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parser is constructible from other body types

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Vinnie Falco
2017-06-05 16:09:38 -07:00
parent d89809fb45
commit a007eba09c
6 changed files with 237 additions and 50 deletions
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doc/5_http_examples.qbk
+45 -23
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@@ -44,29 +44,6 @@ synchronous version of this server action looks like this:
[section Send Child Process Output]
Sometimes it is necessary to send a message whose body is not conveniently
described by a single container. For example, when implementing an HTTP relay
function a robust implementation needs to present body buffers individually
as they become available from the downstream host. These buffers should be
fixed in size, otherwise creating the unnecessary and inefficient burden of
reading the complete message body before forwarding it to the upstream host.
To enable these use-cases, the body type __buffer_body__ is provided. This
body uses a caller-provided pointer and size instead of an owned container.
To use this body, instantiate an instance of the serializer and fill in
the pointer and size fields before calling a stream write function.
This example reads from a child process and sends the output back in an
HTTP response. The output of the process is sent as it becomes available:
[http_sample_send_cgi_response]
[endsect]
[section HEAD request (Client)]
The
@@ -134,6 +111,51 @@ parses an HTTP message from a `std::istream`:
[section Send Child Process Output]
Sometimes it is necessary to send a message whose body is not conveniently
described by a single container. For example, when implementing an HTTP relay
function a robust implementation needs to present body buffers individually
as they become available from the downstream host. These buffers should be
fixed in size, otherwise creating the unnecessary and inefficient burden of
reading the complete message body before forwarding it to the upstream host.
To enable these use-cases, the body type __buffer_body__ is provided. This
body uses a caller-provided pointer and size instead of an owned container.
To use this body, instantiate an instance of the serializer and fill in
the pointer and size fields before calling a stream write function.
This example reads from a child process and sends the output back in an
HTTP response. The output of the process is sent as it becomes available:
[http_sample_send_cgi_response]
[endsect]
[section Defer Body Type]
Sophisticated servers may wish to defer the choice of the Body template type
until after the header is available. Then, a body type may be chosen
depending on the header contents. For example, depending on the verb,
target path, or target query parameters. To accomplish this, a parser
is declared to read in the header only, using a trivial body type such as
[link beast.ref.http__empty_body `empty_body`]. Then, a new parser is constructed
from this existing parser where the body type is conditionally determined
by information from the header or elsewhere.
This example illustrates how a server may make the commitment of a body
type depending on the method verb:
[http_sample_defer_body]
[endsect]
[section HTTP Relay]
An HTTP proxy acts as a relay between client and server. The proxy reads a