114 lines
4.3 KiB
TeX
114 lines
4.3 KiB
TeX
\chapter{Parsing and Processing URLs}\label{cha:url}
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%
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The \ex{url} structure contains procedures to parse and unparse URLs.
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Until now, only the parsing of HTTP URLs is implemented.
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\section{Server Records}
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A \textit{server} value describes path prefixes of the form
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\var{user}:\var{password}@\var{host}:\var{port}. These are
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frequently used as the initial prefix of URLs describing Internet
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resources.
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\defun{make-server}{user password host port}{server}
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\defunx{server?}{thing}{boolean}
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\defunx{server-user}{server}{string-or-\sharpf}
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\defunx{server-password}{server}{string-or-\sharpf}
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\defunx{server-host}{server}{string-or-\sharpf}
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\defunx{server-port}{server}{string-or-\sharpf}
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\begin{desc}
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\ex{Make-server} creates a new server record. Each slot is a
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decoded string or \sharpf. (\var{Port} is also a string.)
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\ex{server?} is the corresponding predicate, \ex{server-user},
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\ex{server-password}, \ex{server-host} and \ex{server-port}
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are the correspondig selectors.
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\end{desc}
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\defun{parse-server}{path default}{server}
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\defunx{server->string}{server}{string}
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\begin{desc}
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\ex{Parse-server} parses a URI path \var{path} (a list representing
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a path, not a string) into a server value. Default values are taken
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from the server \var{default} except for the host. The values
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are unescaped and stored into a server record that is returned.
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\ex{Fatal-syntax-error} is called, if the specified path has no
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initial to slashes (i.e., it starts with `//\ldots').
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\ex{server->string} just does the inverse job: it unparses
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\var{server} into a string. The elements of the record
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are escaped before they are put together.
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Example:
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\begin{alltt}
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> (define default (make-server "andreas" "se ret" "www.sf.net" "80"))
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> (server->string default)
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"andreas:se\%20ret@www.sf.net:80"
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> (parse-server '("" "" "foo\%20bar@www.scsh.net" "docu" "index.html")
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default)
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'#{server}
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> (server->string ##)
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"foo\%20bar:se\%20ret@www.scsh.net:80"
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\end{alltt}
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%
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For details about escaping and unescaping see Chapter~\ref{cha:uri}.
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\end{desc}
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\section{HTTP URLs}
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\defun{make-http-url}{server path search frag-id}{http-url}
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\defunx{http-url?}{thing}{boolean}
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\defunx{http-url-server}{http-url}{server}
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\defunx{http-url-path}{http-url}{list}
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\defunx{http-url-search}{http-url}{string-or-\sharpf}
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\defunx{http-url-fragment-identifier}{http-url}{string-or-\sharpf}
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%
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\begin{desc}
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\ex{Make-http-url} creates a new \ex{httpd-url} record.
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\var{Server} is a record, containing the initial part of the address
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(like \ex{anonymous@clark.lcs.mit.edu:80}). \var{Path} contains the
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URL's URI path ( a list). These elements are in raw, unescaped
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format. To convert them back to a string, use
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\ex{(uri-path->uri (map escape-uri pathlist))}. \var{Search}
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and \var{frag-id} are the last two parts of the URL. (See
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Chapter~\ref{cha:uri} about parts of an URI.)
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\ex{Http-url?} is the predicate for HTTP URL values, and
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\ex{http-url-server}, \ex{http-url-path}, \ex{http-url-search} and
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\ex{http-url-fragment-identifier} are the corresponding selectors.
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\end{desc}
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\defun{parse-http-url}{path search frag-id}{http-url}
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\begin{defundescx}{http-url->string}{http-url}{string}
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This constructs an HTTP URL record from a URI path (a list of path
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components), a search, and a frag-id component.
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\ex{Http-url->string} just does the inverse job. It converts an
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HTTP URL record into a string.
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\end{defundescx}
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%
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Note: The URI parser \ex{parse-uri} maps a string to four parts:
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\var{scheme}, \var{path}, \var{search} and \var{frag-id} (see
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Section~\ref{proc:parse-uri} for details). If \var{scheme} is
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\ex{http}, then the other three parts can be passed to
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\ex{parse-http-url}, which parses them into a \ex{http-url} record.
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All strings come back from the URI parser encoded. \var{Search} and
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\var{frag-id} are left that way; this parser decodes the path
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elements. The first two list elements of the path indicating the
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leading double-slash are omitted.
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The following procedure combines the jobs of \ex{parse-uri} and
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\ex{parse-http-url}:
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\defun{parse-http-url-string}{string}{http-url}
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\begin{desc}
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This parses an HTTP URL and returns the corresponding URL value; it
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calls \ex{fatal-syntax-error} if the URL string doesn't have an
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\ex{http} scheme.
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\end{desc}
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%%% Local Variables:
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%%% mode: latex
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%%% TeX-master: "man"
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%%% End:
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