-/*
-* Matt McCutchen's Big Integer Library
-* http://mysite.verizon.net/mccutchen/bigint/
-*/
-
-#ifndef NUMBERLIKEARRAY
-#define NUMBERLIKEARRAY
-
-/*
-* A NumberlikeArray<Block> object holds a dynamically
-* allocated array of Blocks. It provides certain basic
-* memory management features needed by both BigUnsigned
-* and BigUnsignedInABase, which are both derived from it.
-*
-* NumberlikeArray provides no information hiding, so make
-* sure you know what you are doing if you use it directly.
-* Classes derived from it will probably wish to pass on
-* some members of NumberlikeArray to their clients while
-* keeping some safe for themselves. These classes should
-* use protected inheritance and manually make some members
-* public with declarations like this:
-*
-* public:
-* NumberlikeArray< whatever >::getLength;
-*/
+#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:
-
- typedef unsigned int Index; // Type for the index of a block in the array
-
- // FIELDS
- Index cap; // The current allocated capacity of this NumberlikeArray (in blocks)
- Index len; // The actual length of the value stored in this NumberlikeArray (in blocks)
- Blk *blk; // Dynamically allocated array of the blocks
-
- // MANAGEMENT
- NumberlikeArray(int, Index c) : cap(c), len(0) { // Creates a NumberlikeArray with a capacity
- blk = new Blk[cap];
+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;
}
- void allocate(Index c); // Ensures the array has at least the indicated capacity, maybe discarding contents
- void allocateAndCopy(Index c); // Ensures the array has at least the indicated capacity, preserving its contents
-
- NumberlikeArray() : cap(0), len(0) { // Default constructor (empty array)
- blk = new Blk[0];
+
+ /* 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;
}
- NumberlikeArray(const NumberlikeArray<Blk> &x); // Copy constructor
- void operator=(const NumberlikeArray<Blk> &x); // Assignment operator
- NumberlikeArray(const Blk *b, Index l); // Constructor from an array of blocks
- ~NumberlikeArray() { // Destructor
+
+ // Destructor. Note that `delete NULL' is a no-op.
+ ~NumberlikeArray() {
delete [] blk;
}
-
- // PICKING APART
- // These accessors can be used to get the pieces of the value
- 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 arrays have same length and matching values
- // Derived classes may wish to override these if differing arrays can
- // sometimes be considered equivalent.
+
+ /* 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;
-
+
+ bool operator !=(const NumberlikeArray<Blk> &x) const {
+ return !operator ==(x);
+ }
};
-/*
-* BELOW THIS POINT are template definitions; above are declarations.
-*
-* Definitions would ordinarily belong in a file NumberlikeArray.cc so that they would
-* be compiled once into NumberlikeArray.o and then linked.
-*
-* However, because of the way templates are usually implemented,
-* template ``definitions'' are treated as declarations by the compiler.
-* When someone uses an instance of the template, definitions are generated,
-* and the linker is smart enough to toss duplicate definitions for the same
-* instance generated by different files.
-*
-* Thus, the template ``definitions'' for NumberlikeArray must appear in this header file
-* so other files including NumberlikeArray will be able to generate real definitions.
-*/
-
-// MANAGEMENT
-
-// This routine is called to ensure the array is at least a
-// certain size before another value is written into it.
+/* 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...
}
}
-// This routine is called to ensure the array is at least a
-// certain size without losing its contents.
template <class Blk>
void NumberlikeArray<Blk>::allocateAndCopy(Index c) {
// If the requested capacity is more than the current capacity...
}
}
-// Copy constructor
template <class Blk>
-NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x) : len(x.len) {
+NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x)
+ : len(x.len) {
// Create array
cap = len;
blk = new Blk[cap];
blk[i] = x.blk[i];
}
-// Assignment operator
template <class Blk>
void NumberlikeArray<Blk>::operator=(const NumberlikeArray<Blk> &x) {
- // Calls like a = a have no effect
+ /* Calls like a = a have no effect; catch them before the aliasing
+ * causes a problem */
if (this == &x)
return;
// Copy length
blk[i] = x.blk[i];
}
-// Constructor from an array of blocks
template <class Blk>
-NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index l) : cap(l), len(l) {
+NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index blen)
+ : cap(blen), len(blen) {
// Create array
blk = new Blk[cap];
// Copy blocks
blk[i] = b[i];
}
-
-// EQUALITY TEST
-// This uses == to compare Blks for equality.
-// Therefore, Blks must have an == operator with the desired semantics.
template <class Blk>
bool NumberlikeArray<Blk>::operator ==(const NumberlikeArray<Blk> &x) const {
- // Different lengths imply different objects.
if (len != x.len)
+ // Definitely unequal.
return false;
else {
- // Compare matching blocks one by one.
+ // Compare corresponding blocks one by one.
Index i;
for (i = 0; i < len; i++)
if (blk[i] != x.blk[i])
return false;
- // If no blocks differed, the objects are equal.
+ // No blocks differed, so the objects are equal.
return true;
}
}
Matt McCutchen's Web Site / bigint / bigint.git / blobdiff