NumberlikeArray.hh

Go to the documentation of this file.

#ifndef NUMBERLIKEARRAY_H
#define NUMBERLIKEARRAY_H

// Make sure we have NULL.
#ifndef NULL
#define NULL 0
#endif

/* A NumberlikeArray<Blk> object holds a heap-allocated array of Blk with a
 * length and a capacity and provides basic memory management features.
 * BigUnsigned and BigUnsignedInABase both subclass it.
 *
 * NumberlikeArray provides no information hiding.  Subclasses should use
 * nonpublic inheritance and manually expose members as desired using
 * declarations like this:
 *
 * public:
 *     NumberlikeArray< the-type-argument >::getLength;
 */
template <class Blk>
class NumberlikeArray {
public:

    // Type for the index of a block in the array
    typedef unsigned int Index;
    // The number of bits in a block, defined below.
    static const unsigned int N;

    // The current allocated capacity of this NumberlikeArray (in blocks)
    Index cap;
    // The actual length of the value stored in this NumberlikeArray (in blocks)
    Index len;
    // Heap-allocated array of the blocks (can be NULL if len == 0)
    Blk *blk;

    // Constructs a ``zero'' NumberlikeArray with the given capacity.
    NumberlikeArray(Index c) : cap(c), len(0) { 
        blk = (cap > 0) ? (new Blk[cap]) : NULL;
    }

    /* Constructs a zero NumberlikeArray without allocating a backing array.
     * A subclass that doesn't know the needed capacity at initialization
     * time can use this constructor and then overwrite blk without first
     * deleting it. */
    NumberlikeArray() : cap(0), len(0) {
        blk = NULL;
    }

    // Destructor.  Note that `delete NULL' is a no-op.
    ~NumberlikeArray() {
        delete [] blk;
    }

    /* Ensures that the array has at least the requested capacity; may
     * destroy the contents. */
    void allocate(Index c);

    /* Ensures that the array has at least the requested capacity; does not
     * destroy the contents. */
    void allocateAndCopy(Index c);

    // Copy constructor
    NumberlikeArray(const NumberlikeArray<Blk> &x);

    // Assignment operator
    void operator=(const NumberlikeArray<Blk> &x);

    // Constructor that copies from a given array of blocks
    NumberlikeArray(const Blk *b, Index blen);

    // ACCESSORS
    Index getCapacity()     const { return cap;      }
    Index getLength()       const { return len;      }
    Blk   getBlock(Index i) const { return blk[i];   }
    bool  isEmpty()         const { return len == 0; }

    /* Equality comparison: checks if both objects have the same length and
     * equal (==) array elements to that length.  Subclasses may wish to
     * override. */
    bool operator ==(const NumberlikeArray<Blk> &x) const;

    bool operator !=(const NumberlikeArray<Blk> &x) const {
        return !operator ==(x);
    }
};

/* BEGIN TEMPLATE DEFINITIONS.  They are present here so that source files that
 * include this header file can generate the necessary real definitions. */

template <class Blk>
const unsigned int NumberlikeArray<Blk>::N = 8 * sizeof(Blk);

template <class Blk>
void NumberlikeArray<Blk>::allocate(Index c) {
    // If the requested capacity is more than the current capacity...
    if (c > cap) {
        // Delete the old number array
        delete [] blk;
        // Allocate the new array
        cap = c;
        blk = new Blk[cap];
    }
}

template <class Blk>
void NumberlikeArray<Blk>::allocateAndCopy(Index c) {
    // If the requested capacity is more than the current capacity...
    if (c > cap) {
        Blk *oldBlk = blk;
        // Allocate the new number array
        cap = c;
        blk = new Blk[cap];
        // Copy number blocks
        Index i;
        for (i = 0; i < len; i++)
            blk[i] = oldBlk[i];
        // Delete the old array
        delete [] oldBlk;
    }
}

template <class Blk>
NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x)
        : len(x.len) {
    // Create array
    cap = len;
    blk = new Blk[cap];
    // Copy blocks
    Index i;
    for (i = 0; i < len; i++)
        blk[i] = x.blk[i];
}

template <class Blk>
void NumberlikeArray<Blk>::operator=(const NumberlikeArray<Blk> &x) {
    /* Calls like a = a have no effect; catch them before the aliasing
     * causes a problem */
    if (this == &x)
        return;
    // Copy length
    len = x.len;
    // Expand array if necessary
    allocate(len);
    // Copy number blocks
    Index i;
    for (i = 0; i < len; i++)
        blk[i] = x.blk[i];
}

template <class Blk>
NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index blen)
        : cap(blen), len(blen) {
    // Create array
    blk = new Blk[cap];
    // Copy blocks
    Index i;
    for (i = 0; i < len; i++)
        blk[i] = b[i];
}

template <class Blk>
bool NumberlikeArray<Blk>::operator ==(const NumberlikeArray<Blk> &x) const {
    if (len != x.len)
        // Definitely unequal.
        return false;
    else {
        // Compare corresponding blocks one by one.
        Index i;
        for (i = 0; i < len; i++)
            if (blk[i] != x.blk[i])
                return false;
        // No blocks differed, so the objects are equal.
        return true;
    }
}

#endif