readptr.c

UNIX编程高级环境（第二版）的网络套接字部分的程序源码

#include    "db.h"

/* Read a chain ptr field from anywhere in the index file:
 * the free list pointer, a hash table chain ptr, or an
 * index record chain ptr.  */

off_t
_db_readptr(DB *db, off_t offset)
{
    char    asciiptr[PTR_SZ + 1];

    if (lseek(db->idxfd, offset, SEEK_SET) == -1)
        err_dump("lseek error to ptr field");
    if (read(db->idxfd, asciiptr, PTR_SZ) != PTR_SZ)
        err_dump("read error of ptr field");

    asciiptr[PTR_SZ] = 0;        /* null terminate */
    return(atol(asciiptr));
}