AKMW Phantasy Star RLE

decompress.asm

; 0x293
decompressPhantasyStarRLEToVRAM:
	ld b, $04
-:
	push bc
	push de
	call decompressBitplaneToVRAM
	pop de
	inc de
	pop bc
	djnz -
	ret

; Alex Kidd in Miracle World uses "Phantasy Star RLE" for tile data compression
; This function decompresses data from HL to VRAM DE.
;
; 0x2A0
decompressBitplaneToVRAM:
	ld a, (hl)
	inc hl
    ; Return if we hit $0000
	or a
	ret z
	; b = Number of block bytes
	ld b, a
	; c = Run type control bit
	ld c, a
	res 7, b
-:
	ld a, e
	out (Port_VDPAddress), a
	ld a, d
	out (Port_VDPAddress), a
	ld a, (hl)
	out (Port_VDPData), a

	bit 7, c
	jp z, +
	inc hl
+:
	inc de
	inc de
	inc de
	inc de
	djnz -
	jp nz, decompressBitplaneToVRAM
	inc hl
	jp decompressBitplaneToVRAM

decompress.wiz

bank prg @ 0x0000 : [constdata; 0x1000];

in prg @ 0x293 {
    func decompressPhantasyStarRLEToVRAM(dest: *u8 in de, source: *u8 in hl) {
        b = 4;
        do {
            push(bc);
            push(dest);
            decompressBitplaneToVram(dest, source);
            dest = pop() as *u8;
            dest++;
            bc = pop();
        } while --b != 0;
    }

    /**
     * Alex Kidd in Miracle World uses "Phantasy Star RLE" for tile data
     * compression. This function decompresses data from HL to VRAM DE.
     */
    #[fallthrough]
    func decompressBitplaneToVram(dest: *u8 in de, source: *u8 in hl) {
        var current_byte: u8 in a;
        var block_bytes_count: u8 in b;
        var block_control_byte: u8 in c;

        ^do {
            ^do {
                current_byte = *source;
                source++;

                return if current_byte == 0x00;

                block_bytes_count = current_byte;
                block_control_byte = current_byte;
                // Reset run type bit
                block_bytes_count$7 = false;

                do {
                    io_write(0xBF, a = <:dest);
                    io_write(0xBF, a = >:dest);
                    io_write(0xBE, a = *source);

                    ^if block_control_byte$7 {
                        source++;
                    }

                    inline for in 1..4 {
                        dest++;
                    }
                } while --block_bytes_count != 0;
            } while !zero;

            source++;
        } while true;
    }
}