2 * Matt McCutchen's Big Integer Library
3 * http://hashproduct.metaesthetics.net/bigint/
7 * This mechanism prevents files from being included twice.
8 * Each file gets its own `id' (here `NUMBERLIKEARRAY').
9 * When `#include'd, this file checks whether its `id' has
10 * already been flagged. If not, it flags the `id' and
11 * loads the declarations.
13 #ifndef NUMBERLIKEARRAY
14 #define NUMBERLIKEARRAY
16 // An essential memory-management constant.
17 // I wish this were built into C++ just as it is in Java.
23 * A NumberlikeArray<Blk> object holds a dynamically
24 * allocated array of Blk. It provides certain basic
25 * memory management features needed by both BigUnsigned
26 * and BigUnsignedInABase, which are both derived from it.
28 * NumberlikeArray provides no information hiding, so make
29 * sure you know what you are doing if you use it directly.
30 * Classes derived from it will probably wish to pass on
31 * some members of NumberlikeArray to their clients while
32 * keeping some safe for themselves. These classes should
33 * use protected inheritance and manually make some members
34 * public with declarations like this:
37 * NumberlikeArray< whatever >::getLength;
41 class NumberlikeArray {
44 typedef unsigned int Index; // Type for the index of a block in the array
45 static const unsigned int N; // The number of bits in a block, defined below.
48 Index cap; // The current allocated capacity of this NumberlikeArray (in blocks)
49 Index len; // The actual length of the value stored in this NumberlikeArray (in blocks)
50 Blk *blk; // Dynamically allocated array of the blocks
53 * Change made on 2005.01.06:
55 * If a zero-length NumberlikeArray is desired, no array is actually allocated.
56 * Instead, `blk' is set to `NULL', and `cap' and `len' are zero as usual.
58 * `blk' is never dereferenced if the array has zero length. Furthermore,
59 * `delete NULL;' does nothing and causes no error. Therefore, we can use
60 * `NULL' as if it were a zero-length array from `new'.
62 * This is a great convenience because the only code that need be changed
63 * is the array allocation code. All other code will still work fine.
67 NumberlikeArray(Index c) : cap(c), len(0) { // Creates a NumberlikeArray with a capacity
68 blk = (cap > 0) ? (new Blk[cap]) : NULL;
70 void allocate(Index c); // Ensures the array has at least the indicated capacity, maybe discarding contents
71 void allocateAndCopy(Index c); // Ensures the array has at least the indicated capacity, preserving its contents
74 * Default constructor.
76 * If a class derived from NumberlikeArray knows at initializer time what size array
77 * it wants, it can call the first constructor listed above in an initializer.
79 * Otherwise, this default constructor will be implicitly invoked, pointing `blk' to
80 * `NULL', a fake zero-length block array. The derived class can allocate the desired
81 * array itself and overwrite `blk'; it need not `delete [] blk' first.
83 * This change fixes a memory leak reported by Milan Tomic on 2005.01.06.
84 * Integer-type-to-BigUnsigned (and BigInteger) conversion constructors have always
85 * allocated their own array of length 0 or 1 after seeing whether the input is zero.
86 * But when the NumberlikeArray transition occurred, these constructors contained an
87 * implicit initializer call to the old NumberlikeArray default constructor, which
88 * created a real `new'-allocated zero-length array. This array would then be lost,
89 * causing a small but annoying memory leak.
91 NumberlikeArray() : cap(0), len(0) {
94 NumberlikeArray(const NumberlikeArray<Blk> &x); // Copy constructor
95 void operator=(const NumberlikeArray<Blk> &x); // Assignment operator
96 NumberlikeArray(const Blk *b, Index l); // Constructor from an array of blocks
97 ~NumberlikeArray() { // Destructor
98 delete [] blk; // Does nothing and causes no error if `blk' is null.
102 // These accessors can be used to get the pieces of the value
103 Index getCapacity() const { return cap; }
104 Index getLength() const { return len; }
105 Blk getBlock(Index i) const { return blk[i]; };
106 bool isEmpty() const { return len == 0; }
108 // Equality comparison: checks if arrays have same length and matching values
109 // Derived classes may wish to override these if differing arrays can
110 // sometimes be considered equivalent.
111 bool operator ==(const NumberlikeArray<Blk> &x) const;
112 bool operator !=(const NumberlikeArray<Blk> &x) const { return !operator ==(x); }
117 * =================================
118 * BELOW THIS POINT are template definitions; above are declarations.
120 * Definitions would ordinarily belong in a file NumberlikeArray.cc so that they would
121 * be compiled once into NumberlikeArray.o and then linked.
123 * However, because of the way templates are usually implemented,
124 * template ``definitions'' are treated as declarations by the compiler.
125 * When someone uses an instance of the template, definitions are generated,
126 * and the linker is smart enough to toss duplicate definitions for the same
127 * instance generated by different files.
129 * Thus, the template ``definitions'' for NumberlikeArray must appear in this header file
130 * so other files including NumberlikeArray will be able to generate real definitions.
134 const unsigned int NumberlikeArray<Blk>::N = 8 * sizeof(Blk);
138 // This routine is called to ensure the array is at least a
139 // certain size before another value is written into it.
141 void NumberlikeArray<Blk>::allocate(Index c) {
142 // If the requested capacity is more than the current capacity...
144 // Delete the old number array
146 // Allocate the new array
152 // This routine is called to ensure the array is at least a
153 // certain size without losing its contents.
155 void NumberlikeArray<Blk>::allocateAndCopy(Index c) {
156 // If the requested capacity is more than the current capacity...
159 // Allocate the new number array
162 // Copy number blocks
164 for (i = 0; i < len; i++)
166 // Delete the old array
173 NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x) : len(x.len) {
179 for (i = 0; i < len; i++)
183 // Assignment operator
185 void NumberlikeArray<Blk>::operator=(const NumberlikeArray<Blk> &x) {
186 // Calls like a = a have no effect
191 // Expand array if necessary
193 // Copy number blocks
195 for (i = 0; i < len; i++)
199 // Constructor from an array of blocks
201 NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index l) : cap(l), len(l) {
206 for (i = 0; i < len; i++)
212 // This uses == to compare Blks for equality.
213 // Therefore, Blks must have an == operator with the desired semantics.
215 bool NumberlikeArray<Blk>::operator ==(const NumberlikeArray<Blk> &x) const {
216 // Different lengths imply different objects.
220 // Compare matching blocks one by one.
222 for (i = 0; i < len; i++)
223 if (blk[i] != x.blk[i])
225 // If no blocks differed, the objects are equal.