mmaptest.c

来自「Solaris下的虚拟内存编程,sun公司培训用例.」· C语言 代码 · 共 55 行

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>

void *addr = (void*)0x10000000, *map_addr;

int main(int argc, char** argv)
{
	int fildes, len;
	struct stat statinfo;
	char c, buffer[256];

	if (argc < 2) {
		printf("File name is required!\n");
		return 0;
	}
			
	if ((fildes = open(argv[1], O_RDWR)) < 0 || fstat(fildes, &statinfo)) {
		printf("File operation error!\n");
		return -1;
	}
	
	len = statinfo.st_size;
	printf("Pause 1. Press enter to continue...\n");
	gets(buffer);
	
	if ((map_addr = mmap(addr, len, PROT_READ | PROT_WRITE,
		MAP_SHARED | MAP_FIXED, fildes, 0)) == MAP_FAILED)
		printf("Map failed!\n");
	else {
		printf("Mapped address is %p\n", map_addr);

		// touch each page of the segment
		for (int i = 0; i < len; i += 4096)
			c = ((char*)map_addr)[i];
		
		printf("Pause 2. Press enter to continue...\n");
		gets(buffer);

		// write a character at the beginning of the file
		((char*)map_addr)[0] = 'z';

		printf("Pause 3. Press enter to exit...\n");
		getchar();
		
		munmap(map_addr, statinfo.st_size);
	}

	close(fildes);
	return 0;
}