fat32知道mbr怎么找到dbr。c语言代码

在传统的MS-DOS和Windows操作系统中，MBR (Master Boot Record) 和 DBR (Disk Boot Record) 都位于硬盘的第一个扇区（0磁道0面1扇区）。MBR 包含引导程序、分区表等信息，而DBR 则是活动分区的引导记录，用于标识当前引导的分区。

当你在C语言中寻找DBR时，实际上是在处理BIOS中断（INT 13h）提供的磁盘I/O服务。下面是一个简单的示例，展示如何在C语言中读取DBR（DOS分区表的前几个字节），假设我们已经初始化了设备文件描述符（如fd）：

#include <stdio.h>
#include <sys/ioctl.h>

#define BIOS_DRIVE_NUM 0x80

// BIOS read sector function prototype
unsigned char *read_sect(int fd, unsigned int sector);

int main() {
    int fd;
    // Open the disk device using BIOS drive number
    if ((fd = open("/dev/hda", O_RDONLY | O_BINARY)) == -1) {
        perror("Opening disk failed");
        return 1;
    }

    // Seek to the MBR location (sector 0)
    if (lseek(fd, BIOS_DRIVE_NUM * 512, SEEK_SET) != BIOS_DRIVE_NUM * 512) {
        perror("Seeking to MBR failed");
        close(fd);
        return 1;
    }

    // Read the first sector (MBR) into memory
    unsigned char *mbr = read_sect(fd, 0);
    
    // The DBR is typically located immediately after the MBR, at offset 446 bytes (DBR size is 446 bytes)
    unsigned char *dbr = &mbr[446];

    // Now dbr contains the information of the active partition's boot record
    printf("DBR contents:\n");

    // Print the content for demonstration purposes
    // In practice, you would parse these values according to the structure defined in your code.
    for (int i = 0; i < sizeof(dbr); ++i) {
        printf("%02X ", dbr[i]);
    }
    printf("\n");

    close(fd);
    return 0;
}

// BIOS read sector helper function
unsigned char *read_sect(int fd, unsigned int sector) {
    static char buffer[512];
    if (pread(fd, buffer, 512, sector * 512) != 512) {
        perror("Reading sector failed");
        return NULL;
    }
    return buffer;
}

注意：这个例子假设你正在Linux环境下，并且需要先安装`ioctls`库来支持BIOS中断操作。在实际环境中，具体的细节可能会有所不同，比如设备路径和磁盘访问函数可能需要根据你的硬件和环境进行调整。