Source file src/pkg/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 "unicode"
     8	
     9	// firstSentenceLen returns the length of the first sentence in s.
    10	// The sentence ends after the first period followed by space and
    11	// not preceded by exactly one uppercase letter.
    12	//
    13	func firstSentenceLen(s string) int {
    14		var ppp, pp, p rune
    15		for i, q := range s {
    16			if q == '\n' || q == '\r' || q == '\t' {
    17				q = ' '
    18			}
    19			if q == ' ' && p == '.' && (!unicode.IsUpper(pp) || unicode.IsUpper(ppp)) {
    20				return i
    21			}
    22			ppp, pp, p = pp, p, q
    23		}
    24		return len(s)
    25	}
    26	
    27	// Synopsis returns a cleaned version of the first sentence in s.
    28	// That sentence ends after the first period followed by space and
    29	// not preceded by exactly one uppercase letter. The result string
    30	// has no \n, \r, or \t characters and uses only single spaces between
    31	// words.
    32	//
    33	func Synopsis(s string) string {
    34		n := firstSentenceLen(s)
    35		var b []byte
    36		p := byte(' ')
    37		for i := 0; i < n; i++ {
    38			q := s[i]
    39			if q == '\n' || q == '\r' || q == '\t' {
    40				q = ' '
    41			}
    42			if q != ' ' || p != ' ' {
    43				b = append(b, q)
    44				p = q
    45			}
    46		}
    47		// remove trailing blank, if any
    48		if n := len(b); n > 0 && p == ' ' {
    49			b = b[0 : n-1]
    50		}
    51		return string(b)
    52	}