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73 lines
2 KiB
Go
73 lines
2 KiB
Go
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// Copyright 2015 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 precis
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import (
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"unicode"
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"unicode/utf8"
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"golang.org/x/text/transform"
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)
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type nickAdditionalMapping struct {
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// TODO: This transformer needs to be stateless somehow…
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notStart bool
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prevSpace bool
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}
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func (t *nickAdditionalMapping) Reset() {
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t.prevSpace = false
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t.notStart = false
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}
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func (t *nickAdditionalMapping) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
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// RFC 8266 §2.1. Rules
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//
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// 2. Additional Mapping Rule: The additional mapping rule consists of
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// the following sub-rules.
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//
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// a. Map any instances of non-ASCII space to SPACE (U+0020); a
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// non-ASCII space is any Unicode code point having a general
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// category of "Zs", naturally with the exception of SPACE
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// (U+0020). (The inclusion of only ASCII space prevents
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// confusion with various non-ASCII space code points, many of
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// which are difficult to reproduce across different input
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// methods.)
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//
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// b. Remove any instances of the ASCII space character at the
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// beginning or end of a nickname (e.g., "stpeter " is mapped to
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// "stpeter").
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//
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// c. Map interior sequences of more than one ASCII space character
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// to a single ASCII space character (e.g., "St Peter" is
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// mapped to "St Peter").
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for nSrc < len(src) {
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r, size := utf8.DecodeRune(src[nSrc:])
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if size == 0 { // Incomplete UTF-8 encoding
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if !atEOF {
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return nDst, nSrc, transform.ErrShortSrc
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}
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size = 1
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}
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if unicode.Is(unicode.Zs, r) {
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t.prevSpace = true
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} else {
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if t.prevSpace && t.notStart {
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dst[nDst] = ' '
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nDst += 1
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}
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if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
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nDst += size
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return nDst, nSrc, transform.ErrShortDst
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}
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nDst += size
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t.prevSpace = false
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t.notStart = true
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}
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nSrc += size
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}
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return nDst, nSrc, nil
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}
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