xmsdemo.c

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// 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) &block;

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);
    }
      }
}