| 1 | /* |
| 2 | * Matt McCutchen's Big Integer Library |
| 3 | * http://hashproduct.metaesthetics.net/bigint/ |
| 4 | */ |
| 5 | |
| 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 | |
| 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 | |
| 33 | // Check the base |
| 34 | if (base < 2) |
| 35 | throw "BigUnsignedInABase(BigUnsigned, Base): The base must be at least 2"; |
| 36 | // Save the base. |
| 37 | // This pattern is seldom seen in C++, but the analogous ``this.'' is common in Java. |
| 38 | this->base = base; |
| 39 | |
| 40 | // Get an upper bound on how much space we need |
| 41 | int maxBitLenOfX = x.getLength() * BigUnsigned::N; |
| 42 | int minBitsPerDigit = bitLen(base) - 1; |
| 43 | int maxDigitLenOfX = ceilingDiv(maxBitLenOfX, minBitsPerDigit); |
| 44 | len = maxDigitLenOfX; // Another change to comply with `staying in bounds'; see `BigUnsigned::divideWithRemainder'. |
| 45 | allocate(len); // Get the space |
| 46 | |
| 47 | BigUnsigned x2(x), buBase(base); |
| 48 | Index digitNum = 0; |
| 49 | |
| 50 | while (!x2.isZero()) { |
| 51 | // Get last digit. This is like `lastDigit = x2 % buBase, x2 /= buBase'. |
| 52 | BigUnsigned lastDigit(x2); |
| 53 | lastDigit.divideWithRemainder(buBase, x2); |
| 54 | // Save the digit. |
| 55 | blk[digitNum] = Digit(lastDigit); // invokes `BigUnsigned ==> unsigned short' converter |
| 56 | // Move on. We can't run out of room: we figured it out above. |
| 57 | digitNum++; |
| 58 | } |
| 59 | |
| 60 | // Save the actual length. |
| 61 | len = digitNum; |
| 62 | } |
| 63 | |
| 64 | BigUnsignedInABase::operator BigUnsigned() const { |
| 65 | BigUnsigned ans(0), buBase(base), temp; |
| 66 | Index digitNum = len; |
| 67 | while (digitNum > 0) { |
| 68 | digitNum--; |
| 69 | temp.multiply(ans, buBase); |
| 70 | ans.add(temp, BigUnsigned(blk[digitNum])); |
| 71 | } |
| 72 | return ans; |
| 73 | } |
| 74 | |
| 75 | BigUnsignedInABase::BigUnsignedInABase(const std::string &s, Base base) { |
| 76 | // Check the base. |
| 77 | if (base > 36) |
| 78 | 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."; |
| 79 | // Save the base. |
| 80 | // This pattern is seldom seen in C++, but the analogous ``this.'' is common in Java. |
| 81 | this->base = base; |
| 82 | |
| 83 | // `s.length()' is a `size_t', while `len' is a `NumberlikeArray::Index', |
| 84 | // also known as an `unsigned int'. Some compilers warn without this cast. |
| 85 | len = Index(s.length()); |
| 86 | allocate(len); |
| 87 | |
| 88 | Index digitNum, symbolNumInString; |
| 89 | for (digitNum = 0; digitNum < len; digitNum++) { |
| 90 | symbolNumInString = len - 1 - digitNum; |
| 91 | char theSymbol = s[symbolNumInString]; |
| 92 | if (theSymbol >= '0' && theSymbol <= '9') |
| 93 | blk[digitNum] = theSymbol - '0'; |
| 94 | else if (theSymbol >= 'A' && theSymbol <= 'Z') |
| 95 | blk[digitNum] = theSymbol - 'A' + 10; |
| 96 | else if (theSymbol >= 'a' && theSymbol <= 'z') |
| 97 | blk[digitNum] = theSymbol - 'a' + 10; |
| 98 | else |
| 99 | throw "BigUnsignedInABase(std::string, Base): Bad symbol in input. Only 0-9, A-Z, a-z are accepted."; |
| 100 | } |
| 101 | zapLeadingZeros(); |
| 102 | } |
| 103 | |
| 104 | BigUnsignedInABase::operator std::string() const { |
| 105 | if (base > 36) |
| 106 | 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."; |
| 107 | if (len == 0) |
| 108 | return std::string("0"); |
| 109 | char *s = new char[len + 1]; |
| 110 | s[len] = '\0'; |
| 111 | Index digitNum, symbolNumInString; |
| 112 | for (symbolNumInString = 0; symbolNumInString < len; symbolNumInString++) { |
| 113 | digitNum = len - 1 - symbolNumInString; |
| 114 | Digit theDigit = blk[digitNum]; |
| 115 | if (theDigit < 10) |
| 116 | s[symbolNumInString] = char('0' + theDigit); |
| 117 | else |
| 118 | s[symbolNumInString] = char('A' + theDigit - 10); |
| 119 | } |
| 120 | std::string s2(s); |
| 121 | delete s; |
| 122 | return s2; |
| 123 | } |