59 lines
1.1 KiB
ArmAsm
59 lines
1.1 KiB
ArmAsm
// Find the BASIC line with number basic_line_number
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basic_find_line:
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// Get pointer to start of BASIC text
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lda basic_start_of_text_ptr+0
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sta basic_current_line_ptr+0
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lda basic_start_of_text_ptr+1
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sta basic_current_line_ptr+1
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basic_find_line_loop:
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// Then search for line number
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// Line number
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ldy #3
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ldx #<basic_current_line_ptr
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jsr peek_under_roms
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cmp basic_line_number+1
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beq !+
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bcs line_num_too_high
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bne not_this_line
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!:
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dey
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jsr peek_under_roms
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cmp basic_line_number+0
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beq !+
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bcs line_num_too_high
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bne not_this_line
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!:
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clc
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rts
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not_this_line:
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// Not this line, so advance to next line
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ldx #<basic_current_line_ptr
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jsr peek_pointer_null_check
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bcs more_lines_exist
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// no more lines exist, return failure
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line_num_too_high:
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sec
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rts
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more_lines_exist:
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// XXX - Add program mangled check here to be triggered
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// if the link goes backwards.
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// Follow link to next line
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ldy #0
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ldx #<basic_current_line_ptr
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jsr peek_under_roms
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sta $0100
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iny
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jsr peek_under_roms
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sta basic_current_line_ptr+1
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lda $0100
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sta basic_current_line_ptr+0
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jmp basic_find_line_loop
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