FilesExpand file tree

master

/

cbtree.c

Copy path

Blame

More file actions

Blame

More file actions

Latest commit

 

History

History

History

150 lines (125 loc) · 3.71 KB

master

/

cbtree.c

Copy path

Top

File metadata and controls

• Code
• Blame

150 lines (125 loc) · 3.71 KB

Raw

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

/*

* crit-bit tree implementation, does no allocations internally

* For more information on crit-bit trees: https://cr.yp.to/critbit.html

* Based on Adam Langley's adaptation of Dan Bernstein's public domain code

* git clone https://github.com/agl/critbit.git

*/

#include "git-compat-util.h"

#include "cbtree.h"

static inline uint8_t *cb_node_key(struct cb_tree *t, struct cb_node *node)

{

return (uint8_t *) node + t->key_offset;

}

static struct cb_node *cb_node_of(const void *p)

{

return (struct cb_node *)((uintptr_t)p - 1);

}

/* locate the best match, does not do a final comparison */

static struct cb_node *cb_internal_best_match(struct cb_node *p,

const uint8_t *k, size_t klen)

{

while (1 & (uintptr_t)p) {

struct cb_node *q = cb_node_of(p);

uint8_t c = q->byte < klen ? k[q->byte] : 0;

size_t direction = (1 + (q->otherbits | c)) >> 8;

p = q->child[direction];

}

return p;

}

/* returns NULL if successful, existing cb_node if duplicate */

struct cb_node *cb_insert(struct cb_tree *t, struct cb_node *node, size_t klen)

{

size_t newbyte, newotherbits;

uint8_t c;

int newdirection;

struct cb_node **wherep, *p;

uint8_t *node_key, *p_key;

assert(!((uintptr_t)node & 1)); /* allocations must be aligned */

if (!t->root) { /* insert into empty tree */

t->root = node;

return NULL; /* success */

}

node_key = cb_node_key(t, node);

/* see if a node already exists */

p = cb_internal_best_match(t->root, node_key, klen);

p_key = cb_node_key(t, p);

/* find first differing byte */

for (newbyte = 0; newbyte < klen; newbyte++) {

if (p_key[newbyte] != node_key[newbyte])

goto different_byte_found;

}

return p; /* element exists, let user deal with it */

different_byte_found:

newotherbits = p_key[newbyte] ^ node_key[newbyte];

newotherbits |= newotherbits >> 1;

newotherbits |= newotherbits >> 2;

newotherbits |= newotherbits >> 4;

newotherbits = (newotherbits & ~(newotherbits >> 1)) ^ 255;

c = p_key[newbyte];

newdirection = (1 + (newotherbits | c)) >> 8;

node->byte = newbyte;

node->otherbits = newotherbits;

node->child[1 - newdirection] = node;

/* find a place to insert it */

wherep = &t->root;

for (;;) {

struct cb_node *q;

size_t direction;

p = *wherep;

if (!(1 & (uintptr_t)p))

break;

q = cb_node_of(p);

if (q->byte > newbyte)

break;

if (q->byte == newbyte && q->otherbits > newotherbits)

break;

c = q->byte < klen ? node_key[q->byte] : 0;

direction = (1 + (q->otherbits | c)) >> 8;

wherep = q->child + direction;

}

node->child[newdirection] = *wherep;

*wherep = (struct cb_node *)(1 + (uintptr_t)node);

return NULL; /* success */

}

struct cb_node *cb_lookup(struct cb_tree *t, const uint8_t *k, size_t klen)

{

struct cb_node *p = cb_internal_best_match(t->root, k, klen);

return p && !memcmp(cb_node_key(t, p), k, klen) ? p : NULL;

}

static int cb_descend(struct cb_node *p, cb_iter fn, void *arg)

{

if (1 & (uintptr_t)p) {

struct cb_node *q = cb_node_of(p);

int ret = cb_descend(q->child[0], fn, arg);

if (ret)

return ret;

return cb_descend(q->child[1], fn, arg);

} else {

return fn(p, arg);

}

}

int cb_each(struct cb_tree *t, const uint8_t *kpfx, size_t klen,

cb_iter fn, void *arg)

{

struct cb_node *p = t->root;

struct cb_node *top = p;

size_t i = 0;

uint8_t *p_key;

if (!p)

return 0; /* empty tree */

/* Walk tree, maintaining top pointer */

while (1 & (uintptr_t)p) {

struct cb_node *q = cb_node_of(p);

uint8_t c = q->byte < klen ? kpfx[q->byte] : 0;

size_t direction = (1 + (q->otherbits | c)) >> 8;

p = q->child[direction];

if (q->byte < klen)

top = p;

}

p_key = cb_node_key(t, p);

for (i = 0; i < klen; i++) {

if (p_key[i] != kpfx[i])

return 0; /* "best" match failed */

}

return cb_descend(top, fn, arg);

}