lib/libc/sys-minix/pread.c

   1 #include <sys/cdefs.h>
   2 #include "namespace.h"
   3 #include <lib.h>
   4
   5 #include <unistd.h>
   6
   7 #ifdef __weak_alias
   8 __weak_alias(pread, _pread)
   9 #endif
  10
  11 #include <lib.h>
  12 #include <unistd.h>
  13 #include <minix/u64.h>
  14
  15 ssize_t pread64(int fd, void *buffer, size_t nbytes, u64_t where)
  16 {
  17         u64_t here;
  18         ssize_t r;
  19
  20         if (lseek64(fd, make64(0,0), SEEK_CUR, &here) < 0) return(-1);
  21         if (lseek64(fd, where, SEEK_SET, NULL) < 0) return(-1);
  22         if ((r = read(fd, buffer, nbytes)) < 0) {
  23                 int e = errno;
  24                 lseek64(fd, here, SEEK_SET, NULL);
  25                 errno = e;
  26                 return(-1);
  27         }
  28
  29         if (lseek64(fd, here, SEEK_SET, NULL) < 0) return(-1);
  30
  31         return(r);
  32 }
  33
  34 ssize_t pread(int fd, void *buffer, size_t nbytes, off_t where)
  35 {
  36         off_t here;
  37         ssize_t r;
  38
  39         if((here = lseek(fd, 0, SEEK_CUR)) < 0)
  40                 return -1;
  41
  42         if(lseek(fd, where, SEEK_SET) < 0)
  43                 return -1;
  44
  45         if((r=read(fd, buffer, nbytes)) < 0) {
  46                 int e = errno;
  47                 lseek(fd, here, SEEK_SET);
  48                 errno = e;
  49                 return -1;
  50         }
  51
  52         if(lseek(fd, here, SEEK_SET) < 0)
  53                 return -1;
  54
  55         return r;
  56 }
  57