chickadee » uri-common

uri-common

Description

The uri-common library provides simple and easy-to-use parsing and manipulation procedures for URIs using common schemes.

These "common schemes" all have the following rules:

Library Procedures

This library replaces most of the procedures in uri-generic. If you need to work with URIs on the uri-generic level or need to work with both uri-generic and uri-common URI objects, you will have to import and prefix or rename procedures.

Constructors and predicates

These constructors fully decode their arguments, so afterwards it is impossible to distinguish between encoded delimiters and unencoded delimiters. This makes uri-common objects decoding endpoints; no further decoding on the URI level is possible (of course, applications are free to decode further information inside the URI). If for some reason, the original URI is still needed, it can be converted to a uri-generic. However, updating a URI component causes this component's original encoding to be lost, so be careful!

(uri-reference STRING) => URI procedure

A URI reference is either a URI or a relative reference (RFC 3986, Section 4.1). If the given string's prefix does not match the syntax of a scheme followed by a colon separator, then the given string is parsed as a relative reference.

(absolute-uri STRING) => URI procedure

Parses the given string as an absolute URI, in which no fragments are allowed. If no URI scheme is found, or a fragment is detected, this raises an error.

Absolute URIs are defined by RFC 3986 as non-relative URI references without a fragment (RFC 3986, Section 4.2). Absolute URIs can be used as a base URI to resolve a relative-ref against, using uri-relative-to (see below).

(make-uri #!key authority scheme path query fragment host port username password) => URI procedure

Constructs a URI from the given components.

Accessors

(uri-scheme uri-common) => symbol procedure
(uri-path uri-common) => list procedure
(uri-query uri-common) => alist procedure
(uri-fragment uri-common) => string procedure
(uri-host uri-common) => string procedure
(uri-port uri-common) => integer procedure
(uri-username uri-common) => string procedure
(uri-password uri-common) => string procedure

Accessors for URI-common objects.

If a component is not defined in the given URI-common, then the corresponding accessor returns #f, except for uri-query and uri-path, which both always return a (possibly empty) list.

Updater

(update-uri URI-common #!key scheme path query fragment host port username password) => URI-common procedure

Update the specified keys in the URI-common object in a functional way (ie, it creates a new copy with the modifications).

Here's a nice tip: If you want to create an URI with only a few components set to dynamic values extracted from elsewhere, you can generally create an empty URI and update its constituent parts.

You can do that like this:

(uri->string (update-uri (uri-reference "") path: '("example" "greeting") query: '((hi . "there"))))
 => "example/greeting?hi=there"

Predicates

There are several predicates to check whether objects are URI references (the most general type of an URI-like object), or more specific types of URIs like absolute URIs or relative references. The classification tree of URI-like objects looks a bit like this:

               uri-reference                         Anything defined by the RFC fits this
               /           \
            uri             relative-ref             Scheme (uri) or no scheme (relative-ref)?
            /               /        \
     absolute-uri    path-relative   path-absolute   No URI fragment(absolute-uri)? | path starts with a slash (path-absolute) or not (path-relative)?
(uri-reference? URI) => BOOL procedure

Is the given object a URI reference? All objects created by URI-common constructors are URI references; they are either URIs or relative references. The constructors below are just more strict checking versions of uri-reference. They all create URI references.

(absolute-uri? URI) => BOOL procedure

Is the given object an absolute URI?

(uri? URI) => BOOL procedure

Is the given object a URI? URIs are all URI references that include a scheme part. The other type of URI references are relative references.

(relative-ref? URI) => BOOL procedure

Is the given object a relative reference? Relative references are defined by RFC 3986 as URI references which are not URIs; they contain no URI scheme and can be resolved against an absolute URI to obtain a complete URI using uri-relative-to.

(uri-path-absolute? URI) => BOOL procedure

Is the URI's path component an absolute path?

(uri-path-relative? URI) => BOOL procedure

Is the URI's path component a relative path?

(uri-default-port? URI) => BOOL procedure

Is the URI's port the default port for the URI's scheme?

Reference Resolution

(uri-relative-to URI URI) => URI procedure

Resolve the first URI as a reference relative to the second URI, returning a new URI (RFC 3986, Section 5.2.2).

(uri-relative-from URI URI) => URI procedure

Constructs a new, possibly relative, URI which represents the location of the first URI with respect to the second URI.

