vram convenience functions that are probably wrong

utilities.asm

@@ -667,5 +667,68 @@ db #00, #01, #01, #02, #01, #02, #02, #03, #01, #02, #02, #03, #02, #03, #03, #0
 ;RTL
 ;--------------------------------------------------------------------------------
 
+;--------------------------------------------------------------------------------
+; WriteVRAMStripe
+; in:	A(w) - VRAM Destination
+; in:	X(w) - Length in Tiles
+; in:	Y(w) - Word to Write
+;--------------------------------------------------------------------------------
+WriteVRAMStripe:
+	PHX
+		LDX $1000 ; get pointer
+		AND.w #$7F : STA $1002, X : INX #2 ; set destination
+	PLA : ASL : AND.w #7FFF : ORA.w #7000 : STA $1002, X : INX #2 ; set length and enable RLE
+	TYA : STA $1002, X : INX #2 ; set tile
+	SEP #$20 ; set 8-bit accumulator
+		LDA.b #$FF : STA $1002, X
+		STX $1000
+		LDA.b #01 : STA $14
+	REP #$20 ; set 16-bit accumulator
+RTL
+;--------------------------------------------------------------------------------
 
+;--------------------------------------------------------------------------------
+; WriteVRAMBlock
+; in:	A(w) - VRAM Destination
+; in:	X(w) - Length in Tiles
+; in:	Y(w) - Address of Data to Copy
+;--------------------------------------------------------------------------------
+WriteVRAMStripe:
+	PHX
+		LDX $1000 ; get pointer
+		AND.w #$7F : STA $1002, X : INX #2 ; set destination
+	PLA : ASL : AND.w #3FFF : STA $1002, X : INX #2 ; set length
+	
+	PHX
+		TYX ; set X to source
+		PHA
+			TXA : !ADD #$1002 : TAY ; set Y to dest
+		PLA
+		;A is already the value we need for mvn
+		MVN $7F7E ; currently we transfer from our buffers in 7F to the vram buffer in 7E
+		
+		!ADD 1, s ; add the length in A to the stack pointer on the top of the stack
+	PLX : TAX ; pull and promptly ignore, copying the value we just got over it
+
+	SEP #$20 ; set 8-bit accumulator
+		LDA.b #$FF : STA $1002, X
+		STX $1000
+		LDA.b #01 : STA $14
+	REP #$20 ; set 16-bit accumulator
+RTL
+;--------------------------------------------------------------------------------
+;Byte 1   byte 2  Byte 3   byte 4
+;Evvvvvvv vvvvvvv DRllllll llllllll
+;
+;E if set indicates that this is not a header, but instead is the terminator byte. Only the topmost bit matters in that case.
+;The v's form a vram address.
+;if D is set, the dma will increment the vram address by a row per word, instead of incrementing by a column (1).
+;R if set enables a run length encoding feature
+;the l's are the number of bytes to upload minus 1 (don't forget this -1, it is important)
+;
+;This is then followed by the bytes to upload, in normal format.
+
+;RLE feature:
+;This feature makes it easy to draw the same tile repeatedly. If this bit is set, the length bits should be set to 2 times the number of copies of the tile to upload. (Without subtracting 1!)
+;It is followed by a single tile (word).  Combining this this with the D bit makes it easy to draw large horizontal or vertical runs of a tile without using much space. Geat for erasing or drawing horizontal or verical box edges.
 ;================================================================================