLen = longestEntityWithoutSemicolon`
157			`}`
158			`for j := maxLen; j > 1; j-- {`
159			`if x := entity[entityName[:j]]; x != 0 {`
160			`return dst + utf8.EncodeRune(b[dst:], x), src + j + 1`
161			`}`
162			`}`
163			`}`
164
165			`dst1, src1 = dst+i, src+i`
166			`copy(b[dst:dst1], b[src:src1])`
167			`return dst1, src1`
168			`}`
169
170			`// unescape unescapes b's entities in-place, so that "a<b" becomes "a`
171			`func unescape(b []byte) []byte {`
172			`for i, c := range b {`
173			`if c == '&' {`
174			`dst, src := unescapeEntity(b, i, i, false)`
175			`for src < len(b) {`
176			`c := b[src]`
177			`if c == '&' {`
178			`dst, src = unescapeEntity(b, dst, src, false)`
179			`} else {`
180			`b[dst] = c`
181			`dst, src = dst+1, src+1`
182			`}`
183			`}`
184			`return b[0:dst]`
185			`}`
186			`}`
187			`return b`
188			`}`
189
190			`// lower lower-cases the A-Z bytes in b in-place, so that "aBc" becomes "abc".`
191			`func lower(b []byte) []byte {`
192			`for i, c := range b {`
193			`if 'A' <= c && c <= 'Z' {`
194			`b[i] = c + 'a' - 'A'`
195			`}`
196			`}`
197			`return b`
198			`}`
199
200			const escapedChars = `&'<>"`
201
202			`func escape(w writer, s string) error {`
203			`i := strings.IndexAny(s, escapedChars)`
204			`for i != -1 {`
205			`if _, err := w.WriteString(s[:i]); err != nil {`
206			`return err`
207			`}`
208			`var esc string`
209			`switch s[i] {`
210			`case '&':`
211			`esc = "&"`
212			`case '\'':`
213			`esc = "'"`
214			`case '<':`
215			`esc = "<"`
216			`case '>':`
217			`esc = ">"`
218			`case '"':`
219			`esc = """`
220			`default:`
221			`panic("unrecognized escape character")`
222			`}`
223			`s = s[i+1:]`
224			`if _, err := w.WriteString(esc); err != nil {`
225			`return err`
226			`}`
227			`i = strings.IndexAny(s, escapedChars)`
228			`}`
229			`_, err := w.WriteString(s)`
230			`return err`
231			`}`
232
233			`// EscapeString escapes special characters like "<" to become "<". It`
234			`// escapes only five such characters: amp, apos, lt, gt and quot.`
235			`// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't`
236			`// always true.`
237			`func EscapeString(s string) string {`
238			`if strings.IndexAny(s, escapedChars) == -1 {`
239			`return s`
240			`}`
241			`var buf bytes.Buffer`
242			`escape(&buf, s)`
243			`return buf.String()`
244			`}`
245
246			`// UnescapeString unescapes entities like "<" to become "<". It unescapes a`
247			`// larger range of entities than EscapeString escapes. For example, "á"`
248			`// unescapes to "á", as does "á" and "&xE1;".`
249			`// UnescapeString(EscapeString(s)) == s always holds, but the converse isn't`
250			`// always true.`
251			`func UnescapeString(s string) string {`
252			`for _, c := range s {`
253			`if c == '&' {`
254			`return string(unescape([]byte(s)))`
255			`}`
256			`}`
257			`return s`
258			`}`