| 1 | /* |
| 2 | * Matt McCutchen's Big Integer Library |
| 3 | * http://mysite.verizon.net/mccutchen/bigint/ |
| 4 | */ |
| 5 | |
| 6 | #include "BigUnsigned.hh" |
| 7 | |
| 8 | // The "management" routines that used to be here are now in NumberlikeArray.hh. |
| 9 | |
| 10 | /* |
| 11 | * The steps for construction of a BigUnsigned |
| 12 | * from an integral value x are as follows: |
| 13 | * 1. If x is zero, create an empty BigUnsigned and stop. |
| 14 | * 2. If x is negative, throw an exception. |
| 15 | * 3. Allocate a one-block number array. |
| 16 | * 4. If x is of a signed type, convert x to the unsigned |
| 17 | * type of the same length. |
| 18 | * 5. Expand x to a Blk, and store it in the number array. |
| 19 | * |
| 20 | * Since 2005.01.06, NumberlikeArray uses `NULL' rather |
| 21 | * than a real array if one of zero length is needed. |
| 22 | * These constructors implicitly call NumberlikeArray's |
| 23 | * default constructor, which sets `blk = NULL, cap = len = 0'. |
| 24 | * So if the input number is zero, they can just return. |
| 25 | * See remarks in `NumberlikeArray.hh'. |
| 26 | */ |
| 27 | |
| 28 | BigUnsigned::BigUnsigned(unsigned long x) { |
| 29 | if (x == 0) |
| 30 | ; // NumberlikeArray already did all the work |
| 31 | else { |
| 32 | cap = 1; |
| 33 | blk = new Blk[1]; |
| 34 | len = 1; |
| 35 | blk[0] = Blk(x); |
| 36 | } |
| 37 | } |
| 38 | |
| 39 | BigUnsigned::BigUnsigned(long x) { |
| 40 | if (x == 0) |
| 41 | ; |
| 42 | else if (x > 0) { |
| 43 | cap = 1; |
| 44 | blk = new Blk[1]; |
| 45 | len = 1; |
| 46 | blk[0] = Blk(x); |
| 47 | } else |
| 48 | throw "BigUnsigned::BigUnsigned(long): Cannot construct a BigUnsigned from a negative number"; |
| 49 | } |
| 50 | |
| 51 | BigUnsigned::BigUnsigned(unsigned int x) { |
| 52 | if (x == 0) |
| 53 | ; |
| 54 | else { |
| 55 | cap = 1; |
| 56 | blk = new Blk[1]; |
| 57 | len = 1; |
| 58 | blk[0] = Blk(x); |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | BigUnsigned::BigUnsigned(int x) { |
| 63 | if (x == 0) |
| 64 | ; |
| 65 | else if (x > 0) { |
| 66 | cap = 1; |
| 67 | blk = new Blk[1]; |
| 68 | len = 1; |
| 69 | blk[0] = Blk(x); |
| 70 | } else |
| 71 | throw "BigUnsigned::BigUnsigned(int): Cannot construct a BigUnsigned from a negative number"; |
| 72 | } |
| 73 | |
| 74 | BigUnsigned::BigUnsigned(unsigned short x) { |
| 75 | if (x == 0) |
| 76 | ; |
| 77 | else { |
| 78 | cap = 1; |
| 79 | blk = new Blk[1]; |
| 80 | len = 1; |
| 81 | blk[0] = Blk(x); |
| 82 | } |
| 83 | } |
| 84 | |
| 85 | BigUnsigned::BigUnsigned(short x) { |
| 86 | if (x == 0) |
| 87 | ; |
| 88 | else if (x > 0) { |
| 89 | cap = 1; |
| 90 | blk = new Blk[1]; |
| 91 | len = 1; |
| 92 | blk[0] = Blk(x); |
| 93 | } else |
| 94 | throw "BigUnsigned::BigUnsigned(short): Cannot construct a BigUnsigned from a negative number"; |
| 95 | } |
| 96 | |
| 97 | // CONVERTERS |
| 98 | /* |
| 99 | * The steps for conversion of a BigUnsigned to an |
| 100 | * integral type are as follows: |
| 101 | * 1. If the BigUnsigned is zero, return zero. |
| 102 | * 2. If it is more than one block long or its lowest |
| 103 | * block has bits set out of the range of the target |
| 104 | * type, throw an exception. |
