minix/lib/libc/sys/pread.c

   1 #include <sys/cdefs.h>
   2 #include "namespace.h"
   3
   4 #include <errno.h>
   5 #include <unistd.h>
   6
   7 #ifdef __weak_alias
   8 __weak_alias(pread, _pread)
   9 #endif
  10
  11 ssize_t pread(int fd, void *buffer, size_t nbytes, off_t where)
  12 {
  13         off_t here;
  14         ssize_t r;
  15
  16         if((here = lseek(fd, 0, SEEK_CUR)) < 0)
  17                 return -1;
  18
  19         if(lseek(fd, where, SEEK_SET) < 0)
  20                 return -1;
  21
  22         if((r=read(fd, buffer, nbytes)) < 0) {
  23                 int e = errno;
  24                 lseek(fd, here, SEEK_SET);
  25                 errno = e;
  26                 return -1;
  27         }
  28
  29         if(lseek(fd, here, SEEK_SET) < 0)
  30                 return -1;
  31
  32         return r;
  33 }
  34