replace strtoul() with simplified version, saves 743 bytes

3 files changed, 65 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 5233651..143fc9b 100644
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ XEX=taipan.xex
 
 # All the C and asm sources for taimain.xex:
 TAIMAIN_HDRS=sounds.h
-TAIMAIN_C_SRC=taipan.c
+TAIMAIN_C_SRC=taipan.c strtonum.c
 TAIMAIN_ASM_SRC=rand.s draw_lorcha.s timed_getch.s portstat.s console.s ultostr.s soundasm.s explosion.s
 
 # Comment these lines out to build without big number support.
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
diff --git a/taipan.c b/taipan.c
index 9380d1d..3c58c47 100644
--- a/taipan.c
+++ b/taipan.c
@@ -1,3 +1,5 @@
+// TODO: replace conio with coffio
+
 #include <conio.h>
 #include <time.h>
 #include <stdlib.h>
@@ -250,6 +252,9 @@ void cprint_taipan_prompt(void);
 void cprint_elder_brother_wu(void);
 void cprint_li_yuen(void);
 
+/* local replacement for strtoul, see strtonum.c */
+unsigned long __fastcall__ strtonum(const char* nptr);
+
 unsigned char firmpos;
 
 /* use page 6 for these buffers, for .xex build. Otherwise they'e BSS. */
@@ -1362,7 +1367,8 @@ unsigned long get_num(void) {
 	}
 	// cursor(0);
 	num_buf[count] = '\0';
-	return strtoul(num_buf, (char **)NULL, 10);
+	// return strtoul(num_buf, (char **)NULL, 10);
+	return strtonum(num_buf);
 }
 
 /* TODO: rewrite in asm */