hxt-8.3.0: src/Text/XML/HXT/Arrow/ReadDocument.hs
-- ------------------------------------------------------------
{- |
Module : Text.XML.HXT.Arrow.ReadDocument
Copyright : Copyright (C) 2005 Uwe Schmidt
License : MIT
Maintainer : Uwe Schmidt (uwe@fh-wedel.de)
Stability : experimental
Portability: portable
Version : $Id: ReadDocument.hs,v 1.10 2006/11/24 07:41:37 hxml Exp $
Compound arrows for reading an XML\/HTML document or an XML\/HTML string
-}
-- ------------------------------------------------------------
module Text.XML.HXT.Arrow.ReadDocument
( readDocument
, readFromDocument
, readString
, readFromString
, hread
, xread
)
where
import Control.Arrow.ListArrows
import Text.XML.HXT.DOM.Interface
import Text.XML.HXT.Arrow.XmlArrow
import Text.XML.HXT.Arrow.XmlIOStateArrow
import Text.XML.HXT.Arrow.Edit
( canonicalizeAllNodes
, canonicalizeForXPath
, canonicalizeContents
, removeDocWhiteSpace
)
import Text.XML.HXT.Arrow.ParserInterface
import Text.XML.HXT.Arrow.ProcessDocument
( getDocumentContents
, parseXmlDocument
, parseHtmlDocument
, propagateAndValidateNamespaces
)
import Text.XML.HXT.RelaxNG.Validator
( validateDocumentWithRelaxSchema
)
import Data.Char
( toLower
)
-- ------------------------------------------------------------
{- |
the main document input filter
this filter can be configured by an option list, a value of type "Attributes"
available options:
* 'a_parse_html': use HTML parser, else use XML parser (default)
- 'a_tagsoup' : use light weight and lasy parser based on tagsoup lib
- 'a_parse_by_mimetype' : select the parser by the mime type of the document
(pulled out of the HTTP header). When the mime type is set to \"text\/html\"
the HTML parser (parsec or tagsoup) is taken, when it\'s set to
\"text\/xml\" or \"text\/xhtml\" the XML parser (parsec or tagsoup) is taken.
If the mime type is something else no further processing is performed,
the contents is given back to the application in form of a single text node.
If the default document encoding ('a_encoding') is set to isoLatin1, this even enables processing
of arbitray binary data.
- 'a_validate' : validate document againsd DTD (default), else skip validation
- 'a_relax_schema' : validate document with Relax NG, the options value is the schema URI
this implies using XML parser, no validation against DTD, and canonicalisation
- 'a_check_namespaces' : check namespaces, else skip namespace processing (default)
- 'a_canonicalize' : canonicalize document (default), else skip canonicalization
- 'a_preserve_comment' : preserve comments during canonicalization, else remove comments (default)
- 'a_remove_whitespace' : remove all whitespace, used for document indentation, else skip this step (default)
- 'a_indent' : indent document by inserting whitespace, else skip this step (default)
- 'a_issue_warnings' : issue warnings, when parsing HTML (default), else ignore HTML parser warnings
- 'a_issue_errors' : issue all error messages on stderr (default), or ignore all error messages
- 'a_ignore_encoding_errors': ignore all encoding errors, default is issue all encoding errors
- 'a_ignore_none_xml_contents': ignore document contents of none XML\/HTML documents.
This option can be useful for implementing crawler like applications, e.g. an URL checker.
In those cases net traffic can be reduced.
- 'a_trace' : trace level: values: 0 - 4
- 'a_proxy' : proxy for http access, e.g. www-cache:3128
- 'a_use_curl' : obsolete and ignored, HTTP acccess is always done with curl bindings for libcurl
- 'a_strict_input' : file input is done strictly using the 'Data.ByteString' input functions. This ensures correct closing of files, especially when working with
the tagsoup parser and not processing the whole input data. Default is off. The @ByteString@ input usually is not faster than the buildin @hGetContents@
for strings.
- 'a_options_curl' : deprecated but for compatibility reasons still supported.
More options passed to the curl binding.
Instead of using this option to set a whole bunch of options at once for curl
it is recomended to use the @curl-.*@ options syntax described below.
- 'a_encoding' : default document encoding ('utf8', 'isoLatin1', 'usAscii', 'iso8859_2', ... , 'iso8859_16', ...).
