@node movedata, memory
@subheading Syntax

@example
#include <sys/movedata.h>

void movedata(unsigned source_selector, unsigned source_offset,
              unsigned dest_selector, unsigned dest_offset,
              size_t length);
@end example

@subheading Description

This function allows the caller to directly transfer information
between conventional and linear memory, and among each as well.  The
selectors passed are @emph{not} segment values like in DOS.  They are
protected mode selectors that can be obtained by the @code{_my_ds} and
@code{_go32_info_block.selector_for_linear_memory} (or just
@code{_dos_ds}) functions (@ref{_my_ds}, @ref{_go32_info_block}).
The offsets are linear offsets.  If the selector is for the program's
data area, this offset corresponds to the address of a buffer (like
@code{(unsigned)&something}).  If the selector is for the conventional
memory area, the offset is the physical address of the memory, which
can be computed from a traditional segment/offset pair as
@code{segment}*16+@code{offset}.  For example, the color text screen
buffer is at offset 0xb8000.

@subheading Return Value

None.

@subheading Portability

@portability !ansi, !posix

@subheading Example

@example
short blank_row_buf[ScreenCols()];
/* scroll screen */
movedata(_dos_ds, 0xb8000 + ScreenCols()*2,
         _dos_ds, 0xb8000,
         ScreenCols() * (ScreenRows()-1) * 2);
/* fill last row */
movedata(_my_ds(), (unsigned)blank_row_buf,
         _dos_ds, 0xb8000 + ScreenCols()*(ScreenRows()-1)*2,
          ScreenCols() * 2);
@end example