| 105 | * 3. Otherwise, convert the lowest block to the |
| 106 | * target type and return it. |
| 107 | */ |
| 108 | |
| 109 | namespace { |
| 110 | // These masks are used to test whether a Blk has bits |
| 111 | // set out of the range of a smaller integral type. Note |
| 112 | // that this range is not considered to include the sign bit. |
| 113 | const BigUnsigned::Blk lMask = ~0 >> 1; |
| 114 | const BigUnsigned::Blk uiMask = (unsigned int)(~0); |
| 115 | const BigUnsigned::Blk iMask = uiMask >> 1; |
| 116 | const BigUnsigned::Blk usMask = (unsigned short)(~0); |
| 117 | const BigUnsigned::Blk sMask = usMask >> 1; |
| 118 | } |
| 119 | |
| 120 | BigUnsigned::operator unsigned long() const { |
| 121 | if (len == 0) |
| 122 | return 0; |
| 123 | else if (len == 1) |
| 124 | return (unsigned long) blk[0]; |
| 125 | else |
| 126 | throw "BigUnsigned::operator unsigned long: Value is too big for an unsigned long"; |
| 127 | } |
| 128 | |
| 129 | BigUnsigned::operator long() const { |
| 130 | if (len == 0) |
| 131 | return 0; |
| 132 | else if (len == 1 && (blk[0] & lMask) == blk[0]) |
| 133 | return (long) blk[0]; |
| 134 | else |
| 135 | throw "BigUnsigned::operator long: Value is too big for a long"; |
| 136 | } |
| 137 | |
| 138 | BigUnsigned::operator unsigned int() const { |
| 139 | if (len == 0) |
| 140 | return 0; |
| 141 | else if (len == 1 && (blk[0] & uiMask) == blk[0]) |
| 142 | return (unsigned int) blk[0]; |
| 143 | else |
| 144 | throw "BigUnsigned::operator unsigned int: Value is too big for an unsigned int"; |
| 145 | } |
| 146 | |
| 147 | BigUnsigned::operator int() const { |
| 148 | if (len == 0) |
| 149 | return 0; |
| 150 | else if (len == 1 && (blk[0] & iMask) == blk[0]) |
| 151 | return (int) blk[0]; |
| 152 | else |
| 153 | throw "BigUnsigned::operator int: Value is too big for an int"; |
| 154 | } |
| 155 | |
| 156 | BigUnsigned::operator unsigned short() const { |
| 157 | if (len == 0) |
| 158 | return 0; |
| 159 | else if (len == 1 && (blk[0] & usMask) == blk[0]) |
| 160 | return (unsigned short) blk[0]; |
| 161 | else |
| 162 | throw "BigUnsigned::operator unsigned short: Value is too big for an unsigned short"; |
| 163 | } |
| 164 | |
| 165 | BigUnsigned::operator short() const { |
| 166 | if (len == 0) |
| 167 | return 0; |
| 168 | else if (len == 1 && (blk[0] & sMask) == blk[0]) |
| 169 | return (short) blk[0]; |
| 170 | else |
| 171 | throw "BigUnsigned::operator short: Value is too big for a short"; |
| 172 | } |
| 173 | |
| 174 | // COMPARISON |
| 175 | BigUnsigned::CmpRes BigUnsigned::compareTo(const BigUnsigned &x) const { |
| 176 | // A bigger length implies a bigger number. |
| 177 | if (len < x.len) |
| 178 | return less; |
| 179 | else if (len > x.len) |
| 180 | return greater; |
| 181 | else { |
| 182 | // Compare blocks one by one from left to right. |
| 183 | Index i = len; |
| 184 | while (i > 0) { |
| 185 | i--; |
| 186 | if (blk[i] == x.blk[i]) |
| 187 | continue; |
| 188 | else if (blk[i] > x.blk[i]) |
| 189 | return greater; |
| 190 | else |
| 191 | return less; |
| 192 | } |
| 193 | // If no blocks differed, the numbers are equal. |
| 194 | return equal; |
| 195 | } |
| 196 | } |
| 197 | |
| 198 | // PUT-HERE OPERATIONS |
| 199 | |
