X-Git-Url: https://mattmccutchen.net/bigint/bigint.git/blobdiff_plain/2f145f11d5d5ab979a7f5a5e3b26fc9882dc345c..a8e1d2a44f8c5815d641a46caadf04c6ef732f45:/BigInteger.cc

diff --git a/BigInteger.cc b/BigInteger.cc
index 471d056..00074cf 100644
--- a/BigInteger.cc
+++ b/BigInteger.cc
@@ -1,6 +1,5 @@
 /*
 * Matt McCutchen's Big Integer Library
-* http://mysite.verizon.net/mccutchen/bigint/
 */
 
 #include "BigInteger.hh"
@@ -67,7 +66,7 @@ BigInteger::BigInteger(unsigned long x) {
 		sign = zero; // NumberlikeArray did the rest
 	else {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
@@ -77,13 +76,13 @@ BigInteger::BigInteger(unsigned long x) {
 BigInteger::BigInteger(long x) {
 	if (x > 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
 	} else if (x < 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = negative;
 		len = 1;
 		blk[0] = Blk(-x);
@@ -96,7 +95,7 @@ BigInteger::BigInteger(unsigned int x) {
 		sign = zero;
 	else {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
@@ -106,13 +105,13 @@ BigInteger::BigInteger(unsigned int x) {
 BigInteger::BigInteger(int x) {
 	if (x > 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
 	} else if (x < 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = negative;
 		len = 1;
 		blk[0] = Blk(-x);
@@ -125,7 +124,7 @@ BigInteger::BigInteger(unsigned short x) {
 		sign = zero;
 	else {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
@@ -135,13 +134,13 @@ BigInteger::BigInteger(unsigned short x) {
 BigInteger::BigInteger(short x) {
 	if (x > 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = positive;
 		len = 1;
 		blk[0] = Blk(x);
 	} else if (x < 0) {
 		cap = 1;
-		blk2 = new Blk[1];
+		blk = new Blk[1];
 		sign = negative;
 		len = 1;
 		blk[0] = Blk(-x);
@@ -311,11 +310,18 @@ BigInteger::CmpRes BigInteger::compareTo(const BigInteger &x) const {
 // These do some messing around to determine the sign of the result,
 // then call one of BigUnsigned's put-heres.
 
+// See remarks about aliased calls in BigUnsigned.cc .
+#define DTRT_ALIASED(cond, op) \
+	if (cond) { \
+		BigInteger tmpThis; \
+		tmpThis.op; \
+		*this = tmpThis; \
+		return; \
+	}
+
 // Addition
 void BigInteger::add(const BigInteger &a, const BigInteger &b) {
-	// Block unsafe calls
-	if (this == &a || this == &b)
-		throw "BigInteger::add: One of the arguments is the invoked object";
+	DTRT_ALIASED(this == &a || this == &b, add(a, b));
 	// If one argument is zero, copy the other.
 	if (a.sign == zero)
 		operator =(b);
@@ -352,15 +358,15 @@ void BigInteger::add(const BigInteger &a, const BigInteger &b) {
 void BigInteger::subtract(const BigInteger &a, const BigInteger &b) {
 	// Notice that this routine is identical to BigInteger::add,
 	// if one replaces b.sign by its opposite.
-	// Block unsafe calls
-	if (this == &a || this == &b)
-		throw "BigInteger::subtract: One of the arguments is the invoked object";
+	DTRT_ALIASED(this == &a || this == &b, subtract(a, b));
 	// If a is zero, copy b and flip its sign.  If b is zero, copy a.
 	if (a.sign == zero) {
 		BigUnsigned::operator =(b);
-		sign = Sign(-sign);
+		// Take the negative of _b_'s, sign, not ours.
+		// Bug pointed out by Sam Larkin on 2005.03.30.
+		sign = Sign(-b.sign);
 	} else if (b.sign == zero)
-    operator =(a);
+		operator =(a);
 	// If their signs differ, take a.sign and add the magnitudes.
 	else if (a.sign != b.sign) {
 		sign = a.sign;
@@ -391,9 +397,7 @@ void BigInteger::subtract(const BigInteger &a, const BigInteger &b) {
 
 // Multiplication
 void BigInteger::multiply(const BigInteger &a, const BigInteger &b) {
-	// Block unsafe calls
-	if (this == &a || this == &b)
-		throw "BigInteger::multiply: One of the arguments is the invoked object";
+	DTRT_ALIASED(this == &a || this == &b, multiply(a, b));
 	// If one object is zero, copy zero and return.
 	if (a.sign == zero || b.sign == zero) {
 		sign = zero;
@@ -430,9 +434,16 @@ void BigInteger::multiply(const BigInteger &a, const BigInteger &b) {
 *	-4	-3	1	-1
 */
 void BigInteger::divideWithRemainder(const BigInteger &b, BigInteger &q) {
-	// Block unsafe calls
-	if (this == &b || this == &q || &b == &q)
-		throw "BigInteger::divideWithRemainder: One of the arguments is the invoked object";
+	// Defend against aliased calls;
+	// same idea as in BigUnsigned::divideWithRemainder .
+	if (this == &q)
+		throw "BigInteger::divideWithRemainder: Cannot write quotient and remainder into the same variable";
+	if (this == &b || &q == &b) {
+		BigInteger tmpB(b);
+		divideWithRemainder(tmpB, q);
+		return;
+	}
+
 	// Division by zero gives quotient 0 and remainder *this
 	if (b.sign == zero) {
 		q.len = 0;
@@ -445,9 +456,9 @@ void BigInteger::divideWithRemainder(const BigInteger &b, BigInteger &q) {
 		q.sign = zero;
 		return;
 	}
-	
+
 	// Here *this != 0, b != 0.
-	
+
 	// Do the operands have the same sign?
 	if (sign == b.sign) {
 		// Yes: easy case.  Quotient is zero or positive.
@@ -478,10 +489,10 @@ void BigInteger::divideWithRemainder(const BigInteger &b, BigInteger &q) {
 		* Find r = (b - 1) - R and give it the desired sign.
 		*/
 	}
-	
+
 	// Divide the magnitudes.
 	BigUnsigned::divideWithRemainder(b, q);
-	
+
 	if (sign != b.sign) {
 		// More for the harder case (as described):
 		// Increase the magnitude of the quotient by one.
@@ -491,24 +502,22 @@ void BigInteger::divideWithRemainder(const BigInteger &b, BigInteger &q) {
 		BigUnsigned::subtract(b, temp);
 		BigUnsigned::operator --();
 	}
-	
+
 	// Sign of the remainder is always the sign of the divisor b.
 	sign = b.sign;
-	
+
 	// Set signs to zero as necessary.  (Thanks David Allen!)
 	if (len == 0)
 		sign = zero;
 	if (q.len == 0)
 		q.sign = zero;
-	
+
 	// WHEW!!!
 }
 
 // Negation
 void BigInteger::negate(const BigInteger &a) {
-	// Block unsafe calls
-	if (this == &a)
-		throw "BigInteger::negate: The argument is the invoked object";
+	DTRT_ALIASED(this == &a, negate(a));
 	// Copy a's magnitude
 	BigUnsigned::operator =(a);
 	// Copy the opposite of a.sign