335 lines
13 KiB
C#
335 lines
13 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="XmlAttributeCache.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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// <owner current="true" primary="true">[....]</owner>
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//------------------------------------------------------------------------------
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namespace System.Xml.Xsl.Runtime {
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using System;
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using System.Diagnostics;
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using System.Xml;
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using System.Xml.XPath;
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using System.Xml.Schema;
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/// <summary>
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/// This writer supports only writer methods which write attributes. Attributes are stored in a
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/// data structure until StartElementContent() is called, at which time the attributes are flushed
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/// to the wrapped writer. In the case of duplicate attributes, the last attribute's value is used.
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/// </summary>
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internal sealed class XmlAttributeCache : XmlRawWriter, IRemovableWriter {
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private XmlRawWriter wrapped;
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private OnRemoveWriter onRemove; // Event handler that is called when cached attributes are flushed to wrapped writer
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private AttrNameVal[] arrAttrs; // List of cached attribute names and value parts
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private int numEntries; // Number of attributes in the cache
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private int idxLastName; // The entry containing the name of the last attribute to be cached
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private int hashCodeUnion; // Set of hash bits that can quickly guarantee a name is not a duplicate
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/// <summary>
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/// Initialize the cache. Use this method instead of a constructor in order to reuse the cache.
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/// </summary>
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public void Init(XmlRawWriter wrapped) {
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SetWrappedWriter(wrapped);
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// Clear attribute list
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this.numEntries = 0;
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this.idxLastName = 0;
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this.hashCodeUnion = 0;
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}
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/// <summary>
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/// Return the number of cached attributes.
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/// </summary>
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public int Count {
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get { return this.numEntries; }
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}
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//-----------------------------------------------
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// IRemovableWriter interface
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//-----------------------------------------------
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/// <summary>
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/// This writer will raise this event once cached attributes have been flushed in order to signal that the cache
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/// no longer needs to be part of the pipeline.
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/// </summary>
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public OnRemoveWriter OnRemoveWriterEvent {
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get { return this.onRemove; }
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set { this.onRemove = value; }
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}
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/// <summary>
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/// The wrapped writer will callback on this method if it wishes to remove itself from the pipeline.
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/// </summary>
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private void SetWrappedWriter(XmlRawWriter writer) {
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// If new writer might remove itself from pipeline, have it callback on this method when its ready to go
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IRemovableWriter removable = writer as IRemovableWriter;
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if (removable != null)
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removable.OnRemoveWriterEvent = SetWrappedWriter;
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this.wrapped = writer;
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}
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//-----------------------------------------------
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// XmlWriter interface
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//-----------------------------------------------
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/// <summary>
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/// Add an attribute to the cache. If an attribute if the same name already exists, replace it.
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/// </summary>
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public override void WriteStartAttribute(string prefix, string localName, string ns) {
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int hashCode;
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int idx = 0;
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Debug.Assert(localName != null && localName.Length != 0 && prefix != null && ns != null);
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// Compute hashcode based on first letter of the localName
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hashCode = (1 << ((int) localName[0] & 31));
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// If the hashcode is not in the union, then name will not be found by a scan
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if ((this.hashCodeUnion & hashCode) != 0) {
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// The name may or may not be present, so scan for it
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Debug.Assert(this.numEntries != 0);
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do {
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if (this.arrAttrs[idx].IsDuplicate(localName, ns, hashCode))
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break;
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// Next attribute name
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idx = this.arrAttrs[idx].NextNameIndex;
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}
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while (idx != 0);
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}
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else {
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// Insert hashcode into union
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this.hashCodeUnion |= hashCode;
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}
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// Insert new attribute; link attribute names together in a list
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EnsureAttributeCache();
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if (this.numEntries != 0)
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this.arrAttrs[this.idxLastName].NextNameIndex = this.numEntries;
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this.idxLastName = this.numEntries++;
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this.arrAttrs[this.idxLastName].Init(prefix, localName, ns, hashCode);
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}
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/// <summary>
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/// No-op.
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/// </summary>
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public override void WriteEndAttribute() {
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}
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/// <summary>
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/// Pass through namespaces to underlying writer. If any attributes have been cached, flush them.
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/// </summary>
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internal override void WriteNamespaceDeclaration(string prefix, string ns) {
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FlushAttributes();
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this.wrapped.WriteNamespaceDeclaration(prefix, ns);
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}
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/// <summary>
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/// Add a block of text to the cache. This text block makes up some or all of the untyped string
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/// value of the current attribute.
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/// </summary>
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public override void WriteString(string text) {
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Debug.Assert(text != null);
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Debug.Assert(this.arrAttrs != null && this.numEntries != 0);
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EnsureAttributeCache();
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this.arrAttrs[this.numEntries++].Init(text);
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}
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/// <summary>
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/// All other WriteValue methods are implemented by XmlWriter to delegate to WriteValue(object) or WriteValue(string), so
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/// only these two methods need to be implemented.
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/// </summary>
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public override void WriteValue(object value) {
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Debug.Assert(value is XmlAtomicValue, "value should always be an XmlAtomicValue, as XmlAttributeCache is only used by XmlQueryOutput");
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Debug.Assert(this.arrAttrs != null && this.numEntries != 0);
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EnsureAttributeCache();
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this.arrAttrs[this.numEntries++].Init((XmlAtomicValue) value);
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}
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public override void WriteValue(string value) {
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WriteValue(value);
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}
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/// <summary>
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/// Send cached, non-overriden attributes to the specified writer. Calling this method has
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/// the side effect of clearing the attribute cache.
