Handlers

A handler must meet the requirements of CopyConstructible types (C++ Std, 20.1.3).

In the table below, X denotes a handler class, h denotes a value of X, p denotes a pointer to a block of allocated memory of type void*, s denotes the size for a block of allocated memory, and f denotes a function object taking no arguments.

Table 15. Handler requirements

expression	return type	assertion/note pre/post-conditions
using asio::asio_handler_allocate; asio_handler_allocate(s, &h);	`void*`	Returns a pointer to a block of memory of size `s`. The pointer must satisfy the same alignment requirements as a pointer returned by `::operator new()`. Throws `bad_alloc` on failure. The `asio_handler_allocate()` function is located using argument-dependent lookup. The function `asio::asio_handler_allocate()` serves as a default if no user-supplied function is available.
using asio::asio_handler_deallocate; asio_handler_deallocate(p, s, &h);		Frees a block of memory associated with a pointer `p`, of at least size `s`, that was previously allocated using `asio_handler_allocate()`. The `asio_handler_deallocate()` function is located using argument-dependent lookup. The function `asio::asio_handler_deallocate()` serves as a default if no user-supplied function is available.
using asio::asio_handler_invoke; asio_handler_invoke(f, &h);		Causes the function object `f` to be executed as if by calling `f()`. The `asio_handler_invoke()` function is located using argument-dependent lookup. The function `asio::asio_handler_invoke()` serves as a default if no user-supplied function is available.

expression

return type

assertion/note
pre/post-conditions

using asio::asio_handler_allocate;
asio_handler_allocate(s, &h);

void*

Returns a pointer to a block of memory of size s. The pointer must satisfy the same alignment requirements as a pointer returned by ::operator new(). Throws bad_alloc on failure.

The asio_handler_allocate() function is located using argument-dependent lookup. The function asio::asio_handler_allocate() serves as a default if no user-supplied function is available.

using asio::asio_handler_deallocate;
asio_handler_deallocate(p, s, &h);

Frees a block of memory associated with a pointer p, of at least size s, that was previously allocated using asio_handler_allocate().

The asio_handler_deallocate() function is located using argument-dependent lookup. The function asio::asio_handler_deallocate() serves as a default if no user-supplied function is available.

using asio::asio_handler_invoke;
asio_handler_invoke(f, &h);

Causes the function object f to be executed as if by calling f().

The asio_handler_invoke() function is located using argument-dependent lookup. The function asio::asio_handler_invoke() serves as a default if no user-supplied function is available.