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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2020 Saxonica Limited
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.pull;
import net.sf.saxon.event.PipelineConfiguration;
import net.sf.saxon.om.*;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.value.AtomicValue;
import java.util.List;
/**
* PullProvider is Saxon's pull-based interface for reading XML documents and XDM sequences.
* A PullProvider can deliver any sequence of nodes or atomic values. An atomic value
* in the sequence is delivered as a single event; a node is delivered as a sequence
* of events equivalent to a recursive walk of the XML tree. Within this sequence,
* the start and end of a document, or of an element, are delivered as separate
* events; other nodes are delivered as individual events.
*/
public interface PullProvider {
// Start by defining the different types of event
enum Event {
/**
* START_OF_INPUT is the initial state when the PullProvider is instantiated.
* This event is never notified by the next() method, but it is returned
* from a call of current() prior to the first call on next().
*/
START_OF_INPUT,
/**
* ATOMIC_VALUE is notified when the PullProvider is reading a sequence of items,
* and one of the items is an atomic value rather than a node. This will always
* be a top-level event (it will never be nested in Start/End Document or
* Start/End Element).
*/
ATOMIC_VALUE,
/**
* START_DOCUMENT is notified when a document node is encountered. This will
* always be a top-level event (it will never be nested in Start/End Document or
* Start/End Element). Note however that multiple document nodes can occur in
* a sequence, and the start and end of each one will be notified.
*/
START_DOCUMENT,
/**
* END_DOCUMENT is notified at the end of processing a document node, that is,
* after all the descendants of the document node have been notified. The event
* will always be preceded by the corresponding START_DOCUMENT event.
*/
END_DOCUMENT,
/**
* START_ELEMENT is notified when an element node is encountered. This may either
* be a top-level element (an element node that participates in the sequence being
* read in its own right) or a nested element (reported because it is a descendant
* of an element or document node that participates in the sequence.)
* Following the notification of START_ELEMENT, the client may obtain information
* about the element node, such as its name and type annotation. The client may also
* call getAttributes() to obtain information about the attributes of the element
* node, and/or getNamespaceDeclarations() to get information about the namespace
* declarations. The client may then do one of the following:
*
* - Call skipToMatchingEnd() to move straight to the corresponding END_ELEMENT event (which
* will then be the current event)
* - Call next(), repeatedly, to be notified of events relating to the children and
* descendants of this element node
* - Call getStringValue() to obtain the string value of the element node, after which
* the next event notified will be the corresponding END_ELEMENT event
* - Call getTypedValue() to obtain the typed value of the element node, after which
* the next event notified will be the corresponding END_ELEMENT event
*
*/
START_ELEMENT,
/**
* END_ELEMENT is notified at the end of an element node, that is, after all the children
* and descendants of the element have either been processed or skipped. It may relate to
* a top-level element, or to a nested element. For an empty element (one with no children)
* the END_ELEMENT event will immediately follow the corresponding START_ELEMENT event.
* No information (such as the element name) is available after an END_ELEMENT event: if the
* client requires such information, it must remember it, typically on a Stack.
*/
END_ELEMENT,
/**
* The ATTRIBUTE event is notified only for an attribute node that appears in its own right
* as a top-level item in the sequence being read. ATTRIBUTE events are not notified for
* the attributes of an element that has been notified: such attributes must be read using the
* {@link #getAttributes()} method.
*/
ATTRIBUTE,
/**
* The NAMESPACE event is notified only for a namespace node that appears in its own right
* as a top-level item in the sequence being read. NAMESPACE events are not notified for
* the namespaces of an element that has been notified: such attributes must be read using the
* {@link #getNamespaceDeclarations()} method.
*/
NAMESPACE,
/**
* A TEXT event is notified for a text node. This may either be a top-level text
* node, or a text node nested within an element or document node. At the top level,
* text nodes may be zero-length and may be consecutive in the sequence being read.
* Nested within an element or document node, text nodes will never be zero-length,
* and adjacent text nodes will have been coalesced into one. (This might not always
* be true when reading third-party data models such as a DOM.) Whitespace-only
* text nodes will be notified unless something has been done (e.g. xsl:strip-space)
* to remove them.
*/
TEXT,
/**
* A COMMENT event is notified for a comment node, which may be either a top-level
* comment or one nested within an element or document node.
*/
COMMENT,
/**
* A PROCESSING_INSTRUCTION event is notified for a processing instruction node,
* which may be either a top-level comment or one nested within an element or document node.
* As defined in the XPath data model, the "target" of a processing instruction is represented
* as the node name (which only has a local part, no prefix or URI), and the "data" of the
* processing instruction is represented as the string-value of the node.
*/
PROCESSING_INSTRUCTION,
/**
* The END_OF_INPUT event is returned to indicate the end of the sequence being read.
* After this event, the result of any further calls on the next() method is undefined.
*/
END_OF_INPUT
}
/**
* Set configuration information. This must only be called before any events
* have been read.
*
* @param pipe the pipeline configuration
*/
void setPipelineConfiguration(PipelineConfiguration pipe);
/**
* Get configuration information.
*
* @return the pipeline configuration
*/
PipelineConfiguration getPipelineConfiguration();
/**
* Get the next event
*
* @return an Event object indicating the type of event. The code
* {@link net.sf.saxon.pull.PullProvider.Event#END_OF_INPUT} is returned at the end of the sequence.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
Event next() throws XPathException;
/**
* Get the event most recently returned by next(), or by other calls that change
* the position, for example getStringValue() and skipToMatchingEnd(). This
* method does not change the position of the PullProvider.
