53 lines
944 B
ArmAsm
53 lines
944 B
ArmAsm
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.define .csa
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! Case 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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.csa: pop h !hl = address of case descriptor
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pop d !de = index
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push b !save localbase
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mov c,m
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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 pointer on stack
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mov a,e
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sub m
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inx h
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mov c,a
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mov a,d
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sbb m
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inx h
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mov b,a !bc = index - lower bound
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jc 1f !get default pointer
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mov a,m
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inx h
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sub c
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mov a,m
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inx h
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sbb b
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jc 1f !upper-lower should be >= index-lower
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dad b
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dad b !hl now points to the wanted pointer
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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 !hl = pointer for index
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ora h
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jz 1f !get default pointer if pointer = 0
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pop b !remove default pointer
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pop b !localbase
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pchl !jump!!!!
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1: pop h !get default pointer
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mov a,l
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ora h
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cz ecase !trap
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pop b !restore localbase
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pchl !jump!!!!
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