hxt-8.5.2: A collection of tools for processing XML with Haskell.

Portabilityportable
Stabilitystable
MaintainerUwe Schmidt (uwe@fh-wedel.de)

Text.XML.HXT.Arrow.XmlIOStateArrow

Contents

Description

the basic state arrows for XML processing

A state is needed for global processing options, like encoding options, document base URI, trace levels and error message handling

The state is separated into a user defined state and a system state. The system state contains variables for error message handling, for tracing, for the document base for accessing XML documents with relative references, e.g. DTDs, and a global key value store. This assoc list has strings as keys and lists of XmlTrees as values. It is used to store arbitrary XML and text values, e.g. user defined global options.

The user defined part of the store is in the default case empty, defined as (). It can be extended with an arbitray data type

Synopsis

Data Types

data XIOState us Source

state datatype consists of a system state and a user state the user state is not fixed

Constructors

XIOState 

Instances

NFData us => NFData (XIOState us) 

data XIOSysState Source

predefined system state data type with all components for the system functions, like trace, error handling, ...

Instances

type IOStateArrow s b c = IOSLA (XIOState s) b cSource

The arrow type for stateful arrows

type IOSArrow b c = IOStateArrow () b cSource

The arrow for stateful arrows with no user defined state

Running Arrows

initialState :: us -> XIOState usSource

the default global state, used as initial state when running an IOSArrow with runIOSLA or runX

runX :: IOSArrow XmlTree c -> IO [c]Source

apply an IOSArrow to an empty root node with initialState () as initial state

the main entry point for running a state arrow with IO

when running runX f an empty XML root node is applied to f. usually f will start with a constant arrow (ignoring the input), e.g. a Text.XML.HXT.Arrow.ReadDocument.readDocument arrow.

for usage see examples with Text.XML.HXT.Arrow.WriteDocument.writeDocument

if input has to be feed into the arrow use runIOSLA like in runIOSLA f emptyX inputDoc

User State Manipulation

getUserState :: IOStateArrow s b sSource

read the user defined part of the state

setUserState :: IOStateArrow s s sSource

set the user defined part of the state

changeUserState :: (b -> s -> s) -> IOStateArrow s b bSource

change the user defined part of the state

withExtendedUserState :: s1 -> IOStateArrow (s1, s0) b c -> IOStateArrow s0 b cSource

extend user state

Run an arrow with an extended user state component, The old component is stored together with a new one in a pair, the arrow is executed with this extended state, and the augmented state component is removed form the state when the arrow has finished its execution

withOtherUserState :: s1 -> IOStateArrow s1 b c -> IOStateArrow s0 b cSource

change the type of user state

This conversion is useful, when running a state arrow with another structure of the user state, e.g. with () when executing some IO arrows

Global System State Access

setParamList :: String -> IOStateArrow s XmlTrees XmlTreeSource

store a list of XML trees in global system state under a given attribute name

setParam :: String -> IOStateArrow s XmlTree XmlTreeSource

store a single XML tree in global state under a given attribute name

unsetParam :: String -> IOStateArrow s b bSource

remove an entry in global state, arrow input remains unchanged

getParam :: String -> IOStateArrow s b XmlTreeSource

read an attribute value from global state

getAllParams :: IOStateArrow s b (AssocList String XmlTrees)Source

read all attributes from global state

getAllParamsString :: IOStateArrow s b (AssocList String String)Source

read all attributes from global state and convert the values to strings

getParamString :: String -> IOStateArrow s b StringSource

read a string value from global state, if parameter not set "" is returned

setParamInt :: String -> Int -> IOStateArrow s b bSource

store an int value in global state

getParamInt :: Int -> String -> IOStateArrow s b IntSource

read an int value from global state

 getParamInt 0 myIntAttr

Error Message Handling

setErrStatus :: IOStateArrow s Int IntSource

set global error variable

getErrStatus :: IOStateArrow s XmlTree IntSource

read current global error status

setErrMsgStatus :: IOStateArrow s XmlTree XmlTreeSource

raise the global error status level to that of the input tree

setErrorMsgHandler :: Bool -> (String -> IO ()) -> IOStateArrow s b bSource

set the error message handler and the flag for collecting the errors

errorMsgStderr :: IOStateArrow s b bSource

the default error message handler: error output to stderr

errorMsgCollect :: IOStateArrow s b bSource

error message handler for collecting errors

errorMsgStderrAndCollect :: IOStateArrow s b bSource

error message handler for output to stderr and collecting

errorMsgIgnore :: IOStateArrow s b bSource

error message handler for ignoring errors

getErrorMessages :: IOStateArrow s b XmlTreeSource

if error messages are collected by the error handler for processing these messages by the calling application, this arrow reads the stored messages and clears the error message store

filterErrorMsg :: IOStateArrow s XmlTree XmlTreeSource

filter error messages from input trees and issue errors

issueWarn :: String -> IOStateArrow s b bSource

generate a warnig message

issueErr :: String -> IOStateArrow s b bSource

generate an error message

issueFatal :: String -> IOStateArrow s b bSource

generate a fatal error message, e.g. document not found

setDocumentStatus :: Int -> String -> IOStateArrow s XmlTree XmlTreeSource

add the error level and the module where the error occured to the attributes of a document root node and remove the children when level is greater or equal to c_err. called by setDocumentStatusFromSystemState when the system state indicates an error

setDocumentStatusFromSystemState :: String -> IOStateArrow s XmlTree XmlTreeSource

check whether the error level attribute in the system state is set to error, in this case the children of the document root are removed and the module name where the error occured and the error level are added as attributes with setDocumentStatus else nothing is changed

documentStatusOk :: ArrowXml a => a XmlTree XmlTreeSource

check whether tree is a document root and the status attribute has a value less than c_err

