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@nathan-fiscaletti nathan-fiscaletti/Base.php
Last active Jul 23, 2019

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A class for manipulating and creating custom numeric formatting
<?php
/**
* Class used for converting between bases
* and custom bases using digit libraries.
*
* @see https://me.nathanf.tk/2019/05/02/creating-a-custom-numeric-base-in-php/
*
* @author Nathan Fiscaletti
*/
class Base
{
/**
* The library to use.
*
* @var array
*/
private $library = [];
/**
* The base to convert to.
*
* @var int
*/
private $base;
/**
* Construct the new BaseConverter.
*
* If base is 36 or below, the library
* for this base will be automatically
* loaded using [0-9][A-Z]. Otherwise,
* you need to load your own library
* using the setLibrary and putLibrary
* member functions.
*
* @param int $base The base to convert to.
*/
public function __construct(int $base)
{
$this->base = $base;
if ($base <= 36) {
$this->setLibraryToBase36();
}
}
/**
* Set the library to a specific library.
* This will override all existing libraries.
*
* @param array $library The new library.
*/
public function setLibrary(array $library)
{
$this->library = [-1 => $library];
}
/**
* Add a new library.
*
* @param array $library The new library.
* @param int $placement The placement to use for this library.
* For Base-10: 0 = 1s place, 1 = 10s place, ...
*/
public function putLibrary(array $library, int $placement = -1)
{
if (count($library) != $this->base) {
throw new \Exception(
'BaseConverter: Invalid library size. Not equal to base.'
);
}
$this->library[$placement] = $library;
return true;
}
/**
* Set the library to base-36 [0-9][a-z].
*/
private function setLibraryToBase36()
{
$this->setLibrary(
array_merge(
explode(' ', '0 1 2 3 4 5 6 7 8 9'),
range('a', 'z')
)
);
}
/**
* Convert a number to the base that this class uses.
*
* @param int $input The number to convert.
* @param int $maxDigits The maximum number of digits the
* resulting number may have.
*
* @return string The number converted to this base.
*/
public function parse(int $input, int $maxDigits = -1)
{
if (! array_key_exists(-1, $this->library)) {
throw new \Exception('Base: Missing default library.');
}
// Compile the indexs to retrieve from the library
// based on the information provided.
$compiled = $this->makeIndexes($input, $maxDigits);
// Retrieve the corresponding entries from
// the library to build the resulting string.
//
// Make sure each words has it's first letter
// set to Upper Case so that digits are
// distinct from one another.
$result = [];
foreach ($compiled as $placement => $compiledDigit) {
$result[] = ucfirst(
(
array_key_exists($placement, $this->library)
? $this->library[$placement][$compiledDigit]
: $this->library[-1 ][$compiledDigit]
)
);
}
// Return the result.
return implode('', array_reverse($result));
}
/**
* Converts a value using this base back to base-10.
*
* @param string $value The value to convert to base-10.
*
* @return number The resulting base-10 number.
*/
public function toBase10(string $value)
{
$pieces = preg_split('/(?=[A-Z0-9])/', $value);
$pieces = array_slice($pieces, 1, count($pieces) - 1);
$pieces = array_reverse($pieces);
$compiled = [];
foreach ($pieces as $placement => $digit) {
$digit = strtolower($digit);
$compiled[] = (
array_key_exists($placement, $this->library)
? array_search($digit, $this->library[$placement], true)
: array_search($digit, $this->library[-1 ], true)
);
}
$result = 0;
foreach ($compiled as $placement => $index)
{
$result += ($index*pow($this->base, $placement));
}
return $result;
}
/**
* Generate the indexes for a converted number based on this base.
*
* @param int $input The number to convert.
* @param int $maxDigits The maximum number of digits the
* resulting number may have.
*
* @return array The resulting indexes as an array in reverse order.
*/
private function makeIndexes(int $input, int $maxDigits = -1)
{
// Make sure our input isn't larger than the maxium
// number allowed based on maxDigits and base.
if ($input > pow($this->base, $maxDigits) && $maxDigits != -1) {
throw new \Exception(
'Base: Input is larger than maximum supported '.
'number based on library size and maximum digits.'
);
}
// Generate our compiled list of digits.
$compiled = [];
do {
$d = (int)($input / $this->base);
$r = $input % $this->base;
$compiled[] = $r;
$input = $d;
} while ($input >= $this->base);
if ($input > 0) {
$compiled[] = $input;
}
return $compiled;
}
/**
* Convert a string conforming to the format of this
* base to another base.
*
* @param string $val The value to convert.
* @param self|int $base The base to convert to.
*
* @return string The value.
*/
public function convert(string $val, $base)
{
if (! ($base instanceof self)) {
if (! is_int($base) || $base < 2 || $base > 36) {
throw new \Exception(
'Base: Inavlid base to convert to. '.
'Must be within range of 2 - 36 (inclusive).'
);
}
$base = new self($base);
}
return $base->parse(
$this->toBase10($val)
);
}
}
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