Mercurial > hg > cdb

comparison cdb.c @ 0:2cb46628feec

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
from cdb-0.75 per http://cr.yp.to/cdb.html, retrieved 2025-01-03, contents appear to have been create on 2000-02-19
author Henry S. Thompson <ht@inf.ed.ac.uk>
date Wed, 29 Jan 2025 10:50:34 +0000
parents
children 41b9b6a160d1
comparison
equal deleted inserted replaced
-1:000000000000 0:2cb46628feec
1 /* Public domain. */
2
3 #include <sys/types.h>
4 #include <sys/stat.h>
5 #include <sys/mman.h>
6 #include "readwrite.h"
7 #include "error.h"
8 #include "seek.h"
9 #include "byte.h"
10 #include "cdb.h"
11
12 void cdb_free(struct cdb *c)
13 {
14 if (c->map) {
15 munmap(c->map,c->size);
16 c->map = 0;
17 }
18 }
19
20 void cdb_findstart(struct cdb *c)
21 {
22 c->loop = 0;
23 }
24
25 void cdb_init(struct cdb *c,int fd)
26 {
27 struct stat st;
28 char *x;
29
30 cdb_free(c);
31 cdb_findstart(c);
32 c->fd = fd;
33
34 if (fstat(fd,&st) == 0)
35 if (st.st_size <= 0xffffffff) {
36 x = mmap(0,st.st_size,PROT_READ,MAP_SHARED,fd,0);
37 if (x + 1) {
38 c->size = st.st_size;
39 c->map = x;
40 }
41 }
42 }
43
44 int cdb_read(struct cdb *c,char *buf,unsigned int len,uint32 pos)
45 {
46 if (c->map) {
47 if ((pos > c->size) || (c->size - pos < len)) goto FORMAT;
48 byte_copy(buf,len,c->map + pos);
49 }
50 else {
51 if (seek_set(c->fd,pos) == -1) return -1;
52 while (len > 0) {
53 int r;
54 do
55 r = read(c->fd,buf,len);
56 while ((r == -1) && (errno == error_intr));
57 if (r == -1) return -1;
58 if (r == 0) goto FORMAT;
59 buf += r;
60 len -= r;
61 }
62 }
63 return 0;
64
65 FORMAT:
66 errno = error_proto;
67 return -1;
68 }
69
70 static int match(struct cdb *c,char *key,unsigned int len,uint32 pos)
71 {
72 char buf[32];
73 int n;
74
75 while (len > 0) {
76 n = sizeof buf;
77 if (n > len) n = len;
78 if (cdb_read(c,buf,n,pos) == -1) return -1;
79 if (byte_diff(buf,n,key)) return 0;
80 pos += n;
81 key += n;
82 len -= n;
83 }
84 return 1;
85 }
86
87 int cdb_findnext(struct cdb *c,char *key,unsigned int len)
88 {
89 char buf[8];
90 uint32 pos;
91 uint32 u;
92
93 if (!c->loop) {
94 u = cdb_hash(key,len);
95 if (cdb_read(c,buf,8,(u << 3) & 2047) == -1) return -1;
96 uint32_unpack(buf + 4,&c->hslots);
97 if (!c->hslots) return 0;
98 uint32_unpack(buf,&c->hpos);
99 c->khash = u;
100 u >>= 8;
101 u %= c->hslots;
102 u <<= 3;
103 c->kpos = c->hpos + u;
104 }
105
106 while (c->loop < c->hslots) {
107 if (cdb_read(c,buf,8,c->kpos) == -1) return -1;
108 uint32_unpack(buf + 4,&pos);
109 if (!pos) return 0;
110 c->loop += 1;
111 c->kpos += 8;
112 if (c->kpos == c->hpos + (c->hslots << 3)) c->kpos = c->hpos;
113 uint32_unpack(buf,&u);
114 if (u == c->khash) {
115 if (cdb_read(c,buf,8,pos) == -1) return -1;
116 uint32_unpack(buf,&u);
117 if (u == len)
118 switch(match(c,key,len,pos + 8)) {
119 case -1:
120 return -1;
121 case 1:
122 uint32_unpack(buf + 4,&c->dlen);
123 c->dpos = pos + 8 + len;
124 return 1;
125 }
126 }
127 }
128
129 return 0;
130 }
131
132 int cdb_find(struct cdb *c,char *key,unsigned int len)
133 {
134 cdb_findstart(c);
135 return cdb_findnext(c,key,len);
136 }