分区体系与文件系统——分区体系（中）

这个是 linux C实现的读取MBR的代码：

（我的系统是 64 位 fedora 18,编译环境是 gcc 4.7.2）                                     

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

#define MBR_TABLE 512 //MBR分区表大小

#define PARTITION_OFFSET 446 //分区表项的起始位置
#define PARTITION_START 16             //分区大小

typedef struct mbr_struct
{
    unsigned char active_record; //0x00表示非活动记录，0x80表示活动记录
    unsigned char start[3];  //起始磁头号，扇区号，柱面号。其中磁头号1字节，扇区号2字节的低6位，柱面号2字节的高2位+3字节
    unsigned char partition_type;     //分区类型
    unsigned char end[3];             //结束磁头号
    unsigned int start_sector;         //逻辑起始扇区号
    unsigned int occupy_sector_num; //占用的扇区数
}mbr_read;


void print_mbr_info(mbr_read *mbr)
{
    printf("(第1字节)分区活动标记： %02hhX\n", mbr->active_record);

    printf("(第2、3、4字节)分区起始磁头、扇区、柱面号：");
    printf("%02hhX%02hhX%02hhX\n", mbr->start[0], mbr->start[1], mbr->start[2]);

    printf("(第5字节)分区类型：     %02hhX\n", mbr->partition_type);

    printf("(第6、7、8字节)分区结束磁头、扇区、柱面号：");
    printf("%02hhX%02hhX%02hhX\n", mbr->end[0], mbr->end[1], mbr->end[2]);

    printf("(第9、10、11、12字节)逻辑起始扇区号：%u\n", mbr->start_sector);

    printf("(第13、14、15、16字节)所占扇区数量：  %u\n", mbr->occupy_sector_num);
}


int main(int argc, char *argv[])
{

    int fd, size, index;
    char mbr_buffer[MBR_TABLE];
    mbr_read *mbr;



    /*打开文件和错误信息处理*/
    fd = open("/dev/sda", O_RDONLY); //这个一定要注意，以只读打开。防止对mbr的误操作
    if ( fd == 0 )
    {
        printf("open failed!\n");
        exit(0);
    }

    size = read(fd, mbr_buffer, sizeof(mbr_buffer));

    if ( size == -1 )
    {
        printf("权限不够，请用root权限操作!\n");
        exit(0);
    }
    close(fd);



    /*打印mbr信息，十六进制码*/
    for (index = 0; index < MBR_TABLE; index++)
    {
        printf("%02hhX ", mbr_buffer[index]);

        if (( index + 1 ) % 32 == 0)
        {
            printf("\n");
        }
    }
    printf("\n\n\n");



    /*打印分区表项信息*/
    printf("打印分区表项信息\n");
    printf("\n分区表项 1：\n\n");
    printf("当前分区数据:");
    for (index = PARTITION_OFFSET + PARTITION_START * 0; index < PARTITION_OFFSET + PARTITION_START * 1; index++)
    {
        printf("%02hhX ", mbr_buffer[index]);
    }
    printf("\n\n");
    print_mbr_info((mbr_read *)(mbr_buffer + PARTITION_OFFSET + PARTITION_START * 0));




    printf("\n\n分区表项 2：\n\n");
    printf("当前分区数据:");
    for (index = PARTITION_OFFSET + PARTITION_START * 1; index < PARTITION_OFFSET + PARTITION_START * 2; index++)
    {
        printf("%02hhX ", mbr_buffer[index]);
    }
    printf("\n\n");
    print_mbr_info((mbr_read *)(mbr_buffer + PARTITION_OFFSET + PARTITION_START * 1));




    printf("\n\n分区表项 3：\n\n");
    printf("当前分区数据:");
    for (index = PARTITION_OFFSET + PARTITION_START * 2; index < PARTITION_OFFSET + PARTITION_START * 3; index++)
    {
        printf("%02hhX ", mbr_buffer[index]);
    }
    printf("\n\n");
    print_mbr_info((mbr_read *)(mbr_buffer + PARTITION_OFFSET + PARTITION_START * 2));




    printf("\n\n分区表项 4：\n\n");
    printf("当前分区数据:");
    for (index =PARTITION_OFFSET + PARTITION_START * 3; index < PARTITION_OFFSET + PARTITION_START * 4; index++)
    {
        printf("%02hhX ", mbr_buffer[index]);
    }
    printf("\n\n");
    print_mbr_info((mbr_read *)(mbr_buffer + PARTITION_OFFSET + PARTITION_START * 3));


    return 0;

}