Examples of net.sf.saxon.om.NamePool

net.sf.saxon.om.NamePool
A NamePool holds a collection of expanded names, each containing a namespace URI, a namespace prefix, and a local name; plus a collection of namespaces, each consisting of a prefix/URI pair.
Each expanded name is allocated a unique integer namecode. The namecode enables all three parts of the expanded name to be determined, that is, the prefix, the URI, and the local name.

The equivalence betweem names depends only on the URI and the local name. The namecode is designed so that if two namecodes represent names with the same URI and local name, the two namecodes are the same in the bottom 20 bits. It is therefore possible to compare two names for equivalence by performing an integer comparison of these 20 bits. The bottom 20 bits of a namecode are referred to as a fingerprint.

The NamePool eliminates duplicate names if they have the same prefix, uri, and local part. It retains duplicates if they have different prefixes

Internally the NamePool is organized as a fixed number of hash chains. The selection of a hash chain is based on hashing the local name, because it is unusual to have many names that share the same local name but use different URIs. There are 1024 hash chains and the identifier of the hash chain forms the bottom ten bits of the namecode. The next ten bits represent the sequential position of an entry within the hash chain. The upper bits represent the selection of prefix, from among the list of prefixes that have been used with a given URI. A prefix part of zero means no prefix; if the two prefixes used with a particular namespace are "xs" and "xsd", say, then these will be prefix codes 1 and 2.

Fingerprints in the range 0 to 1023 are reserved for system use, and are allocated as constants mainly to names in the XSLT and XML Schema namespaces: constants representing these names are found in {@link StandardNames}.
Operations that update the NamePool, or that have the potential to update it, are synchronized. Read-only operations are done without synchronization. Although technically unsafe, this has not led to any problems in practice. Performance problems due to excessive contention on the NamePool have occasionally been observed: if this happens, the best strategy is to consider splitting the workload to use multiple Configurations each with a separate NamePool.

Internal organization of the NamePool

The NamePool holds two kinds of entry: name entries, representing expanded names (local name + prefix + URI), identified by a name code, and namespace entries (prefix + URI) identified by a namespace code.

The data structure of the name table is as follows.

There is a fixed size hash table; names are allocated to slots in this table by hashing on the local name. Each entry in the table is the head of a chain of NameEntry objects representing names that have the same hash code.

Each NameEntry represents a distinct name (same URI and local name). It contains the local name as a string, plus a short integer representing the URI (as an offset into the array uris[] - this is known as the URIcode).

The fingerprint of a name consists of the hash slot number (in the bottom 10 bits) concatenated with the depth of the entry down the chain of hash synonyms (in the next 10 bits). Fingerprints with depth 0 (i.e., in the range 0-1023) are reserved for predefined names (names of XSLT elements and attributes, and of built-in types). These names are not stored in the name pool, but are accessible as if they were.

A nameCode contains the fingerprint in the bottom 20 bits. It also contains a 10-bit prefix index. This distinguishes the prefix used, among all the prefixes that have been used with this namespace URI. If the prefix index is zero, the prefix is null. Otherwise, it indexes an array of prefix Strings associated with the namespace URI. Note that the data structures and algorithms are optimized for the case where URIs usually use the same prefix.

The nameCode -1 is reserved to mean "not known" or inapplicable. The fingerprint -1 has the same meaning. Note that masking the nameCode -1 to extract its bottom 20 bits is incorrect, and will lead to errors.
@author Michael H. Kay

            }
        }
        level++;
        nextReceiver.startElement(nameCode, typeCode, locationId, properties);
        if (seekingHead) {
            NamePool namePool = getNamePool();
            int uriCode = namePool.getURICode(nameCode);
            String localName = namePool.getLocalName(nameCode);
            if (uriCode == requiredURICode && comparesEqual(localName, "head")) {
                foundHead = true;
            }
        }

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    public void startContent() throws XPathException {
        if (foundHead) {
            foundHead = false;
            NamePool namePool = getNamePool();
            nextReceiver.startContent();
            int metaCode = namePool.allocate("", requiredURICode, "meta");
            nextReceiver.startElement(metaCode, StandardNames.XS_UNTYPED, 0, 0);
            int httpEquivCode = namePool.allocate("", "", "http-equiv");
            nextReceiver.attribute(httpEquivCode, StandardNames.XS_UNTYPED_ATOMIC, "Content-Type", 0, 0);
            int contentCode = namePool.allocate("", "", "content");
            nextReceiver.attribute(contentCode, StandardNames.XS_UNTYPED_ATOMIC, mediaType + "; charset=" + encoding, 0, 0);
            nextReceiver.startContent();
            droppingMetaTags = level;
            seekingHead = false;
            attributes = new AttributeCollectionImpl(namePool);

