network-2.5.0.0: Low-level networking interface

Portability | portable
Stability | provisional
Maintainer | Graham Klyne <gk@ninebynine.org>
Safe Haskell | None

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

1. http://www.ietf.org/rfc/rfc2396.txt
2. http://www.ietf.org/rfc/rfc2732.txt
3. http://www.ietf.org/rfc/rfc3986.txt
4. http://www.ietf.org/rfc/rfc1808.txt
5. http://www.w3.org/2000/10/swap/uripath.py

Synopsis

- data URI = URI {
  - uriScheme :: String
  - uriAuthority :: Maybe URIAuth
  - uriPath :: String
  - uriQuery :: String
  - uriFragment :: String
  }
- data URIAuth = URIAuth {
  - uriUserInfo :: String
  - uriRegName :: String
  - uriPort :: String
  }
- nullURI :: URI
- parseURI :: String -> Maybe URI
- parseURIReference :: String -> Maybe URI
- parseRelativeReference :: String -> Maybe URI
- parseAbsoluteURI :: String -> Maybe URI
- isURI :: String -> Bool
- isURIReference :: String -> Bool
- isRelativeReference :: String -> Bool
- isAbsoluteURI :: String -> Bool
- isIPv6address :: String -> Bool
- isIPv4address :: String -> Bool
- uriIsAbsolute :: URI -> Bool
- uriIsRelative :: URI -> Bool
- relativeTo :: URI -> URI -> URI
- nonStrictRelativeTo :: URI -> URI -> URI
- relativeFrom :: URI -> URI -> URI
- uriToString :: (String -> String) -> URI -> ShowS
- isReserved :: Char -> Bool
- isUnreserved :: Char -> Bool
- isAllowedInURI :: Char -> Bool
- isUnescapedInURI :: Char -> Bool
- isUnescapedInURIComponent :: Char -> Bool
- escapeURIChar :: (Char -> Bool) -> Char -> String
- escapeURIString :: (Char -> Bool) -> String -> String
- unEscapeString :: String -> String
- normalizeCase :: String -> String
- normalizeEscape :: String -> String
- normalizePathSegments :: String -> String
- parseabsoluteURI :: String -> Maybe URI
- escapeString :: String -> (Char -> Bool) -> String
- reserved :: Char -> Bool
- unreserved :: Char -> Bool
- scheme :: URI -> String
- authority :: URI -> String
- path :: URI -> String
- query :: URI -> String
- fragment :: URI -> String

# 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 |
Typeable 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 |
Typeable 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

:: (Char -> Bool) | a predicate which returns `False` if the character should be escaped
-> String | the string to process
-> String | the resulting URI string

Can be used to make a string valid for use in a URI.

unEscapeString :: String -> String

Turns all instances of escaped characters in the string back into literal characters.

# URI Normalization functions

normalizeCase :: String -> String

Case normalization; cf. RFC3986 section 6.2.2.1 NOTE: authority case normalization is not performed

normalizeEscape :: String -> String

Encoding normalization; cf. RFC3986 section 6.2.2.2

normalizePathSegments :: String -> String

Path segment normalization; cf. RFC3986 section 6.2.2.4

# Deprecated functions

parseabsoluteURI :: String -> Maybe URI

Deprecated: use parseAbsoluteURI

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

Deprecated: use escapeURIString, and note the flipped arguments

reserved :: Char -> Bool

Deprecated: use isReserved

unreserved :: Char -> Bool

Deprecated: use isUnreserved

scheme :: URI -> String

Deprecated: use uriScheme

authority :: URI -> String

Deprecated: use uriAuthority, and note changed functionality

path :: URI -> String

Deprecated: use uriPath

query :: URI -> String

Deprecated: use uriQuery, and note changed functionality

fragment :: URI -> String

Deprecated: use uriFragment, and note changed functionality