(use uri-common)

(uri->string (uri-relative-to (uri-reference "../qux") (uri-reference "http://example.com/foo/bar/")))
 => "http://example.com/foo/qux"

(uri->string (uri-relative-from (uri-reference "http://example.com/foo/qux") (uri-reference "http://example.com/foo/bar/")))
 => "../qux"

Query encoding and decoding

(form-urlencoded-separator [char-set/char/string]) parameter
(form-urlencode alist #!key (separator (form-urlencoded-separator))) => string procedure
(form-urldecode string #!key (separator (form-urlencoded-separator))) => alist procedure

Encode or decode an alist using the encoding corresponding to the form-urlencoded media type, using the given separator character(s).

The alist contains key/value pairs corresponding to the values in the final urlencoded string. If a value is #f, the key will be omitted from the string. If it is #t the key will be present without a value. In all other cases, the value is converted to a string and urlencoded. The keys are always converted to a string and urlencoded.

When encoding, if separator is a string, the first character will be used as the separator in the resulting querystring. If it is a char-set, it will be converted to a string and its first character will be taken. In either case, all of these characters are encoded if they occur inside the key/value pairs.

When decoding, any character in the set (or string) will be seen as a separator.

The separator defaults to the string ";&". This means that either semicolons or ampersands are allowed as separators when decoding an URI string, but semicolons are used when generating strings.

If you would like to use a different separator, you should parameterize all calls to procedures that return an uri-common object.

Examples:

(form-urlencode '(("lemon" . "ade") (sucks . #f) (rocks . #t) (number . 42)))
=> "lemon=ade;rocks;number=42"

(form-urldecode "lemon=ade;rocks;number=42")
=> ((lemon . "ade") (rocks . #t) (number . "42"))

String encoding and decoding

A little more generic but also more low-level than encoding/decoding whole query strings/alists at a time, you can also encode and decode strings on an individual level.

(uri-encode-string STRING [CHAR-SET]) => STRING procedure

Returns the percent-encoded form of the given string. The optional char-set argument controls which characters should be encoded. It defaults to the complement of char-set:uri-unreserved. This is always safe, but often overly careful; it is allowed to leave certain characters unquoted depending on the context.

(uri-decode-string STRING [CHAR-SET]) => STRING procedure

Returns the decoded form of the given string. The optional char-set argument controls which characters should be decoded. It defaults to char-set:full.

Normalization

(uri-normalize-case URI) => URI procedure

URI case normalization (RFC 3986 section 6.2.2.1)

(uri-normalize-path-segments URI) => URI procedure

URI path segment normalization (RFC 3986 section 6.2.2.3)

uri-generic, string and list representation

(uri->uri-generic uri-common) => uri-generic procedure
(uri-generic->uri uri-common) => uri-common procedure

To convert between uri-generic and uri-common objects, use these procedures. As stated above, this will allow you to retrieve the original encoding of the URI components, but once you update a component from the uri-common side, the original encoding is no longer available (the updated value replaces the original value).

(uri->string uri-common [userinfo]) => string procedure

Reconstructs the given URI into a string; uses a supplied function LAMBDA USERNAME PASSWORD -> STRING to map the userinfo part of the URI. If not given, it represents the userinfo as the username followed by ":******".

(uri->list URI USERINFO) => LIST procedure

Returns a list of the form (SCHEME SPECIFIC FRAGMENT); SPECIFIC is of the form (AUTHORITY PATH QUERY).

Character sets

As a convenience for further sub-parsers or other special-purpose URI handling code like separately URI-encoding strings, there are a couple of character sets exported by uri-common.

char-set:gen-delims constant

Generic delimiters.

 gen-delims  =  ":" / "/" / "?" / "#" / "[" / "]" / "@"
char-set:sub-delims constant

Sub-delimiters.

 sub-delims  =  "!" / "$" / "&" / "'" / "(" / ")" / "*" / "+" / "," / ";" / "="
char-set:uri-reserved constant

The union of gen-delims and sub-delims; all reserved URI characters.

 reserved    =  gen-delims / sub-delims
char-set:uri-unreserved constant

All unreserved characters that are allowed in a URI.

 unreserved  =  ALPHA / DIGIT / "-" / "." / "_" / "~"

Note that this is _not_ the complement of char-set:uri-reserved! There are several characters (even printable, noncontrol characters) which are not allowed at all in a URI.

Requires

Version History

License

 Copyright 2008-2013 Peter Bex
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