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       1                 :             : /* cdb_find.c: cdb_find routine
       2                 :             :  *
       3                 :             :  * This file is a part of tinycdb package.
       4                 :             :  * Copyright (C) 2001-2023 Michael Tokarev <mjt+cdb@corpit.ru>
       5                 :             :  *
       6                 :             :  * Permission is hereby granted, free of charge, to any person obtaining a
       7                 :             :  * copy of this software and associated documentation files (the "Software"),
       8                 :             :  * to deal in the Software without restriction, including without limitation
       9                 :             :  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      10                 :             :  * and/or sell copies of the Software, and to permit persons to whom the
      11                 :             :  * Software is furnished to do so, subject to the following conditions:
      12                 :             :  *
      13                 :             :  * The above copyright notice and this permission notice shall be included
      14                 :             :  * in all copies or substantial portions of the Software.
      15                 :             :  *
      16                 :             :  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      17                 :             :  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      18                 :             :  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
      19                 :             :  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      20                 :             :  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
      21                 :             :  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
      22                 :             :  * DEALINGS IN THE SOFTWARE.
      23                 :             :  */
      24                 :             : 
      25                 :             : #include "cdb_int.h"
      26                 :             : 
      27                 :             : int
      28                 :           0 : cdb_find(struct cdb *cdbp, const void *key, unsigned klen)
      29                 :             : {
      30                 :             :   const unsigned char *htp;     /* hash table pointer */
      31                 :             :   const unsigned char *htab;    /* hash table */
      32                 :             :   const unsigned char *htend;   /* end of hash table */
      33                 :             :   unsigned httodo;              /* ht bytes left to look */
      34                 :             :   unsigned pos, n;
      35                 :             : 
      36                 :             :   unsigned hval;
      37                 :             : 
      38         [ #  # ]:           0 :   if (klen >= cdbp->cdb_dend)     /* if key size is too large */
      39                 :           0 :     return 0;
      40                 :             : 
      41                 :           0 :   hval = cdb_hash(key, klen);
      42                 :             : 
      43                 :             :   /* find (pos,n) hash table to use */
      44                 :             :   /* first 2048 bytes (toc) are always available */
      45                 :             :   /* (hval % 256) * 8 */
      46                 :           0 :   htp = cdbp->cdb_mem + ((hval << 3) & 2047); /* index in toc (256x8) */
      47                 :           0 :   n = cdb_unpack(htp + 4);      /* table size */
      48         [ #  # ]:           0 :   if (!n)                       /* empty table */
      49                 :           0 :     return 0;                   /* not found */
      50                 :           0 :   httodo = n << 3;                /* bytes of htab to lookup */
      51                 :           0 :   pos = cdb_unpack(htp);        /* htab position */
      52         [ #  # ]:           0 :   if (n > (cdbp->cdb_fsize >> 3) /* overflow of httodo ? */
      53         [ #  # ]:           0 :       || pos < cdbp->cdb_dend /* is htab inside data section ? */
      54         [ #  # ]:           0 :       || pos > cdbp->cdb_fsize /* htab start within file ? */
      55         [ #  # ]:           0 :       || httodo > cdbp->cdb_fsize - pos) /* entrie htab within file ? */
      56                 :           0 :     return errno = EPROTO, -1;
      57                 :             : 
      58                 :           0 :   htab = cdbp->cdb_mem + pos;        /* htab pointer */
      59                 :           0 :   htend = htab + httodo;        /* after end of htab */
      60                 :             :   /* htab starting position: rest of hval modulo htsize, 8bytes per elt */
      61                 :           0 :   htp = htab + (((hval >> 8) % n) << 3);
      62                 :             : 
      63                 :             :   for(;;) {
      64                 :           0 :     pos = cdb_unpack(htp + 4);  /* record position */
      65         [ #  # ]:           0 :     if (!pos)
      66                 :           0 :       return 0;
      67         [ #  # ]:           0 :     if (cdb_unpack(htp) == hval) {
      68         [ #  # ]:           0 :       if (pos > cdbp->cdb_dend - 8) /* key+val lengths */
      69                 :           0 :         return errno = EPROTO, -1;
      70         [ #  # ]:           0 :       if (cdb_unpack(cdbp->cdb_mem + pos) == klen) {
      71         [ #  # ]:           0 :         if (cdbp->cdb_dend - klen < pos + 8)
      72                 :           0 :           return errno = EPROTO, -1;
      73         [ #  # ]:           0 :         if (memcmp(key, cdbp->cdb_mem + pos + 8, klen) == 0) {
      74                 :           0 :           n = cdb_unpack(cdbp->cdb_mem + pos + 4);
      75                 :           0 :           pos += 8;
      76   [ #  #  #  # ]:           0 :           if (cdbp->cdb_dend < n || cdbp->cdb_dend - n < pos + klen)
      77                 :           0 :             return errno = EPROTO, -1;
      78                 :           0 :           cdbp->cdb_kpos = pos;
      79                 :           0 :           cdbp->cdb_klen = klen;
      80                 :           0 :           cdbp->cdb_vpos = pos + klen;
      81                 :           0 :           cdbp->cdb_vlen = n;
      82                 :           0 :           return 1;
      83                 :             :         }
      84                 :             :       }
      85                 :             :     }
      86                 :           0 :     httodo -= 8;
      87         [ #  # ]:           0 :     if (!httodo)
      88                 :           0 :       return 0;
      89         [ #  # ]:           0 :     if ((htp += 8) >= htend)
      90                 :           0 :       htp = htab;
      91                 :             :   }
      92                 :             : 
      93                 :             : }