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// Copyright 2015, Joe Tsai. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE.md file.
package brotli
// RFC section 8.
// Maximum buffer size needed to store a word after a transformation.
const maxWordSize = maxDictLen + 13 + 1
// These constants are defined in Appendix B of the RFC.
const (
transformIdentity = iota
transformUppercaseFirst
transformUppercaseAll
transformOmitFirst1
transformOmitFirst2
transformOmitFirst3
transformOmitFirst4
transformOmitFirst5
transformOmitFirst6
transformOmitFirst7
transformOmitFirst8
transformOmitFirst9
transformOmitLast1
transformOmitLast2
transformOmitLast3
transformOmitLast4
transformOmitLast5
transformOmitLast6
transformOmitLast7
transformOmitLast8
transformOmitLast9
)
// This table is defined in Appendix B of the RFC.
var transformLUT = []struct {
prefix string
transform int
suffix string
}{
{"", transformIdentity, ""}, // 0
{"", transformIdentity, " "},
{" ", transformIdentity, " "},
{"", transformOmitFirst1, ""},
{"", transformUppercaseFirst, " "},
{"", transformIdentity, " the "},
{" ", transformIdentity, ""},
{"s ", transformIdentity, " "},
{"", transformIdentity, " of "},
{"", transformUppercaseFirst, ""},
{"", transformIdentity, " and "}, // 10
{"", transformOmitFirst2, ""},
{"", transformOmitLast1, ""},
{", ", transformIdentity, " "},
{"", transformIdentity, ", "},
{" ", transformUppercaseFirst, " "},
{"", transformIdentity, " in "},
{"", transformIdentity, " to "},
{"e ", transformIdentity, " "},
{"", transformIdentity, "\""},
{"", transformIdentity, "."}, // 20
{"", transformIdentity, "\">"},
{"", transformIdentity, "\n"},
{"", transformOmitLast3, ""},
{"", transformIdentity, "]"},
{"", transformIdentity, " for "},
{"", transformOmitFirst3, ""},
{"", transformOmitLast2, ""},
{"", transformIdentity, " a "},
{"", transformIdentity, " that "},
{" ", transformUppercaseFirst, ""}, // 30
{"", transformIdentity, ". "},
{".", transformIdentity, ""},
{" ", transformIdentity, ", "},
{"", transformOmitFirst4, ""},
{"", transformIdentity, " with "},
{"", transformIdentity, "'"},
{"", transformIdentity, " from "},
{"", transformIdentity, " by "},
{"", transformOmitFirst5, ""},
{"", transformOmitFirst6, ""}, // 40
{" the ", transformIdentity, ""},
{"", transformOmitLast4, ""},
{"", transformIdentity, ". The "},
{"", transformUppercaseAll, ""},
{"", transformIdentity, " on "},
{"", transformIdentity, " as "},
{"", transformIdentity, " is "},
{"", transformOmitLast7, ""},
{"", transformOmitLast1, "ing "},
{"", transformIdentity, "\n\t"}, // 50
{"", transformIdentity, ":"},
{" ", transformIdentity, ". "},
{"", transformIdentity, "ed "},
{"", transformOmitFirst9, ""},
{"", transformOmitFirst7, ""},
{"", transformOmitLast6, ""},
{"", transformIdentity, "("},
{"", transformUppercaseFirst, ", "},
{"", transformOmitLast8, ""},
{"", transformIdentity, " at "}, // 60
{"", transformIdentity, "ly "},
{" the ", transformIdentity, " of "},
{"", transformOmitLast5, ""},
{"", transformOmitLast9, ""},
{" ", transformUppercaseFirst, ", "},
{"", transformUppercaseFirst, "\""},
{".", transformIdentity, "("},
{"", transformUppercaseAll, " "},
{"", transformUppercaseFirst, "\">"},
{"", transformIdentity, "=\""}, // 70
{" ", transformIdentity, "."},
{".com/", transformIdentity, ""},
