Source file src/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			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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