1 files changed, 57 insertions, 0 deletions
diff --git a/strtonum.c b/strtonum.c
new file mode 100644
index 0000000..65bd718
--- /dev/null
+++ b/strtonum.c
@@ -0,0 +1,57 @@
+#include <limits.h>
+
+/* Convert a string to a long unsigned int, tiny version.
+	Based on strtoul.c from cc65 libsrc, but stripped down:
+	- only supports base 10.
+	- no leading +, -, 0, 0x support.
+	- does not skip leading spaces.
+	- returns ULONG_MAX on overflow, but does not set errno.
+	- overflows at 4294967290 rather than 4294967296.
+	- no endptr argument, so no way to tell how many character
+	  were converted.
+
+	taipan's input routines stop the player from typing invalid
+	characters, so nobody will miss the error checking. using
+	this instead of strtoul saves 743 bytes.
+ */
+
+/* ULONG_MAX / 10 */
+#define MAX_VAL 429496729
+
+unsigned long __fastcall__ strtonum(const char* nptr) {
+	unsigned long ret = 0;
+	unsigned char digit;
+
+	/* Convert the number */
+	while(*nptr >= '0' && *nptr <= '9') {
+		/* Convert the digit into a numeric value */
+		digit = *nptr - '0';
+
+		/* Don't accept anything that makes the final value invalid */
+		if(ret > MAX_VAL)
+			return ULONG_MAX;
+
+		/* Calculate the next value if digit is not invalid */
+		ret = (ret * 10) + digit;
+
+		/* Next character from input */
+		++nptr;
+	}
+
+	/* Return the result */
+	return ret;
+}
+
+#ifdef STRTONUM_TEST
+#include <stdio.h>
+int main(void) {
+	printf("%lu\n", strtonum("123"));
+	printf("%lu\n", strtonum("98765"));
+	printf("%lu\n", strtonum("429496730"));
+	printf("%lu\n", strtonum("4294967295"));
+	printf("%lu\n", strtonum("5555555555"));
+	printf("%lu\n", strtonum(" "));
+hang: goto hang;
+	return 0;
+}
+#endif