/*
 * Disassembler.
 * Based on old macro code I wrote
 * years ago.
 */

#include <stdio.h>

#define  NONE	0		/* halt */
#define	 RTS	1		/* rts reg */
#define	 DOUBLE	2		/* mov src,dst */
#define	 SWBYTE	3		/* sop[b] dst */
#define	 SINGLE	4		/* sop dst */
#define	 JSR	5		/* jsr reg,dst */
#define  MUL	6		/* mul src,reg */
#define	 BR	7		/* br addr */
#define	 SOB	8		/* sob reg,addr */
#define	 SPL	9		/* spl n */
#define  MARK	10		/* mark n */
#define	 TRAP	11		/* trap n */
#define	 CODE	12		/* se[cvnz] */

struct	tab
{
	int	t_mask;
	int	t_op;
	char	*t_str;
	int	t_kind;
};

static	struct	tab	tab[] = {
	0000000,	0000000,	"halt",		NONE,
	0000000,	0000001,	"wait",		NONE,
	0000000,	0000002,	"rti",		NONE,
	0000000,	0000003,	"bpt",		NONE,
	0000000,	0000004,	"iot",		NONE,
	0000000,	0000005,	"reset",	NONE,
	0000000,	0000006,	"rtt",		NONE,
	0000007,	0000000,	"illop",	NONE,
	0000077,	0000100,	"jmp",		SINGLE,
	0000007,	0000200,	"rts",		RTS,
	0000017,	0000210,	"illop",	NONE,
	0000007,	0000230,	"spl",		SPL,
	0000000,	0000240,	"nop",		NONE,
	0000000,	0000241,	"clc",		NONE,
	0000017,	0000240,	"clear",	CODE,
	0000000,	0000261,	"sec",		NONE,
	0000017,	0000260,	"set",		CODE,
	0000077,	0000300,	"swab",		SINGLE,
	0000377,	0000400,	"br",		BR,
	0000377,	0001000,	"bne",		BR,
	0000377,	0001400,	"beq",		BR,
	0000377,	0002000,	"bge",		BR,
	0000377,	0002400,	"blt",		BR,
	0000377,	0003000,	"bgt",		BR,
	0000377,	0003400,	"ble",		BR,
	0000777,	0004000,	"jsr",		JSR,
	0100077,	0005000,	"clr",		SWBYTE,
	0100077,	0005100,	"com",		SWBYTE,
	0100077,	0005200,	"inc",		SWBYTE,
	0100077,	0005300,	"dec",		SWBYTE,
	0100077,	0005400,	"neg",		SWBYTE,
	0100077,	0005500,	"adc",		SWBYTE,
	0100077,	0005600,	"sbc",		SWBYTE,
	0100077,	0005700,	"tst",		SWBYTE,
	0100077,	0006000,	"ror",		SWBYTE,
	0100077,	0006100,	"rol",		SWBYTE,
	0100077,	0006200,	"asr",		SWBYTE,
	0100077,	0006300,	"asl",		SWBYTE,
	0000077,	0006400,	"mark",		MARK,
	0000077,	0006500,	"mfpi",		SINGLE,
	0000077,	0006600,	"mtpi",		SINGLE,
	0000077,	0006700,	"sxt",		SINGLE,
	0000777,	0007000,	"illop",	NONE,
	0107777,	0010000,	"mov",		DOUBLE,
	0107777,	0020000,	"cmp",		DOUBLE,
	0107777,	0030000,	"bit",		DOUBLE,
	0107777,	0040000,	"bic",		DOUBLE,
	0107777,	0050000,	"bis",		DOUBLE,
	0007777,	0060000,	"add",		DOUBLE,
	0007777,	0160000,	"su",		DOUBLE,
	0000777,	0070000,	"mul",		MUL,
	0000777,	0071000,	"div",		MUL,
	0000777,	0072000,	"ash",		MUL,
	0000777,	0073000,	"ashc",		MUL,
	0000777,	0074000,	"xor",		JSR,
	0000007,	0075000,	"fadd",		RTS,
	0000007,	0075010,	"fsub",		RTS,
	0000007,	0075020,	"fmul",		RTS,
	0000007,	0075030,	"fdiv",		RTS,
	0000777,	0077000,	"sob",		SOB,
	0003777,	0074000,	"illop",	NONE,
	0000377,	0100000,	"bpl",		BR,
	0000377,	0100400,	"bmi",		BR,
	0000377,	0101000,	"bhi",		BR,
	0000377,	0101400,	"blos",		BR,
	0000377,	0102000,	"bvc",		BR,
	0000377,	0102400,	"bvs",		BR,
	0000377,	0103000,	"bhis",		BR,
	0000377,	0103400,	"blo",		BR,
	0000377,	0104000,	"emt",		TRAP,
	0000377,	0104400,	"trap",		TRAP,
	0000077,	0106400,	"illop",	NONE,
	0000077,	0106500,	"mfpd",		SINGLE,
	0000077,	0106600,	"mtpd",		SINGLE,
	0001777,	0106000,	"illop",	NONE,
	0007777,	0170000,	"45fpp",	NONE,
	0177777,	0000000,	"illop",	NONE
};

