58 lines
1 KiB
ArmAsm
58 lines
1 KiB
ArmAsm
.define .csb
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.sect .text
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.sect .rom
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.sect .data
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.sect .bss
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.sect .text
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! Table lookup jump
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! Expects on stack: address of case descriptor
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! case index
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! This is not a subroutine, but just a piece of code that computes
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! the jump address and jumps to it.
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! Traps if resulting address is zero.
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.csb: pop h !hl = pointer to descriptor
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pop d !de = case index
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push b !save localbase
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mov c,m !bc = default pointer
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inx h
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mov b,m
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inx h
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push b !save default on stack
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mov c,m !bc = number of entries
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inx h
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mov b,m
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inx h
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!loop: try to find the case index in the descriptor
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1: mov a,b
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ora c
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jz 4f !done, index not found
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mov a,m !do we have the right index?
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inx h
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cmp e
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jnz 2f !no
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mov a,m
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inx h
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cmp d
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jnz 3f !no
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mov a,m
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inx h
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mov h,m
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mov l,a
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pop psw !remove default pointer
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jmp 5f
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2: inx h !skip high byte of index
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3: inx h !skip jump address
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inx h
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dcx b
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jmp 1b
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4: pop h !take default exit
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5: pop b !restore localbase
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mov a,l !jump address is zero?
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ora h
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cz ecase !trap
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pchl !jump!!!!
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