{" the ", transformIdentity, " of the "},
{"", transformUppercaseFirst, "'"},
{"", transformIdentity, ". This "},
{"", transformIdentity, ","},
{".", transformIdentity, " "},
{"", transformUppercaseFirst, "("},
{"", transformUppercaseFirst, "."},
{"", transformIdentity, " not "}, // 80
{" ", transformIdentity, "=\""},
{"", transformIdentity, "er "},
{" ", transformUppercaseAll, " "},
{"", transformIdentity, "al "},
{" ", transformUppercaseAll, ""},
{"", transformIdentity, "='"},
{"", transformUppercaseAll, "\""},
{"", transformUppercaseFirst, ". "},
{" ", transformIdentity, "("},
{"", transformIdentity, "ful "}, // 90
{" ", transformUppercaseFirst, ". "},
{"", transformIdentity, "ive "},
{"", transformIdentity, "less "},
{"", transformUppercaseAll, "'"},
{"", transformIdentity, "est "},
{" ", transformUppercaseFirst, "."},
{"", transformUppercaseAll, "\">"},
{" ", transformIdentity, "='"},
{"", transformUppercaseFirst, ","},
{"", transformIdentity, "ize "}, // 100
{"", transformUppercaseAll, "."},
{"\xc2\xa0", transformIdentity, ""},
{" ", transformIdentity, ","},
{"", transformUppercaseFirst, "=\""},
{"", transformUppercaseAll, "=\""},
{"", transformIdentity, "ous "},
{"", transformUppercaseAll, ", "},
{"", transformUppercaseFirst, "='"},
{" ", transformUppercaseFirst, ","},
{" ", transformUppercaseAll, "=\""}, // 110
{" ", transformUppercaseAll, ", "},
{"", transformUppercaseAll, ","},
{"", transformUppercaseAll, "("},
{"", transformUppercaseAll, ". "},
{" ", transformUppercaseAll, "."},
{"", transformUppercaseAll, "='"},
{" ", transformUppercaseAll, ". "},
{" ", transformUppercaseFirst, "=\""},
{" ", transformUppercaseAll, "='"},
{" ", transformUppercaseFirst, "='"}, // 120
}
// transformWord transform the input word and places the result in buf according
// to the transform primitives defined in RFC section 8.
//
// The following invariants must be kept:
//
// 0 <= id < len(transformLUT)
// len(word) <= maxDictLen
// len(buf) >= maxWordSize
func transformWord(buf, word []byte, id int) (cnt int) {
transform := transformLUT[id]
tid := transform.transform
cnt = copy(buf, transform.prefix)
switch {
case tid == transformIdentity:
cnt += copy(buf[cnt:], word)
case tid == transformUppercaseFirst:
buf2 := buf[cnt:]
cnt += copy(buf2, word)
transformUppercase(buf2[:len(word)], true)
case tid == transformUppercaseAll:
buf2 := buf[cnt:]
cnt += copy(buf2, word)
transformUppercase(buf2[:len(word)], false)
case tid <= transformOmitFirst9:
cut := tid - transformOmitFirst1 + 1 // 1..9
if len(word) > cut {
cnt += copy(buf[cnt:], word[cut:])
}
case tid <= transformOmitLast9:
cut := tid - transformOmitLast1 + 1 // 1..9
if len(word) > cut {
cnt += copy(buf[cnt:], word[:len(word)-cut])
}
}
cnt += copy(buf[cnt:], transform.suffix)
return cnt
}
// transformUppercase transform the word to be in uppercase using the algorithm
// presented in RFC section 8. If once is set, then loop only executes once.
func transformUppercase(word []byte, once bool) {
for i := 0; i < len(word); {
c := word[i]
if c < 192 {
if c >= 97 && c <= 122 {
word[i] ^= 32
}
i += 1
} else if c < 224 {
if i+1 < len(word) {
word[i+1] ^= 32
}
i += 2
} else {
if i+2 < len(word) {
word[i+2] ^= 5
}
i += 3
}
if once {
return
}
}
}
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