;;; mmblocks.a86
;;;
;;; count number of flash data blocks that will
;;; become free by next memory management
;;;
;;; unsigned int mmblocks();
;;;
;;; Author: J. Steingraeber
;;; Date: 2004-10-16
;;;
;;; Released to the Public Domain

mmblocks_TEXT CSEG

	.186

mmblocks_::
	push bp
	mov bp,sp
	sub sp,0x80		; read FAT in pieces of 0x80 bytes
	
	push cx
	push dx
	push si
	push di

	cld
	xor di,di		; result = 0
	mov bx,0x0600		; first data sector is #6
	push ss
	pop es
mmbl_secloop:
	xor dx,dx
mmbl_offsloop:
	push di
	lea di,[bp-0x80]
	mov cx,0x80
	mov ah,0xF0
	int 0x2E		; FLASHBIO
	pop di
	or ax,ax
	jnz mmbl_ready		; error while reading data

	lea si,[bp-0x80]
	mov cx,0x40
mmbl_cntloop:
	db 0x36			; ss: (just in case)
	lodsw
	test ax,0x4000
	jnz mmbl_cnt
	inc di
mmbl_cnt:
	loop mmbl_cntloop

	;; next offset
	add dx,0x80
	cmp dx,0x07A0		; FAT ends here, 0x7A0..0x7FF will be unmarked
	jb mmbl_offsloop

	;; next sector
	inc bh
	cmp bh,0x40
	jb mmbl_secloop
	
mmbl_ready:	
	mov ax,di
	pop di
	pop si
	pop dx
	pop cx
	mov sp,bp
	pop bp
	retf
	
	end