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Source file src/go/doc/synopsis.go

Documentation: go/doc

  // 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 ""
  		}
  	}
  	return s
  }
  
  var IllegalPrefixes = []string{
  	"copyright",
  	"all rights",
  	"author",
  }
  

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