synopsis.go

Documentation: go/doc

		 1  // Copyright 2012 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  package doc
		 6  
		 7  import (
		 8  	"strings"
		 9  	"unicode"
		10  )
		11  
		12  // firstSentenceLen returns the length of the first sentence in s.
		13  // The sentence ends after the first period followed by space and
		14  // not preceded by exactly one uppercase letter.
		15  //
		16  func firstSentenceLen(s string) int {
		17  	var ppp, pp, p rune
		18  	for i, q := range s {
		19  		if q == '\n' || q == '\r' || q == '\t' {
		20  			q = ' '
		21  		}
		22  		if q == ' ' && p == '.' && (!unicode.IsUpper(pp) || unicode.IsUpper(ppp)) {
		23  			return i
		24  		}
		25  		if p == '。' || p == '．' {
		26  			return i
		27  		}
		28  		ppp, pp, p = pp, p, q
		29  	}
		30  	return len(s)
		31  }
		32  
		33  const (
		34  	keepNL = 1 << iota
		35  )
		36  
		37  // clean replaces each sequence of space, \n, \r, or \t characters
		38  // with a single space and removes any trailing and leading spaces.
		39  // If the keepNL flag is set, newline characters are passed through
		40  // instead of being change to spaces.
		41  func clean(s string, flags int) string {
		42  	var b []byte
		43  	p := byte(' ')
		44  	for i := 0; i < len(s); i++ {
		45  		q := s[i]
		46  		if (flags&keepNL) == 0 && q == '\n' || q == '\r' || q == '\t' {
		47  			q = ' '
		48  		}
		49  		if q != ' ' || p != ' ' {
		50  			b = append(b, q)
		51  			p = q
		52  		}
		53  	}
		54  	// remove trailing blank, if any
		55  	if n := len(b); n > 0 && p == ' ' {
		56  		b = b[0 : n-1]
		57  	}
		58  	return string(b)
		59  }
		60  
		61  // Synopsis returns a cleaned version of the first sentence in s.
		62  // That sentence ends after the first period followed by space and
		63  // not preceded by exactly one uppercase letter. The result string
		64  // has no \n, \r, or \t characters and uses only single spaces between
		65  // words. If s starts with any of the IllegalPrefixes, the result
		66  // is the empty string.
		67  //
		68  func Synopsis(s string) string {
		69  	s = clean(s[0:firstSentenceLen(s)], 0)
		70  	for _, prefix := range IllegalPrefixes {
		71  		if strings.HasPrefix(strings.ToLower(s), prefix) {
		72  			return ""
		73  		}
		74  	}
		75  	s = convertQuotes(s)
		76  	return s
		77  }
		78  
		79  var IllegalPrefixes = []string{
		80  	"copyright",
		81  	"all rights",
		82  	"author",
		83  }
		84
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