Copyright	(c) 2004, Graham Klyne
License	BSD-style (see end of this file)
Maintainer	Graham Klyne <gk@ninebynine.org>
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Network.URI

Contents

The URI type
Parsing
Test for strings containing various kinds of URI
Predicates
Relative URIs
Operations on URI strings
URI Normalization functions
Deprecated functions

Description

This module defines functions for handling URIs. It presents substantially the same interface as the older GHC Network.URI module, but is implemented using Parsec rather than a Regex library that is not available with Hugs. The internal representation of URI has been changed so that URI strings are more completely preserved when round-tripping to a URI value and back.

In addition, four methods are provided for parsing different kinds of URI string (as noted in RFC3986): parseURI, parseURIReference, parseRelativeReference and parseAbsoluteURI.

Further, four methods are provided for classifying different kinds of URI string (as noted in RFC3986): isURI, isURIReference, isRelativeReference and isAbsoluteURI.

The long-standing official reference for URI handling was RFC2396 [1], as updated by RFC 2732 [2], but this was replaced by a new specification, RFC3986 [3] in January 2005. This latter specification has been used as the primary reference for constructing the URI parser implemented here, and it is intended that there is a direct relationship between the syntax definition in that document and this parser implementation.

RFC 1808 [4] contains a number of test cases for relative URI handling. Dan Connolly's Python module uripath.py [5] also contains useful details and test cases.

Some of the code has been copied from the previous GHC implementation, but the parser is replaced with one that performs more complete syntax checking of the URI itself, according to RFC3986 [3].

References

Synopsis

The URI type

data URI

Represents a general universal resource identifier using its component parts.

For example, for the URI

  foo://anonymous@www.haskell.org:42/ghc?query#frag

the components are:

Constructors

URI
Fields uriScheme :: String foo: uriAuthority :: Maybe URIAuth //anonymous@www.haskell.org:42 uriPath :: String /ghc uriQuery :: String ?query uriFragment :: String #frag

Instances

Eq URI
Data URI
Ord URI
Show URI
Generic URI
NFData URI
type Rep URI

data URIAuth

Type for authority value within a URI

Constructors

URIAuth
Fields uriUserInfo :: String anonymous@ uriRegName :: String www.haskell.org uriPort :: String :42

Instances

Eq URIAuth
Data URIAuth
Ord URIAuth
Show URIAuth
NFData URIAuth

nullURI :: URI

Blank URI

Parsing

parseURI :: String -> Maybe URI

Turn a string containing a URI into a URI. Returns Nothing if the string is not a valid URI; (an absolute URI with optional fragment identifier).

NOTE: this is different from the previous network.URI, whose parseURI function works like parseURIReference in this module.

parseURIReference :: String -> Maybe URI

Parse a URI reference to a URI value. Returns Nothing if the string is not a valid URI reference. (an absolute or relative URI with optional fragment identifier).

parseRelativeReference :: String -> Maybe URI

Parse a relative URI to a URI value. Returns Nothing if the string is not a valid relative URI. (a relative URI with optional fragment identifier).

parseAbsoluteURI :: String -> Maybe URI

Parse an absolute URI to a URI value. Returns Nothing if the string is not a valid absolute URI. (an absolute URI without a fragment identifier).

Test for strings containing various kinds of URI

isURI :: String -> Bool

Test if string contains a valid URI (an absolute URI with optional fragment identifier).

isURIReference :: String -> Bool

Test if string contains a valid URI reference (an absolute or relative URI with optional fragment identifier).

isRelativeReference :: String -> Bool

Test if string contains a valid relative URI (a relative URI with optional fragment identifier).

isAbsoluteURI :: String -> Bool

Test if string contains a valid absolute URI (an absolute URI without a fragment identifier).

isIPv6address :: String -> Bool

Test if string contains a valid IPv6 address

isIPv4address :: String -> Bool

Test if string contains a valid IPv4 address

Predicates

uriIsAbsolute :: URI -> Bool

uriIsRelative :: URI -> Bool

Relative URIs

relativeTo :: URI -> URI -> URI

Returns a new URI which represents the value of the first URI interpreted as relative to the second URI.

Algorithm from RFC3986 [3], section 5.2

nonStrictRelativeTo :: URI -> URI -> URI

Returns a new URI which represents the value of the first URI interpreted as relative to the second URI. For example:

"foo" `relativeTo` "http://bar.org/" = "http://bar.org/foo"
"http:foo" `nonStrictRelativeTo` "http://bar.org/" = "http://bar.org/foo"

Algorithm from RFC3986 [3], section 5.2.2

relativeFrom :: URI -> URI -> URI

Returns a new URI which represents the relative location of the first URI with respect to the second URI. Thus, the values supplied are expected to be absolute URIs, and the result returned may be a relative URI.

Example:

"http://example.com/Root/sub1/name2#frag"
  `relativeFrom` "http://example.com/Root/sub2/name2#frag"
  == "../sub1/name2#frag"

There is no single correct implementation of this function, but any acceptable implementation must satisfy the following:

(uabs `relativeFrom` ubase) `relativeTo` ubase == uabs

For any valid absolute URI. (cf. http://lists.w3.org/Archives/Public/uri/2003Jan/0008.html http://lists.w3.org/Archives/Public/uri/2003Jan/0005.html)

Operations on URI strings

Support for putting strings into URI-friendly escaped format and getting them back again. This can't be done transparently in all cases, because certain characters have different meanings in different kinds of URI. The URI spec [3], section 2.4, indicates that all URI components should be escaped before they are assembled as a URI: "Once produced, a URI is always in its percent-encoded form"

uriToString :: (String -> String) -> URI -> ShowS

Turn a URI into a string.

Uses a supplied function to map the userinfo part of the URI.

The Show instance for URI uses a mapping that hides any password that may be present in the URI. Use this function with argument id to preserve the password in the formatted output.

isReserved :: Char -> Bool

Returns True if the character is a "reserved" character in a URI. To include a literal instance of one of these characters in a component of a URI, it must be escaped.

isUnreserved :: Char -> Bool

Returns True if the character is an "unreserved" character in a URI. These characters do not need to be escaped in a URI. The only characters allowed in a URI are either "reserved", "unreserved", or an escape sequence (% followed by two hex digits).

isAllowedInURI :: Char -> Bool

Returns True if the character is allowed in a URI.

isUnescapedInURI :: Char -> Bool

Returns True if the character is allowed unescaped in a URI.

isUnescapedInURIComponent :: Char -> Bool

Returns True if the character is allowed unescaped in a URI component.

escapeURIChar :: (Char -> Bool) -> Char -> String

Escape character if supplied predicate is not satisfied, otherwise return character as singleton string.

escapeURIString

Arguments