#define  NTAB	(sizeof(tab) / sizeof(tab[0]))

int *
pinst(pc)
register *pc;
{
	register struct tab *tp;
	register op;
	int i, m;
	int *paddr();

	printf("%06o\t", pc);
	op = *pc++;
	tp = &tab[0];
	while (tp < &tab[NTAB]) {
		if ((op&~tp->t_mask) == tp->t_op)
			break;
		++tp;
	}
	if (tp == &tab[NTAB]) {
		printf("[No match]\n");
		return (pc);
	}
	printf("%s", tp->t_str);
	switch (tp->t_kind) {

	case SPL:
		printf("\t%d", op&07);
		break;

	case RTS:
		putchar('\t');
		preg(op);
		break;

	case SWBYTE:
		if (op < 0)
			putchar('b');
	case SINGLE:
		putchar('\t');
		pc = paddr(pc, op);
		break;

	case DOUBLE:
		if (op < 0)
			putchar('b'); /* sub and bytes */
		putchar('\t');
		pc = paddr(pc, op>>6);
		putchar(',');
		pc = paddr(pc, op);
		break;

	case JSR:
		putchar('\t');
		preg(op>>6);
		putchar(',');
		pc = paddr(pc, op);
		break;

	case MUL:
		putchar('\t');
		pc = paddr(pc, op);
		putchar(',');
		preg(op>>6);
		break;

	case BR:
		putchar('\t');
		op &= 0377;
		if ((op & 0200) != 0)
			op |= ~0377;
		printf("%o", (int)pc + (op<<1));
		break;

	case SOB:
		putchar('\t');
		preg(op>>6);
		putchar(',');
		printf("%o", (int)pc + ((op|~077)<<1));
		break;

	case MARK:
	case TRAP:
		putchar('\t');
		if (tp->t_kind == MARK)
			op &= 077;
		else
			op &= 0377;
		printf("%o", op);
		break;

	case CODE:
		putchar('\t');
		m = 01;
		for (i=0; i<4; ++i) {
			if ((op & m) != 0)
				putchar("czvn"[i]);
			m <<= 1;
		}
	}
	putchar('\n');
	return (pc);
}

int *
paddr(pc, m)
register *pc;
{
	register r, x;

	r = m&07;
	switch (m&070) {

	case 0:
		preg(r);
		break;

	case 010:
		putchar('(');
		preg(r);
		putchar(')');
		break;

	case 030:
		putchar('*');
	case 020:
		if (r == 7) {
			putchar('$');
			printf("%o", *pc++);
			break;
		}
		putchar('(');
		preg(r);
		putchar(')');
		putchar('+');
		break;

	case 050:
		putchar('*');
	case 040:
		putchar('-');
		putchar('(');
		preg(r);
		putchar(')');
		break;

	case 070:
		putchar('*');
	case 060:
		x = *pc++;
		if (r == 7) {
			printf("%o", (int)pc + x);
			break;
		}
		printf("%o(", x);
		preg(r);
		putchar(')');
	}
	return (pc);
}

preg(r)
register r;
{
	r &= 07;
	if (r == 7)
		printf("pc");
	else if (r == 6)
		printf("sp");
	else
		printf("r%d", r);
}