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Code: Select all

ParseDirectoryEntry:
	mov	ecx, [es:bx+0x0A]
	mov	eax, [es:bx+0x02]

	push	ax
	xor	eax, eax
	pop	ax
	xor	ah, ah

	cmp	eax, 0
	je	ParseDirectoryEntry

	cmp	cl, 0
	je	.zero

	ret

	.zero:
		mov	cl, 1
		ret

Code: Select all

;Parse A Directory Entry
;
;This routine checks some stuff in a thingy-whatsit that may or may not be related to some
;sort of (page directory, phone directory?) entry; and may return some sort of values and other
;stuff (but might not return too).

;Input
; es:bx    The address of a thingy-whatsit
;
;Output
; eax      Something that's guaranteed to be non-zero
; ecx      "stuff" in the highest 24-bits, with maybe some sort of flag in the lowest byte?
;_______________________________________________________________________________________________

ParseDirectoryEntry:
   mov ecx,[es:bx+0x0A]              ;ecx = something
   movzx eax,byte [es:bx+0x02]       ;eax = something else
   xor cl,cl                         ;ecx = assumed value to return, with "stuff" in highest 24-bits
   test al,al                        ;Is something else zero?
   je ParseDirectoryEntry            ; yes, keep looping until an IRQ changes the thingy-whatsit

   cmp [es:bx+0x0A],1                ;Is something less than one (or, is something zero)?
   adc cl,0                          ;Set CL=1 if something was zero, else leave CL=0 (and don't upset the "stuff"!)
   ret

Code: Select all

;************************************************;
; Reads a series of sectors
; Cx=>Number of blocks to read
; EAX=>Starting sector		- Anything above B6 causes an err???
; ES:BX=>Buffer to read to
; DL=>Drive #
; Carry set on err
;************************************************;

ReadSectors:
	.MAIN:
		mov	[DriveNum], dl
		mov	di, 5

		push	ax
		mov	ah, 45h
		mov	al, 0x00	; Lock drive to prevent tray opening

		int	0x13

		cmp	ah, 0
		pop	ax
		jne	.End

	.SECTORLOOP:
		push	eax
		push	ds
		push	es
		push	bx
		push	cx
		push	di

		push	dword 0	;Block number
		push	dword eax
		push	word es	; Read to es:bx
		push	word bx
		push	word cx
		push	word 10h	; Size: 10h

		mov	ah, 0x42

		push	ss
		pop	ds

		mov	si, sp

		mov	dl, [DriveNum]
		int	0x13

		push	ax
		mov	al, ah
		mov	ah, 0x0E
		int	0x10
		pop	ax

		add	esp, 0x10

	.CONTINUE:
		pop	di
		pop	cx
		pop	bx
		pop	es
		pop	ds

		cmp	ah, 0
		pop	eax
		je	.SUCCESS

	.LOOP:
		dec	di
		jnz	.SECTORLOOP

	.SUCCESS:
		clc

		push	ax
		mov	ax, 0x4501	; Unlock drive

		mov	dl, [DriveNum]
		int	0x13

		cmp	ah, 0
		pop	ax
		jne	.SUCCESS

	.End:
		ret