/** * Converts base-2, base-10, base-16, and binary strings (eg. base-256) to BigIntegers. * * If the second parameter - $base - is negative, then it will be assumed that the number's are encoded using * two's compliment. The sole exception to this is -10, which is treated the same as 10 is. * * Here's an example: * <code> * <?php * include('Math/BigInteger.php'); * * $a = new Math_BigInteger('0x32', 16); // 50 in base-16 * * echo $a->toString(); // outputs 50 * ?> * </code> * * @param string[optional] $x base-10 number or base-$base number if $base set. * @param integer[optional] $base * @return Math_BigInteger * @access public */ public function __construct($x = 0, $base = 10) { if (null === self::$mode) { switch (true) { case extension_loaded('gmp'): self::$mode = Math_BigInteger::MODE_GMP; break; case extension_loaded('bcmath'): self::$mode = Math_BigInteger::MODE_BCMATH; break; default: self::$mode = Math_BigInteger::MODE_INTERNAL; } } switch (self::$mode) { case Math_BigInteger::MODE_GMP: if (is_resource($x) && get_resource_type($x) == 'GMP integer') { $this->value = $x; return; } $this->value = gmp_init(0); break; case Math_BigInteger::MODE_BCMATH: $this->value = '0'; break; default: $this->value = array(); } if (empty($x)) { return; } switch ($base) { case -256: if (ord($x[0]) & 0x80) { $x = ~$x; $this->is_negative = true; } case 256: switch (self::$mode) { case Math_BigInteger::MODE_GMP: $sign = $this->is_negative ? '-' : ''; $this->value = gmp_init($sign . '0x' . bin2hex($x)); break; case Math_BigInteger::MODE_BCMATH: // round $len to the nearest 4 (thanks, DavidMJ!) $len = strlen($x) + 3 & 0xfffffffc; $x = str_pad($x, $len, chr(0), STR_PAD_LEFT); for ($i = 0; $i < $len; $i += 4) { $this->value = bcmul($this->value, '4294967296', 0); // 4294967296 == 2**32 $this->value = bcadd($this->value, 0x1000000 * ord($x[$i]) + (ord($x[$i + 1]) << 16 | ord($x[$i + 2]) << 8 | ord($x[$i + 3])), 0); } if ($this->is_negative) { $this->value = '-' . $this->value; } break; // converts a base-2**8 (big endian / msb) number to base-2**26 (little endian / lsb) // converts a base-2**8 (big endian / msb) number to base-2**26 (little endian / lsb) default: while (strlen($x)) { $this->value[] = $this->_bytes2int($this->_base256_rshift($x, 26)); } } if ($this->is_negative) { if (self::$mode != Math_BigInteger::MODE_INTERNAL) { $this->is_negative = false; } $temp = $this->add(new Math_BigInteger('-1')); $this->value = $temp->value; } break; case 16: case -16: if ($base > 0 && $x[0] == '-') { $this->is_negative = true; $x = substr($x, 1); } $x = preg_replace('#^(?:0x)?([A-Fa-f0-9]*).*#', '$1', $x); $is_negative = false; if ($base < 0 && hexdec($x[0]) >= 8) { $this->is_negative = $is_negative = true; $x = bin2hex(~pack('H*', $x)); } switch (self::$mode) { case Math_BigInteger::MODE_GMP: $temp = $this->is_negative ? '-0x' . $x : '0x' . $x; $this->value = gmp_init($temp); $this->is_negative = false; break; case Math_BigInteger::MODE_BCMATH: $x = strlen($x) & 1 ? '0' . $x : $x; $temp = new Math_BigInteger(pack('H*', $x), 256); $this->value = $this->is_negative ? '-' . $temp->value : $temp->value; $this->is_negative = false; break; default: $x = strlen($x) & 1 ? '0' . $x : $x; $temp = new Math_BigInteger(pack('H*', $x), 256); $this->value = $temp->value; } if ($is_negative) { $temp = $this->add(new Math_BigInteger('-1')); $this->value = $temp->value; } break; case 10: case -10: $x = preg_replace('#^(-?[0-9]*).*#', '$1', $x); switch (self::$mode) { case Math_BigInteger::MODE_GMP: $this->value = gmp_init($x); break; case Math_BigInteger::MODE_BCMATH: // explicitly casting $x to a string is necessary, here, since doing $x[0] on -1 yields different // results then doing it on '-1' does (modInverse does $x[0]) $this->value = (string) $x; break; default: $temp = new Math_BigInteger(); // array(10000000) is 10**7 in base-2**26. 10**7 is the closest to 2**26 we can get without passing it. $multiplier = new Math_BigInteger(); $multiplier->value = array(10000000); if ($x[0] == '-') { $this->is_negative = true; $x = substr($x, 1); } $x = str_pad($x, strlen($x) + 6 * strlen($x) % 7, 0, STR_PAD_LEFT); while (strlen($x)) { $temp = $temp->multiply($multiplier); $temp = $temp->add(new Math_BigInteger($this->_int2bytes(substr($x, 0, 7)), 256)); $x = substr($x, 7); } $this->value = $temp->value; } break; case 2: // base-2 support originally implemented by Lluis Pamies - thanks! // base-2 support originally implemented by Lluis Pamies - thanks! case -2: if ($base > 0 && $x[0] == '-') { $this->is_negative = true; $x = substr($x, 1); } $x = preg_replace('#^([01]*).*#', '$1', $x); $x = str_pad($x, strlen($x) + 3 * strlen($x) % 4, 0, STR_PAD_LEFT); $str = '0x'; while (strlen($x)) { $part = substr($x, 0, 4); $str .= dechex(bindec($part)); $x = substr($x, 4); } if ($this->is_negative) { $str = '-' . $str; } $temp = new Math_BigInteger($str, 8 * $base); // ie. either -16 or +16 $this->value = $temp->value; $this->is_negative = $temp->is_negative; break; default: // base not supported, so we'll let $this == 0 } }