| 200 | // Addition |
| 201 | void BigUnsigned::add(const BigUnsigned &a, const BigUnsigned &b) { |
| 202 | // Block unsafe calls |
| 203 | if (this == &a || this == &b) |
| 204 | throw "BigUnsigned::add: One of the arguments is the invoked object"; |
| 205 | // If one argument is zero, copy the other. |
| 206 | if (a.len == 0) { |
| 207 | operator =(b); |
| 208 | return; |
| 209 | } else if (b.len == 0) { |
| 210 | operator =(a); |
| 211 | return; |
| 212 | } |
| 213 | // Carries in and out of an addition stage |
| 214 | bool carryIn, carryOut; |
| 215 | Blk temp; |
| 216 | Index i; |
| 217 | // a2 points to the longer input, b2 points to the shorter |
| 218 | const BigUnsigned *a2, *b2; |
| 219 | if (a.len >= b.len) { |
| 220 | a2 = &a; |
| 221 | b2 = &b; |
| 222 | } else { |
| 223 | a2 = &b; |
| 224 | b2 = &a; |
| 225 | } |
| 226 | // Set prelimiary length and make room in this BigUnsigned |
| 227 | len = a2->len + 1; |
| 228 | allocate(len); |
| 229 | // For each block index that is present in both inputs... |
| 230 | for (i = 0, carryIn = false; i < b2->len; i++) { |
| 231 | // Add input blocks |
| 232 | temp = a2->blk[i] + b2->blk[i]; |
| 233 | // If a rollover occurred, the result is less than either input. |
| 234 | // This test is used many times in the BigUnsigned code. |
| 235 | carryOut = (temp < a2->blk[i]); |
| 236 | // If a carry was input, handle it |
| 237 | if (carryIn) { |
| 238 | temp++; |
| 239 | carryOut |= (temp == 0); |
| 240 | } |
| 241 | blk[i] = temp; // Save the addition result |
| 242 | carryIn = carryOut; // Pass the carry along |
| 243 | } |
| 244 | // If there is a carry left over, increase blocks until |
| 245 | // one does not roll over. |
| 246 | for (; i < a2->len && carryIn; i++) { |
| 247 | temp = a2->blk[i] + 1; |
| 248 | carryIn = (temp == 0); |
| 249 | blk[i] = temp; |
| 250 | } |
| 251 | // If the carry was resolved but the larger number |
| 252 | // still has blocks, copy them over. |
| 253 | for (; i < a2->len; i++) |
| 254 | blk[i] = a2->blk[i]; |
| 255 | // Set the extra block if there's still a carry, decrease length otherwise |
| 256 | if (carryIn) |
| 257 | blk[i] = 1; |
| 258 | else |
| 259 | len--; |
| 260 | } |
| 261 | |
| 262 | // Subtraction |
| 263 | void BigUnsigned::subtract(const BigUnsigned &a, const BigUnsigned &b) { |
| 264 | // Block unsafe calls |
| 265 | if (this == &a || this == &b) |
| 266 | throw "BigUnsigned::subtract: One of the arguments is the invoked object"; |
| 267 | // If b is zero, copy a. If a is shorter than b, the result is negative. |
| 268 | if (b.len == 0) { |
| 269 | operator =(a); |
| 270 | return; |
| 271 | } else if (a.len < b.len) |
| 272 | throw "BigUnsigned::subtract: Negative result in unsigned calculation"; |
| 273 | bool borrowIn, borrowOut; |
| 274 | Blk temp; |
| 275 | Index i; |
| 276 | // Set preliminary length and make room |
| 277 | len = a.len; |
| 278 | allocate(len); |
| 279 | // For each block index that is present in both inputs... |
| 280 | for (i = 0, borrowIn = false; i < b.len; i++) { |
| 281 | temp = a.blk[i] - b.blk[i]; |
| 282 | // If a reverse rollover occurred, the result is greater than the block from a. |
| 283 | borrowOut = (temp > a.blk[i]); |
