Routines
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42366: Find Buffer Address
Used by the routine at DrawSprites.
Finds the address in the buffer at 63488 of the top left of a sprite in the rectangle that is being drawn by DrawSprites.
Input
H Vertical position
L Horizontal position
Output
HL Address in the buffer
FindBufferAddress 42366 LD A,(23596) Fetch the left of the rectangle.
42369 LD C,A Store it in C.
42370 LD A,L Fetch the horizontal position.
42371 SUB C Subtract the left of the rectangle.
42372 SRL A Divide it by eight to get the number of bytes across.
42374 SRL A
42376 SRL A
42378 LD L,A Store it in L.
42379 LD A,(23597) Fetch the bottom of the rectangle.
42382 SUB H Subtract the vertical position to get the number of rows up.
42383 JR Z,FindBufferAddress_Page Jump to FindBufferAddress_Page if the sprite is at the bottom.
42385 LD C,A Store the number of rows in C.
42386 LD A,(52789) Fetch the number of bytes in a row.
42389 LD H,A Store it in H.
FindBufferAddress_Row 42390 LD A,L Fetch the offset.
42391 ADD A,H Add the number of bytes in a row.
42392 LD L,A Store the offset.
42393 DEC C Count the rows.
42394 JR NZ,FindBufferAddress_Row Loop back to FindBufferAddress_Row for each row.
FindBufferAddress_Page 42396 LD H,248 Use the buffer.
42398 RET Return.
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