Only XML and HTML documents are decoded, documents with none XML\/HTML mime types are not decoded. The whole content is returned in a single text node
- 'a_mime_types' : set the mime type table for file input with given file. The format of this config file must be in the syntax of a debian linux \"mime.types\" config file
- curl options : the HTTP interface with libcurl can be configured with a lot of options. To support these options in an easy way, there is a naming convetion:
Every option, which has the prefix @curl@ and the rest of the name forms an option as described in the curl man page, is passed to the curl binding lib.
See 'Text.XML.HXT.IO.GetHTTPLibCurl.getCont' for examples. Currently most of the options concerning HTTP requests are implemented.
All attributes not evaluated by readDocument are stored in the created document root node for easy access of the various
options in e.g. the input\/output modules
If the document name is the empty string or an uri of the form \"stdin:\", the document is read from standard input.
examples:
> readDocument [ ] "test.xml"
reads and validates a document \"test.xml\", no namespace propagation, only canonicalization is performed
> readDocument [ (a_validate, "0")
> , (a_encoding, isoLatin1)
> , (a_parse_by_mimetype, "1")
> ] "http://localhost/test.php"
reads document \"test.php\", parses it as HTML or XML depending on the mimetype given from the server, but without validation, default encoding 'isoLatin1'.
> readDocument [ (a_parse_html, "1")
> , (a_encoding, isoLatin1)
> ] ""
reads a HTML document from standard input, no validation is done when parsing HTML, default encoding is 'isoLatin1',
parsing is done with tagsoup parser, but input is read strictly
> readDocument [ (a_encoding, isoLatin1)
> , (a_mime_type, "/etc/mime.types")
> , (a_tagsoup, "1")
> , (a_strict_input, "1")
> ] "test.svg"
reads an SVG document from standard input, sets the mime type by looking in the system mimetype config file, default encoding is 'isoLatin1',
parsing is done with the lightweight tagsoup parser, which implies no validation.
> readDocument [ (a_parse_html, "1")
> , (a_proxy, "www-cache:3128")
> , (a_curl, "1")
> , (a_issue_warnings, "0")
> ] "http://www.haskell.org/"
reads Haskell homepage with HTML parser ignoring any warnings, with http access via external program curl and proxy \"www-cache\" at port 3128
> readDocument [ (a_validate, "1")
> , (a_check_namespace, "1")
> , (a_remove_whitespace, "1")
> , (a_trace, "2")
> ] "http://www.w3c.org/"
read w3c home page (xhtml), validate and check namespaces, remove whitespace between tags, trace activities with level 2
for minimal complete examples see 'Text.XML.HXT.Arrow.WriteDocument.writeDocument' and 'runX', the main starting point for running an XML arrow.
-}
readDocument :: Attributes -> String -> IOStateArrow s b XmlTree
readDocument userOptions src
= traceLevel
>>>
addInputOptionsToSystemState
>>>
getDocumentContents options src
>>>
( processDoc $< getMimeType )
>>>
traceMsg 1 ("readDocument: " ++ show src ++ " processed")
>>>
traceSource
>>>
traceTree
where
options
= addEntries userOptions defaultOptions
defaultOptions
= [ ( a_parse_html, v_0 )
, ( a_tagsoup, v_0 )
, ( a_strict_input, v_0 )
, ( a_validate, v_1 )
, ( a_issue_warnings, v_1 )
, ( a_check_namespaces, v_0 )
, ( a_canonicalize, v_1 )
, ( a_preserve_comment, v_0 )
, ( a_remove_whitespace, v_0 )
, ( a_parse_by_mimetype, v_0 )
, ( a_ignore_encoding_errors, v_0 )
, ( a_ignore_none_xml_contents, v_0 )
]
traceLevel
= maybe this (setTraceLevel . read) . lookup a_trace $ options
addInputOptionsToSystemState
= addSysOptions options
>>>
loadMineTypes (lookup1 a_mime_types userOptions)
where
addSysOptions
= seqA . map (uncurry setParamString)
loadMineTypes "" = this
loadMineTypes f = setMimeTypeTableFromFile f
getMimeType
= getAttrValue transferMimeType >>^ map toLower
processDoc mimeType
