check for cash int overflow, WIP

2 files changed, 98 insertions, 62 deletions

diff --git a/bignum.h b/bignum.h
index 185d118..67ae902 100644
--- a/bignum.h
+++ b/bignum.h
@@ -24,6 +24,7 @@
 #define bignum(x) char x[6]
 #define bignump char *
 
+/****** constants ******/
 /* zero */
 #define BIG_0 { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }
 
@@ -41,17 +42,36 @@
 /* max value for a ulong */
 #define BIG_MAX_ULONG { 0x44, 0x42, 0x94, 0x96, 0x72, 0x95 }
 
+/****** functions ******/
+
+/* copy dest to src. could be a wrapper for memcpy() */
 extern void __fastcall__ big_copy(bignump dest, bignump src);
 
+/* these 2 would be easy to implement, but aren't really needed */
 // void int_to_big(int i, bignum *b);
 // void uint_to_big(unsigned int i, bignum *b);
 
+/* convert an unsigned long to a bignum */
 extern void __fastcall__ ulong_to_big(const unsigned long l, bignump b);
 
-/* returns 0 for success, nonzero for fail (overflow or negative) */
+/* convert a bignum to an unsigned long
+	returns 0 for success, nonzero for fail (overflow or negative) */
 extern char __fastcall__ big_to_ulong(bignump b, unsigned long *l);
 
-// extern unsigned long __fastcall__ cformat_big(char *magnitude, const bignum *b);
+/* compare two bignums. like Perl's spaceship operator, <=>
+	returns  | if
+	---------+----------------
+	    0    | a == b
+	 positive| a > b
+	 negative| a < b
+
+BEWARE: unlike perl's <=>, the return value is *not* guaranteed to
+	be 0, 1, or -1. This is more like C's strcmp() or memcmp().
+	Do not depend on any particular positive or negative return
+	value from this:
+	if(big_cmp(a, b) == -1) // WRONG!
+	if(big_cmp(a, b) < 0) // Right.  */
+extern signed char __fastcall__ big_cmp(bignump a, bignump b);
 
 /* basic math functions. conceptually they return a boolean for
 	success, but only division has error checking.
@@ -74,19 +94,7 @@ extern char __cdecl__ big_div(bignump dest, bignump dividend, bignump divisor);
  */
 extern char __fastcall__ bank_maxed_out(bignump b);
 
-/* comparison. Perl spaceship operator, <=>
-	returns  | if
-	---------+----------------
-	    0    | a == b
-	 positive| a > b
-	 negative| a < b
-
-BEWARE: unlike perl's <=>, the return value is *not* guaranteed to
-	be 0, 1, or -1. This is more like C's strcmp() or memcmp().
- */
 // signed char big_cmp(const bignum *a, const bignum *b)
 
-extern signed char __fastcall__ big_cmp(bignump a, bignump b);
-
 extern unsigned long cformat_big(char *magnitude, bignump b);
 extern void cprintfancy_big(bignump b);
diff --git a/taipan.c b/taipan.c
index 96f6d84..fd471e8 100644
--- a/taipan.c
+++ b/taipan.c
@@ -5,6 +5,7 @@
 #include <ctype.h>
 #include <string.h> /* only for memcpy() */
 #include <peekpoke.h>
+#include <stdint.h>
 
 #include "sounds.h"
 
@@ -208,7 +209,6 @@ char wu_assassin = 0;
 /* title screen now a separate xex segment (see Makefile for details) */
 // void splash_intro(void);
 
-// int get_one(void);
 #define get_one() agetc();
 long get_num(void);
 void name_firm(void);
@@ -227,7 +227,6 @@ void visit_bank(void);
 void transfer(void);
 void quit(void);
 void overload(void);
-// void fancy_numbers(unsigned long num, char *fancy);
 int sea_battle(int id, int num_ships);
 void fight_stats(int ships, int orders);
 void mchenry(void);
@@ -238,14 +237,12 @@ void you_only_have(unsigned char in_bank);
 void cprintulong(unsigned long ul);
 void cprintfancy_ctr(unsigned long num, unsigned char center);
 #define cprintfancy(num) cprintfancy_ctr(num, 0)
+void too_much_cash(void);
+char would_overflow(unsigned long a, unsigned long b);
 
 unsigned char firmpos;
 
-/*
-char    firm[23],
-        fancy_num[24];
-		  */
-
+/* use page 6 for these buffers */
 char *firm = (char *) 0x680;
 char *fancy_buf = (char *) 0x600;
 