*
* @return the current event
*/
Event current();
/**
* Get the attributes associated with the current element. This method must
* be called only after a START_ELEMENT event has been notified. The contents
* of the returned AttributeMap are immutable.
* Attributes may be read before or after reading the namespaces of an element,
* but must not be read after the first child node has been read, or after calling
* one of the methods skipToMatchingEnd(), getStringValue(), or getTypedValue().
*
* @return an AttributeMap representing the attributes of the element
* that has just been notified.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
AttributeMap getAttributes() throws XPathException;
/**
* Get the namespace declarations associated with the current element. This method must
* be called only after a START_ELEMENT event has been notified. In the case of a top-level
* START_ELEMENT event (that is, an element that either has no parent node, or whose parent
* is not included in the sequence being read), the NamespaceDeclarations object returned
* will contain a namespace declaration for each namespace that is in-scope for this element
* node. In the case of a non-top-level element, the NamespaceDeclarations will contain
* a set of namespace declarations and undeclarations, representing the differences between
* this element and its parent.
* It is permissible for this method to return namespace declarations that are redundant.
* The NamespaceDeclarations object is guaranteed to remain unchanged until the next START_ELEMENT
* event, but may then be overwritten. The object should not be modified by the client.
* Namespaces may be read before or after reading the attributes of an element,
* but must not be read after the first child node has been read, or after calling
* one of the methods skipToMatchingEnd(), getStringValue(), or getTypedValue().
*
* @return the namespace declarations associated with the current START_ELEMENT event.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
NamespaceBinding[] getNamespaceDeclarations() throws XPathException;
/**
* Skip the current subtree. This method may be called only immediately after
* a START_DOCUMENT or START_ELEMENT event. This call returns the matching
* END_DOCUMENT or END_ELEMENT event; the next call on next() will return
* the event following the END_DOCUMENT or END_ELEMENT.
*
* @return the matching END_DOCUMENT or END_ELEMENT event
* @throws IllegalStateException if the method is called at any time other than
* immediately after a START_DOCUMENT or START_ELEMENT event.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
Event skipToMatchingEnd() throws XPathException;
/**
* Close the event reader. This indicates that no further events are required.
* It is not necessary to close an event reader after {@link net.sf.saxon.pull.PullProvider.Event#END_OF_INPUT} has
* been reported, but it is recommended to close it if reading terminates
* prematurely. Once an event reader has been closed, the effect of further
* calls on next() is undefined.
*/
void close();
/**
* Get the NodeName identifying the name of the current node. This method
* can be used after the {@link net.sf.saxon.pull.PullProvider.Event#START_ELEMENT}, {@link net.sf.saxon.pull.PullProvider.Event#PROCESSING_INSTRUCTION},
* {@link net.sf.saxon.pull.PullProvider.Event#ATTRIBUTE}, or {@link net.sf.saxon.pull.PullProvider.Event#NAMESPACE} events. With some PullProvider implementations,
* it can also be used after {@link net.sf.saxon.pull.PullProvider.Event#END_ELEMENT}, but this is not guaranteed.
* If called at other times, the result is undefined and may result in an IllegalStateException.
* If called when the current node is an unnamed namespace node (a node representing the default namespace)
* the returned value is null.
*
* @return the NodeName. The NodeName can be used to obtain the prefix, local name,
* and namespace URI.
*/
NodeName getNodeName();
/**
* Get the string value of the current element, text node, processing-instruction,
* or top-level attribute or namespace node, or atomic value.
* In other situations the result is undefined and may result in an IllegalStateException.
* If the most recent event was a {@link net.sf.saxon.pull.PullProvider.Event#START_ELEMENT}, this method causes the content
* of the element to be read. The current event on completion of this method will be the
* corresponding {@link net.sf.saxon.pull.PullProvider.Event#END_ELEMENT}. The next call of next() will return the event following
* the END_ELEMENT event.
*
* @return the String Value of the node in question, defined according to the rules in the
* XPath data model.
* @throws net.sf.saxon.trans.XPathException
* if a dynamic error occurs
*/
/*@Nullable*/
CharSequence getStringValue() throws XPathException;
/**
* Get the type annotation of the current attribute or element node, or atomic value.
* The result of this method is undefined unless the most recent event was START_ELEMENT,
* ATTRIBUTE, or ATOMIC_VALUE.
*
* @return the type annotation.
* @since 9.4; replace the method getTypeAnnotation() which returned the integer fingerprint of the type
*/
SchemaType getSchemaType();
/**
* Get an atomic value. This call may be used only when the last event reported was
* ATOMIC_VALUE. This indicates that the PullProvider is reading a sequence that contains
* a free-standing atomic value; it is never used when reading the content of a node.
*
* @return the atomic value
*/
AtomicValue getAtomicValue();
/**
* Get the location of the current event.
* For an event stream representing a real document, the location information
* should identify the location in the lexical XML source. For a constructed document, it should
* identify the location in the query or stylesheet that caused the node to be created.
* A value of null can be returned if no location information is available.
*
* @return the SourceLocator giving the location of the current event, or null if
* no location information is available
*/
Location getSourceLocator();
/**
* Get a list of unparsed entities.
*
* @return a list of unparsed entities, or null if the information is not available, or
* an empty list if there are no unparsed entities. Each item in the list will
* be an instance of {@link net.sf.saxon.pull.UnparsedEntity}
*/
List getUnparsedEntities();
}
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