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// Copyright 2014 PDFium Authors. All rights reserved.
// 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
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
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