int wasm_dis(WasmOp *op, const unsigned char *buf, int buf_len) {
	op->len = 1;
	op->op = buf[0];
	if (op->op > 0xbf) {
		return 1;
	}
	// add support for extension opcodes (SIMD + atomics)
	WasmOpDef *opdef = &opcodes[op->op];
	switch (op->op) {
	case WASM_OP_TRAP:
	case WASM_OP_NOP:
	case WASM_OP_ELSE:
	case WASM_OP_RETURN:
	case WASM_OP_DROP:
	case WASM_OP_SELECT:
	case WASM_OP_I32EQZ: 
	case WASM_OP_I32EQ: 
	case WASM_OP_I32NE: 
	case WASM_OP_I32LTS: 
	case WASM_OP_I32LTU: 
	case WASM_OP_I32GTS: 
	case WASM_OP_I32GTU: 
	case WASM_OP_I32LES: 
	case WASM_OP_I32LEU: 
	case WASM_OP_I32GES: 
	case WASM_OP_I32GEU: 
	case WASM_OP_I64EQZ: 
	case WASM_OP_I64EQ: 
	case WASM_OP_I64NE: 
	case WASM_OP_I64LTS: 
	case WASM_OP_I64LTU: 
	case WASM_OP_I64GTS: 
	case WASM_OP_I64GTU: 
	case WASM_OP_I64LES: 
	case WASM_OP_I64LEU: 
	case WASM_OP_I64GES: 
	case WASM_OP_I64GEU: 
	case WASM_OP_F32EQ: 
	case WASM_OP_F32NE: 
	case WASM_OP_F32LT: 
	case WASM_OP_F32GT: 
	case WASM_OP_F32LE: 
	case WASM_OP_F32GE: 
	case WASM_OP_F64EQ: 
	case WASM_OP_F64NE: 
	case WASM_OP_F64LT: 
	case WASM_OP_F64GT: 
	case WASM_OP_F64LE: 
	case WASM_OP_F64GE: 
	case WASM_OP_I32CLZ: 
	case WASM_OP_I32CTZ: 
	case WASM_OP_I32POPCNT: 
	case WASM_OP_I32ADD: 
	case WASM_OP_I32SUB: 
	case WASM_OP_I32MUL: 
	case WASM_OP_I32DIVS: 
	case WASM_OP_I32DIVU: 
	case WASM_OP_I32REMS: 
	case WASM_OP_I32REMU: 
	case WASM_OP_I32AND: 
	case WASM_OP_I32OR: 
	case WASM_OP_I32XOR: 
	case WASM_OP_I32SHL: 
	case WASM_OP_I32SHRS: 
	case WASM_OP_I32SHRU: 
	case WASM_OP_I32ROTL: 
	case WASM_OP_I32ROTR: 
	case WASM_OP_I64CLZ: 
	case WASM_OP_I64CTZ: 
	case WASM_OP_I64POPCNT: 
	case WASM_OP_I64ADD: 
	case WASM_OP_I64SUB: 
	case WASM_OP_I64MUL: 
	case WASM_OP_I64DIVS: 
	case WASM_OP_I64DIVU: 
	case WASM_OP_I64REMS: 
	case WASM_OP_I64REMU: 
	case WASM_OP_I64AND: 
	case WASM_OP_I64OR: 
	case WASM_OP_I64XOR: 
	case WASM_OP_I64SHL: 
	case WASM_OP_I64SHRS: 
	case WASM_OP_I64SHRU: 
	case WASM_OP_I64ROTL: 
	case WASM_OP_I64ROTR: 
	case WASM_OP_F32ABS: 
	case WASM_OP_F32NEG: 
	case WASM_OP_F32CEIL: 
	case WASM_OP_F32FLOOR: 
	case WASM_OP_F32TRUNC: 
	case WASM_OP_F32NEAREST: 
	case WASM_OP_F32SQRT: 
	case WASM_OP_F32ADD: 
	case WASM_OP_F32SUB: 
	case WASM_OP_F32MUL: 
	case WASM_OP_F32DIV: 
	case WASM_OP_F32MIN: 
	case WASM_OP_F32MAX: 
	case WASM_OP_F32COPYSIGN: 
	case WASM_OP_F64ABS: 
	case WASM_OP_F64NEG: 
	case WASM_OP_F64CEIL: 
	case WASM_OP_F64FLOOR: 
	case WASM_OP_F64TRUNC: 
	case WASM_OP_F64NEAREST: 
	case WASM_OP_F64SQRT: 
	case WASM_OP_F64ADD: 
	case WASM_OP_F64SUB: 
	case WASM_OP_F64MUL: 
	case WASM_OP_F64DIV: 
	case WASM_OP_F64MIN: 
	case WASM_OP_F64MAX: 
	case WASM_OP_F64COPYSIGN: 
	case WASM_OP_I32WRAPI64: 
	case WASM_OP_I32TRUNCSF32: 
	case WASM_OP_I32TRUNCUF32: 
	case WASM_OP_I32TRUNCSF64: 
	case WASM_OP_I32TRUNCUF64: 
	case WASM_OP_I64EXTENDSI32: 
	case WASM_OP_I64EXTENDUI32: 
