76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
/* cdb_find.c: cdb_find routine
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*
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* This file is a part of tinycdb package by Michael Tokarev, mjt+cdb@corpit.ru.
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* Public domain.
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*/
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#include "cdb_int.h"
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int
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cdb_find(struct cdb *cdbp, const void *key, unsigned klen)
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{
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const unsigned char *htp; /* hash table pointer */
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const unsigned char *htab; /* hash table */
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const unsigned char *htend; /* end of hash table */
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unsigned httodo; /* ht bytes left to look */
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unsigned pos, n;
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unsigned hval;
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if (klen >= cdbp->cdb_dend) /* if key size is too large */
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return 0;
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hval = cdb_hash(key, klen);
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/* find (pos,n) hash table to use */
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/* first 2048 bytes (toc) are always available */
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/* (hval % 256) * 8 */
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htp = cdbp->cdb_mem + ((hval << 3) & 2047); /* index in toc (256x8) */
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n = cdb_unpack(htp + 4); /* table size */
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if (!n) /* empty table */
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return 0; /* not found */
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httodo = n << 3; /* bytes of htab to lookup */
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pos = cdb_unpack(htp); /* htab position */
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if (n > (cdbp->cdb_fsize >> 3) /* overflow of httodo ? */
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|| pos < cdbp->cdb_dend /* is htab inside data section ? */
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|| pos > cdbp->cdb_fsize /* htab start within file ? */
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|| httodo > cdbp->cdb_fsize - pos) /* entrie htab within file ? */
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return errno = EPROTO, -1;
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htab = cdbp->cdb_mem + pos; /* htab pointer */
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htend = htab + httodo; /* after end of htab */
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/* htab starting position: rest of hval modulo htsize, 8bytes per elt */
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htp = htab + (((hval >> 8) % n) << 3);
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for(;;) {
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pos = cdb_unpack(htp + 4); /* record position */
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if (!pos)
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return 0;
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if (cdb_unpack(htp) == hval) {
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if (pos > cdbp->cdb_dend - 8) /* key+val lengths */
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return errno = EPROTO, -1;
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if (cdb_unpack(cdbp->cdb_mem + pos) == klen) {
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if (cdbp->cdb_dend - klen < pos + 8)
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return errno = EPROTO, -1;
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if (memcmp(key, cdbp->cdb_mem + pos + 8, klen) == 0) {
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n = cdb_unpack(cdbp->cdb_mem + pos + 4);
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pos += 8;
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if (cdbp->cdb_dend < n || cdbp->cdb_dend - n < pos + klen)
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return errno = EPROTO, -1;
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cdbp->cdb_kpos = pos;
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cdbp->cdb_klen = klen;
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cdbp->cdb_vpos = pos + klen;
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cdbp->cdb_vlen = n;
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return 1;
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}
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}
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}
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httodo -= 8;
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if (!httodo)
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return 0;
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if ((htp += 8) >= htend)
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htp = htab;
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}
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}
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