Routines
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57620: Add Map Objects
Used by the routine at LoadMapObjects.
Puts the objects of one column of the map in free slots of the map objects. An object is skipped if the current player has destroyed it (bit 7 of its byte in the table at MapTable is set, or bit 6 for player two), if it is not on one of the two rows that are on the screen or if there is already a slot for it. It is put in the first free slot of the first three slots, or in the fourth if none of them is free. Its column, row, position and kind are set from the tables. The slot holds the index of the object in offsets 24 and 25 so that the object can be marked as destroyed later.
Input
B Number of objects in the column
C Column
HL Address of the first object in MapTable
IX Address of the first object in TerrainData
AddMapObjects 57620 AND A Return if A is zero.
57621 RET Z
AddMapObjects_Next2 57622 PUSH BC Stash BC on the stack.
57623 BIT 7,(HL) Jump to AddMapObjects_Skip if bit 7 of the byte at the address in HL is set.
57625 JP NZ,AddMapObjects_Skip
57628 LD A,(IX+1) Read offset 1 of IX.
57631 AND %00011111 Keep the bits of A that are set in 31.
57633 LD E,A E=A.
57634 LD A,(52824) The map row.
57637 CP E Jump to AddMapObjects_Search if A is E.
57638 JR Z,AddMapObjects_Search
57640 INC A Advance A.
57641 CP E Jump to AddMapObjects_Skip if A is not E.
57642 JP NZ,AddMapObjects_Skip
AddMapObjects_Search 57645 LD IY,43019 The map object slots.
57649 LD B,4 B=4.
AddMapObjects_Search2 57651 LD A,(IY+0) Read offset 0 of IY.
57654 INC A Advance A.
57655 JR Z,AddMapObjects_Next Jump to AddMapObjects_Next if the zero flag is set.
57657 LD A,(IY+1) Read offset 1 of IY.
57660 CP C Jump to AddMapObjects_Next if A is not C.
57661 JR NZ,AddMapObjects_Next
57663 LD A,(IY+4) Read offset 4 of IY.
57666 CP E Jump to AddMapObjects_Skip if A is E.
57667 JP Z,AddMapObjects_Skip
AddMapObjects_Next 57670 LD A,E A=E.
57671 LD DE,26 DE=26.
57674 ADD IY,DE IY gains DE.
57676 LD E,A E=A.
57677 DJNZ AddMapObjects_Search2 Decrease B and jump to AddMapObjects_Search2 until none remain.
AddMapObjects_Free 57679 LD IY,43019 The map object slots.
57683 LD B,3 B=3.
AddMapObjects_SearchSecond 57685 LD A,(IY+0) Read offset 0 of IY.
57688 INC A Advance A.
57689 JR Z,AddMapObjects_Fill Jump to AddMapObjects_Fill if the zero flag is set.
57691 LD A,E A=E.
57692 LD DE,26 DE=26.
57695 ADD IY,DE IY gains DE.
57697 LD E,A E=A.
57698 DJNZ AddMapObjects_SearchSecond Decrease B and jump to AddMapObjects_SearchSecond until none remain.
AddMapObjects_Fill 57700 PUSH IX Stash IX on the stack.
57702 PUSH IY Stash IY on the stack.
57704 POP IX Bring IX back off the stack.
57706 POP IY Bring IY back off the stack.
57708 CALL FreeObjectSlot Call FreeObjectSlot.
57711 PUSH IX Stash IX on the stack.
57713 PUSH IY Stash IY on the stack.
57715 POP IX Bring IX back off the stack.
57717 POP IY Bring IY back off the stack.
57719 LD (IY+4),E Write E to offset 4 of IY.
57722 LD (IY+0),13 Store 13 at offset 0 of IY.
57726 LD A,(HL) Read HL.
57727 AND %00111111 Keep the bits of A that are set in 63.
57729 LD (IY+19),A Write A to offset 19 of IY.
57732 PUSH HL Stash HL on the stack.
57733 LD HL,57861 The object attributes.
57736 CALL AddAToHL Call AddAToHL.
57739 LD A,(HL) Read HL.
57740 LD (IY+13),A Write A to offset 13 of IY.
57743 LD HL,57597 The object kinds.
57746 LD A,(IY+19) Read offset 19 of IY.
57749 CALL AddAToHL Call AddAToHL.
57752 LD A,(HL) Read HL.
57753 AND %11100000 Keep the bits of A that are set in 224.
57755 SRL A Shift A right.
57757 SRL A Shift A right.
57759 SRL A Shift A right.
57761 SRL A Shift A right.
57763 LD (IY+24),A Write A to offset 24 of IY.
57766 BIT 4,(HL) Jump to AddMapObjects_Position if bit 4 of the byte at the address in HL is clear.
57768 JR Z,AddMapObjects_Position
57770 LD A,(HL) Read HL.
57771 AND %00001111 Keep the bits of A that are set in 15.
57773 LD HL,57614 The special object states.
57776 CALL AddAToHL Call AddAToHL.
57779 LD A,(HL) Read HL.
57780 LD (IY+19),A Write A to offset 19 of IY.
57783 INC HL Advance HL.
57784 LD A,(HL) Read HL.
57785 LD (IY+20),A Write A to offset 20 of IY.
57788 LD (IY+21),128 Store 128 at offset 21 of IY.
57792 LD (IY+0),27 Store 27 at offset 0 of IY.
AddMapObjects_Position 57796 POP HL Bring HL back off the stack.
57797 LD DE,(52794) Fetch the word at ScratchValues into DE.
57801 LD A,D A=D.
57802 OR (IY+24) Set the bits of A that are set in the byte at offset 24 of IY.
57805 LD (IY+24),A Write A to offset 24 of IY.
57808 LD (IY+25),E Write E to offset 25 of IY.
57811 LD (IY+1),C Write C to offset 1 of IY.
57814 LD A,(IX+0) Read offset 0 of IX.
57817 AND %11111100 Keep the bits of A that are set in 252.
57819 DEC A Step A back.
57820 LD (IY+5),A Write A to offset 5 of IY.
57823 LD A,(IX+0) Read offset 0 of IX.
57826 AND %00000011 Keep the bits of A that are set in 3.
57828 ADD A,A Double A.
57829 ADD A,A Double A.
57830 ADD A,A Double A.
57831 LD E,A E=A.
57832 LD A,(IX+1) Read offset 1 of IX.
57835 AND %11100000 Keep the bits of A that are set in 224.
57837 OR E Set the bits of A that are set in E.
57838 LD (IY+2),A Write A to offset 2 of IY.
AddMapObjects_Skip 57841 INC IX Advance IX.
57843 INC IX Advance IX.
57845 INC HL Advance HL.
57846 LD DE,(52794) Fetch the word at ScratchValues into DE.
57850 INC DE Advance DE.
57851 LD (52794),DE The next object in the column.
57855 POP BC Bring BC back off the stack.
57856 DEC B Step B back.
57857 JP NZ,AddMapObjects_Next2 Jump to AddMapObjects_Next2 if the zero flag is clear.
57860 RET Return.
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