Implement limited integer literal parsing

1 files changed, 38 insertions, 13 deletions

diff --git a/asm.c b/asm.c
index 022ec5f..5200ffc 100644
--- a/asm.c
+++ b/asm.c
@@ -2,6 +2,7 @@
 #include "util.h"
 #include "tpu.h"
 
+#include <ctype.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <string.h>
@@ -72,13 +73,13 @@ static const char *tok_reprs[] = {
 static bool
 is_lit(const char *str)
 {
-	unsigned long v;
-	char *end;
-
-	v = strtoul(str, &end, 10);
-	if (!end || *end) return false;
+	const char *c;
 
-	return v < 256;
+	c = str;
+	if (*c == '-') c++;
+	else if (*c == '+') c++;
+	for (; *c && isdigit(*c); c++);
+	return !*c;
 }
 
 static bool
@@ -94,10 +95,35 @@ is_int(const char *str)
 	return true;
 }
 
-static uint8_t
+static int
 str_to_lit(const char *str)
 {
-	return (uint8_t) atoi(str);
+	int m, v, b, i, o;
+
+	if (*str == '-') {
+		m = -1;
+		o = 1;
+	} else if (*str == '+') {
+		m = 1;
+		o = 1;
+	} else {
+		m = 1;
+		o = 0;
+	}
+
+	for (b = 1, i = o; str[i]; i++)
+		b *= 10;
+
+	if (i >= 4 + o) {
+		v = 1000;
+	} else {
+		for (v = 0, i = o; str[i]; i++) {
+			b /= 10;
+			v += b * (str[i] - '0');
+		}
+	}
+
+	return MIN(MAX(m * v, -999), 999);
 }
 
 enum tpu_inst_type
@@ -133,10 +159,10 @@ tok_to_op(struct asm_tokenizer *tokenizer, enum asm_tok tok)
 static size_t
 strlcat_op_name(char *buf, struct tpu_inst_op *op, size_t n)
 {
-	char hhbuf[4];
+	char hhbuf[5];
 
 	if (op->type == OP_LIT) {
-		snprintf(hhbuf, 4, "%i", op->val.lit);
+		snprintf(hhbuf, 5, "%i", op->val.lit);
 		return strdcat(buf, hhbuf, n);
 	} else if (op->type == OP_LABEL) {
 		return strdcat(buf, op->val.label, n);
@@ -263,15 +289,14 @@ tok_next_in(struct asm_tokenizer *tokenizer, ...)
 static void
 tpu_validate(struct tpu *tpu)
 {
-	size_t dst;
-	int i;
+	int dst, i;
 
 	for (i = 0; i < tpu->inst_cnt; i++) {
 		if (tpu->insts[i].opcnt >= 1
 				&& tpu->insts[i].ops[0].type == OP_LABEL) {
 			dst = label_map_get(&tpu->label_map,
 				tpu->insts[i].ops[0].val.label);
-			if (dst == TPU_MAX_INST_CNT)
+			if (dst < 0)
 				die("load: tpu X%i Y%i, label '%s' not defined",
 					tpu->x, tpu->y,
 					tpu->insts[i].ops[0].val.label);