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60 lines
1.2 KiB
NASM
60 lines
1.2 KiB
NASM
// Experiments with malloc() - a word array
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// Commodore 64 PRG executable file
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.file [name="malloc-1.prg", type="prg", segments="Program"]
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.segmentdef Program [segments="Basic, Code, Data"]
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.segmentdef Basic [start=$0801]
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.segmentdef Code [start=$80d]
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.segmentdef Data [startAfter="Code"]
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.segment Basic
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:BasicUpstart(__start)
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.const SIZEOF_WORD = 2
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// Top of the heap used by malloc()
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.label HEAP_TOP = $a000
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.label WORDS = malloc.return
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.segment Code
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__start: {
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// malloc(0x200)
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jsr malloc
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jsr main
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rts
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}
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// Allocates a block of size chars of memory, returning a pointer to the beginning of the block.
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// The content of the newly allocated block of memory is not initialized, remaining with indeterminate values.
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malloc: {
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.const size = $200
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.label mem = HEAP_TOP-size
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.label return = mem
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// }
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rts
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}
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main: {
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.label w = 2
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lda #<WORDS
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sta.z w
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lda #>WORDS
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sta.z w+1
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ldx #0
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__b1:
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// *w++ = i
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txa
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ldy #0
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sta (w),y
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tya
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iny
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sta (w),y
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// *w++ = i;
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lda #SIZEOF_WORD
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clc
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adc.z w
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sta.z w
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bcc !+
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inc.z w+1
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!:
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// for( byte i: 0..255)
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inx
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cpx #0
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bne __b1
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// }
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rts
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}
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