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