#include "platform.h"
#include "diskstru.h"
extern St_DOS_BootRecord g_stBootRecord;

static BYTE s_bHead;
static BYTE s_bTrack;
static BYTE s_bSector;
static void Lba2CHS(UINT Lba)
{
    _asm mov ax, Lba
	_asm xor dx, dx
	_asm mov bx, g_stBootRecord.BPB.SectorsPerTrack
	_asm div bx
	_asm inc dx
	_asm mov s_bSector, dl
	_asm xor dx, dx
	_asm mov bx, g_stBootRecord.BPB.Sides
	_asm div bx
	_asm mov s_bHead, dl
	_asm mov s_bTrack, al
}

static int pascal ReadSector( void far * lpBuff )
{
	_asm{
        mov ax, word ptr [lpBuff+2]
	mov es, ax
		mov bx, word ptr [lpBuff]
		mov ah, 02h
		mov al, 1
		mov ch, s_bTrack
		mov cl, s_bSector
		mov dh, s_bHead
		mov dl, 0
		int 13h
		jc l_error
		jmp short l_ret
	}
l_error:
		return 0;
l_ret:
		return 1;
}


static const char s_szStarting[] = "Starting Myself Operating system...";
static const char s_szFail[] = "Fail to load OsLoader, system halt.";

static void TextOut(BYTE x, BYTE y, const char * szText, int n)
{
    _asm {
		mov cx, n
		mov dh, y
		mov dl, x
		mov bx, 15
		mov ax, szText
		push bp
		mov bp, ax
		mov ax, 1300h
		int 10h
		pop bp
    }
}

void start(void)
{
	UINT uLba, i;
	BYTE far * lpSect = (BYTE far *)0x80000000;

	//	Clear screen
	_asm{
		mov ax, 3
		int 10h
    }

    //	Display the logo information
	TextOut( 0, 0, s_szStarting, sizeof(s_szStarting)-1 );

	//	Calculate the sector number of the first data sector
	uLba = g_stBootRecord.BPB.ReservedSectors +
		g_stBootRecord.BPB.FAT_Copies * g_stBootRecord.BPB.SectorsPerFAT +
		(g_stBootRecord.BPB.RootDirEntries >> 4);

	uLba = 6;
	//	Load the first 128 data sectors into memory at address 8000h:0000h
	for( i = 0; i < 10; i ++ )
	{
		Lba2CHS( uLba );
		if( !ReadSector( lpSect ) )
		{
			goto l_Fail;
		}

		uLba ++;
		lpSect += 512;
	}

	//  Execute the fetched OS loader at address 8000h:0100h
	_asm {
		mov ax, 0x8000
		mov ds, ax
		mov es, ax
		mov ss, ax
		mov sp, 0xFFF0
		push ax	//push cs
		mov ax, 0x100
		push ax	//push ip(0)
		retf	//	execute OS
	}

l_Fail:
	TextOut( 0, 1, s_szFail, sizeof(s_szFail)-1 );
	for(;;);
}