83 lines
1.8 KiB
ArmAsm
83 lines
1.8 KiB
ArmAsm
// Delete the current BASIC line, which is assumed to have already
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// been found with basic_find_line.
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// Really only consists of copying memory down.
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// The only complication is that we have to do the copy with ROMs
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// banked out. Oh, yes, and we have to update all the links in
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// the following basic lines.
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basic_delete_line:
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// jsr printf
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// .text "DELETING LINE AT $"
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// .byte $f1,<basic_current_line_ptr,>basic_current_line_ptr
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// .byte $f0,<basic_current_line_ptr,>basic_current_line_ptr
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// .byte $0d,0
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// Get address of next line
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ldy #0
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#if CONFIG_MEMORY_MODEL_60K
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ldx #<basic_current_line_ptr
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jsr peek_under_roms
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#else // CONFIG_MEMORY_MODEL_38K
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lda (basic_current_line_ptr),y
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#endif
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sta tokenise_work3
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iny
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#if CONFIG_MEMORY_MODEL_60K
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jsr peek_under_roms
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#else // CONFIG_MEMORY_MODEL_38K
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lda (basic_current_line_ptr),y
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#endif
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sta tokenise_work4
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// Work out length of this line by looking at the pointer
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lda tokenise_work3
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sec
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sbc basic_current_line_ptr+0
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sta tokenise_work3
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lda tokenise_work4
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sbc basic_current_line_ptr+1
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sta tokenise_work4
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// jsr printf
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// .text "LINE LENGTH IS $"
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// .byte $f0,<tokenise_work4,>tokenise_work4
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// .byte $f0,<tokenise_work3,>tokenise_work3
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// .byte $0d,0
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lda tokenise_work4
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sbc #0
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cmp #$00
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beq !+
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// Line length is <0 or >255 bytes.
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// Either way, things are bad, so abort.
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jmp do_MEMORY_CORRUPT_error
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!:
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// Length can now be safely assumed to be in the low
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// byte only, i.e., stored in tokenise_work3
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lda tokenise_work3
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pha
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tax
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// Shuffle everything down
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jsr basic_shift_mem_down_and_relink
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// Now decrease top of BASIC mem
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pla
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sta tokenise_work3
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lda basic_end_of_text_ptr+0
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sec
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sbc tokenise_work3
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sta basic_end_of_text_ptr+0
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lda basic_end_of_text_ptr+1
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sbc #0
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sta basic_end_of_text_ptr+1
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clc
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rts
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