cdbread.c

Go to the documentation of this file.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <unistd.h>
#include "error.h"
#include "seek.h"
#include "byte.h"
#include "cdbread.h"
 
uint32 cdb_unpack(unsigned char *buf)
{
  uint32 num;
  num = buf[3]; num <<= 8;
  num += buf[2]; num <<= 8;
  num += buf[1]; num <<= 8;
  num += buf[0];
  return num;
}
 
void cdb_free(struct cdb *c)
{
  if (c->map) {
    munmap(c->map,c->size);
    c->map = 0;
  }
}
 
void cdb_findstart(struct cdb *c)
{
  c->loop = 0;
}
 
void cdb_init(struct cdb *c,int fd)
{
  struct stat st;
  char *x;
 
  cdb_free(c);
  cdb_findstart(c);
  c->fd = fd;
 
  if (fstat(fd,&st) == 0)
    if (st.st_size <= 0xffffffff) {
      x = mmap(0,st.st_size,PROT_READ,MAP_SHARED,fd,0);
      if (x + 1) {  // FIXME x + 1 means outside legal memory area; don't do it this way
        c->size = st.st_size;
        c->map = x;
      }
    }
}
 
int cdb_read(struct cdb *c,char *buf,unsigned int len,uint32 pos)
{
  if (c->map) {
    if ((pos > c->size) || (c->size - pos < len)) goto FORMAT;
    byte_copy(buf,len,c->map + pos);
  }
  else {
    if (seek_set(c->fd,pos) == -1) return -1;
    while (len > 0) {
      int r;
      do
        r = read(c->fd,buf,len);
      while ((r == -1) && (errno == EINTR));
      if (r == -1) return -1;
      if (r == 0) goto FORMAT;
      buf += r;
      len -= r;
    }
  }
  return 0;
 
  FORMAT:
  errno = EPROTO;
  return -1;
}
 
static int match(struct cdb *c,char *key,unsigned int len,uint32 pos)
{
  char buf[32];
  int n;
 
  while (len > 0) {
    n = sizeof(buf);
    if (n > len) n = len;
    if (cdb_read(c,buf,n,pos) == -1) return -1;
    if (byte_diff(buf,n,key)) return 0;
    pos += n;
    key += n;
    len -= n;
  }
  return 1;
}
 
int cdb_findnext(struct cdb *c,char *key,unsigned int len)
{
  char buf[8];
  uint32 pos;
  uint32 u;
 
  if (!c->loop) {
    u = cdb_hash(key,len);
    if (cdb_read(c,buf,8,(u << 3) & 2047) == -1) return -1;
    uint32_unpack(buf + 4,&c->hslots);
    if (!c->hslots) return 0;
    uint32_unpack(buf,&c->hpos);
    c->khash = u;
    u >>= 8;
    u %= c->hslots;
    u <<= 3;
    c->kpos = c->hpos + u;
  }
 
  while (c->loop < c->hslots) {
    if (cdb_read(c,buf,8,c->kpos) == -1) return -1;
    uint32_unpack(buf + 4,&pos);
    if (!pos) return 0;
    c->loop += 1;
    c->kpos += 8;
    if (c->kpos == c->hpos + (c->hslots << 3)) c->kpos = c->hpos;
    uint32_unpack(buf,&u);
    if (u == c->khash) {
      if (cdb_read(c,buf,8,pos) == -1) return -1;
      uint32_unpack(buf,&u);
      if (u == len)
      switch(match(c,key,len,pos + 8)) {
        case -1:
          return -1;
        case 1:
          uint32_unpack(buf + 4,&c->dlen);
          c->dpos = pos + 8 + len;
          return 1;
      }
    }
  }
 
  return 0;
}
 
int cdb_find(struct cdb *c,char *key,unsigned int len)
{
  cdb_findstart(c);
  return cdb_findnext(c,key,len);
}
 
uint32 cdb_hashadd(uint32 h,unsigned char c)
{
  h += (h << 5);
  return h ^ c;
}
 
uint32 cdb_hash(char *buf,unsigned int len)
{
  uint32 h;
 
  h = CDB_HASHSTART;
  while (len) {
    h = cdb_hashadd(h,*buf++);
    --len;
  }
  return h;
}