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/* cdb_seek.c: old interface for reading cdb file
*
* This file is a part of tinycdb package.
* Copyright (C) 2001-2023 Michael Tokarev <mjt+cdb@corpit.ru>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <unistd.h>
#include "cdb_int.h"
#ifndef SEEK_SET
# define SEEK_SET 0
#endif
/* read a chunk from file, ignoring interrupts (EINTR) */
int
cdb_bread(int fd, void *buf, int len)
{
int l;
while(len > 0) {
do l = read(fd, buf, len);
while(l < 0 && errno == EINTR);
if (l <= 0) {
if (!l)
errno = EIO;
return -1;
}
buf = (char*)buf + l;
len -= l;
}
return 0;
}
/* find a given key in cdb file, seek a file pointer to it's value and
place data length to *dlenp. */
int
cdb_seek(int fd, const void *key, unsigned klen, unsigned *dlenp)
{
unsigned htstart; /* hash table start position */
unsigned htsize; /* number of elements in a hash table */
unsigned httodo; /* hash table elements left to look */
unsigned hti; /* hash table index */
unsigned pos; /* position in a file */
unsigned hval; /* key's hash value */
unsigned char rbuf[64]; /* read buffer */
int needseek = 1; /* if we should seek to a hash slot */
hval = cdb_hash(key, klen);
pos = (hval & 0xff) << 3; /* position in TOC */
/* read the hash table parameters */
if (lseek(fd, pos, SEEK_SET) < 0 || cdb_bread(fd, rbuf, 8) < 0)
return -1;
if ((htsize = cdb_unpack(rbuf + 4)) == 0)
return 0;
hti = (hval >> 8) % htsize; /* start position in hash table */
httodo = htsize;
htstart = cdb_unpack(rbuf);
for(;;) {
if (needseek && lseek(fd, htstart + (hti << 3), SEEK_SET) < 0)
return -1;
if (cdb_bread(fd, rbuf, 8) < 0)
return -1;
if ((pos = cdb_unpack(rbuf + 4)) == 0) /* not found */
return 0;
if (cdb_unpack(rbuf) != hval) /* hash value not matched */
needseek = 0;
else { /* hash value matched */
if (lseek(fd, pos, SEEK_SET) < 0 || cdb_bread(fd, rbuf, 8) < 0)
return -1;
if (cdb_unpack(rbuf) == klen) { /* key length matches */
/* read the key from file and compare with wanted */
unsigned l = klen, c;
const char *k = (const char*)key;
if (dlenp)
*dlenp = cdb_unpack(rbuf + 4); /* save value length */
for(;;) {
if (!l) /* the whole key read and matches, return */
return 1;
c = l > sizeof(rbuf) ? sizeof(rbuf) : l;
if (cdb_bread(fd, rbuf, c) < 0)
return -1;
if (memcmp(rbuf, k, c) != 0) /* no, it differs, stop here */
break;
k += c; l -= c;
}
}
needseek = 1; /* we're looked to other place, should seek back */
}
if (!--httodo)
return 0;
if (++hti == htsize) {
hti = 0;
needseek = 1;
}
}
}
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