96 lines
4.1 KiB
Scheme
96 lines
4.1 KiB
Scheme
;;; NCSA's WWW Common Gateway Interface -- script-side code -*- Scheme -*-
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;;; Copyright (c) 1995 by Olin Shivers.
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;;; See http://hoohoo.ncsa.uiuc.edu/cgi/interface.html for a sort of "spec".
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;;; Imports and non-R4RS'isms
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;;; switch (control structure)
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;;; getenv read-string (scsh)
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;;; error
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;;; parse-html-form-query (parse-html-forms package)
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;;; This file provides routines to help you write programs in Scheme
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;;; that can interface to HTTP servers using the CGI program interface
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;;; to carry out HTTP transactions.
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;;; Other files/packages that will be of help:
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;;; rfc822 For reading headers from entities.
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;;; uri url For parsing and unparsing these things. Also for generally
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;;; URI-decoding strings.
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;;; htmlout For generating HTML output.
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;;; About HTML forms
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; This info is in fact independent of CGI, but important to know about,
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;;; as many CGI scripts are written for responding to forms-entry in
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;;; HTML browsers.
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;;;
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;;; The form's field data are turned into a single string, of the form
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;;; name=val&name=val
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;;; where the <name> and <val> parts are URI encoded to hide their
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;;; &, =, and + chars, among other things. After URI encoding, the
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;;; space chars are converted to + chars, just for fun. It is important
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;;; to encode the spaces this way, because the perfectly general %xx escape
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;;; mechanism might be insufficiently confusing. This variant encoding is
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;;; called "form-url encoding."
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;;;
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;;; If the form's method is POST,
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;;; Browser sends the form's field data in the entity block, e.g.,
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;;; "button=on&ans=yes". The request's Content-type: is application/
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;;; x-www-form-urlencoded, and the request's Content-length: is the
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;;; number of bytes in the form data.
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;;;
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;;; If the form's method is GET,
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;;; Browser sends the form's field data in the URL's <search> part.
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;;; (So the server will pass to the CGI script as $QUERY_STRING,
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;;; and perhaps also on in argv[]).
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;;;
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;;; In either case, the data is "form-url encoded" (as described above).
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;;; ISINDEX queries:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; (Likewise for ISINDEX URL queries from browsers.)
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;;; Browser url-form encodes the query (see above), which then becomes the
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;;; ?<search> part of the URI. (Hence the CGI script will split the individual
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;;; fields into argv[].)
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;;; CGI interface:
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; - The URL's <search> part is assigned to env var $QUERY_STRING, undecoded.
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;;; - If it contains no raw "=" chars, it is split at "+" chars. The
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;;; substrings are URI decoded, and become the elts of argv[]. You aren't
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;;; supposed to rely on this unless you are replying to ISINDEX queries.
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;;; - The CGI script is run with stdin hooked up to the socket. If it's going
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;;; to read the entity, it should read $CONTENT_LENGTH bytes worth.
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;;; - A bunch of env vars are set with useful values.
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;;; - Entity block is passed to script on stdin;
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;;; script writes reply to stdout.
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;;; - If the script begins with "nph-" its output is the entire reply.
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;;; Otherwise, when it replies to the server, it sends back a special
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;;; little header that tells the server how to construct the real header
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;;; for the reply.
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;;; See the "spec" for further details. (URL above)
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;;; (cgi-form-query)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Return the form data as an alist of decoded strings.
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;;; So a query string like "button=on&reply=Oh,%20yes" becomes alist
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;;; (("button" . "on") ("reply" . "Oh, yes"))
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;;; This only works for GET and POST methods.
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(define (cgi-form-query)
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(let ((request-method (getenv "REQUEST_METHOD")))
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(cond
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((string=? request-method "GET")
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(parse-html-form-query (getenv "QUERY_STRING")))
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((string=? request-method "POST")
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(let ((nchars (string->number (getenv "CONTENT_LENGTH"))))
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(parse-html-form-query (read-string nchars))))
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(else (error "Method not handled."))))) ; Don't be calling me.
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