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Start an asynchronous write.

    typename ConstBufferSequence,
    typename WriteToken = default_completion_token_t<executor_type>>
DEDUCED async_write_some(
    const ConstBufferSequence & buffers,
    WriteToken && token = default_completion_token_t< executor_type >());

This function is used to asynchronously write one or more bytes of data to the stream. It is an initiating function for an asynchronous operation, and always returns immediately.



The data to be written to the stream. Although the buffers object may be copied as necessary, ownership of the underlying buffers is retained by the caller, which must guarantee that they remain valid until the completion handler is called.


The completion token that will be used to produce a completion handler, which will be called when the write completes. Potential completion tokens include use_future, use_awaitable, yield_context, or a function object with the correct completion signature. The function signature of the completion handler must be:

void handler(
  const boost::system::error_code& error, // Result of operation.
  std::size_t bytes_transferred // Number of bytes written.

Regardless of whether the asynchronous operation completes immediately or not, the completion handler will not be invoked from within this function. On immediate completion, invocation of the handler will be performed in a manner equivalent to using post.

Completion Signature
void(boost::system::error_code, std::size_t)

The async_write_some operation may not transmit all of the data to the peer. Consider using the async_write function if you need to ensure that all data is written before the asynchronous operation completes.

Per-Operation Cancellation

This asynchronous operation supports cancellation for the following cancellation_type values:

if they are also supported by the Stream type's async_read_some and async_write_some operations.