100 lines
2.6 KiB
C
100 lines
2.6 KiB
C
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/* cdb_seek.c: old interface for reading cdb file
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*
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* This file is a part of tinycdb package by Michael Tokarev, mjt@corpit.ru.
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* Public domain.
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*/
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#include <unistd.h>
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#include "cdb_int.h"
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#ifndef SEEK_SET
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# define SEEK_SET 0
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#endif
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/* read a chunk from file, ignoring interrupts (EINTR) */
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int
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cdb_bread(int fd, void *buf, int len)
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{
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int l;
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while(len > 0) {
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do l = read(fd, buf, len);
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while(l < 0 && errno == EINTR);
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if (l <= 0) {
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if (!l)
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errno = EIO;
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return -1;
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}
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buf = (char*)buf + l;
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len -= l;
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}
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return 0;
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}
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/* find a given key in cdb file, seek a file pointer to it's value and
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place data length to *dlenp. */
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int
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cdb_seek(int fd, const void *key, unsigned klen, unsigned *dlenp)
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{
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unsigned htstart; /* hash table start position */
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unsigned htsize; /* number of elements in a hash table */
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unsigned httodo; /* hash table elements left to look */
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unsigned hti; /* hash table index */
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unsigned pos; /* position in a file */
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unsigned hval; /* key's hash value */
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unsigned char rbuf[64]; /* read buffer */
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int needseek = 1; /* if we should seek to a hash slot */
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hval = cdb_hash(key, klen);
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pos = (hval & 0xff) << 3; /* position in TOC */
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/* read the hash table parameters */
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if (lseek(fd, pos, SEEK_SET) < 0 || cdb_bread(fd, rbuf, 8) < 0)
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return -1;
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if ((htsize = cdb_unpack(rbuf + 4)) == 0)
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return 0;
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hti = (hval >> 8) % htsize; /* start position in hash table */
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httodo = htsize;
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htstart = cdb_unpack(rbuf);
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for(;;) {
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if (needseek && lseek(fd, htstart + (hti << 3), SEEK_SET) < 0)
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return -1;
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if (cdb_bread(fd, rbuf, 8) < 0)
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return -1;
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if ((pos = cdb_unpack(rbuf + 4)) == 0) /* not found */
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return 0;
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if (cdb_unpack(rbuf) != hval) /* hash value not matched */
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needseek = 0;
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else { /* hash value matched */
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if (lseek(fd, pos, SEEK_SET) < 0 || cdb_bread(fd, rbuf, 8) < 0)
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return -1;
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if (cdb_unpack(rbuf) == klen) { /* key length matches */
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/* read the key from file and compare with wanted */
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unsigned l = klen, c;
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const char *k = (const char*)key;
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if (dlenp)
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*dlenp = cdb_unpack(rbuf + 4); /* save value length */
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for(;;) {
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if (!l) /* the whole key read and matches, return */
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return 1;
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c = l > sizeof(rbuf) ? sizeof(rbuf) : l;
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if (cdb_bread(fd, rbuf, c) < 0)
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return -1;
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if (memcmp(rbuf, k, c) != 0) /* no, it differs, stop here */
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break;
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k += c; l -= c;
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}
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}
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needseek = 1; /* we're looked to other place, should seek back */
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}
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if (!--httodo)
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return 0;
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if (++hti == htsize) {
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hti = 0;
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needseek = 1;
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}
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}
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}
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