= traceMsg 1 ("readDocument: " ++ show src ++ " (mime type: " ++ show mimeType ++ ") will be processed")
>>>
parse
>>>
( if isXmlOrHtml
then ( checknamespaces
>>>
canonicalize
>>>
whitespace
>>>
relax
)
else this
)
where
parse
| isHtml
||
withTagSoup = parseHtmlDocument -- parse as HTML or with tagsoup XML
withTagSoup
withNamespaces
issueW
(not (hasOption a_canonicalize) && preserveCmt)
removeWS
isHtml
| validateWithRelax = parseXmlDocument False -- for Relax NG use XML parser without validation
| isXml = parseXmlDocument validate -- parse as XML
| removeNoneXml = replaceChildren none -- don't parse, if mime type is not XML nore HTML
| otherwise = this -- but remove contents when option is set
checknamespaces
| (withNamespaces && not withTagSoup)
||
validateWithRelax = propagateAndValidateNamespaces
| otherwise = this
canonicalize
| withTagSoup = this -- tagsoup already removes redundant struff
| validateWithRelax = canonicalizeAllNodes
| hasOption a_canonicalize
&&
preserveCmt = canonicalizeForXPath
| hasOption a_canonicalize = canonicalizeAllNodes
| otherwise = this
relax
| validateWithRelax = validateDocumentWithRelaxSchema options relaxSchema
| otherwise = this
whitespace
| removeWS
&&
not withTagSoup = removeDocWhiteSpace -- tagsoup already removes whitespace
| otherwise = this
validateWithRelax = hasEntry a_relax_schema options
relaxSchema = lookup1 a_relax_schema options
parseHtml = hasOption a_parse_html
isHtml = parseHtml -- force HTML
||
( parseByMimeType && isHtmlMimeType mimeType )
isXml = ( not parseByMimeType && not parseHtml )
||
( parseByMimeType
&&
( isXmlMimeType mimeType
||
null mimeType
) -- mime type is XML or not known
)
isXmlOrHtml = isHtml || isXml
parseByMimeType = hasOption a_parse_by_mimetype
validate = hasOption a_validate
withNamespaces = hasOption a_check_namespaces
withTagSoup = hasOption a_tagsoup
issueW = hasOption a_issue_warnings
removeWS = hasOption a_remove_whitespace
preserveCmt = hasOption a_preserve_comment
removeNoneXml = hasOption a_ignore_none_xml_contents
hasOption n = optionIsSet n options
-- ------------------------------------------------------------
-- |
-- the arrow version of 'readDocument', the arrow input is the source URI
readFromDocument :: Attributes -> IOStateArrow s String XmlTree
readFromDocument userOptions
= applyA ( arr $ \ s -> readDocument userOptions s )
-- ------------------------------------------------------------
-- |
-- read a document that is stored in a normal Haskell String
--
-- the same function as readDocument, but the parameter forms the input.
-- All options available for 'readDocument' are applicable for readString.
--
-- Default encoding: No encoding is done, the String argument is taken as Unicode string
readString :: Attributes -> String -> IOStateArrow s b XmlTree
readString userOptions content
= readDocument ( (a_encoding, unicodeString) : userOptions ) (stringProtocol ++ content)
-- ------------------------------------------------------------
-- |
-- the arrow version of 'readString', the arrow input is the source URI
readFromString :: Attributes -> IOStateArrow s String XmlTree
readFromString userOptions
= applyA ( arr $ \ s -> readString userOptions s )
-- ------------------------------------------------------------
-- |
-- parse a string as HTML content, substitute all HTML entity refs and canonicalize tree
-- (substitute char refs, ...). Errors are ignored.
--
-- A simpler version of 'readFromString' but with less functionality.
-- Does not run in the IO monad
hread :: ArrowXml a => a String XmlTree
hread
= parseHtmlContent
>>>
substHtmlEntityRefs
>>>
processTopDown ( none `when` isError )
>>>
canonicalizeContents
-- |
-- parse a string as XML content, substitute all predefined XML entity refs and canonicalize tree
-- (substitute char refs, ...)
xread :: ArrowXml a => a String XmlTree
xread
= parseXmlContent
>>>
substXmlEntityRefs
>>>
canonicalizeContents
-- ------------------------------------------------------------