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180 lines
3.5 KiB
Go
180 lines
3.5 KiB
Go
package mahonia
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// decoding HTML entities
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import (
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"sort"
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)
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// EntityDecoder returns a Decoder that decodes HTML character entities.
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// If there is no valid character entity at the current position, it returns INVALID_CHAR.
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// So it needs to be combined with another Decoder via FallbackDecoder.
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func EntityDecoder() Decoder {
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var leftover rune // leftover rune from two-rune entity
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return func(p []byte) (r rune, size int, status Status) {
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if leftover != 0 {
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r = leftover
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leftover = 0
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return r, 0, SUCCESS
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}
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if len(p) == 0 {
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return 0, 0, NO_ROOM
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}
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if p[0] != '&' {
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return 0xfffd, 1, INVALID_CHAR
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}
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if len(p) < 3 {
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return 0, 1, NO_ROOM
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}
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r, size, status = 0xfffd, 1, INVALID_CHAR
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n := 1 // number of bytes read so far
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if p[n] == '#' {
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n++
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c := p[n]
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hex := false
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if c == 'x' || c == 'X' {
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hex = true
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n++
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}
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var x rune
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for n < len(p) {
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c = p[n]
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n++
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if hex {
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if '0' <= c && c <= '9' {
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x = 16*x + rune(c) - '0'
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continue
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} else if 'a' <= c && c <= 'f' {
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x = 16*x + rune(c) - 'a' + 10
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continue
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} else if 'A' <= c && c <= 'F' {
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x = 16*x + rune(c) - 'A' + 10
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continue
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}
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} else if '0' <= c && c <= '9' {
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x = 10*x + rune(c) - '0'
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continue
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}
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if c != ';' {
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n--
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}
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break
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}
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if n == len(p) && p[n-1] != ';' {
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return 0, 0, NO_ROOM
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}
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size = n
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if p[n-1] == ';' {
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n--
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}
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if hex {
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n--
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}
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n--
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// Now n is the number of actual digits read.
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if n == 0 {
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return 0xfffd, 1, INVALID_CHAR
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}
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if 0x80 <= x && x <= 0x9F {
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// Replace characters from Windows-1252 with UTF-8 equivalents.
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x = replacementTable[x-0x80]
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} else if x == 0 || (0xD800 <= x && x <= 0xDFFF) || x > 0x10FFFF {
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// Replace invalid characters with the replacement character.
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return 0xfffd, size, INVALID_CHAR
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}
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r = x
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status = SUCCESS
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return
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}
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// Look for a named entity in EntityList.
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possible := entityList
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for len(possible) > 0 {
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if len(p) <= n {
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leftover = 0
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return 0, 0, NO_ROOM
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}
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c := p[n]
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// Narrow down the selection in possible to those items that have c in the
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// appropriate byte.
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first := sort.Search(len(possible), func(i int) bool {
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e := possible[i].name
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if len(e) < n {
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return false
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}
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return e[n-1] >= c
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})
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possible = possible[first:]
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last := sort.Search(len(possible), func(i int) bool {
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return possible[i].name[n-1] > c
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})
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possible = possible[:last]
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n++
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if len(possible) > 0 && len(possible[0].name) == n-1 {
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r, leftover = possible[0].r1, possible[0].r2
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size = n
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status = SUCCESS
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// but don't return yet, since we need the longest match
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}
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}
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return
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}
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}
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// This table is copied from /src/pkg/html/escape.go in the Go source
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//
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// These replacements permit compatibility with old numeric entities that
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// assumed Windows-1252 encoding.
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// http://www.whatwg.org/specs/web-apps/current-work/multipage/tokenization.html#consume-a-character-reference
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var replacementTable = [...]rune{
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'\u20AC', // First entry is what 0x80 should be replaced with.
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'\u0081',
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'\u201A',
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'\u0192',
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'\u201E',
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'\u2026',
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'\u2020',
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'\u2021',
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'\u02C6',
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'\u2030',
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'\u0160',
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'\u2039',
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'\u0152',
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'\u008D',
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'\u017D',
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'\u008F',
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'\u0090',
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'\u2018',
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'\u2019',
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'\u201C',
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'\u201D',
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'\u2022',
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'\u2013',
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'\u2014',
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'\u02DC',
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'\u2122',
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'\u0161',
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'\u203A',
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'\u0153',
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'\u009D',
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'\u017E',
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'\u0178', // Last entry is 0x9F.
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// 0x00->'\uFFFD' is handled programmatically.
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// 0x0D->'\u000D' is a no-op.
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}
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