bigint: Added some more helpers.

core/math/bigint/logical.odin

@@ -0,0 +1,113 @@
+package bigint
+
+/*
+	Copyright 2021 Jeroen van Rijn <nom@duclavier.com>.
+	Made available under Odin's BSD-2 license.
+
+	A BigInt implementation in Odin.
+	For the theoretical underpinnings, see Knuth's The Art of Computer Programming, Volume 2, section 4.3.
+	The code started out as an idiomatic source port of libTomMath, which is in the public domain, with thanks.
+
+	This file contains logical operations like `and`, `or` and `xor`.
+*/
+
+import "core:fmt"
+
+@private
+Operator :: enum u8 {
+	And = 1,
+	Or  = 2,
+	Xor = 3,
+}
+
+/*
+	2's complement `and`, returns `dest = a & b;`
+*/
+
+_binary_op :: proc(dest, a, b: ^Int, op: Operator) -> (err: Error) {
+	assert_initialized(dest); assert_initialized(a); assert_initialized(b);
+
+	used := max(a.used, b.used) + 1;
+	neg: bool;
+
+	switch(op) {
+	case .And:
+		neg  = is_neg(a) && is_neg(b);
+	case .Or:
+		neg  = is_neg(a) || is_neg(b);
+	case .Xor:
+		neg  = is_neg(a) != is_neg(b);
+	case:
+		return .Invalid_Input;
+	}
+
+	ac, bc, cc := DIGIT(1), DIGIT(1), DIGIT(1);
+
+	/*
+		Grow the destination to accomodate the result.
+	*/
+	if err = grow(dest, used); err != .OK {
+		return err;
+	}
+
+	for i := 0; i < used; i += 1 {
+		x, y: DIGIT;
+
+		/*
+			Convert to 2's complement if negative.
+		*/
+		if is_neg(a) {
+			ac += _MASK if i >= a.used else (~a.digit[i] & _MASK);
+			x = ac & _MASK;
+			ac >>= _DIGIT_BITS;
+		} else {
+			x = 0 if i >= a.used else a.digit[i];
+		}
+
+		/*
+			Convert to 2's complement if negative.
+		*/
+		if is_neg(a) {
+			bc += _MASK if i >= b.used else (~b.digit[i] & _MASK);
+			y = bc & _MASK;
+			bc >>= _DIGIT_BITS;
+		} else {
+			y = 0 if i >= b.used else b.digit[i];
+		}
+
+		switch(op) {
+		case .And:
+			dest.digit[i] = x & y;
+		case .Or:
+			dest.digit[i] = x | y;
+		case .Xor:
+			dest.digit[i] = x ~ y;
+		}
+
+		/*
+			Convert to to sign-magnitude if negative.
+		*/
+		if neg {
+			cc += ~dest.digit[i] & _MASK;
+			dest.digit[i] = cc & _MASK;
+			cc >>= _DIGIT_BITS;
+		}
+	}
+
+	dest.used = used;
+	dest.sign = .Negative if neg else .Zero_or_Positive;
+	clamp(dest);
+	return .OK;
+}
+
+and :: proc(dest, a, b: ^Int) -> (err: Error) {
+	return _binary_op(dest, a, b, .And);
+}
+
+or  :: proc(dest, a, b: ^Int) -> (err: Error) {
+	return _binary_op(dest, a, b, .Or);
+}
+
+xor :: proc(dest, a, b: ^Int) -> (err: Error) {
+	return _binary_op(dest, a, b, .Xor);
+}