| 284 | // Handle an incoming borrow |
| 285 | if (borrowIn) { |
| 286 | borrowOut |= (temp == 0); |
| 287 | temp--; |
| 288 | } |
| 289 | blk[i] = temp; // Save the subtraction result |
| 290 | borrowIn = borrowOut; // Pass the borrow along |
| 291 | } |
| 292 | // If there is a borrow left over, decrease blocks until |
| 293 | // one does not reverse rollover. |
| 294 | for (; i < a.len && borrowIn; i++) { |
| 295 | borrowIn = (a.blk[i] == 0); |
| 296 | blk[i] = a.blk[i] - 1; |
| 297 | } |
| 298 | // If there's still a borrow, the result is negative. |
| 299 | // Throw an exception, but zero out this object first just in case. |
| 300 | if (borrowIn) { |
| 301 | len = 0; |
| 302 | throw "BigUnsigned::subtract: Negative result in unsigned calculation"; |
| 303 | } else // Copy over the rest of the blocks |
| 304 | for (; i < a.len; i++) |
| 305 | blk[i] = a.blk[i]; |
| 306 | // Zap leading zeros |
| 307 | zapLeadingZeros(); |
| 308 | } |
| 309 | |
| 310 | // Multiplication |
| 311 | void BigUnsigned::multiply(const BigUnsigned &a, const BigUnsigned &b) { |
| 312 | // Block unsafe calls |
| 313 | if (this == &a || this == &b) |
| 314 | throw "BigUnsigned::multiply: One of the arguments is the invoked object"; |
| 315 | // If either a or b is zero, set to zero. |
| 316 | if (a.len == 0 || b.len == 0) { |
| 317 | len = 0; |
| 318 | return; |
| 319 | } |
| 320 | // Overall method: this = 0, then for each 1-bit of a, add b |
| 321 | // to this shifted the appropriate amount. |
| 322 | // Variables for the calculation |
| 323 | Index i, j, k; |
| 324 | unsigned int i2; |
| 325 | Blk aBlk, bHigh, temp; |
| 326 | bool carryIn, carryOut; |
| 327 | // Set preliminary length and make room |
| 328 | len = a.len + b.len; |
| 329 | allocate(len); |
| 330 | // Zero out this object |
| 331 | for (i = 0; i < len; i++) |
| 332 | blk[i] = 0; |
| 333 | // For each block of the first number... |
| 334 | for (i = 0; i < a.len; i++) { |
| 335 | // For each 1-bit of that block... |
| 336 | for (i2 = 0, aBlk = a.blk[i]; aBlk != 0; i2++, aBlk >>= 1) { |
| 337 | if ((aBlk & 1) == 0) |
| 338 | continue; |
| 339 | /* Add b to this, shifted left i blocks and i2 bits. |
| 340 | * j is the index in b, and k = i + j is the index in this. |
| 341 | * The low bits of b.blk[j] are shifted and added to blk[k]. |
| 342 | * bHigh is used to carry the high bits to the next addition. */ |
| 343 | bHigh = 0; |
| 344 | for (j = 0, k = i, carryIn = false; j < b.len; j++, k++) { |
| 345 | temp = blk[k] + ((b.blk[j] << i2) | bHigh); |
| 346 | carryOut = (temp < blk[k]); |
| 347 | if (carryIn) { |
| 348 | temp++; |
| 349 | carryOut |= (temp == 0); |
| 350 | } |
| 351 | blk[k] = temp; |
| 352 | carryIn = carryOut; |
| 353 | bHigh = (i2 == 0) ? 0 : b.blk[j] >> (8 * sizeof(Blk) - i2); |
| 354 | } |
| 355 | temp = blk[k] + bHigh; |
| 356 | carryOut = (temp < blk[k]); |
| 357 | if (carryIn) { |
| 358 | temp++; |
| 359 | carryOut |= (temp == 0); |
| 360 | } |
| 361 | blk[k] = temp; |
| 362 | carryIn = carryOut; |
| 363 | k++; // Added by Matt 2004.12.23: Move to the next block. It belongs here (and there was a corresponding line in the division routine), but I'm not certain whether it ever matters. |
| 364 | for (; carryIn; k++) { |
