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Read handler requirements

A read handler must meet the requirements for a handler. A value h of a read handler class should work correctly in the expression h(ec, s), where ec is an lvalue of type const error_code and s is an lvalue of type const size_t.

Examples

A free function as a read handler:

void read_handler(
    const boost::system::error_code& ec,
    std::size_t bytes_transferred)
{
  ...
}

A read handler function object:

struct read_handler
{
  ...
  void operator()(
      const boost::system::error_code& ec,
      std::size_t bytes_transferred)
  {
    ...
  }
  ...
};

A non-static class member function adapted to a read handler using bind():

void my_class::read_handler(
    const boost::system::error_code& ec,
    std::size_t bytes_transferred)
{
  ...
}
...
socket.async_read(...,
    boost::bind(&my_class::read_handler,
      this, boost::asio::placeholders::error,
      boost::asio::placeholders::bytes_transferred));

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