finally adapt documentation to new uri lib procs
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\chapter{Parsing and Processing URIs}\label{cha:uri}
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\chapter{Processing URIs}\label{cha:uri}
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The \ex{uri} structure contains a library for dealing with URIs.
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The \ex{uri} structure contains library functions for dealing with URIs.
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and is out-of-date by now---it is build up on RFC 1360 of 1994 which
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was replaced by RFC 1738, RFC 1808, and finally RFC 2396 of 1998.
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\section{Notes on URI Syntax}
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\section{Notes on URI Syntax}
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A URI (Uniform Resource Identifier) is of following syntax:
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The generic syntax of URI (Uniform Resource Identifier) is defined in
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%
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RFC 2396; see Appendix A for a collected BNF of URI.
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\begin{inset}
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[\var{scheme}] \verb|:| \var{path} [\verb|?| \var{search}] [\verb|#| \var{fragid}]
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\end{inset}
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%
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Parts in brackets may be omitted.
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The URI contains characters like \verb|:| to indicate its different
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Within URI non-printable Ascii characters are represented by an
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parts. Some special characters are \emph{escaped} if they are a
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\emph{escape encoding}. \emph{Reserved} characters used as
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regular part of a name and not indicators for the structure of a URI.
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delimiters indicating the different parts of a URI also must be
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Escape sequences are of following scheme: \verb|%|\var{h}\var{h} where \var{h}
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\emph{escaped} if they are to be regular data of a URI component. The
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is a hexadecimal digit. The hexadecimal number refers to the
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set of characters actually \emph{reserved} within any given URI
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ASCII of the escaped character, e.g.\ \verb|%20| is space (ASCII
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component is defined by that component. Therefore
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32) and \verb|%61| is `a' (ASCII 97). This module
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\emph{escaping} can only be done when the URI is being created from
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provides procedures to escape and unescape strings that are meant to
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its component parts; likewise, a URI must be separated into its
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be used in a URI.
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component parts before \emph{unescaping} can be done.
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Escape sequences are of following scheme: \verb|%| \var{h}\var{h}
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where \var{h}\var{h} are the two hexadecimal digits representing the octet code. For
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example \verb|%20| is the escaped encoding for the US-ASCII space character.
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\section{Procedures}
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\section{Procedures}
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\defun{unescape-uri}{string [start] [end]}{string}
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\defun{unescape}{string}{string}
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\begin{desc}
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\begin{desc}
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\ex{Unescape-uri} unescapes a string. If \var{start} and/or \var{end} are
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\ex{Unescape} unescapes a string.
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specified, they specify start and end positions within \var{string}
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should be unescaped.
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\end{desc}
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\end{desc}
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%
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%
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This procedure should only be used \emph{after} the URI was parsed,
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This procedure may only be used \emph{after} the URI was parsed into
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since unescaping may introduce characters that blow up the
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its component parts (see above).
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parse---that's why escape sequences are used in URIs.
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\defvar{uri-escaped-chars}{char-set}
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\defun{escape} {string regexp} {string}
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\begin{desc}
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\begin{desc}
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This is a set of characters (in the sense of SRFI~14) which are
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\ex{Escape} replaces reserved or excluded characters in \var{string}
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escaped in URIs. RFC 2396 defines this set as all characters which
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by their escaped representation. \var{regexp} defines which
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are neither letters, nor digits, nor one of the following characters:
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characters are reserved or excluded within the particular URI component
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\verb|-|, \verb|_|, \verb|.|, \verb|!|, %$
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being escaped.
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\verb|~|, \verb|*|, \verb|'|, \verb|(|, \verb|)|.
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\end{desc}
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\end{desc}
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\defun{escape-uri} {string [escaped-chars]} {string}
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This procedure may only be used on a URI component part, not on a
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\begin{desc}
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complete URI made up of several component parts (see above). Use it to
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This procedure escapes characters of \var{string} that are in
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write specialized escape-procedures for the respective component
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\var{escaped\=chars}. \var{Escaped\=chars} defaults to
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part. (See the \ex{url} structure for examples).
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\ex{uri\=escaped\=chars}.
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\end{desc}
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%
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Be careful with using this procedure to chunks of text with
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syntactically meaningful reserved characters (e.g., paths with URI
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slashes or colons)---they'll be escaped, and lose their special
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meaning. E.g.\ it would be a mistake to apply \ex{escape-uri} to
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\begin{verbatim}
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//lcs.mit.edu:8001/foo/bar.html
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\end{verbatim}
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%
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because the sla\-shes and co\-lons would be escaped.
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\defun{split-uri}{uri start end} {list}
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\begin{desc}
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This procedure splits \var{uri} at slashes. Only the substring given
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with \var{start} (inclusive) and \var{end} (exclusive) as indices is
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considered. \var{start} and $\var{end} - 1$ have to be within the
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range of \var{uri}. Otherwise an \ex{index-out-of-range} exception
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will be raised.
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Example: \codex{(split-uri "foo/bar/colon" 4 11)} returns
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\codex{("bar" "col")}
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\end{desc}
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\defun{uri-path->uri}{path}{string}
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\begin{desc}
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This procedure generates a path out of a URI path list by inserting
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slashes between the elements of \var{plist}.
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\end{desc}
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%
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If you want to use the resulting string for further operation, you
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should escape the elements of \var{plist} in case they contain
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slashes, like so:
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%
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\begin{verbatim}
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(uri-path->uri (map escape-uri pathlist))
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\end{verbatim}
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\defun{simplify-uri-path}{path}{list}
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\begin{desc}
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This procedure simplifies a URI path. It removes \verb|"."| and
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\verb|"/.."| entries from path, and removes parts before a root.
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The result is a list, or \sharpf{} if the path tries to back up past
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root.
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\end{desc}
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%
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According to RFC~2396, relative paths are considered not to start with
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\verb|/|. They are appended to a base URL path and then simplified.
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So before you start to simplify a URL try to find out if it is a
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relative path (i.e. it does not start with a \verb|/|).
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Examples:
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%
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\begin{alltt}
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(simplify-uri-path (split-uri "/foo/bar/baz/.." 0 15))
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\(\Rightarrow\) ("" "foo" "bar")
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(simplify-uri-path (split-uri "foo/bar/baz/../../.." 0 20))
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\(\Rightarrow\) ()
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(simplify-uri-path (split-uri "/foo/../.." 0 10))
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\(\Rightarrow\) #f
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(simplify-uri-path (split-uri "foo/bar//" 0 9))
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\(\Rightarrow\) ("")
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(simplify-uri-path (split-uri "foo/bar/" 0 8))
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\(\Rightarrow\) ("")
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(simplify-uri-path (split-uri "/foo/bar//baz/../.." 0 19))
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\(\Rightarrow\) #f
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\end{alltt}
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%%% Local Variables:
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%%% Local Variables:
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%%% mode: latex
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%%% mode: latex
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