	case WASM_OP_I64TRUNCSF32: 
	case WASM_OP_I64TRUNCUF32: 
	case WASM_OP_I64TRUNCSF64: 
	case WASM_OP_I64TRUNCUF64: 
	case WASM_OP_F32CONVERTSI32: 
	case WASM_OP_F32CONVERTUI32: 
	case WASM_OP_F32CONVERTSI64: 
	case WASM_OP_F32CONVERTUI64: 
	case WASM_OP_F32DEMOTEF64: 
	case WASM_OP_F64CONVERTSI32: 
	case WASM_OP_F64CONVERTUI32: 
	case WASM_OP_F64CONVERTSI64: 
	case WASM_OP_F64CONVERTUI64: 
	case WASM_OP_F64PROMOTEF32: 
	case WASM_OP_I32REINTERPRETF32: 
	case WASM_OP_I64REINTERPRETF64: 
	case WASM_OP_F32REINTERPRETI32: 
	case WASM_OP_F64REINTERPRETI64:
	case WASM_OP_END:
		{
			snprintf (op->txt, R_ASM_BUFSIZE, "%s", opdef->txt);
		}
		break;
	case WASM_OP_BLOCK:
	case WASM_OP_LOOP:
	case WASM_OP_IF:
		{
			st32 val = 0;
			size_t n = read_i32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			switch (0x80 - val) {
			case R_BIN_WASM_VALUETYPE_EMPTY:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s", opdef->txt);
				break;
			case R_BIN_WASM_VALUETYPE_i32:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s (result i32)", opdef->txt);
				break;
			case R_BIN_WASM_VALUETYPE_i64:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s (result i64)", opdef->txt);
				break;
			case R_BIN_WASM_VALUETYPE_f32:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s (result f32)", opdef->txt);
				break;
			case R_BIN_WASM_VALUETYPE_f64:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s (result f64)", opdef->txt);
				break;
			default:
				snprintf (op->txt, R_ASM_BUFSIZE, "%s (result ?)", opdef->txt);
				break;
			}
			op->len += n;
		}
		break;
	case WASM_OP_BR:
	case WASM_OP_BRIF:
	case WASM_OP_CALL:
		{
			ut32 val = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d", opdef->txt, val);
			op->len += n;
		}
		break;
	case WASM_OP_BRTABLE:
		{
			ut32 count = 0, *table = NULL, def = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &count);
			if (!(n > 0 && n < buf_len)) {
				goto err;
			}
			if (!(table = calloc (count, sizeof (ut32)))) {
				goto err;
			}
			int i = 0;
			op->len += n;
			for (i = 0; i < count; i++) {
				n = read_u32_leb128 (buf + op->len, buf + buf_len, &table[i]);
				if (!(op->len + n <= buf_len)) {
					goto beach;
				}
				op->len += n;
			}
			n = read_u32_leb128 (buf + op->len, buf + buf_len, &def);
			if (!(n > 0 && n + op->len < buf_len)) {
				goto beach;
			}
			op->len += n;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d ", opdef->txt, count);
			for (i = 0; i < count && strlen (op->txt) + 10 < R_ASM_BUFSIZE; i++) {
				int optxtlen = strlen (op->txt);
				snprintf (op->txt + optxtlen, R_ASM_BUFSIZE - optxtlen, "%d ", table[i]);
			}	
			snprintf (op->txt + strlen (op->txt), R_ASM_BUFSIZE, "%d", def);
			free (table);
			break;
			beach:
			free (table);
			goto err;
		}
		break;
	case WASM_OP_CALLINDIRECT:
		{
			ut32 val = 0, reserved = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			op->len += n;
