A subclass of __basic_parser__ can be invoked directly, without using the provided stream operations. This could be useful for implementing algorithms on objects whose interface does not conform to __Stream__. For example, a [@http://zeromq.org/ *ZeroMQ* socket]. The basic parser interface is interactive; the caller invokes the function [link beast.ref.boost__beast__http__basic_parser.put `basic_parser::put`] repeatedly with buffers until an error occurs or the parsing is done. The function [link beast.ref.boost__beast__http__basic_parser.put_eof `basic_parser::put_eof`] Is used when the caller knows that there will never be more data (for example, if the underlying connection is closed),
Normally the parser returns after successfully parsing a structured element (header, chunk header, or chunk body) even if there are octets remaining in the input. This is necessary when attempting to parse the header first, or when the caller wants to inspect information which may be invalidated by subsequent parsing, such as a chunk extension. The `eager` option controls whether the parser keeps going after parsing structured element if there are octets remaining in the buffer and no error occurs. This option is automatically set or cleared during certain stream operations to improve performance with no change in functionality.
This option controls whether or not the parser expects to see an HTTP body, regardless of the presence or absence of certain fields such as Content-Length or a chunked Transfer-Encoding. Depending on the request, some responses do not carry a body. For example, a 200 response to a [@https://tools.ietf.org/html/rfc7231#section-4.3.6 CONNECT] request from a tunneling proxy, or a response to a [@https://tools.ietf.org/html/rfc7231#section-4.3.2 HEAD] request. In these cases, callers may use this function inform the parser that no body is expected. The parser will consider the message complete after the header has been received.
This function sets the maximum allowed size of the content body. When a body larger than the specified size is detected, an error is generated and parsing terminates. This setting helps protect servers from resource exhaustion attacks. The default limit when parsing requests is 1MB, and for parsing responses 8MB.
This function sets the maximum allowed size of the header including all field name, value, and delimiter characters and also including the CRLF sequences in the serialized input.
The standard library provides the type `std::istream` for performing high level read operations on character streams. The variable `std::cin` is based on this input stream. This example uses the buffer oriented interface of __basic_parser__ to build a stream operation which parses an HTTP message from a `std::istream`: