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) &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);

       } 

      }

  } 

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