| 365 | blk[k]++; |
| 366 | carryIn = (blk[k] == 0); |
| 367 | } |
| 368 | } |
| 369 | } |
| 370 | // Zap possible leading zero |
| 371 | if (blk[len - 1] == 0) |
| 372 | len--; |
| 373 | } |
| 374 | |
| 375 | /* |
| 376 | * DIVISION WITH REMAINDER |
| 377 | * The functionality of divide, modulo, and %= is included in this one monstrous call, |
| 378 | * which deserves some explanation. |
| 379 | * |
| 380 | * The division *this / b is performed. |
| 381 | * Afterwards, q has the quotient, and *this has the remainder. |
| 382 | * Thus, a call is like q = *this / b, *this %= b. |
| 383 | * |
| 384 | * This seemingly bizarre pattern of inputs and outputs has a justification. The |
| 385 | * ``put-here operations'' are supposed to be fast. Therefore, they accept inputs |
| 386 | * and provide outputs in the most convenient places so that no value ever needs |
| 387 | * to be copied in its entirety. That way, the client can perform exactly the |
| 388 | * copying it needs depending on where the inputs are and where it wants the output. |
| 389 | */ |
| 390 | void BigUnsigned::divideWithRemainder(const BigUnsigned &b, BigUnsigned &q) { |
| 391 | // Block unsafe calls |
| 392 | if (this == &b || &q == &b || this == &q) |
| 393 | throw "BigUnsigned::divideWithRemainder: Some two objects involved are the same"; |
| 394 | |
| 395 | /* |
| 396 | * Note that the mathematical definition of mod (I'm trusting Knuth) is somewhat |
| 397 | * different from the way the normal C++ % operator behaves in the case of division by 0. |
| 398 | * This function does it Knuth's way. |
| 399 | * |
| 400 | * We let a / 0 == 0 (it doesn't matter) and a % 0 == a, no exceptions thrown. |
| 401 | * This allows us to preserve both Knuth's demand that a mod 0 == a |
| 402 | * and the useful property that (a / b) * b + (a % b) == a. |
| 403 | */ |
| 404 | if (b.len == 0) { |
| 405 | q.len = 0; |
| 406 | return; |
| 407 | } |
| 408 | |
| 409 | /* |
| 410 | * If *this.len < b.len, then *this < b, and we can be sure that b doesn't go into |
| 411 | * *this at all. The quotient is 0 and *this is already the remainder (so leave it alone). |
| 412 | */ |
| 413 | if (len < b.len) { |
| 414 | q.len = 0; |
| 415 | return; |
| 416 | } |
| 417 | |
| 418 | /* |
| 419 | * At this point we know *this > b > 0. (Whew!) |
| 420 | */ |
| 421 | |
| 422 | /* DEBUG * |
| 423 | std::cout << "divideWithRemainder starting\n" |
| 424 | << "length of dividend: " << len |
| 425 | << "\nlast block of dividend: " << getBlock(0) |
| 426 | << "\nlength of divisor: " << b.len |
| 427 | << "\nlast block of divisor: " << b.getBlock(0) |
| 428 | << std::endl; */ |
| 429 | |
| 430 | /* |
| 431 | * Overall method: Subtract b, shifted varying amounts to |
| 432 | * the left, from this, setting the bit in the quotient q |
| 433 | * whenever the subtraction succeeds. Eventually q will contain the entire |
| 434 | * quotient, and this will be left with the remainder. |
| 435 | * |
| 436 | * We use work2 to temporarily store the result of a subtraction. |
| 437 | * But we don't even compute the i lowest blocks of the result, |
| 438 | * because they are unaffected (we shift left i places). |
| 439 | * */ |
