// Copyright 2012 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 doc
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import (
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"strings"
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"unicode"
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)
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// firstSentenceLen returns the length of the first sentence in s.
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// The sentence ends after the first period followed by space and
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// not preceded by exactly one uppercase letter.
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//
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func firstSentenceLen(s string) int {
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var ppp, pp, p rune
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for i, q := range s {
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if q == '\n' || q == '\r' || q == '\t' {
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q = ' '
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}
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if q == ' ' && p == '.' && (!unicode.IsUpper(pp) || unicode.IsUpper(ppp)) {
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return i
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}
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if p == '。' || p == '．' {
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return i
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}
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ppp, pp, p = pp, p, q
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}
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return len(s)
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}
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const (
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keepNL = 1 << iota
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)
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// clean replaces each sequence of space, \n, \r, or \t characters
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// with a single space and removes any trailing and leading spaces.
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// If the keepNL flag is set, newline characters are passed through
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// instead of being change to spaces.
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func clean(s string, flags int) string {
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var b []byte
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p := byte(' ')
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for i := 0; i < len(s); i++ {
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q := s[i]
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if (flags&keepNL) == 0 && q == '\n' || q == '\r' || q == '\t' {
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q = ' '
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}
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if q != ' ' || p != ' ' {
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b = append(b, q)
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p = q
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}
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}
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// remove trailing blank, if any
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if n := len(b); n > 0 && p == ' ' {
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b = b[0 : n-1]
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}
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return string(b)
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}
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// Synopsis returns a cleaned version of the first sentence in s.
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// That sentence ends after the first period followed by space and
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// not preceded by exactly one uppercase letter. The result string
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// has no \n, \r, or \t characters and uses only single spaces between
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// words. If s starts with any of the IllegalPrefixes, the result
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// is the empty string.
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//
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func Synopsis(s string) string {
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s = clean(s[0:firstSentenceLen(s)], 0)
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for _, prefix := range IllegalPrefixes {
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if strings.HasPrefix(strings.ToLower(s), prefix) {
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return ""
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}
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}
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s = convertQuotes(s)
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return s
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}
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var IllegalPrefixes = []string{
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"copyright",
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"all rights",
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"author",
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}
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