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05780f4b MM |
1 | /* |
2 | * Matt McCutchen's Big Integer Library | |
3 | * http://mysite.verizon.net/mccutchen/bigint/ | |
4 | */ | |
5 | ||
b3fe29df MM |
6 | /* |
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. | |
12 | */ | |
05780f4b MM |
13 | #ifndef NUMBERLIKEARRAY |
14 | #define NUMBERLIKEARRAY | |
15 | ||
b3fe29df MM |
16 | // An essential memory-management constant. |
17 | // I wish this were built into C++ just as it is in Java. | |
18 | #ifndef NULL | |
19 | #define NULL 0 | |
20 | #endif | |
21 | ||
05780f4b MM |
22 | /* |
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. | |
27 | * | |
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: | |
35 | * | |
36 | * public: | |
37 | * NumberlikeArray< whatever >::getLength; | |
38 | */ | |
39 | ||
40 | template <class Blk> | |
41 | class NumberlikeArray { | |
42 | public: | |
43 | ||
44 | typedef unsigned int Index; // Type for the index of a block in the array | |
45 | ||
46 | // FIELDS | |
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 | |
b3fe29df MM |
50 | /* |
51 | * Change made on 2005.01.06: | |
52 | * | |
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. | |
55 | * | |
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'. | |
59 | * | |
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. | |
62 | */ | |
05780f4b MM |
63 | |
64 | // MANAGEMENT | |
b3fe29df MM |
65 | NumberlikeArray(Index c) : cap(c), len(0) { // Creates a NumberlikeArray with a capacity |
66 | blk = (cap > 0) ? (new Blk[cap]) : NULL; | |
05780f4b MM |
67 | } |
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 | |
70 | ||
b3fe29df MM |
71 | /* |
72 | * Default constructor. | |
73 | * | |
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. | |
76 | * | |
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. | |
80 | * | |
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. | |
88 | */ | |
89 | NumberlikeArray() : cap(0), len(0) { | |
90 | blk = NULL; | |
05780f4b MM |
91 | } |
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 | |
b3fe29df | 96 | delete [] blk; // Does nothing and causes no error if `blk' is null. |
05780f4b MM |
97 | } |
98 | ||
99 | // PICKING APART | |
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; } | |
105 | ||
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; | |
111 | ||
112 | }; | |
113 | ||
114 | /* | |
115 | * BELOW THIS POINT are template definitions; above are declarations. | |
116 | * | |
117 | * Definitions would ordinarily belong in a file NumberlikeArray.cc so that they would | |
118 | * be compiled once into NumberlikeArray.o and then linked. | |
119 | * | |
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. | |
125 | * | |
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. | |
128 | */ | |
129 | ||
130 | // MANAGEMENT | |
131 | ||
132 | // This routine is called to ensure the array is at least a | |
133 | // certain size before another value is written into it. | |
134 | template <class Blk> | |
135 | void NumberlikeArray<Blk>::allocate(Index c) { | |
136 | // If the requested capacity is more than the current capacity... | |
137 | if (c > cap) { | |
138 | // Delete the old number array | |
139 | delete [] blk; | |
140 | // Allocate the new array | |
141 | cap = c; | |
142 | blk = new Blk[cap]; | |
143 | } | |
144 | } | |
145 | ||
146 | // This routine is called to ensure the array is at least a | |
147 | // certain size without losing its contents. | |
148 | template <class Blk> | |
149 | void NumberlikeArray<Blk>::allocateAndCopy(Index c) { | |
150 | // If the requested capacity is more than the current capacity... | |
151 | if (c > cap) { | |
152 | Blk *oldBlk = blk; | |
153 | // Allocate the new number array | |
154 | cap = c; | |
155 | blk = new Blk[cap]; | |
156 | // Copy number blocks | |
157 | Index i; | |
158 | for (i = 0; i < len; i++) | |
159 | blk[i] = oldBlk[i]; | |
160 | // Delete the old array | |
161 | delete [] oldBlk; | |
162 | } | |
163 | } | |
164 | ||
165 | // Copy constructor | |
166 | template <class Blk> | |
167 | NumberlikeArray<Blk>::NumberlikeArray(const NumberlikeArray<Blk> &x) : len(x.len) { | |
168 | // Create array | |
169 | cap = len; | |
170 | blk = new Blk[cap]; | |
171 | // Copy blocks | |
172 | Index i; | |
173 | for (i = 0; i < len; i++) | |
174 | blk[i] = x.blk[i]; | |
175 | } | |
176 | ||
177 | // Assignment operator | |
178 | template <class Blk> | |
179 | void NumberlikeArray<Blk>::operator=(const NumberlikeArray<Blk> &x) { | |
180 | // Calls like a = a have no effect | |
181 | if (this == &x) | |
182 | return; | |
183 | // Copy length | |
184 | len = x.len; | |
185 | // Expand array if necessary | |
186 | allocate(len); | |
187 | // Copy number blocks | |
188 | Index i; | |
189 | for (i = 0; i < len; i++) | |
190 | blk[i] = x.blk[i]; | |
191 | } | |
192 | ||
193 | // Constructor from an array of blocks | |
194 | template <class Blk> | |
195 | NumberlikeArray<Blk>::NumberlikeArray(const Blk *b, Index l) : cap(l), len(l) { | |
196 | // Create array | |
197 | blk = new Blk[cap]; | |
198 | // Copy blocks | |
199 | Index i; | |
200 | for (i = 0; i < len; i++) | |
201 | blk[i] = b[i]; | |
202 | } | |
203 | ||
204 | ||
205 | // EQUALITY TEST | |
206 | // This uses == to compare Blks for equality. | |
207 | // Therefore, Blks must have an == operator with the desired semantics. | |
208 | template <class Blk> | |
209 | bool NumberlikeArray<Blk>::operator ==(const NumberlikeArray<Blk> &x) const { | |
210 | // Different lengths imply different objects. | |
211 | if (len != x.len) | |
212 | return false; | |
213 | else { | |
214 | // Compare matching blocks one by one. | |
215 | Index i; | |
216 | for (i = 0; i < len; i++) | |
217 | if (blk[i] != x.blk[i]) | |
218 | return false; | |
219 | // If no blocks differed, the objects are equal. | |
220 | return true; | |
221 | } | |
222 | } | |
223 | ||
224 | #endif |