Baskı Partition Table C programı

Question

C programlama dilini kullanarak bir bölümleme listesine çalışıyorum

, her şey iyi çalışıyor görünüyor: Açılış ve okuma, ancak çöp değerlerini yazdırıyor neden anlamıyorum.

struct partition 
{ 
    unsigned char drive; 
    unsigned char chs_begin[3]; 
    unsigned char sys_type; 
    unsigned char chs_end[3]; 
    unsigned char start_sector[4]; 
    unsigned char nr_sector[4]; 
}; 

int main() 
{ 
    int gc = 0, i = 1, nr = 0, pos = -1, nw = 0; 
    int fd =0; 
    char buf[512] ; 
    struct partition *sp; 
    printf("Ok "); 

    if ((fd = open("/dev/sda", O_RDONLY | O_SYNC)) == -1) 
    { 
     perror("Open"); 
     exit(1); 
    } 
    printf("fd is %d \n", fd); 

    pos = lseek (fd, 0, SEEK_CUR); 

    printf("Position of pointer is :%d\n", pos); 
    if ((nr = read(fd, buf, sizeof(buf))) == -1) 
    { 
     perror("Read"); 
     exit(1); 
    } 

    close(fd); 

    printf("Size of buf = %d\n and number of bytes read are %d ", sizeof(buf), nr); 


    if ((nw = write(1, buf, 64)) == -1) 
    { 
     printf("Write: Error"); 
     exit(1); 
    } 

    printf("\n\n %d bytes are just been written on stdout\n", nw,"this can also be printed\n"); 

    printf("\n\t\t*************Partition Table****************\n\n"); 

    for (i=0 ; i<4 ; i++) 
    { 
     sp = (struct partition *)(buf + 446 + (16 * i)); 
     putchar(sp -> drive); 
    } 


    return 0; 
} 

yerine bölümleme tablosunun çöp yazdırıyor: Burada

kodudur.

Ben bazı temel anlayış sorunları olabilir ama ben uzun zamandır Google ile arama ama gerçekten yardımcı olmadı. Ayrıca fdisk'in kaynak kodunu gördüm ama bu noktada benim anlayışımın ötesinde. Lütfen bana rehberlik edebilir misiniz? Birisinin hatamı temizlemesini ve çalışma kodunu vermesini beklemiyorum. Sadece bir cümle veya iki - veya herhangi bir bağlantı.

Answer 1

bu deneyin:

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

struct partition 
{ 
     unsigned char boot_flag;  /* 0 = Not active, 0x80 = Active */ 
     unsigned char chs_begin[3]; 
     unsigned char sys_type;   /* For example : 82 --> Linux swap, 83 --> Linux native partition, ... */ 
     unsigned char chs_end[3]; 
     unsigned char start_sector[4]; 
     unsigned char nr_sector[4]; 
}; 

void string_in_hex(void *in_string, int in_string_size); 
void dump_partition(struct partition *part, int partition_number); 

void dump_partition(struct partition *part, int partition_number) 
{ 
     printf("Partition /dev/sda%d\n", partition_number + 1); 
     printf("boot_flag = %02X\n", part->boot_flag); 
     printf("chs_begin = "); 
     string_in_hex(part->chs_begin, 3); 
     printf("sys_type = %02X\n", part->sys_type); 
     printf("chs_end = "); 
     string_in_hex(part->chs_end, 3); 
     printf("start_sector = "); 
     string_in_hex(part->start_sector, 4); 
     printf("nr_sector = "); 
     string_in_hex(part->nr_sector, 4); 
} 

void string_in_hex(void *in_string, int in_string_size) 
{ 
     int i; 
     int k = 0; 

     for (i = 0; i < in_string_size; i++) 
     { 
       printf("%02x ", ((char *)in_string)[i]& 0xFF); 
       k = k + 1; 
       if (k == 16) 
       { 
         printf("\n"); 
         k = 0; 
       } 
     } 
     printf("\n"); 
} 

int main(int argc, char **argv) 
{ 
     int /*gc = 0,*/ i = 1, nr = 0, pos = -1/*, nw = 0*/; 
     int fd = 0; 
     char buf[512] ; 
     struct partition *sp; 
     int ret = 0; 

     printf("Ok "); 

     if ((fd = open("/dev/sda", O_RDONLY | O_SYNC)) == -1) 
     { 
       perror("Open"); 
       exit(1); 
     } 
     printf("fd is %d\n", fd); 

     pos = lseek (fd, 0, SEEK_CUR); 

     printf("Position of pointer is :%d\n", pos); 
     if ((nr = read(fd, buf, sizeof(buf))) == -1) 
     { 
       perror("Read"); 
       exit(1); 
     } 

     ret = close(fd); 
     if (ret == -1) 
     { 
       perror("close"); 
       exit(1); 
     } 

     /* Dump the MBR buffer, you can compare it on your system with the output of the command: 
     * hexdump -n 512 -C /dev/sda 
     */ 
     string_in_hex(buf, 512); 

     printf("Size of buf = %d - and number of bytes read are %d\n", sizeof(buf), nr); 
     /*if ((nw = write(1, buf, 64)) == -1) 
     { 
       printf("Write: Error"); 
       exit(1); 
     } 

     printf("\n\n%d bytes are just been written on stdout\nthis can also be printed\n", nw); 
     */ 
     //printf("\n\t\t*************Partition Table****************\n\n"); 
     printf("\n\t\t*************THE 4 MAIN PARTITIONS****************\n\n"); 

     /* Dump main partitions (4 partitions) */ 
     /* Note : the 4 partitions you are trying to dump are not necessarily existing! */ 
     for (i = 0 ; i < 4 ; i++) 
     { 
       sp = (struct partition *)(buf + 446 + (16 * i)); 
       //putchar(sp->boot_flag); 
       dump_partition(sp, i); 
     } 

     return 0; 
}