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cdb_seek.c (1783B)

      1 #include <sys/types.h>
      2 #include <errno.h>
      3 #include <unistd.h>
      4 #include "cdb.h"
      5 
      6 #ifndef SEEK_SET
      7 #define SEEK_SET 0
      8 #endif
      9 
     10 int cdb_bread(fd,buf,len)
     11 int fd;
     12 char *buf;
     13 int len;
     14 {
     15   int r;
     16   while (len > 0) {
     17     do
     18       r = read(fd,buf,len);
     19     while ((r == -1) && (errno == EINTR));
     20     if (r == -1) return -1;
     21     if (r == 0) { errno = EIO; return -1; }
     22     buf += r;
     23     len -= r;
     24   }
     25   return 0;
     26 }
     27 
     28 static int match(fd,key,len)
     29 int fd;
     30 char *key;
     31 unsigned int len;
     32 {
     33   char buf[32];
     34   int n;
     35   int i;
     36 
     37   while (len > 0) {
     38     n = sizeof(buf);
     39     if (n > len) n = len;
     40     if (cdb_bread(fd,buf,n) == -1) return -1;
     41     for (i = 0;i < n;++i) if (buf[i] != key[i]) return 0;
     42     key += n;
     43     len -= n;
     44   }
     45   return 1;
     46 }
     47 
     48 int cdb_seek(fd,key,len,dlen)
     49 int fd;
     50 char *key;
     51 unsigned int len;
     52 uint32 *dlen;
     53 {
     54   char packbuf[8];
     55   uint32 pos;
     56   uint32 h;
     57   uint32 lenhash;
     58   uint32 h2;
     59   uint32 loop;
     60   uint32 poskd;
     61 
     62   h = cdb_hash(key,len);
     63 
     64   pos = 8 * (h & 255);
     65   if (lseek(fd,(off_t) pos,SEEK_SET) == -1) return -1;
     66 
     67   if (cdb_bread(fd,packbuf,8) == -1) return -1;
     68 
     69   pos = cdb_unpack(packbuf);
     70   lenhash = cdb_unpack(packbuf + 4);
     71 
     72   if (!lenhash) return 0;
     73   h2 = (h >> 8) % lenhash;
     74 
     75   for (loop = 0;loop < lenhash;++loop) {
     76     if (lseek(fd,(off_t) (pos + 8 * h2),SEEK_SET) == -1) return -1;
     77     if (cdb_bread(fd,packbuf,8) == -1) return -1;
     78     poskd = cdb_unpack(packbuf + 4);
     79     if (!poskd) return 0;
     80     if (cdb_unpack(packbuf) == h) {
     81       if (lseek(fd,(off_t) poskd,SEEK_SET) == -1) return -1;
     82       if (cdb_bread(fd,packbuf,8) == -1) return -1;
     83       if (cdb_unpack(packbuf) == len)
     84 	switch(match(fd,key,len)) {
     85 	  case -1:
     86 	    return -1;
     87 	  case 1:
     88 	    *dlen = cdb_unpack(packbuf + 4);
     89 	    return 1;
     90 	}
     91     }
     92     if (++h2 == lenhash) h2 = 0;
     93   }
     94   return 0;
     95 }