Document Base

setBaseURI :: IOStateArrow s String StringSource

set the base URI of a document, used e.g. for reading includes, e.g. external entities, the input must be an absolute URI

getBaseURI :: IOStateArrow s b StringSource

read the base URI from the globale state

changeBaseURI :: IOStateArrow s String StringSource

change the base URI with a possibly relative URI, can be used for evaluating the xml:base attribute. Returns the new absolute base URI. Fails, if input is not parsable with parseURIReference

see also: setBaseURI, mkAbsURI

setDefaultBaseURI :: String -> IOStateArrow s b StringSource

set the default base URI, if parameter is null, the system base ( file:///<cwd>/ ) is used, else the parameter, must be called before any document is read

getDefaultBaseURI :: IOStateArrow s b StringSource

get the default base URI

runInLocalURIContext :: IOStateArrow s b c -> IOStateArrow s b cSource

remember base uri, run an arrow and restore the base URI, used with external entity substitution

Tracing

setTraceLevel :: Int -> IOStateArrow s b bSource

set the global trace level

getTraceLevel :: IOStateArrow s b IntSource

read the global trace level

withTraceLevel :: Int -> IOStateArrow s b c -> IOStateArrow s b cSource

run an arrow with a given trace level, the old trace level is restored after the arrow execution

setTraceCmd :: (Int -> String -> IO ()) -> IOStateArrow s b bSource

set the global trace command. This command does the trace output

getTraceCmd :: IOStateArrow a b (Int -> String -> IO ())Source

acces the command for trace output

trace :: Int -> IOStateArrow s b String -> IOStateArrow s b bSource

apply a trace arrow and issue message to stderr

traceMsg :: Int -> String -> IOStateArrow s b bSource

issue a string message as trace

traceValue :: Int -> (b -> String) -> IOStateArrow s b bSource

trace the current value transfered in a sequence of arrows.

The value is formated by a string conversion function. This is a substitute for the old and less general traceString function

traceString :: Int -> (b -> String) -> IOStateArrow s b bSource

an old alias for traceValue

traceSource :: IOStateArrow s XmlTree XmlTreeSource

issue the source representation of a document if trace level >= 3

for better readability the source is formated with indentDoc

traceTree :: IOStateArrow s XmlTree XmlTreeSource

issue the tree representation of a document if trace level >= 4

traceDoc :: String -> IOStateArrow s XmlTree XmlTreeSource

trace a main computation step issue a message when trace level >= 1, issue document source if level >= 3, issue tree when level is >= 4

traceState :: IOStateArrow s b bSource

trace the global state

URI Manipulation

expandURIString :: String -> String -> Maybe StringSource

compute the absolut URI for a given URI and a base URI

expandURI :: ArrowXml a => a (String, String) StringSource

arrow variant of expandURIString, fails if expandURIString returns Nothing

mkAbsURI :: IOStateArrow s String StringSource

arrow for expanding an input URI into an absolute URI using global base URI, fails if input is not a legal URI

getFragmentFromURI :: ArrowList a => a String StringSource

arrow for computing the fragment component of an URI, fails if input is not a legal URI

getPathFromURI :: ArrowList a => a String StringSource

arrow for computing the path component of an URI, fails if input is not a legal URI

getPortFromURI :: ArrowList a => a String StringSource

arrow for selecting the port number of the URI without leading ':', fails if input is not a legal URI

getQueryFromURI :: ArrowList a => a String StringSource

arrow for computing the query component of an URI, fails if input is not a legal URI

getRegNameFromURI :: ArrowList a => a String StringSource

arrow for selecting the registered name (host) of the URI, fails if input is not a legal URI

getSchemeFromURI :: ArrowList a => a String StringSource

arrow for selecting the scheme (protocol) of the URI, fails if input is not a legal URI.

See Network.URI for URI components

getUserInfoFromURI :: ArrowList a => a String StringSource

arrow for selecting the user info of the URI without trailing '@', fails if input is not a legal URI

Mime Type Handling

setMimeTypeTable :: MimeTypeTable -> IOStateArrow s b bSource

set the table mapping of file extensions to mime types in the system state

Default table is defined in Text.XML.HXT.DOM.MimeTypeDefaults. This table is used when reading loacl files, (file: protocol) to determine the mime type

setMimeTypeTableFromFile :: FilePath -> IOStateArrow s b bSource

set the table mapping of file extensions to mime types by an external config file

The config file must follow the conventions of etcmime.types on a debian linux system, that means all empty lines and all lines starting with a # are ignored. The other lines must consist of a mime type followed by a possible empty list of extensions. The list of extenstions and mime types overwrites the default list in the system state of the IOStateArrow