@@ -310,6 +307,7 @@ long damage = 0, capacity = 60, newdamage;
 bignum(big1M) = BIG_1M;
 bignum(big100M) = BIG_100M;
 bignum(big1B) = BIG_1B;
+bignum(big0) = BIG_0;
 
 /*
 Requires a bit of explanation. b's value will always be zero or
@@ -353,10 +351,8 @@ void cprintfancy_big(bignump b) {
 		cprintulong(l);
 	} else {
 		if(l > 100) {
-			// cprintf("%lu ", l / 10L);
 			cprintulong(l / 10L);
 		} else {
-			// cprintf("%lu.%lu ", l / 10L, l % 10L);
 			cprintulong(l / 10L);
 			cputc('.');
 			cprintulong(l % 10L);
@@ -423,7 +419,6 @@ void new_ship(void) {
    int  choice = 0,
         time;
 
-   // float amount;
    unsigned long amount;
 
    time = ((year - 1860) * 12) + month;
@@ -433,8 +428,6 @@ void new_ship(void) {
       return;
    }
 
-   // fancy_numbers(amount, fancy_num);
-
 	compradores_report();
    cputs("Do you wish to trade in your ");
    if(damage > 0) {
@@ -446,7 +439,6 @@ void new_ship(void) {
    }
    cputs("\r\nship for one with 50 more capacity by\r\n");
    cputs("paying an additional ");
-   // cputs(fancy_num);
 	cprintfancy(amount);
    cputs(", Taipan? ");
 
@@ -692,6 +684,9 @@ int sea_battle(int id, int num_ships) {
 	ik = 1;
 
    booty = (time / 4 * 1000 * num_ships) + randi()%1000 + 250;
+	if(would_overflow(cash, booty)) {
+		booty = 0L;
+	}
 
    for(i = 0; i <= 9; i++) {
       ships_on_screen[i] = 0;
@@ -1577,24 +1572,46 @@ void retire(void)
 
 void final_stats(void)
 {
-#ifdef BIGNUM
-#else
-	/* TODO: write cprintlong() to print signed value */
-	long finalcash;
-
    int years = year - 1860,
        time = ((year - 1860) * 12) + month,
        choice = 0;
 
+#ifdef BIGNUM
+	long score;
+	bignum(finalcash);
+	bignum(big_100) = BIG_100;
+	bignum(bigscore);
+	bignum(bigtmp);
+
+	ulong_to_big(cash, finalcash);
+	ulong_to_big(debt, bigtmp);
+	big_add(finalcash, finalcash, bank);
+	big_sub(finalcash, finalcash, bigtmp);
+
+	big_div(bigscore, finalcash, big_100);
+	ulong_to_big((unsigned long)time, bigtmp);
+	big_div(bigscore, bigscore, bigtmp);
+
+	if(big_cmp(bigscore, big1M) > 0)
+		score = 1000000L;
+	else
+		big_to_ulong(bigscore, (unsigned long*)&score);
+#else
+	/* TODO: write cprintlong() to print signed value */
+	long finalcash = cash + bank - debt;
+	long score = finalcash / 100 / time;
+#endif
+
 	port_stat_dirty = 1;
 
    clrscr();
    cputs("Your final status:\r\n\r\n");
-   finalcash = cash + bank - debt;
-   // fancy_numbers(finalcash, fancy_num);
 	cputs("Net cash:  ");
-	// cputs(fancy_num);
+#ifdef BIGNUM
+	cprintfancy_big(finalcash);
+#else
 	cprintfancy(finalcash);
+#endif
 	cputs("\r\nShip size: ");
 	cprintulong(capacity);
 	cputs(" units with ");
@@ -1615,16 +1632,19 @@ void final_stats(void)
       cputc('s');
    }
    cputs("\r\n\r\n");
-   finalcash = finalcash / 100 / time;
 	revers(1);
 	cputs("Your score is ");
-	cprintulong(finalcash);
+#ifdef BIGNUM
+	cprintfancy_big(bigscore);
+#else
+	cprintulong(score);
 	cputs(".\r\n");
+#endif
 	revers(0);
-   if ((finalcash < 100) && (finalcash >= 0))
+   if ((score < 100) && (score >= 0))
    {
       cputs("Have you considered a land based job?\r\n\r\n\r\n");
-   } else if (finalcash < 0) {
+   } else if (score < 0) {
       cputs("The crew has requested that you stay on\r\n");
       cputs("shore for their safety!!\r\n\r\n");
    } else {
@@ -1637,7 +1657,7 @@ void final_stats(void)
 	cputs("\r\n");
    cputc('|');
 
