XMSDEMO.txt
#include <stdio.h>
#include <dos.h>
#include <string.h>
// Note: If you want to use XMS function 0xB, this simple
// xms_access routine only works for tiny, small, or medium
// models where the value of the data segment does not change.
void xms_access (union REGS *inregs, union REGS *outregs)
{
union REGS in, out;
struct SREGS segs;
unsigned segs_ds, save_bx;
unsigned flags;
void far (*xms)(void); // pointer to the XMS services
// Get the entry point to the XMS services
in.x.ax = 0x4310;
int86x (0x2F, &in, &out, &segs);
xms = (void far *) (((long) (segs.es) << 16) + out.x.bx);
// Assign the input registers to the actual registers
_AX = inregs->x.ax;
_CX = inregs->x.cx;
_DX = inregs->x.dx;
_SI = inregs->x.si;
_DI = inregs->x.di;
_BX = inregs->x.bx;
xms(); // Call the XMS entry point.
// Assign the registers to the output register structure
asm {
pushf
push bx
pop save_bx
pop flags
}
outregs->x.ax = _AX;
outregs->x.bx = save_bx;
outregs->x.cx = _CX;
outregs->x.dx = _DX;
outregs->x.si = _SI;
outregs->x.di = _DI;
outregs->x.cflag = flags & 1;
outregs->x.flags = flags;
}
void main (void)
{
union REGS inregs, outregs;
struct SREGS segs;
FILE *data;
char data_buffer[256];
struct xms_move {
long byte_count; // Number of bytes to move
unsigned source_handle; // Data to move
long source_offset;
unsigned destination_handle;
long destination_offset;
} block;
unsigned handle;
int string_length;
long character_count = 0L;
int transfer_error = 0; // 1 if a transfer error occurs
int i, extra_byte;
void xms_access (union REGS *, union REGS *);
inregs.x.ax = 0x4300;
int86 (0x2F, &inregs, &outregs);
if (outregs.h.al != 0x80)
printf ("XMS driver not installed\n");
else
{
// Allocate the extended memory
inregs.h.ah = 9;
inregs.x.dx = 64; // Size 64Kb
xms_access (&inregs, &outregs);
if (outregs.x.ax == 0)
printf ("Error allocating extended memory %2xH\n",
outregs.h.bl);
else
{
handle = outregs.x.dx;
// Read the file into a conventional memory
// buffer and then move the data to extended memory
if ((data = fopen ("\\AUTOEXEC.BAT", "r")) == NULL)
printf ("Error opening AUTOEXEC.BAT\n");
else
{
segread (&segs);
while (fgets (data_buffer, sizeof(data_buffer), data))
{
// Copy data_buffer to extended memory
string_length = strlen(data_buffer);
block.byte_count = string_length + 1;
// transfer amount must be even
if (block.byte_count % 2)
block.byte_count++;
block.source_handle = 0;
block.source_offset = (void far *)
MK_FP(segs.ds, data_buffer);
block.destination_handle = handle;
block.destination_offset = character_count;
character_count += string_length + 1;
inregs.h.ah = 0xB;
inregs.x.si = (unsigned) █
xms_access (&inregs, &outregs);
if (outregs.x.ax == 0)
{
transfer_error = 1;
break;
}
}
}
if (transfer_error)
printf ("Error in data transfer\n");
else
{
block.destination_handle = 0;
block.source_handle = handle;
block.destination_offset = (void far *)
MK_FP(segs.ds, data_buffer);
block.source_offset = 0L;
block.byte_count = sizeof(data_buffer);
while (block.source_offset <
character_count)
{
if ((block.byte_count + block.source_offset)
> character_count)
block.byte_count = character_count -
block.source_offset;
// Transfer amount must be even
if (block.byte_count % 2)
{
block.byte_count++;
extra_byte = 1;
}
else
extra_byte = 0;
xms_access (&inregs, &outregs);
if (outregs.x.ax == 0)
{
transfer_error = 1;
break;
}
for (i = 0; i < (block.byte_count -
extra_byte); i++)
if (data_buffer[i])
putchar(data_buffer[i]);
block.source_offset += block.byte_count;
}
}
if (transfer_error)
printf ("Error in data transfer\n");
// Release extended memory
inregs.h.ah = 0x0A;
inregs.x.dx = handle;
xms_access (&inregs, &outregs);
if (outregs.x.ax == 0)
printf ("Error releasing extending memory %2xH\n",
outregs.h.bl);
}
}
}