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/// </summary>
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internal override void StartElementContent() {
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FlushAttributes();
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// Call StartElementContent on wrapped writer
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this.wrapped.StartElementContent();
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}
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public override void WriteStartElement(string prefix, string localName, string ns) {
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Debug.Assert(false, "Should never be called on XmlAttributeCache.");
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}
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internal override void WriteEndElement(string prefix, string localName, string ns) {
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Debug.Assert(false, "Should never be called on XmlAttributeCache.");
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}
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public override void WriteComment(string text) {
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Debug.Assert(false, "Should never be called on XmlAttributeCache.");
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}
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public override void WriteProcessingInstruction(string name, string text) {
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Debug.Assert(false, "Should never be called on XmlAttributeCache.");
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}
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public override void WriteEntityRef(string name) {
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Debug.Assert(false, "Should never be called on XmlAttributeCache.");
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}
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/// <summary>
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/// Forward call to wrapped writer.
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/// </summary>
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public override void Close() {
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this.wrapped.Close();
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}
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/// <summary>
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/// Forward call to wrapped writer.
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/// </summary>
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public override void Flush() {
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this.wrapped.Flush();
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}
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//-----------------------------------------------
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// Helper methods
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//-----------------------------------------------
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private void FlushAttributes() {
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int idx = 0, idxNext;
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string localName;
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while (idx != this.numEntries) {
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// Get index of next attribute's name (0 if this is the last attribute)
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idxNext = this.arrAttrs[idx].NextNameIndex;
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if (idxNext == 0)
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idxNext = this.numEntries;
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// If localName is null, then this is a duplicate attribute that has been marked as "deleted"
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localName = this.arrAttrs[idx].LocalName;
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if (localName != null) {
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string prefix = this.arrAttrs[idx].Prefix;
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string ns = this.arrAttrs[idx].Namespace;
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this.wrapped.WriteStartAttribute(prefix, localName, ns);
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// Output all of this attribute's text or typed values
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while (++idx != idxNext) {
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string text = this.arrAttrs[idx].Text;
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if (text != null)
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this.wrapped.WriteString(text);
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else
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this.wrapped.WriteValue(this.arrAttrs[idx].Value);
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}
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this.wrapped.WriteEndAttribute();
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}
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else {
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// Skip over duplicate attributes
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idx = idxNext;
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}
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}
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// Notify event listener that attributes have been flushed
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if (this.onRemove != null)
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this.onRemove(this.wrapped);
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}
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private struct AttrNameVal {
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private string localName;
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private string prefix;
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private string namespaceName;
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private string text;
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private XmlAtomicValue value;
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private int hashCode;
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private int nextNameIndex;
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public string LocalName { get { return this.localName; } }
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public string Prefix { get { return this.prefix; } }
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public string Namespace { get { return this.namespaceName; } }
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public string Text { get { return this.text; } }
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public XmlAtomicValue Value { get { return this.value; } }
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public int NextNameIndex { get { return this.nextNameIndex; } set { this.nextNameIndex = value; } }
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/// <summary>
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/// Cache an attribute's name and type.
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/// </summary>
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public void Init(string prefix, string localName, string ns, int hashCode) {
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this.localName = localName;
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this.prefix = prefix;
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this.namespaceName = ns;
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this.hashCode = hashCode;
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this.nextNameIndex = 0;
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}
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/// <summary>
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/// Cache all or part of the attribute's string value.
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/// </summary>
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public void Init(string text) {
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this.text = text;
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this.value = null;
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}
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/// <summary>
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/// Cache all or part of the attribute's typed value.
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/// </summary>
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public void Init(XmlAtomicValue value) {
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this.text = null;
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this.value = value;
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}
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/// <summary>
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/// Returns true if this attribute has the specified name (and thus is a duplicate).
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/// </summary>
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public bool IsDuplicate(string localName, string ns, int hashCode) {
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// If attribute is not marked as deleted
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if (this.localName != null) {
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// And if hash codes match,
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if (this.hashCode == hashCode) {
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// And if local names match,
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if (this.localName.Equals(localName)) {
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// And if namespaces match,
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if (this.namespaceName.Equals(ns)) {
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// Then found duplicate attribute, so mark the attribute as deleted
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this.localName = null;
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return true;
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}
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}
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}
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}
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return false;
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}
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}
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#if DEBUG
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private const int DefaultCacheSize = 2;
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#else
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private const int DefaultCacheSize = 32;
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#endif
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/// <summary>
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/// Ensure that attribute array has been created and is large enough for at least one
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/// additional entry.
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/// </summary>
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private void EnsureAttributeCache() {
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if (this.arrAttrs == null) {
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// Create caching array
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this.arrAttrs = new AttrNameVal[DefaultCacheSize];
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}
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else if (this.numEntries >= this.arrAttrs.Length) {
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// Resize caching array
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Debug.Assert(this.numEntries == this.arrAttrs.Length);
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AttrNameVal[] arrNew = new AttrNameVal[this.numEntries * 2];
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Array.Copy(this.arrAttrs, arrNew, this.numEntries);
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this.arrAttrs = arrNew;
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}
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}
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}
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}
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