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http_wrapper.pl -- Server processing of an HTTP request
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This library provides the core of the implementation of the HTTP protocol at the server side and is mainly intended for internal use. It is used by library(thread_httpd) and library(inet_httpd) (deprecated).

Still, it provides a few predicates that are occasinally useful for applications:

  • http_current_request/1 finds the current request for occasional usage in places where it is not avaialable otherwise.
  • http_peer/2 finds the (IP4) peer address, getting the original address if we are behind a proxy (X-Forwarded-For)
  • http_relative_path/2 can be used to find a relative path from the current request.
Source http_wrapper(:Goal, +In, +Out, -Close, +Options) is det
Simple wrapper to read and decode an HTTP header from `In', call :Goal while watching for exceptions and send the result to the stream `Out'.

The goal is assumed to write the reply to current_output preceeded by an HTTP header, closed by a blank line. The header must contain a Content-type: <type> line. It may optionally contain a line Transfer-encoding: chunked to request chunked encoding.

Options:

request(-Request)
Return the full request to the caller
peer(+Peer)
IP address of client
Arguments:
Close- Unified to one of close, Keep-Alive or spawned(ThreadId).
Source http_wrap_spawned(:Goal, -Request, -Close) is det
Internal use only. Helper for wrapping the handler for http_spawn/2.
See also
- http_spawned/1, http_spawn/2.
Source http_spawned(+ThreadId)
Internal use only. Indicate that the request is handed to thread ThreadId.
Source http_send_header(+Header)
This API provides an alternative for writing the header field as a CGI header. Header has the format Name(Value), as produced by http_read_header/2.
deprecated
- Use CGI lines instead
Source http_current_request(-Request) is semidet
Returns the HTTP request currently being processed. Fails silently if there is no current request. This typically happens if a goal is run outside the HTTP server context.
Source http_peer(+Request, -PeerIP:atom) is semidet
True when PeerIP is the IP address of the connection peer. If the connection is established via a proxy or CDN we try to find the initiating peer. Currently supports:
  • Fastly-client-ip
  • X-real-ip
  • X-forwarded-for
  • Direct connections
bug
- The X-forwarded-for header is problematic. According to Wikipedia, the original client is the first, while according to AWS it is the last.
Source http_relative_path(+AbsPath, -RelPath) is det
Convert an absolute path (without host, fragment or search) into a path relative to the current page. This call is intended to create reusable components returning relative paths for easier support of reverse proxies.