OpenCoverage

str-kmp.h

Absolute File Name:

/home/opencoverage/opencoverage/guest-scripts/coreutils/src/lib/str-kmp.h

Source code

Switch to Preprocessed file

Line Source Count

1 /* Substring search in a NUL terminated string of UNIT elements, -

2 using the Knuth-Morris-Pratt algorithm. -

4 Written by Bruno Haible <bruno@clisp.org>, 2005. -

5 -

6 This program is free software; you can redistribute it and/or modify -

7 it under the terms of the GNU General Public License as published by -

8 the Free Software Foundation; either version 3, or (at your option) -

9 any later version. -

10 -

11 This program is distributed in the hope that it will be useful, -

12 but WITHOUT ANY WARRANTY; without even the implied warranty of -

13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -

14 GNU General Public License for more details. -

15 -

16 You should have received a copy of the GNU General Public License -

17 along with this program; if not, see <https://www.gnu.org/licenses/>. */ -

18 -

19 /* Before including this file, you need to define: -

20 UNIT The element type of the needle and haystack. -

21 CANON_ELEMENT(c) A macro that canonicalizes an element right after -

22 it has been fetched from needle or haystack. -

23 The argument is of type UNIT; the result must be -

24 of type UNIT as well. */ -

25 -

26 /* Knuth-Morris-Pratt algorithm. -

27 See https://en.wikipedia.org/wiki/Knuth-Morris-Pratt_algorithm -

28 HAYSTACK is the NUL terminated string in which to search for. -

29 NEEDLE is the string to search for in HAYSTACK, consisting of NEEDLE_LEN -

30 units. -

31 Return a boolean indicating success: -

32 Return true and set *RESULTP if the search was completed. -

33 Return false if it was aborted because not enough memory was available. */ -

34 static bool -

35 knuth_morris_pratt (const UNIT *haystack, -

36 const UNIT *needle, size_t needle_len, -

37 const UNIT **resultp) -

38 { -

39 size_t m = needle_len; -

40 -

41 /* Allocate the table. */ -

42 size_t *table = (size_t *) nmalloca (m, sizeof (size_t)); -

if (table == NULL)

table == ((void *)0)	Description
TRUE	never evaluated
FALSE	never evaluated

return false;

never executed: return 0 ;

45 /* Fill the table. -

46 For 0 < i < m: -

47 0 < table[i] <= i is defined such that -

48 forall 0 < x < table[i]: needle[x..i-1] != needle[0..i-1-x], -

49 and table[i] is as large as possible with this property. -

50 This implies: -

51 1) For 0 < i < m: -

52 If table[i] < i, -

53 needle[table[i]..i-1] = needle[0..i-1-table[i]]. -

54 2) For 0 < i < m: -

55 rhaystack[0..i-1] == needle[0..i-1] -

56 and exists h, i <= h < m: rhaystack[h] != needle[h] -

57 implies -

58 forall 0 <= x < table[i]: rhaystack[x..x+m-1] != needle[0..m-1]. -

59 table[0] remains uninitialized. */ -

60 { -

61 size_t i, j; -

62 -

63 /* i = 1: Nothing to verify for x = 0. */ -

64 table[1] = 1; -

65 j = 0; -

66 -

for (i = 2; i < m; i++)

i < m	Description
TRUE	never evaluated
FALSE	never evaluated

68 { -

69 /* Here: j = i-1 - table[i-1]. -

70 The inequality needle[x..i-1] != needle[0..i-1-x] is known to hold -

71 for x < table[i-1], by induction. -

72 Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1]. */ -

73 UNIT b = CANON_ELEMENT (needle[i - 1]); -

74 -

75 for (;;) -

76 { -

77 /* Invariants: The inequality needle[x..i-1] != needle[0..i-1-x] -

78 is known to hold for x < i-1-j. -

79 Furthermore, if j>0: needle[i-1-j..i-2] = needle[0..j-1]. */ -

if (b == CANON_ELEMENT (needle[j]))

b == needle[j]	Description
TRUE	never evaluated
FALSE	never evaluated

81 { -

82 /* Set table[i] := i-1-j. */ -

83 table[i] = i - ++j; -

break;

never executed: break;

85 } -

86 /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds -

87 for x = i-1-j, because -

88 needle[i-1] != needle[j] = needle[i-1-x]. */ -

if (j == 0)

j == 0	Description
TRUE	never evaluated
FALSE	never evaluated

90 { -

91 /* The inequality holds for all possible x. */ -

92 table[i] = i; -

break;

never executed: break;

94 } -

95 /* The inequality needle[x..i-1] != needle[0..i-1-x] also holds -

96 for i-1-j < x < i-1-j+table[j], because for these x: -

97 needle[x..i-2] -

98 = needle[x-(i-1-j)..j-1] -

99 != needle[0..j-1-(x-(i-1-j))] (by definition of table[j]) -

100 = needle[0..i-2-x], -

101 hence needle[x..i-1] != needle[0..i-1-x]. -

102 Furthermore -

103 needle[i-1-j+table[j]..i-2] -

104 = needle[table[j]..j-1] -

105 = needle[0..j-1-table[j]] (by definition of table[j]). */ -

106 j = j - table[j]; -

107

}

never executed: end of block

108 /* Here: j = i - table[i]. */ -

109

}

never executed: end of block

110 } -

111 -

112 /* Search, using the table to accelerate the processing. */ -

113 { -

114 size_t j; -

115 const UNIT *rhaystack; -

116 const UNIT *phaystack; -

117 -

118 *resultp = NULL; -

119 j = 0; -

120 rhaystack = haystack; -

121 phaystack = haystack; -

122 /* Invariant: phaystack = rhaystack + j. */ -

123

while (*phaystack != 0)

*phaystack != 0	Description
TRUE	never evaluated
FALSE	never evaluated

124

if (CANON_ELEMENT (needle[j]) == CANON_ELEMENT (*phaystack))

needle[j] == *phaystack	Description
TRUE	never evaluated
FALSE	never evaluated

125 { -

126 j++; -

127 phaystack++; -

128

if (j == m)

j == m	Description
TRUE	never evaluated
FALSE	never evaluated

129 { -

130 /* The entire needle has been found. */ -

131 *resultp = rhaystack; -

132

break;

never executed: break;

133 } -

134

}

never executed: end of block

135

else if (j > 0)

j > 0	Description
TRUE	never evaluated
FALSE	never evaluated

136 { -

137 /* Found a match of needle[0..j-1], mismatch at needle[j]. */ -

138 rhaystack += table[j]; -

139 j -= table[j]; -

140

}

never executed: end of block

141 else -

142 { -

143 /* Found a mismatch at needle[0] already. */ -

144 rhaystack++; -

145 phaystack++; -

146

}

never executed: end of block

147 } -

148 -

149 freea (table); -

150

return true;

never executed: return 1 ;

151 } -

152 -

153 #undef CANON_ELEMENT -

Source code

Switch to Preprocessed file

Generated by Squish Coco 4.1.2