Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Read a complete message header asynchronously from a stream using a parser.
Defined in header <boost/beast/http/read.hpp>
template< class AsyncReadStream, class DynamicBuffer, bool isRequest, class ReadHandler = net::default_completion_token_t< executor_type<AsyncReadStream>>> DEDUCED async_read_header( AsyncReadStream& stream, DynamicBuffer& buffer, basic_parser< isRequest >& parser, ReadHandler&& handler = net::default_completion_token_t< executor_type< AsyncReadStream >>{});
This function is used to asynchronously read a complete message header from
a stream into an instance of basic_parser. The function call
always returns immediately. The asynchronous operation will continue until
one of the following conditions is true:
basic_parser::is_header_done returns true
This operation is implemented in terms of zero 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 reads until this operation completes.
The implementation may read additional bytes from the stream that lie past
the end of the message being read. These additional bytes are stored in the
dynamic buffer, which must be preserved for subsequent reads. If the end
of file error is received while reading from the stream, then the error returned
from this function will be:
error::end_of_stream
if no bytes were parsed, or
error::partial_message
if any bytes were parsed but the message was incomplete, otherwise:
error::end_of_stream
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Name |
Description |
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The stream from which the data is to be read. The type must meet the AsyncReadStream requirements. |
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Storage for additional bytes read by the implementation from the stream. This is both an input and an output parameter; on entry, the parser will be presented with any remaining data in the dynamic buffer's readable bytes sequence first. The type must meet the DynamicBuffer requirements. The object must remain valid at least until the handler is called; ownership is not transferred. |
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The parser to use. The object must remain valid at least until the handler is called; ownership is not transferred. |
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The completion handler to invoke when the operation completes. The implementation takes ownership of the handler by performing a decay-copy. The equivalent function signature of the handler must be: void handler( error_code const& error, // result of operation std::size_t bytes_transferred // the total number of bytes transferred from the stream );
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 |
The completion handler will receive as a parameter the total number of bytes
transferred from the stream. This may be zero for the case where there is
sufficient pre-existing message data in the dynamic buffer. The implementation
will call basic_parser::eager with the value false on the parser passed in.