| description | title | ms.date | f1_keywords | helpviewer_keywords | ms.assetid | ||
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Learn more about: reinterpret_cast Operator | reinterpret_cast Operator | 11/04/2016 |
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| eb3283c7-7f88-467e-affd-407d37b46d6c |
Allows any pointer to be converted into any other pointer type. Also allows any integral type to be converted into any pointer type and vice versa.
reinterpret_cast < type-id > ( expression ) Misuse of the reinterpret_cast operator can easily be unsafe. Unless the desired conversion is inherently low-level, you should use one of the other cast operators.
The reinterpret_cast operator can be used for conversions such as char* to int*, or One_class* to Unrelated_class*, which are inherently unsafe.
The result of a reinterpret_cast cannot safely be used for anything other than being cast back to its original type. Other uses are, at best, nonportable.
The reinterpret_cast operator cannot cast away the const, volatile, or __unaligned attributes. See const_cast Operator for information on removing these attributes.
The reinterpret_cast operator converts a null pointer value to the null pointer value of the destination type.
One practical use of reinterpret_cast is in a hash function, which maps a value to an index in such a way that two distinct values rarely end up with the same index.
#include<iostream>usingnamespacestd;// Returns a hash code based on an addressunsignedshortHash( void *p ) { unsignedint val = reinterpret_cast<unsignedint>( p ); return ( unsignedshort )( val ^ (val >> 16)); } usingnamespacestd;intmain() { int a[20]; for ( int i = 0; i < 20; i++ ) cout << Hash( a + i ) << endl; } Output: 6464164645648896489364881648856487364877648656486964857648616484964853648416484564833648376482564829The reinterpret_cast allows the pointer to be treated as an integral type. The result is then bit-shifted and XORed with itself to produce a unique index (unique to a high degree of probability). The index is then truncated by a standard C-style cast to the return type of the function.
