| // Copyright 2014 The PDFium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // Original code by Matt McCutchen, see the LICENSE file. |
| |
| #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 |
| BigUnsignedInABase& operator =(const BigUnsignedInABase &x) { |
| NumberlikeArray<Digit>::operator =(x); |
| base = x.base; |
| return *this; |
| } |
| |
| // 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 |