| Home | Libraries | People | FAQ | More

##### http::read_header (2 of 2 overloads)

Read a header from a stream using a parser.

###### Synopsis

Defined in header `<boost/beast/http/read.hpp>`

    template<
        class SyncReadStream,
        class DynamicBuffer,
        bool isRequest,
        class Derived>
    std::size_t
    read_header(
        SyncReadStream& stream,
        DynamicBuffer& buffer,
        basic_parser< isRequest, Derived >& parser,
        error_code& ec);

###### Description

This function is used to read a header from a stream into a subclass of `http::basic_parser`. The call will block until one of the following conditions is true:

- `http::basic_parser::is_header_done` returns `true`
- An error occurs.

This operation is implemented in terms of one or more calls to the stream's `read_some` function. The implementation may read additional octets that lie past the end of the message being read. This additional data is stored in the dynamic buffer, which must be retained for subsequent reads.

If the stream returns the error `boost::asio::error::eof` indicating the end of file during a read, the error returned from this function will be:

- `http::end_of_stream` if no octets were parsed, or
- `http::partial_message` if any octets were parsed but the message was incomplete, otherwise:
- A successful result. A subsequent attempt to read will return `http::end_of_stream`

###### Parameters

Name | Description
--- | ---
`stream` | The stream from which the data is to be read. The type must support the SyncReadStream concept.
`buffer` | 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 dynamic buffer's input sequence will be given to the parser first.
`parser` | The parser to use.
`ec` | Set to the error, if any occurred.

###### Return Value

The number of bytes transferred to the parser.

###### Remarks

The implementation will call `http::basic_parser::eager` with the value `false` on the parser passed in.

Convenience header `<boost/beast/http.hpp>`