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Diffstat (limited to 'c/src/lib/libc/lseek.c')
-rw-r--r--c/src/lib/libc/lseek.c32
1 files changed, 26 insertions, 6 deletions
diff --git a/c/src/lib/libc/lseek.c b/c/src/lib/libc/lseek.c
index 069952ff8e..910b81d231 100644
--- a/c/src/lib/libc/lseek.c
+++ b/c/src/lib/libc/lseek.c
@@ -26,15 +26,25 @@ off_t lseek(
)
{
rtems_libio_t *iop;
+ off_t old_offset;
+ off_t status;
rtems_libio_check_fd( fd );
iop = rtems_libio_iop( fd );
rtems_libio_check_is_open(iop);
/*
+ * Check as many errors as possible before touching iop->offset.
+ */
+
+ if ( !iop->handlers->lseek_h )
+ set_errno_and_return_minus_one( ENOTSUP );
+
+ /*
* Now process the lseek().
*/
+ old_offset = iop->offset;
switch ( whence ) {
case SEEK_SET:
iop->offset = offset;
@@ -45,18 +55,28 @@ off_t lseek(
break;
case SEEK_END:
- iop->offset = iop->size - offset;
+ iop->offset = iop->size + offset;
break;
default:
- errno = EINVAL;
- return -1;
+ set_errno_and_return_minus_one( EINVAL );
}
- if ( !iop->handlers->lseek_h )
- set_errno_and_return_minus_one( ENOTSUP );
+ /*
+ * At this time, handlers assume iop->offset has the desired
+ * new offset.
+ */
+
+ status = (*iop->handlers->lseek_h)( iop, offset, whence );
+ if ( !status )
+ return 0;
+
+ /*
+ * So if the operation failed, we have to restore iop->offset.
+ */
- return (*iop->handlers->lseek_h)( iop, offset, whence );
+ iop->offset = old_offset;
+ return status;
}
/*