			n = read_u32_leb128 (buf + op->len, buf + buf_len, &reserved);
			if (!(n == 1 && op->len + n <= buf_len)) goto err;
			reserved &= 0x1;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d %d", opdef->txt, val, reserved);
			op->len += n;
		}
		break;
	case WASM_OP_GETLOCAL:
	case WASM_OP_SETLOCAL:
	case WASM_OP_TEELOCAL:
	case WASM_OP_GETGLOBAL:
	case WASM_OP_SETGLOBAL:
		{
			ut32 val = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d", opdef->txt, val);
			op->len += n;
		}
		break;
	case WASM_OP_I32LOAD:
	case WASM_OP_I64LOAD: 
	case WASM_OP_F32LOAD: 
	case WASM_OP_F64LOAD: 
	case WASM_OP_I32LOAD8S: 
	case WASM_OP_I32LOAD8U: 
	case WASM_OP_I32LOAD16S: 
	case WASM_OP_I32LOAD16U: 
	case WASM_OP_I64LOAD8S: 
	case WASM_OP_I64LOAD8U: 
	case WASM_OP_I64LOAD16S: 
	case WASM_OP_I64LOAD16U: 
	case WASM_OP_I64LOAD32S: 
	case WASM_OP_I64LOAD32U: 
	case WASM_OP_I32STORE: 
	case WASM_OP_I64STORE: 
	case WASM_OP_F32STORE: 
	case WASM_OP_F64STORE: 
	case WASM_OP_I32STORE8: 
	case WASM_OP_I32STORE16: 
	case WASM_OP_I64STORE8: 
	case WASM_OP_I64STORE16: 
	case WASM_OP_I64STORE32: 
		{
			ut32 flag = 0, offset = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &flag);
			if (!(n > 0 && n < buf_len)) goto err;
			op->len += n;
			n = read_u32_leb128 (buf + op->len, buf + buf_len, &offset);
			if (!(n > 0 && op->len + n <= buf_len)) goto err;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d %d", opdef->txt, flag, offset);
			op->len += n;
		}
		break;
	case WASM_OP_CURRENTMEMORY:
	case WASM_OP_GROWMEMORY:
		{
			ut32 reserved = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &reserved);
			if (!(n == 1 && n < buf_len)) goto err;
			reserved &= 0x1;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %d", opdef->txt, reserved); 
			op->len += n;
		}
		break;

	case WASM_OP_I32CONST:
		{
			st32 val = 0;
			size_t n = read_i32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %" PFMT32d, opdef->txt, val);
			op->len += n;
		}
		break;
	case WASM_OP_I64CONST:
		{
			st64 val = 0;
			size_t n = read_i64_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %" PFMT64d, opdef->txt, val);
			op->len += n;
		}
		break;
	case WASM_OP_F32CONST:
		{
			ut32 val = 0;
			size_t n = read_u32_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			long double d =  (long double)val;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %" LDBLFMT, opdef->txt, d);
			op->len += n;
		}
		break;
	case WASM_OP_F64CONST:
		{
			ut64 val = 0;
			size_t n = read_u64_leb128 (buf + 1, buf + buf_len, &val);
			if (!(n > 0 && n < buf_len)) goto err;
			long double d =  (long double)val;
			snprintf (op->txt, R_ASM_BUFSIZE, "%s %" LDBLFMT, opdef->txt, d);
			op->len += n;
		}
		break;
	default:
		goto err;
	}

	return op->len;

err:
	op->len = 1;
	snprintf (op->txt, R_ASM_BUFSIZE, "invalid");
	return op->len;
}