Routines
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25636: Copy Level Data to Level Buffer
Used by the routine at InitialiseLevel.
Input
HL Source data pointer
DE Destination buffer pointer
CopyLevelDataToBuffer 25636 LD C,5 Set a counter in C for 5 rows to copy.
CopyLevelDataToBuffer_CopyRow 25638 LD B,32 Set a counter in B for 32 bytes per row.
CopyLevelDataToBuffer_CopyByte 25640 LD A,(HL) Fetch a terrain byte from the source data.
25641 INC HL Move to the next source data byte.
25642 LD (DE),A Write the byte to the destination buffer.
25643 INC E Move to the next destination buffer position.
25644 DJNZ CopyLevelDataToBuffer_CopyByte Decrease the bytes-per-row counter by one and loop back to CopyLevelDataToBuffer_CopyByte until the whole row has been copied.
Handle updating the destination pointer positioning after each row.
25646 DEC E Step back one position.
25647 LD A,E Align to a 32 byte boundary.
25648 AND %11100000 Keep only the upper 3 bits of the E co-ordinate.
25650 LD E,A Reset to the start of the current 32 byte block.
25651 INC D Move down one row.
25652 DEC C Decrease the row counter by one.
25653 JR NZ,CopyLevelDataToBuffer_CopyRow Jump back to CopyLevelDataToBuffer_CopyRow until all the rows have been copied.
Adjust the destination pointer after copying a complete 5x32 block.
25655 ADD A,32 Move to the next block horizontally.
25657 LD E,A Load the new horizontal position into E.
25658 RET Z Return if E wrapped around to 0 (we reached the end of the buffer).
Move the destination pointer back up 5 rows to the original vertical position.
25659 LD A,D D-=5.
25660 SUB 5
25662 LD D,A
25663 RET Return.
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