minix3/lib/libc/sys/pread.c

35 lines
519 B
C

#include <sys/cdefs.h>
#include "namespace.h"
#include <errno.h>
#include <unistd.h>
#ifdef __weak_alias
__weak_alias(pread, _pread)
#endif
ssize_t pread(int fd, void *buffer, size_t nbytes, off_t where)
{
off_t here;
ssize_t r;
if((here = lseek(fd, 0, SEEK_CUR)) < 0)
return -1;
if(lseek(fd, where, SEEK_SET) < 0)
return -1;
if((r=read(fd, buffer, nbytes)) < 0) {
int e = errno;
lseek(fd, here, SEEK_SET);
errno = e;
return -1;
}
if(lseek(fd, here, SEEK_SET) < 0)
return -1;
return r;
}