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authorClifford Wolf <clifford@clifford.at>2013-02-27 09:32:19 +0100
committerClifford Wolf <clifford@clifford.at>2013-02-27 09:32:19 +0100
commita321a5c412090d04dfaea4b4876c4901c42cfe44 (patch)
treeb08d286e0aea76be9aab7a543df0b51e76b6ede4 /libs/bigint/BigUnsignedInABase.hh
parent4f0c2862a0d7e1ca247e0a4d54301c7f8cc92fd8 (diff)
Moved stand-alone libs to libs/ directory and added libs/subcircuit
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+#ifndef BIGUNSIGNEDINABASE_H
+#define BIGUNSIGNEDINABASE_H
+
+#include "NumberlikeArray.hh"
+#include "BigUnsigned.hh"
+#include <string>
+
+/*
+ * A BigUnsignedInABase object represents a nonnegative integer of size limited
+ * only by available memory, represented in a user-specified base that can fit
+ * in an `unsigned short' (most can, and this saves memory).
+ *
+ * BigUnsignedInABase is intended as an intermediary class with little
+ * functionality of its own. BigUnsignedInABase objects can be constructed
+ * from, and converted to, BigUnsigneds (requiring multiplication, mods, etc.)
+ * and `std::string's (by switching digit values for appropriate characters).
+ *
+ * BigUnsignedInABase is similar to BigUnsigned. Note the following:
+ *
+ * (1) They represent the number in exactly the same way, except that
+ * BigUnsignedInABase uses ``digits'' (or Digit) where BigUnsigned uses
+ * ``blocks'' (or Blk).
+ *
+ * (2) Both use the management features of NumberlikeArray. (In fact, my desire
+ * to add a BigUnsignedInABase class without duplicating a lot of code led me to
+ * introduce NumberlikeArray.)
+ *
+ * (3) The only arithmetic operation supported by BigUnsignedInABase is an
+ * equality test. Use BigUnsigned for arithmetic.
+ */
+
+class BigUnsignedInABase : protected NumberlikeArray<unsigned short> {
+
+public:
+ // The digits of a BigUnsignedInABase are unsigned shorts.
+ typedef unsigned short Digit;
+ // That's also the type of a base.
+ typedef Digit Base;
+
+protected:
+ // The base in which this BigUnsignedInABase is expressed
+ Base base;
+
+ // Creates a BigUnsignedInABase with a capacity; for internal use.
+ BigUnsignedInABase(int, Index c) : NumberlikeArray<Digit>(0, c) {}
+
+ // Decreases len to eliminate any leading zero digits.
+ void zapLeadingZeros() {
+ while (len > 0 && blk[len - 1] == 0)
+ len--;
+ }
+
+public:
+ // Constructs zero in base 2.
+ BigUnsignedInABase() : NumberlikeArray<Digit>(), base(2) {}
+
+ // Copy constructor
+ BigUnsignedInABase(const BigUnsignedInABase &x) : NumberlikeArray<Digit>(x), base(x.base) {}
+
+ // Assignment operator
+ void operator =(const BigUnsignedInABase &x) {
+ NumberlikeArray<Digit>::operator =(x);
+ base = x.base;
+ }
+
+ // Constructor that copies from a given array of digits.
+ BigUnsignedInABase(const Digit *d, Index l, Base base);
+
+ // Destructor. NumberlikeArray does the delete for us.
+ ~BigUnsignedInABase() {}
+
+ // LINKS TO BIGUNSIGNED
+ BigUnsignedInABase(const BigUnsigned &x, Base base);
+ operator BigUnsigned() const;
+
+ /* LINKS TO STRINGS
+ *
+ * These use the symbols ``0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'' to
+ * represent digits of 0 through 35. When parsing strings, lowercase is
+ * also accepted.
+ *
+ * All string representations are big-endian (big-place-value digits
+ * first). (Computer scientists have adopted zero-based counting; why
+ * can't they tolerate little-endian numbers?)
+ *
+ * No string representation has a ``base indicator'' like ``0x''.
+ *
+ * An exception is made for zero: it is converted to ``0'' and not the
+ * empty string.
+ *
+ * If you want different conventions, write your own routines to go
+ * between BigUnsignedInABase and strings. It's not hard.
+ */
+ operator std::string() const;
+ BigUnsignedInABase(const std::string &s, Base base);
+
+public:
+
+ // ACCESSORS
+ Base getBase() const { return base; }
+
+ // Expose these from NumberlikeArray directly.
+ using NumberlikeArray<Digit>::getCapacity;
+ using NumberlikeArray<Digit>::getLength;
+
+ /* Returns the requested digit, or 0 if it is beyond the length (as if
+ * the number had 0s infinitely to the left). */
+ Digit getDigit(Index i) const { return i >= len ? 0 : blk[i]; }
+
+ // The number is zero if and only if the canonical length is zero.
+ bool isZero() const { return NumberlikeArray<Digit>::isEmpty(); }
+
+ /* Equality test. For the purposes of this test, two BigUnsignedInABase
+ * values must have the same base to be equal. */
+ bool operator ==(const BigUnsignedInABase &x) const {
+ return base == x.base && NumberlikeArray<Digit>::operator ==(x);
+ }
+ bool operator !=(const BigUnsignedInABase &x) const { return !operator ==(x); }
+
+};
+
+#endif