-   if (finalcash > 49999L)
+   if (score > 49999L)
    {
 		revers(1);
    }
@@ -1646,7 +1666,7 @@ void final_stats(void)
    cputs("         50,000 and over |\r\n");
    cputc('|');
 
-   if ((finalcash < 50000L) && (finalcash > 7999L))
+   if ((score < 50000L) && (score > 7999L))
    {
 		revers(1);
    }
@@ -1655,7 +1675,7 @@ void final_stats(void)
    cputs("   8,000 to 49,999|\r\n");
    cputc('|');
 
-   if ((finalcash < 8000L) && (finalcash > 999L))
+   if ((score < 8000L) && (score > 999L))
    {
 		revers(1);
    }
@@ -1664,7 +1684,7 @@ void final_stats(void)
    cputs("          1,000 to  7,999|\r\n");
    cputc('|');
 
-   if ((finalcash < 1000) && (finalcash > 499))
+   if ((score < 1000) && (score > 499))
    {
 		revers(1);
    }
@@ -1673,7 +1693,7 @@ void final_stats(void)
    cputs("        500 to    999|\r\n");
    cputc('|');
 
-   if (finalcash < 500)
+   if (score < 500)
    {
 		revers(1);
    }
@@ -1689,19 +1709,9 @@ void final_stats(void)
 	cputs("Play again? ");
 	choice = yngetc(0);
 
-	/*
-   while ((choice != 'Y') && (choice != 'y') &&
-          (choice != 'N') && (choice != 'n'))
-   {
-      gotoxy(0, 22);
-      cputs("Play again? ");
-      choice = get_one();
-   }
-	*/
-
    if(choice == 'y') {
 #ifdef BIGNUM
-		bank = BIG_0;
+		big_copy(bank, big0);
 #else
       bank         = 0;
 #endif
@@ -1726,7 +1736,6 @@ void final_stats(void)
 
       return;
    }
-#endif
 	/* restore ROM character set. TODO: save old PEEK(756)
 		in newtitle.s, restore that here instead of using
 		hardcoded value. */
@@ -2336,11 +2345,11 @@ void elder_brother_wu(void)
             cputs("borrow? ");
 
             wu = get_num();
-            if (wu == -1)
+            if(wu == -1)
             {
                wu = (cash * 2);
             }
-            if (wu <= (cash * 2))
+            if((wu <= (cash * 2)) && !would_overflow(cash, wu))
             {
                cash += wu;
                debt += wu;
@@ -2708,6 +2717,12 @@ void sell(void) {
       {
          amount = hold_[choice];
       }
+
+		if(would_overflow(cash, amount)) {
+			too_much_cash();
+			continue;
+		}
+
       if (hold_[choice] >= amount)
       {
          hold_[choice] -= amount;
@@ -2721,6 +2736,18 @@ void sell(void) {
    return;
 }
 
+char would_overflow(unsigned long a, unsigned long b) {
+	return ((UINT32_MAX - b) <= a);
+}
+
+void too_much_cash(void) {
+	cputs("\r\nYou cannot carry so much cash, Taipan!");
+	cputs("\r\nYour ship would sink under the weight");
+	cputs("\r\nof your riches.\r\n");
+	bad_joss_sound();
+	timed_getch(TMOUT_3S);
+}
+
 void visit_bank(void)
 {
    long amount = 0;
@@ -2772,6 +2799,8 @@ void visit_bank(void)
 
 		ulong_to_big(cash, bigcash);
 		big_sub(biglimit, big_max_ulong, bigcash);
+
+		/*
 		cputs("\rcash  ");
 		cprintfancy_big(bigcash);
 		agetc();
@@ -2781,11 +2810,10 @@ void visit_bank(void)
 		cputs("\rlimit ");
 		cprintfancy_big(biglimit);
 		agetc();
+		*/
+
 		if(big_cmp(bigamt, biglimit) >= 0) {
-// hangx: goto hangx;
-			cputs("\r\nYou cannot carry so much cash, Taipan!");
-			bad_joss_sound();
-			timed_getch(TMOUT_1S);
+			too_much_cash();
 			continue;
 		}