Text.XML.HXT.Arrow.XmlIOStateArrow

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

Data Types

data XIOState us

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

Constructors

XIOState

Fields

xio_sysState :: !XIOSysState

xio_userState :: !us

Instances

NFData us => NFData (XIOState us)

data XIOSysState

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

Constructors

XIOSys

Fields

xio_trace :: !Int

xio_traceCmd :: Int -> String -> IO ()

xio_errorStatus :: !Int

xio_errorModule :: !String

xio_errorMsgHandler :: String -> IO ()

xio_errorMsgCollect :: !Bool

xio_errorMsgList :: !XmlTrees

xio_baseURI :: !String

xio_defaultBaseURI :: !String

xio_attrList :: !(AssocList String XmlTrees)

xio_mimeTypes :: MimeTypeTable

Instances

NFData XIOSysState

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

The arrow type for stateful arrows

type IOSArrow b c = IOStateArrow () b c

The arrow for stateful arrows with no user defined state

Running Arrows

initialState :: us -> XIOState us

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

initialSysState :: XIOSysState

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

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 s

read the user defined part of the state

setUserState :: IOStateArrow s s s

set the user defined part of the state

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

change the user defined part of the state

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

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 c

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

getSysParam :: (XIOSysState -> c) -> IOStateArrow s b c

changeSysParam :: (b -> XIOSysState -> XIOSysState) -> IOStateArrow s b b

setParamList :: String -> IOStateArrow s XmlTrees XmlTree

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

setParam :: String -> IOStateArrow s XmlTree XmlTree

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

unsetParam :: String -> IOStateArrow s b b

remove an entry in global state, arrow input remains unchanged

getParam :: String -> IOStateArrow s b XmlTree

read an attribute value from global state

getAllParams :: IOStateArrow s b (AssocList String XmlTrees)

read all attributes from global state

getAllParamsString :: IOStateArrow s b (AssocList String String)

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

setParamString :: String -> String -> IOStateArrow s b b

getParamString :: String -> IOStateArrow s b String

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

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

store an int value in global state

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

read an int value from global state

 getParamInt 0 myIntAttr

Error Message Handling

clearErrStatus :: IOStateArrow s b b

setErrStatus :: IOStateArrow s Int Int

set global error variable

getErrStatus :: IOStateArrow s XmlTree Int

read current global error status

setErrMsgStatus :: IOStateArrow s XmlTree XmlTree

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

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

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

errorMsgStderr :: IOStateArrow s b b

the default error message handler: error output to stderr

errorMsgCollect :: IOStateArrow s b b

error message handler for collecting errors

errorMsgStderrAndCollect :: IOStateArrow s b b

error message handler for output to stderr and collecting

errorMsgIgnore :: IOStateArrow s b b

error message handler for ignoring errors

getErrorMessages :: IOStateArrow s b XmlTree

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 XmlTree

filter error messages from input trees and issue errors

issueWarn :: String -> IOStateArrow s b b

generate a warnig message

issueErr :: String -> IOStateArrow s b b

generate an error message

issueFatal :: String -> IOStateArrow s b b

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

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

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 XmlTree

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 XmlTree

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

Document Base

setBaseURI :: IOStateArrow s String String

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 String

read the base URI from the globale state

changeBaseURI :: IOStateArrow s String String

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 String

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 String

get the default base URI

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

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

Tracing

setTraceLevel :: Int -> IOStateArrow s b b

set the global trace level

getTraceLevel :: IOStateArrow s b Int

read the global trace level

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

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 b

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

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

acces the command for trace output

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

apply a trace arrow and issue message to stderr

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

issue a string message as trace

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

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 b

an old alias for traceValue

traceSource :: IOStateArrow s XmlTree XmlTree

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

for better readability the source is formated with indentDoc

traceTree :: IOStateArrow s XmlTree XmlTree

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

traceDoc :: String -> IOStateArrow s XmlTree XmlTree

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 b

trace the global state

URI Manipulation

expandURIString :: String -> String -> Maybe String

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

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

arrow variant of expandURIString, fails if expandURIString returns Nothing

mkAbsURI :: IOStateArrow s String String

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 String

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

getPathFromURI :: ArrowList a => a String String

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

getPortFromURI :: ArrowList a => a String String

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

getQueryFromURI :: ArrowList a => a String String

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

getRegNameFromURI :: ArrowList a => a String String

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

getSchemeFromURI :: ArrowList a => a String String

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 String

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 b

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 b

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