2 * Matt McCutchen's Big Integer Library
3 * http://mysite.verizon.net/mccutchen/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<Block> object holds a dynamically
24 * allocated array of Blocks. 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
47 Index cap; // The current allocated capacity of this NumberlikeArray (in blocks)
48 Index len; // The actual length of the value stored in this NumberlikeArray (in blocks)
49 Blk *blk; // Dynamically allocated array of the blocks
51 * Change made on 2005.01.06:
53 * If a zero-length NumberlikeArray is desired, no array is actually allocated.
54 * Instead, `blk' is set to `NULL', and `cap' and `len' are zero as usual.
56 * `blk' is never dereferenced if the array has zero length. Furthermore,
57 * `delete NULL;' does nothing and causes no error. Therefore, we can use
58 * `NULL' as if it were a zero-length array from `new'.
60 * This is a great convenience because the only code that need be changed
61 * is the array allocation code. All other code will still work file.
65 NumberlikeArray(Index c) : cap(c), len(0) { // Creates a NumberlikeArray with a capacity
66 blk = (cap > 0) ? (new Blk[cap]) : NULL;
68 void allocate(Index c); // Ensures the array has at least the indicated capacity, maybe discarding contents
69 void allocateAndCopy(Index c); // Ensures the array has at least the indicated capacity, preserving its contents
72 * Default constructor.
74 * If a class derived from NumberlikeArray knows at initializer time what size array
75 * it wants, it can call the first constructor listed above in an initializer.
77 * Otherwise, this default constructor will be implicitly invoked, pointing `blk' to
78 * `NULL', a fake zero-length block array. The derived class can allocate the desired
79 * array itself and overwrite `blk'; it need not `delete [] blk' first.
81 * This change fixes a memory leak reported by Milan Tomic on 2005.01.06.
82 * Integer-type-to-BigUnsigned (and BigInteger) conversion constructors have always
83 * allocated their own array of length 0 or 1 after seeing whether the input is zero.
84 * But when the NumberlikeArray transition occurred, these constructors contained an
85 * implicit initializer call to the old NumberlikeArray default constructor, which
86 * created a real `new'-allocated zero-length array. This array would then be lost,
87 * causing a small but annoying memory leak.
89 NumberlikeArray() : cap(0), len(0) {
92 NumberlikeArray(const NumberlikeArray<Blk> &x); // Copy constructor
93 void operator=(const NumberlikeArray<Blk> &x); // Assignment operator
94 NumberlikeArray(const Blk *b, Index l); // Constructor from an array of blocks
95 ~NumberlikeArray() { // Destructor
96 delete [] blk; // Does nothing and causes no error if `blk' is null.
100 // These accessors can be used to get the pieces of the value
101 Index getCapacity() const { return cap; }
102 Index getLength() const { return len; }
103 Blk getBlock(Index i) const { return blk[i]; };
104 bool isEmpty() const { return len == 0; }
106 // Equality comparison: checks if arrays have same length and matching values
107 // Derived classes may wish to override these if differing arrays can
108 // sometimes be considered equivalent.
109 bool operator ==(const NumberlikeArray<Blk> &x) const;
110 bool operator !=(const NumberlikeArray<Blk> &x) const;
115 * BELOW THIS POINT are template definitions; above are declarations.
117 * Definitions would ordinarily belong in a file NumberlikeArray.cc so that they would
118 * be compiled once into NumberlikeArray.o and then linked.
120 * However, because of the way templates are usually implemented,
121 * template ``definitions'' are treated as declarations by the compiler.
122 * When someone uses an instance of the template, definitions are generated,
123 * and the linker is smart enough to toss duplicate definitions for the same
124 * instance generated by different files.
126 * Thus, the template ``definitions'' for NumberlikeArray must appear in this header file
127 * so other files including NumberlikeArray will be able to generate real definitions.
132 // This routine is called to ensure the array is at least a
133 // certain size before another value is written into it.
135 void NumberlikeArray<Blk>::allocate(Index c) {
136 // If the requested capacity is more than the current capacity...
138 // Delete the old number array
140 // Allocate the new array
146 // This routine is called to ensure the array is at least a
147 // certain size without losing its contents.
149 void NumberlikeArray<Blk>::allocateAndCopy(Index c) {
150 // If the requested capacity is more than the current capacity...
153 // Allocate the new number array
156 // Copy number blocks
158 for (i = 0; i < len; i++)
160 // Delete the old array
167 NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x) : len(x.len) {
173 for (i = 0; i < len; i++)
177 // Assignment operator
179 void NumberlikeArray<Blk>::operator=(const NumberlikeArray<Blk> &x) {
180 // Calls like a = a have no effect
185 // Expand array if necessary
187 // Copy number blocks
189 for (i = 0; i < len; i++)
193 // Constructor from an array of blocks
195 NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index l) : cap(l), len(l) {
200 for (i = 0; i < len; i++)
206 // This uses == to compare Blks for equality.
207 // Therefore, Blks must have an == operator with the desired semantics.
209 bool NumberlikeArray<Blk>::operator ==(const NumberlikeArray<Blk> &x) const {
210 // Different lengths imply different objects.
214 // Compare matching blocks one by one.
216 for (i = 0; i < len; i++)
217 if (blk[i] != x.blk[i])
219 // If no blocks differed, the objects are equal.