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/**
* This file is part of the phpcommon/comparison package.
*
* (c) Marcos Passos <marcos@marcospassos.com>
*
* For the full copyright and license information, please view the LICENSE file
* that was distributed with this source code.
*/
namespace PhpCommon\Comparison\Hasher;
use PhpCommon\Comparison\Equatable;
use PhpCommon\Comparison\Hasher;
use PhpCommon\IntMath\IntMath as Math;
/**
* Provides an external means for producing hash codes and comparing values for
* identity.
*
* This equivalence relation uses the strict equal operator (`===`) to compare
* values, while hashing strategy varies according to the type of value.
*
* @author Marcos Passos <marcos@marcospassos.com>
*/
class IdentityHasher extends GenericHasher
{
/**
* Constant used to compute hash codes for `null`
*/
const HASH_NULL = 0;
/**
* Constant used to compute hash codes for arrays
*/
const HASH_ARRAY = 991;
/**
* The hash code for the boolean value `false`
*/
const HASH_FALSE = 1237;
/**
* The hash code for the boolean value `true`
*/
const HASH_TRUE = 1231;
/**
* Constant used to compute hash codes for objects
*/
const HASH_OBJECT = 1093;
/**
* Constant used to compute hash codes for resources
*/
const HASH_RESOURCE = 1471;
/**
* Constant used to compute hash codes for strings
*/
const HASH_STRING = 1321;
/**
* Checks whether the current relation is considered equal to another.
*
* Since this class is stateless, its instances will always be considered
* equal if they are of the same type.
*/
public function equals(Equatable $other)
{
return static::class === get_class($other);
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also an array and they both contain the same
* number of entries, in the same order and each pair of corresponding
* entries is equivalent according to this relation. Empty arrays are
* equivalent to one another.
*/
protected function equivalentArray(array $left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also a boolean and both are `true` or both are
* `false`.
*/
protected function equivalentBoolean($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also a float and they are numerically equal
* (have the same number value). Positive and negative zeros are equal
* to one another. {@link NAN} is not equal to anything, including
* {@link NAN}.
*/
protected function equivalentFloat($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also an integer and they are numerically equal
* (have the same number value). Positive and negative zeros are equal
* to one another.
*/
protected function equivalentInteger($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified value is considered equivalent to `null` if and only if it
* is strictly equal to `null`.
*/
protected function equivalentNull($right)
{
return null === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also an object and both are references to the
* same instance.
*/
protected function equivalentObject($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also a resource and both have the same unique
* resource number.
*/
protected function equivalentResource($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The specified values are considered equivalent if and only if the
* right-hand value is also a string and both have the same sequence of
* characters.
*/
protected function equivalentString($left, $right)
{
return $left === $right;
}
/**
* {@inheritdoc}
*
* The hash code is based on the _deep contents_ of the specified array.
* More precisely, it is computed as follows:
*
* ```php
* $hashCode = IdentityEquivalence::HASH_ARRAY;
* foreach ($array => $key => $element)
* $hashCode = 31 * $hashCode + (hash($key) ^ hash($element));
* ```
*
* Where `hash()` is a function that returns a hash code for a given value.
* Note that the hash code of an empty array is the constant
* {@link IdentityEquivalence::HASH_ARRAY} itself.
*/
protected function hashArray(array $value)
{
$hash = self::HASH_ARRAY;
foreach ($value as $key => $current) {
$keyHash = $this->hashString($key);
$valueHash = $this->hash($current);
$hash = $hash * 31 + ($keyHash ^ $valueHash);
}
return $hash;
}
/**
* {@inheritdoc}
*
* It is defined by mapping the values `true` and `false` to
* integer numbers defined by {@link IdentityEquivalence::HASH_TRUE} and
* {@link IdentityEquivalence::HASH_FALSE} respectively.
*/
protected function hashBoolean($value)
{
return $value ? self::HASH_TRUE : self::HASH_FALSE;
}
/**
* {@inheritdoc}
*
* It is computed by converting the float value to the integer bit
* representation, according to the IEEE 754 floating-point single format
* bit layout.
*
* @link https://pt.wikipedia.org/wiki/IEEE_754 IEEE Standard for
* Floating-Point Arithmetic.
*
*/
protected function hashFloat($value)
{
return unpack('i', pack('f', $value))[1];
}
/**
* {@inheritdoc}
*
* This method uses the integer number as the hash code itself.
*/
protected function hashInteger($value)
{
return $value;
}
/**
* {@inheritdoc}
*
* The hash code for `null` is a constant defined by
* {@link IdentityEquivalence::HASH_NULL}.
*/
protected function hashNull()
{
return self::HASH_NULL;
}
/**
* {@inheritdoc}
*
* The hash code is computed as follows:
*
* ```php
* $k = IdentityEquivalence::HASH_OBJECT;
* $hashCode = $k * hashString(spl_object_hash($object));
* ```
*
* Where {@link IdentityEquivalence::HASH_OBJECT} is a constant and
* `hashString()` is a function that returns a hash code for a given
* string.
*/
protected function hashObject($value)
{
return self::HASH_OBJECT * $this->hashString(spl_object_hash($value));
}
/**
* {@inheritdoc}
*
* The hash code is computed as follows:
*
* ```php
* $hashCode = IdentityEquivalence::HASH_STRING;
* for ($i = 0; $i < length($string); $i++)
* $hashCode = $hashCode * 31 + charCode($string[$i]);
* ```
*
* Where {@link IdentityEquivalence::HASH_STRING} is a constant, `$i` is
* the position of the current character in the string, `$string[$i]` is
* the ith character of the string, `length()` is a function that returns
* the length of the string, `charCode()` is a function that returns the
* ASCII code (as an integer) of a given character, and `^` indicates
* exponentiation. Note that the hash code of a zero length string is the
* constant {@link IdentityEquivalence::HASH_STRING} itself.
*/
protected function hashString($value)
{
$hash = self::HASH_STRING;
$value = strval($value);
$length = strlen($value);
if ($length === 0) {
return $hash;
}
for ($i = 0; $i < $length; $i++) {
$hash = Math::add(Math::multiply($hash, 31), ord($value[$i]));
}
return $hash;
}
/**
* {@inheritdoc}
*
* The hash code is computed as follows:
*
* ```php
* $k = IdentityEquivalence::HASH_RESOURCE;
* $hashCode = $k * (1 + resourceId($value));
* ```
*
* Where `$k` is a constant defined by
* {@link IdentityEquivalence::HASH_RESOURCE} and `resourceId()` is a
* function that returns the unique resource number assigned to the
* resource by PHP at runtime.
*/
protected function hashResource($value)
{
return self::HASH_RESOURCE * (1 + (int) $value);
}
}