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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.event;
import net.sf.saxon.om.*;
import net.sf.saxon.s9api.Location;
import net.sf.saxon.str.UnicodeString;
import net.sf.saxon.trace.ExpressionPresenter;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.trans.rules.Rule;
import net.sf.saxon.trans.rules.RuleTarget;
import net.sf.saxon.type.ComplexType;
import net.sf.saxon.type.SchemaType;
import net.sf.saxon.type.Untyped;
import net.sf.saxon.value.Whitespace;
import java.util.Arrays;
/**
* The {@code Stripper} class performs whitespace stripping according to the rules of
* the xsl:strip-space and xsl:preserve-space instructions.
* It maintains details of which elements need to be stripped.
* The code is written to act as a SAX-like filter to do the stripping.
*
* If you found this code as a result of a Google search, sorry about the disappointment.
*/
public class Stripper extends ProxyReceiver {
public final static StripRuleTarget STRIP = new StripRuleTarget() {
};
public final static StripRuleTarget PRESERVE = new StripRuleTarget() {
};
protected SpaceStrippingRule rule;
public Stripper(/*@NotNull*/ SpaceStrippingRule rule, /*@NotNull*/ Receiver next) {
super(next);
assert rule != null;
this.rule = rule;
}
// stripStack is used to hold information used while stripping nodes. We avoid allocating
// space on the tree itself to keep the size of nodes down. Each entry on the stack is two
// booleans, one indicates the current value of xml-space is "preserve", the other indicates
// that we are in a space-preserving element. See masks below for information about other bits.
// We implement our own stack to avoid the overhead of allocating objects.
private int[] stripStack = new int[100];
private int top = 0;
/**
* Decide whether an element is in the set of white-space preserving element types
*
* @param name Identifies the name of the element whose whitespace is (or is not) to
* be preserved
* @param type The schema type of this element
* @return ALWAYS_PRESERVE if the element is in the set of white-space preserving
* element types, ALWAYS_STRIP if the element is to be stripped regardless of the
* xml:space setting, and STRIP_DEFAULT otherwise
* @throws XPathException if the rules are ambiguous and ambiguities are to be
* reported as errors
*/
private int isSpacePreserving(NodeName name, SchemaType type) throws XPathException {
return rule.isSpacePreserving(name, type);
}
public static final int ALWAYS_PRESERVE = 0x01; // whitespace always preserved (e.g. xsl:text)
public static final int ALWAYS_STRIP = 0x02; // whitespace always stripped (e.g. xsl:choose)
public static final int STRIP_DEFAULT = 0x00; // no special action
public static final int PRESERVE_PARENT = 0x04; // parent element specifies xml:space="preserve"
public static final int SIMPLE_CONTENT = 0x08; // type annotation indicates simple typed content
public static final int ASSERTIONS_EXIST = 0x10; // XSD 1.1 assertions are in scope
/**
* Callback interface for SAX: not for application use
*/
@Override
public void open() throws XPathException {
// System.err.println("Stripper#startDocument()");
top = 0;
stripStack[top] = ALWAYS_PRESERVE; // {xml:space = default, preserve this element = true}
super.open();
}
@Override
public void startElement(NodeName elemName, SchemaType type,
AttributeMap attributes, NamespaceMap namespaces,
Location location, int properties) throws XPathException {
//System.err.println("startElement " + elemName.getDisplayName());
nextReceiver.startElement(elemName, type, attributes, namespaces, location, properties);
int preserveParent = stripStack[top];
int preserve = preserveParent & (PRESERVE_PARENT | ASSERTIONS_EXIST);
int elementStrip = isSpacePreserving(elemName, type);
if (elementStrip == ALWAYS_PRESERVE) {
preserve |= ALWAYS_PRESERVE;
} else if (elementStrip == ALWAYS_STRIP) {
preserve |= ALWAYS_STRIP;
}
if (type != Untyped.getInstance()) {
if (preserve == 0) {
// if the element has simple content, whitespace stripping is disabled
if (type.isSimpleType() || ((ComplexType) type).isSimpleContent()) {
preserve |= SIMPLE_CONTENT;
}
}
if (type instanceof ComplexType && ((ComplexType) type).hasAssertions()) {
preserve |= ASSERTIONS_EXIST;
}
}
// put "preserve" value on top of stack
top++;
if (top >= stripStack.length) {
stripStack = Arrays.copyOf(stripStack, top * 2);
}
stripStack[top] = preserve;
String xmlSpace = attributes.getValue(NamespaceUri.XML, "space");
if (xmlSpace != null) {
if (Whitespace.trim(xmlSpace).equals("preserve")) {
stripStack[top] |= PRESERVE_PARENT;
} else {
stripStack[top] &= ~PRESERVE_PARENT;
}
}
}
/**
* Handle an end-of-element event
*/
@Override
public void endElement() throws XPathException {
nextReceiver.endElement();
top--;
}
/**
* Handle a text node
*/
@Override
public void characters(UnicodeString chars, Location locationId, int properties) throws XPathException {
// assume adjacent chunks of text are already concatenated
if (((((stripStack[top] & (ALWAYS_PRESERVE | PRESERVE_PARENT | SIMPLE_CONTENT | ASSERTIONS_EXIST)) != 0) &&
(stripStack[top] & ALWAYS_STRIP) == 0)
|| !Whitespace.isAllWhite(chars))
&& !chars.isEmpty()) {
nextReceiver.characters(chars, locationId, properties);
}
}
/**
* Ask whether this Receiver (or the downstream pipeline) makes any use of the type annotations
* supplied on element and attribute events
*
* @return true if the Receiver makes any use of this information. If false, the caller
* may supply untyped nodes instead of supplying the type annotation
*/
@Override
public boolean usesTypeAnnotations() {
return true;
}
public static class StripRuleTarget implements RuleTarget {
@Override
public void export(ExpressionPresenter presenter) throws XPathException {
// no-op
}
@Override
public void registerRule(Rule rule) {
// no action
}
}
}