中国DOS联盟

我现在要写一个程序，可以读写4GB的内存空间，用的是DJGPP的编译器！有高手能指教以下吗？

经过一天的研究，找到了解决方法，现在贴出来，其实该程序就是根据http://www.delorie.com/djgpp/dl/apps/ 里的Peritool的exsample.c改的。


#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
#include <pc.h>
#include <dpmi.h>
#include <sys\farptr.h>
#include <go32.h>

#define u_int unsigned int
#define u_long unsigned long

u_int map(u_int addr, u_int size);

char mem_read(u_long pci_addr)
{
u_int slctr;
char pci_data;
slctr=map(pci_addr,0xff);
if (slctr == -1)
printf ("error selecting memory\n");
else
{ pci_data=(u_int)_farpeekb(slctr,0);}

return pci_data;
}

char mem_write(u_long pci_addr,char pci_data)
{
u_int slctr;
slctr=map(pci_addr,0xff);
if (slctr == -1)
printf ("error selecting memory\n");
else
_farpokeb(slctr,0,pci_data);

return 0;
}

u_int map(u_int addr, u_int size)
{
__dpmi_meminfo mi;
int selector;

/* addr &= (size - 1); */
mi.handle = 0;
mi.address = addr;
mi.size = size;
if (__dpmi_physical_address_mapping(&mi))
{
printf ("__dpmi_physical_address_mapping failed\n");
return -1;
}
selector = __dpmi_allocate_ldt_descriptors(1);
if (selector == -1)
{
printf ("__dpmi_allocate_ldt_descriptors failed\n");
return -1;
}
if(__dpmi_set_segment_base_address(selector,mi.address))
{
printf ("__dpmi_set_segment_base_address failed\n");
return -1;
}
if(__dpmi_set_segment_limit(selector,mi.size-1))
{
printf ("__dpmi_set_segment_limit failed\n");
return -1;
}
return selector;
}


int main()
{
u_long address;
printf("please input the address:");
scanf("%x",&address);
printf("data before write=%x\n",mem_read(address));
mem_write(address,0x66);
printf("data after write=%x\n",mem_read(address));
}