| 440 | // Variables for the calculation |
| 441 | Index i, j, k; |
| 442 | unsigned int i2; |
| 443 | Blk bHigh, temp; |
| 444 | bool borrowIn, borrowOut; |
| 445 | |
| 446 | // Make sure we have an extra zero block just past the value, |
| 447 | // but don't increase the logical length. A shifted subtraction |
| 448 | // (for example, subtracting 1 << 2 from 4) might stick into |
| 449 | // this block. |
| 450 | allocateAndCopy(len + 1); |
| 451 | blk[len] = 0; |
| 452 | |
| 453 | // work2 holds part of the result of a subtraction. |
| 454 | // (There's no work1. The name work2 is from a previous version.) |
| 455 | Blk *work2 = new Blk[len]; |
| 456 | |
| 457 | // Set preliminary length for quotient and make room |
| 458 | q.len = len - b.len + 1; |
| 459 | q.allocate(q.len); |
| 460 | // Zero out the quotient |
| 461 | for (i = 0; i < q.len; i++) |
| 462 | q.blk[i] = 0; |
| 463 | |
| 464 | // For each possible left-shift of b in blocks... |
| 465 | i = q.len; |
| 466 | while (i > 0) { |
| 467 | i--; |
| 468 | // For each possible left-shift of b in bits... |
| 469 | q.blk[i] = 0; |
| 470 | i2 = 8 * sizeof(Blk); |
| 471 | while (i2 > 0) { |
| 472 | i2--; |
| 473 | /* |
| 474 | * Subtract b, shifted left i blocks and i2 bits, from this. |
| 475 | * and store the answer in work2. |
| 476 | * |
| 477 | * Compare this to the middle section of `multiply'. They |
| 478 | * are in many ways analogous. |
| 479 | */ |
| 480 | bHigh = 0; |
| 481 | for (j = 0, k = i, borrowIn = false; j < b.len; j++, k++) { |
| 482 | temp = blk[k] - ((b.blk[j] << i2) | bHigh); |
| 483 | borrowOut = (temp > blk[k]); |
| 484 | if (borrowIn) { |
| 485 | borrowOut |= (temp == 0); |
| 486 | temp--; |
| 487 | } |
| 488 | work2[j] = temp; |
| 489 | borrowIn = borrowOut; |
| 490 | bHigh = (i2 == 0) ? 0 : b.blk[j] >> (8 * sizeof(Blk) - i2); |
| 491 | } |
| 492 | temp = blk[k] - bHigh; |
| 493 | borrowOut = (temp > blk[k]); |
| 494 | if (borrowIn) { |
| 495 | borrowOut |= (temp == 0); |
| 496 | temp--; |
| 497 | } |
| 498 | work2[j] = temp; |
| 499 | borrowIn = borrowOut; |
| 500 | j++; |
| 501 | k++; |
| 502 | for (; k < len && borrowIn; j++, k++) { |
| 503 | borrowIn = (blk[k] == 0); |
| 504 | work2[j] = blk[k] - 1; |
| 505 | } |
| 506 | /* If the subtraction was performed successfully (!borrowIn), set bit i2 |
| 507 | * in block i of the quotient, and copy the changed portion of |
| 508 | * work2 back to this. Otherwise, reset that bit and move on. */ |
| 509 | if (!borrowIn) { |
| 510 | q.blk[i] |= (1 << i2); |
| 511 | while (j > 0) { |
| 512 | j--; |
| 513 | k--; |
| 514 | blk[k] = work2[j]; |
| 515 | } |
| 516 | } |
| 517 | } |
| 518 | } |
| 519 | // Zap possible leading zero in quotient |
| 520 | if (q.blk[q.len - 1] == 0) |
| 521 | q.len--; |
| 522 | // Zap any/all leading zeros in remainder |
| 523 | zapLeadingZeros(); |
| 524 | // Deallocate temporary array. |
| 525 | // (Thanks to Brad Spencer for noticing my accidental omission of this!) |
| 526 | delete [] work2; |
| 527 | |
| 528 | /* DEBUG * |
| 529 | std::cout << "divideWithRemainder complete\n" |
| 530 | << "length of quotient: " << q.len |
| 531 | << "\nlast block of quotient: " << q.getBlock(0) |
| 532 | << "\nlength of remainder: " << len |
