#define??STRING_CHAR
#define??STRING_TO_NUM
#include?“dpt.h“
#include?“partition.h“
#include?“para.h“
#include?“error.h“
#include?“sector-rw.h“
extern?char?*argp[];
extern?char?*devname;
extern?pts??*pt_save;
/*
?*change?boot?partition?to?the?specified?partition.
?*if?it?is?successful?return?0;
?*if?there?is?no?mathched?partition?return?-ENOMATCHPAR.
?*if?failedreturn?a?negative?number?for?error?.
?*/
int?do_change_boot（char?*devnameunsigned?char?partition_num）
{
??int?iretfound=0;
??char?*diskbuf;
??unsigned?long?secrel_sec;
??pt?pt1[PT_HOLES];
??ret=get_pt（devname）;
??if（ret<0）?return?ret;
??/*檢查分區號碼是否有效，啟動分區只能是1-4.?*/
??if（partition_num>?PT_HOLES?||?partition_num?	printf（“?the?partition?number?is?invalid.\n“）?;
	printf（“?the?valid?number?is?from?1?to?4?.\n“）;
	return?0;
??}
??/*如果要改變的分區已經是啟動分區，返回。*/
??if（（pt_save+partition_num）->partition.active==0x80）?
	return?0;
??diskbuf=malloc（BLKSIZE）;
??if（diskbuf==NULL）?return?-ENOMEM;
??/*保存在分區表里的rel_sec此為判斷的依據。?*/
??rel_sec=（pt_save+partition_num）->partition.rel_sec;
??sec=MBR_SECTOR;/*?所在扇區只能是MBR即第0扇區。*/
??ret=read_sec_to_buff（devnamesec1diskbuf）;
??if（ret?<=?0）?{
	free（diskbuf）;
	return?ret;
??}
??for（i=0;i	memcpy?（&pt1[i]													\
			（pt?*）&diskbuf[PARTITION_TABLE_START?+?i*sizeof（pt）]		\
			sizeof（pt））;
	/*兩者相等，我們才認為是同一分區且此分區扇區數必須大于零而且分區id不為空，否則不修改。*/
	if（pt1[i].rel_sec==rel_sec?&&?pt1[i].nr_sec?>?0?&&?pt1[i].id?!=?0x00）{
	??found=1;???????????????
	??diskbuf[PARTITION_TABLE_START?+?i*sizeof（pt）+offset（ptactive）]=0x80;?
	}
	/*其他的啟動分區改為非啟動分區，因為只能有一個啟動分區。*/
	else?if（pt1[i].active==0x80）?{
	??diskbuf[PARTITION_TABLE_START?+?i*sizeof（pt）+offset（ptactive）]=0x00;?	
	}
??}
??if（found）?{/*找到了，才真正進行修改，否則返回。*/
	ret=write_buff_to_sec（diskbufBLKSIZEdevnamesec）;
	free（diskbuf）;
	return?ret;?
??}
??free（diskbuf）;
??return?-ENOMATCHPAR;/*沒有找到匹配的分區，返回。?*/
}		
/*
?*parse?the?parameters?or?get?the?partition?numberand?
?*then?call?the?function?to?do?the?real?work.
?*/
int?change_boot（?）
{
??int?t1ret;
??char?*pnum=argp[0];
??unsigned?char?par_num;
??t1=parse_para（pnum）;
??if（t1==DEC）?{
	par_num=strtoul（pnum&pnum10）;
??}
??else?{
	printf（“?Please?input?the?partition?number?you?want?to?boot?from?:\n“）;
	printf（“?The?valid?number?is?from?1?to?4.\n“）;
	par_num=get_dec_num（?）;
??}
??ret=do_change_boot（devnamepar_num）;
??if（ret<0）?{
	printf（“Failed?to?change?partition?%d?to?boot?partition?!?\n“par_num）;
	return?ret;
??}
??printf（“?The?partition?%d?has?changed?to?boot?partition?successfully.\n“par_num）;
??return?ret;
}