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Start an asynchronous operation to parse an object from a stream.

    class AsyncReadStream,
    class DynamicBuffer,
    class Parser,
    class ReadHandler>
    AsyncReadStream& stream,
    DynamicBuffer& dynabuf,
    Parser& parser,
    ReadHandler&& handler);

This function is used to asynchronously read from a stream and pass the data to the specified parser. The function call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:

This operation is implemented in terms of one or more calls to the next layer's async_read_some function, and is known as a composed operation. The program must ensure that the stream performs no other operations until this operation completes. The implementation may read additional octets that lie past the end of the object being parsed. This additional data is stored in the stream buffer, which may be used in subsequent calls.



The stream from which the data is to be read. The type must support the AsyncReadStream concept.


A DynamicBuffer holding additional bytes read by the implementation from the stream. This is both an input and an output parameter; on entry, any data in the stream buffer's input sequence will be given to the parser first.


An object meeting the requirements of Parser which will receive the data. This object must remain valid until the completion handler is invoked.


The handler to be called when the request completes. Copies will be made of the handler as required. The equivalent function signature of the handler must be:

 void handler(
    error_code const& error // result of operation

Regardless of whether the asynchronous operation completes immediately or not, the handler will not be invoked from within this function. Invocation of the handler will be performed in a manner equivalent to using boost::asio::io_service::post.


Header: beast/http/parse.hpp

Convenience header: beast/http.hpp