| 533 | << "\nlast block of remainder: " << getBlock(0) |
| 534 | << std::endl; */ |
| 535 | } |
| 536 | |
| 537 | // Bitwise and |
| 538 | void BigUnsigned::bitAnd(const BigUnsigned &a, const BigUnsigned &b) { |
| 539 | // Block unsafe calls |
| 540 | if (this == &a || this == &b) |
| 541 | throw "BigUnsigned::bitAnd: One of the arguments is the invoked object"; |
| 542 | len = (a.len >= b.len) ? b.len : a.len; |
| 543 | allocate(len); |
| 544 | Index i; |
| 545 | for (i = 0; i < len; i++) |
| 546 | blk[i] = a.blk[i] & b.blk[i]; |
| 547 | zapLeadingZeros(); |
| 548 | } |
| 549 | |
| 550 | // Bitwise or |
| 551 | void BigUnsigned::bitOr(const BigUnsigned &a, const BigUnsigned &b) { |
| 552 | // Block unsafe calls |
| 553 | if (this == &a || this == &b) |
| 554 | throw "BigUnsigned::bitOr: One of the arguments is the invoked object"; |
| 555 | Index i; |
| 556 | const BigUnsigned *a2, *b2; |
| 557 | if (a.len >= b.len) { |
| 558 | a2 = &a; |
| 559 | b2 = &b; |
| 560 | } else { |
| 561 | a2 = &b; |
| 562 | b2 = &a; |
| 563 | } |
| 564 | allocate(a2->len); |
| 565 | for (i = 0; i < b2->len; i++) |
| 566 | blk[i] = a2->blk[i] | b2->blk[i]; |
| 567 | for (; i < a2->len; i++) |
| 568 | blk[i] = a2->blk[i]; |
| 569 | len = a2->len; |
| 570 | } |
| 571 | |
| 572 | // Bitwise xor |
| 573 | void BigUnsigned::bitXor(const BigUnsigned &a, const BigUnsigned &b) { |
| 574 | // Block unsafe calls |
| 575 | if (this == &a || this == &b) |
| 576 | throw "BigUnsigned::bitXor: One of the arguments is the invoked object"; |
| 577 | Index i; |
| 578 | const BigUnsigned *a2, *b2; |
| 579 | if (a.len >= b.len) { |
| 580 | a2 = &a; |
| 581 | b2 = &b; |
| 582 | } else { |
| 583 | a2 = &b; |
| 584 | b2 = &a; |
| 585 | } |
| 586 | allocate(b2->len); |
| 587 | for (i = 0; i < b2->len; i++) |
| 588 | blk[i] = a2->blk[i] ^ b2->blk[i]; |
| 589 | for (; i < a2->len; i++) |
| 590 | blk[i] = a2->blk[i]; |
| 591 | len = a2->len; |
| 592 | zapLeadingZeros(); |
| 593 | } |
| 594 | |
| 595 | // INCREMENT/DECREMENT OPERATORS |
| 596 | |
| 597 | // Prefix increment |
| 598 | void BigUnsigned::operator ++() { |
| 599 | Index i; |
| 600 | bool carry = true; |
| 601 | for (i = 0; i < len && carry; i++) { |
| 602 | blk[i]++; |
| 603 | carry = (blk[i] == 0); |
| 604 | } |
| 605 | if (carry) { |
| 606 | // Matt fixed a bug 2004.12.24: next 2 lines used to say allocateAndCopy(len + 1) |
| 607 | len++; |
| 608 | allocateAndCopy(len); |
| 609 | blk[i] = 1; |
| 610 | } |
| 611 | } |
| 612 | |
| 613 | // Postfix increment: same as prefix |
| 614 | void BigUnsigned::operator ++(int) { |
| 615 | operator ++(); |
| 616 | } |
| 617 | |
| 618 | // Prefix decrement |
| 619 | void BigUnsigned::operator --() { |
| 620 | if (len == 0) |
| 621 | throw "BigUnsigned::operator --(): Cannot decrement an unsigned zero"; |
| 622 | Index i; |
| 623 | bool borrow = true; |
| 624 | for (i = 0; borrow; i++) { |
| 625 | borrow = (blk[i] == 0); |
| 626 | blk[i]--; |
| 627 | } |
| 628 | // Zap possible leading zero (there can only be one) |
| 629 | if (blk[len - 1] == 0) |
| 630 | len--; |
| 631 | } |
| 632 | |
| 633 | // Postfix decrement: same as prefix |
| 634 | void BigUnsigned::operator --(int) { |
| 635 | operator --(); |
| 636 | } |