lib/libc/posix/pread.c

   1 #include <lib.h>
   2 #include <unistd.h>
   3
   4 ssize_t pread(int fd, void *buffer, size_t nbytes, off_t where)
   5 {
   6         off_t here;
   7         ssize_t r;
   8
   9         if((here = lseek(fd, 0, SEEK_CUR)) < 0)
  10                 return -1;
  11
  12         if(lseek(fd, where, SEEK_SET) < 0)
  13                 return -1;
  14
  15         if((r=read(fd, buffer, nbytes)) < 0) {
  16                 int e = errno;
  17                 lseek(fd, here, SEEK_SET);
  18                 errno = e;
  19                 return -1;
  20         }
  21
  22         if(lseek(fd, here, SEEK_SET) < 0)
  23                 return -1;
  24
  25         return r;
  26 }
  27