60 lines
934 B
ArmAsm
60 lines
934 B
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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! this is not a subroutine, but just a
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! piece of code that computes the jump-
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! address and jumps to it.
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! traps if resulting address is zero
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.csb:
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pop hl ! pointer to descriptor
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pop de ! case index
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ld c,(hl) ! bc := default offset
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inc hl
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ld b,(hl)
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inc hl
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push bc ! save default on stack
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ld c,(hl) ! bc := #entries
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inc hl
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ld b,(hl)
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inc hl
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1:
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! loop, try to find the case index
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! in the descriptor
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ld a,b
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or c
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jr z,noteq ! done, index not found
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ld a,(hl) ! is de=(hl) ?
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inc hl
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cp e
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jr nz,2f ! no
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ld a,(hl)
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inc hl
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cp d
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jr nz,3f ! no
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ld a,(hl) ! yes, get jump address
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inc hl
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ld h,(hl)
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ld l,a
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pop af ! remove default
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jr 4f
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2:
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inc hl ! skip high byte of index
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3:
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inc hl ! skip jump address
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inc hl
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dec bc
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jr 1b
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noteq:
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pop hl ! take default exit
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4:
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ld a,l ! jump address is zero?
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or h
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jr z,.trp.z ! yes, trap
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jp (hl)
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