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The Standard Template Library overloads its built-in swap function to exchange the contents of containers efficiently this way. [1] As pointer variables are usually of a fixed size (e.g., most desktop computers have pointers 64 bits long), and they are numeric, they can be swapped quickly using XOR swap.
Using the XOR swap algorithm to exchange nibbles between variables without the use of temporary storage. In computer programming, the exclusive or swap (sometimes shortened to XOR swap) is an algorithm that uses the exclusive or bitwise operation to swap the values of two variables without using the temporary variable which is normally required.
For its operation, it requires two operands. It shifts each bit in its left operand to the right. The number following the operator decides the number of places the bits are shifted (i.e. the right operand). Thus by doing ch >> 3 all the bits will be shifted to the right by three places and so on.
An autorelative pointer is a pointer whose value is interpreted as an offset from the address of the pointer itself; thus, if a data structure has an autorelative pointer member that points to some portion of the data structure itself, then the data structure may be relocated in memory without having to update the value of the auto relative ...
Because in this program, swap operates on pointers and cannot change the pointers themselves, but only the values the pointers point to, this view holds that C's main evaluation strategy is more similar to call-by-sharing. C++ confuses the issue further by allowing swap to be declared and used with a very lightweight "reference" syntax: [50]
On many common platforms, this use of pointer punning can create problems if different pointers are aligned in machine-specific ways. Furthermore, pointers of different sizes can alias accesses to the same memory, causing problems that are unchecked by the compiler. Even when data size and pointer representation match, however, compilers can ...
Single compare, double swap Compares one pointer but writes two. The Itanium's cmp8xchg16 instruction implements this, [15] where the two written pointers are adjacent. Multi-word compare-and-swap Is a generalisation of normal compare-and-swap. It can be used to atomically swap an arbitrary number of arbitrarily located memory locations.
The A::max_size() member function returns the largest number of objects of type T that could be expected to be successfully allocated by an invocation of A::allocate; the value returned is typically A::size_type(-1) / sizeof(T). [14] Also, the A::address member function returns an A::pointer denoting the address of an object, given an A::reference.