52 lines
1.3 KiB
Awk
52 lines
1.3 KiB
Awk
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# $Id: asm.awk,v 1.4 2007/09/27 11:33:45 bacon Exp $
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#
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# Taken from the book "The AWK Programming Language"
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#
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BEGIN {
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srcfile = ARGV[1];
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ARGV[1] = "";
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tempfile = "asm.temp";
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n = split("const get put ld st add sub jpos jz j halt", x);
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for (i = 1; i <= n; i++) op[x[i]] = i - 1;
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# PASS 1
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FS = "[ \t]+";
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while (getline <srcfile > 0) {
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sub (/#.*/, "");
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symtab[$1] = nextmem;
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if ($2 != "") {
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print $2 "\t" $3 >tempfile;
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nextmem++;
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}
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}
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close (tempfile);
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# PASS 2
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nextmem = 0;
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while (getline <tempfile > 0) {
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if ($2 !~ /^[0-9]*$/) $2 = symtab[$2];
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mem[nextmem++] = 1000 * op[$1] + $2;
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}
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# INTERPRETER
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for (pc = 0; pc >= 0; ) {
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addr = mem[pc] % 1000;
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code = int(mem[pc++] / 1000);
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if (code == op["get"]) { if (getline acc <= 0) acc = 0; }
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else if (code == op["put"]) { print acc; }
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else if (code == op["st"]) { mem[addr] = acc; }
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else if (code == op["ld"]) { acc = mem[addr]; }
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else if (code == op["add"]) { acc += mem[addr]; }
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else if (code == op["sub"]) { acc -= mem[addr]; }
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else if (code == op["jpos"]) { if (acc > 0) pc = addr; }
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else if (code == op["jz"]) { if (acc == 0) pc = addr; }
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else if (code == op["j"]) { pc = addr; }
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else if (code == op["halt"]) { pc = -1; }
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else { pc = -1; }
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}
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}
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