libgo/go/go/doc/synopsis.go

   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                 ppp, pp, p = pp, p, q
  26         }
  27         return len(s)
  28 }
  29
  30 const (
  31         keepNL = 1 << iota
  32 )
  33
  34 // clean replaces each sequence of space, \n, \r, or \t characters
  35 // with a single space and removes any trailing and leading spaces.
  36 // If the keepNL flag is set, newline characters are passed through
  37 // instead of being change to spaces.
  38 func clean(s string, flags int) string {
  39         var b []byte
  40         p := byte(' ')
  41         for i := 0; i < len(s); i++ {
  42                 q := s[i]
  43                 if (flags&keepNL) == 0 && q == '\n' || q == '\r' || q == '\t' {
  44                         q = ' '
  45                 }
  46                 if q != ' ' || p != ' ' {
  47                         b = append(b, q)
  48                         p = q
  49                 }
  50         }
  51         // remove trailing blank, if any
  52         if n := len(b); n > 0 && p == ' ' {
  53                 b = b[0 : n-1]
  54         }
  55         return string(b)
  56 }
  57
  58 // Synopsis returns a cleaned version of the first sentence in s.
  59 // That sentence ends after the first period followed by space and
  60 // not preceded by exactly one uppercase letter. The result string
  61 // has no \n, \r, or \t characters and uses only single spaces between
  62 // words. If s starts with any of the IllegalPrefixes, the result
  63 // is the empty string.
  64 //
  65 func Synopsis(s string) string {
  66         s = clean(s[0:firstSentenceLen(s)], 0)
  67         for _, prefix := range IllegalPrefixes {
  68                 if strings.HasPrefix(strings.ToLower(s), prefix) {
  69                         return ""
  70                 }
  71         }
  72         return s
  73 }
  74
  75 var IllegalPrefixes = []string{
  76         "copyright",
  77         "all rights",
  78         "author",
  79 }