From:	Jon Slaughter <lobo AT iamerica DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	source code help
Date:	Wed, 23 Oct 1996 19:53:02 -0500
Organization:	none
Lines:	127
Message-ID:	<326EBDEE.4ED@iamerica.net>
NNTP-Posting-Host:	205.173.253.150
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

here is some code that is supose to read the boot sector and print out
all the information in BOOT_RECORD. But for some reason, it doesn't :( I
have no idea why. It would seem that I left some variable out of the
structure because the first two are ok, but I've looked over it and
couldn't find anything wrong. It also could be the strings since I have
no idea of how c handles them(except that they are null terminated)...
Its probably something stupid, but if anyone can help me, please!!



#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <memory.h>
#include <bios.h>


#define BYTE unsigned char
#define WORD unsigned short
#define DWORD unsigned long

#define disk_drive = 0;

struct BOOT_RECORD_STRUCT {
        BYTE jump[3];
        BYTE oem_name[8];
        WORD bytes_per_sector;
        BYTE sectors_per_cluster;
        WORD number_of_reserved_sectors;
        BYTE number_of_fats;
        WORD number_of_root_dir_entries;
        WORD number_of_total_sectors;
        BYTE media_descriptor_byte;
        WORD sectors_per_fat;
        WORD sectors_per_track;
        WORD number_of_heads;
        WORD number_of_hidden_sectors1;
        WORD number_of_hidden_sectors2;
        DWORD number_of_sectors;
        BYTE physical_drive_number;
        BYTE reserved;
        BYTE signature_byte;
        DWORD volume_serial_number;
        BYTE volume_label[11];
        BYTE fat_type_char_str[8];
        BYTE filler[500];
};

struct BOOT_RECORD_STRUCT BOOT_RECORD;

void load_boot_record()
{
struct _diskinfo_t diskinfo;
diskinfo.track = 0;
diskinfo.sector = 1;
diskinfo.head = 0;
diskinfo.nsectors = 1;
diskinfo.buffer = &BOOT_RECORD;
_bios_disk(_DISK_READ,&diskinfo);
}


void read_sector(int linear_sector,void *buf)
{
struct _diskinfo_t diskinfo;
diskinfo.sector = 1 + (linear_sector % BOOT_RECORD.sectors_per_track);
diskinfo.track = linear_sector / (BOOT_RECORD.sectors_per_track *
BOOT_RECORD.number_of_heads);
diskinfo.head = (linear_sector / BOOT_RECORD.sectors_per_track) %
BOOT_RECORD.number_of_heads;
diskinfo.nsectors = 1;
diskinfo.buffer = buf;
_bios_disk(_DISK_READ,&diskinfo);
}


void main (void)
{
BYTE *tmp_str = (BYTE *)malloc(15);
load_boot_record();
strncpy(tmp_str,BOOT_RECORD.jump,sizeof(BOOT_RECORD.jump));tmp_str[sizeof(BOOT_RECORD.jump)]
= 0;
printf("\nJump chars                       = %s",tmp_str);
strncpy(tmp_str,BOOT_RECORD.oem_name,sizeof(BOOT_RECORD.oem_name));tmp_str[sizeof(BOOT_RECORD.oem_name)]
= 0;
printf("\nOEM                              = %s",tmp_str);
printf("\nBytes per sector                 =
%d",BOOT_RECORD.bytes_per_sector);
printf("\nSectors per cluster              =
%d",BOOT_RECORD.sectors_per_cluster);
printf("\nReserved sectors                 =
%d",BOOT_RECORD.number_of_reserved_sectors);
printf("\nNumber of FAT's on disk          =
%d",BOOT_RECORD.number_of_fats);
printf("\nNumber of root directory entries =
%d",BOOT_RECORD.number_of_root_dir_entries);
if (BOOT_RECORD.number_of_total_sectors != 0)
        printf("\nTotal number of sectors on disk  =
%d",BOOT_RECORD.number_of_total_sectors);
printf("\nMedia descriptor byte            =
%d",BOOT_RECORD.media_descriptor_byte);
printf("\nFat size(sectors)                =
%d",BOOT_RECORD.sectors_per_fat);
printf("\nSectors per track                =
%d",BOOT_RECORD.sectors_per_track);
printf("\nNumber of heads                  =
%d",BOOT_RECORD.number_of_heads);
printf("\nNumber of hidden sectors         =
%d",BOOT_RECORD.number_of_hidden_sectors1);
if (BOOT_RECORD.number_of_total_sectors == 0)
        printf("\nTotal number of sectors on disk  =
%ld",BOOT_RECORD.number_of_sectors);
printf("\nPhysical drive number            =
%d",BOOT_RECORD.physical_drive_number);
printf("\nSignature byte (29h)             =
%Xh",BOOT_RECORD.signature_byte);
printf("\nVolume serial number             =
%lX",BOOT_RECORD.volume_serial_number);
strncpy(tmp_str,BOOT_RECORD.volume_label,11);tmp_str[11] = 0;
printf("\nVolume label                     = %s",tmp_str);
strncpy(tmp_str,BOOT_RECORD.fat_type_char_str,8);tmp_str[8] = 0;
printf("\nFAT str type                     = %s",tmp_str);



//read_sector(1,&BOOT_RECORD);
}

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