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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 | * Milan Tomic had trouble compiling this file on Microsoft | |
8 | * Visual C++ 6 because, in the libraries that come with | |
9 | * Visual C++ 6, the `std::string::push_back' method apparently | |
10 | * does not exist. To get around the problem, I rewrote | |
11 | * `BigUnsignedInABase::operator std::string' (at the bottom | |
12 | * of this file) so it doesn't use `push_back'. | |
13 | */ | |
14 | ||
05780f4b MM |
15 | #include "BigUnsignedInABase.hh" |
16 | ||
17 | namespace { | |
18 | unsigned int bitLen(unsigned int x) { | |
19 | unsigned int len = 0; | |
20 | while (x > 0) { | |
21 | x >>= 1; | |
22 | len++; | |
23 | } | |
24 | return len; | |
25 | } | |
26 | unsigned int ceilingDiv(unsigned int a, unsigned int b) { | |
27 | return (a + b - 1) / b; | |
28 | } | |
29 | } | |
30 | ||
31 | BigUnsignedInABase::BigUnsignedInABase(const BigUnsigned &x, Base base) { | |
32 | // Check the base | |
33 | if (base < 2) | |
34 | throw "BigUnsignedInABase(BigUnsigned, Base): The base must be at least 2"; | |
35 | // Save the base. | |
36 | // This pattern is seldom seen in C++, but the analogous ``this.'' is common in Java. | |
37 | this->base = base; | |
38 | ||
39 | // Get an upper bound on how much space we need | |
40 | int maxBitLenOfX = x.getLength() * 8 * sizeof(BigUnsigned::Blk); | |
41 | int minBitsPerDigit = bitLen(base) - 1; | |
42 | int maxDigitLenOfX = ceilingDiv(maxBitLenOfX, minBitsPerDigit); | |
43 | allocate(maxDigitLenOfX); // Get the space | |
44 | ||
45 | BigUnsigned x2(x), buBase(base); | |
46 | Index digitNum = 0; | |
47 | ||
48 | while (!x2.isZero()) { | |
49 | // Get last digit. This is like `lastDigit = x2 % buBase, x2 /= buBase'. | |
50 | BigUnsigned lastDigit(x2); | |
51 | lastDigit.divideWithRemainder(buBase, x2); | |
52 | // Save the digit. | |
53 | blk[digitNum] = Digit(lastDigit); // invokes `BigUnsigned ==> unsigned short' converter | |
54 | // Move on. We can't run out of room: we figured it out above. | |
55 | digitNum++; | |
56 | } | |
57 | ||
58 | // Save the eventual length. | |
59 | len = digitNum; | |
60 | } | |
61 | ||
62 | BigUnsignedInABase::operator BigUnsigned() const { | |
63 | BigUnsigned ans(0), buBase(base), temp; | |
64 | Index digitNum = len; | |
65 | while (digitNum > 0) { | |
66 | digitNum--; | |
67 | temp.multiply(ans, buBase); | |
68 | ans.add(temp, BigUnsigned(blk[digitNum])); | |
69 | } | |
70 | return ans; | |
71 | } | |
72 | ||
73 | BigUnsignedInABase::BigUnsignedInABase(const std::string &s, Base base) { | |
74 | // Check the base. | |
75 | if (base > 36) | |
76 | throw "BigUnsignedInABase(std::string, Base): The default string conversion routines use the symbol set 0-9, A-Z and therefore support only up to base 36. You tried a conversion with a base over 36; write your own string conversion routine."; | |
77 | // Save the base. | |
78 | // This pattern is seldom seen in C++, but the analogous ``this.'' is common in Java. | |
79 | this->base = base; | |
80 | ||
81 | len = s.length(); | |
82 | allocate(len); | |
83 | ||
84 | Index digitNum, symbolNumInString; | |
85 | for (digitNum = 0; digitNum < len; digitNum++) { | |
86 | symbolNumInString = len - 1 - digitNum; | |
87 | char theSymbol = s[symbolNumInString]; | |
88 | if (theSymbol >= '0' && theSymbol <= '9') | |
89 | blk[digitNum] = theSymbol - '0'; | |
90 | else if (theSymbol >= 'A' && theSymbol <= 'Z') | |
91 | blk[digitNum] = theSymbol - 'A' + 10; | |
92 | else if (theSymbol >= 'a' && theSymbol <= 'z') | |
93 | blk[digitNum] = theSymbol - 'a' + 10; | |
94 | else | |
95 | throw "BigUnsignedInABase(std::string, Base): Bad symbol in input. Only 0-9, A-Z, a-z are accepted."; | |
96 | } | |
97 | zapLeadingZeros(); | |
98 | } | |
99 | ||
100 | BigUnsignedInABase::operator std::string() const { | |
101 | if (base > 36) | |
102 | throw "BigUnsignedInABase ==> std::string: The default string conversion routines use the symbol set 0-9, A-Z and therefore support only up to base 36. You tried a conversion with a base over 36; write your own string conversion routine."; | |
103 | if (len == 0) | |
104 | return std::string("0"); | |
b3fe29df MM |
105 | char *s = new char[len + 1]; |
106 | s[len] = '\0'; | |
05780f4b MM |
107 | Index digitNum, symbolNumInString; |
108 | for (symbolNumInString = 0; symbolNumInString < len; symbolNumInString++) { | |
109 | digitNum = len - 1 - symbolNumInString; | |
110 | Digit theDigit = blk[digitNum]; | |
111 | if (theDigit < 10) | |
b3fe29df | 112 | s[symbolNumInString] = char('0' + theDigit); |
05780f4b | 113 | else |
b3fe29df | 114 | s[symbolNumInString] = char('A' + theDigit - 10); |
05780f4b | 115 | } |
b3fe29df | 116 | return std::string(s); |
05780f4b | 117 | } |