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            NodeInfo node = (NodeInfo)item;
            switch (node.getNodeKind()) {
                case DOCUMENT:
                    return "document-node()";
                case ELEMENT:
                    NamePool pool = node.getNamePool();
                    int annotation = node.getTypeAnnotation();
                    return "element(" +
                            ((NodeInfo)item).getDisplayName() + ", " +
                            (annotation == -1 ?
                                "xs:untyped)" :
                                pool.getDisplayName(annotation) + ')');
                case ATTRIBUTE:
                    NamePool pool2 = node.getNamePool();
                    int annotation2 = node.getTypeAnnotation() & NamePool.FP_MASK;
                    return "attribute(" +
                            ((NodeInfo)item).getDisplayName()+ ", " +
                            (annotation2 == -1 ?
                                "xs:untypedAtomic)" :
                                pool2.getDisplayName(annotation2) + ')');
                case TEXT:      return "text()";
                case COMMENT:   return "comment()";
                case PROCESSING_INSTRUCTION:
                                return "processing-instruction()";
                case NAMESPACE: return "namespace()";

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    private HashSet urlTable;


    private synchronized void buildURIAttributeTable() {
        // Reuse the attribute table for all XHTMLEmitters sharing the same namepool
        NamePool pool = getPipelineConfiguration().getConfiguration().getNamePool();
        urlTable = (HashSet)pool.getClientData(this.getClass());
        if (urlTable == null) {
            urlTable = new HashSet(40);
            pool.setClientData(this.getClass(), urlTable);
        }
        setUrlAttribute(pool, "form", "action");
        setUrlAttribute(pool, "object", "archive");
        setUrlAttribute(pool, "body", "background");
        setUrlAttribute(pool, "q", "cite");

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     * @throws net.sf.saxon.trans.XPathException
     *
     */


    protected void openDocument() throws XPathException {
        NamePool pool = getPipelineConfiguration().getConfiguration().getNamePool();
        for (int i=0; i<emptyTagNames.length; i++) {
            emptyTags.add(pool.allocate("", NamespaceConstant.XHTML, emptyTagNames[i]) & NamePool.FP_MASK);
        }
        super.openDocument();
    }

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     *                   prefix is ""
     * @return the uri for the namespace, or null if the prefix is not in scope
     */


    public String getURIForPrefix(String prefix, boolean useDefault) {
        NamePool pool = getNamePool();
        if ((prefix==null || prefix.length()==0) && !useDefault) {
            return "";
        } else if ("xml".equals(prefix)) {
            return NamespaceConstant.XML;
        } else {
            short prefixCode = pool.getCodeForPrefix(prefix);
            short uriCode = getURICode(prefixCode);
            if (uriCode == -1) {
                return null;
            }
            return pool.getURIFromURICode(uriCode);
        }
    }

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     * Get an iterator over all the prefixes declared in this namespace context. This will include
     * the default namespace (prefix="") and the XML namespace where appropriate
     */


    public Iterator iteratePrefixes() {
        NamePool pool = getNamePool();
        List prefixes = new ArrayList(namespacesSize);
        for (int i=namespacesSize-1; i>=0; i--) {
            String prefix = pool.getPrefixFromNamespaceCode(namespaces[i]);
            if (!prefixes.contains(prefix)) {
                prefixes.add(prefix);
            }
        }
        prefixes.add("xml");

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     * @param seq sequence number of attribute, used for generating distinctive prefixes
     * @return the actual allocated name, which may be different.
    */


    private int checkProposedPrefix(int nameCode, int seq) throws XPathException {
        NamePool namePool = getNamePool();
        int nscode = namePool.getNamespaceCode(nameCode);
        if (nscode == -1) {
            // avoid calling allocate where possible, because it's synchronized
            nscode = namePool.allocateNamespaceCode(nameCode);
        }
        int nsprefix = nscode>>16;


        short existingURICode = getURICode((short)nsprefix);
        if (existingURICode == -1) {
            // prefix has not been declared: declare it now (namespace fixup)
            namespace(nscode, 0);
            return nameCode;
        } else {
            if ((nscode & 0xffff) == existingURICode) {
                // prefix is already bound to this URI
                return nameCode;  // all is well
            } else {
                // conflict: prefix is currently bound to a different URI
                String prefix = getSubstitutePrefix(nscode, seq);


                int newCode = namePool.allocate(
                                    prefix,
                                    namePool.getURI(nameCode),
                                    namePool.getLocalName(nameCode));
                namespace(namePool.allocateNamespaceCode(newCode), 0);
                return newCode;
            }
        }
    }

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     *                   prefix is ""
     * @return the uri for the namespace, or null if the prefix is not in scope
     */


    public String getURIForPrefix(String prefix, boolean useDefault) {
        NamePool pool = getNamePool();
        if ((prefix==null || prefix.length()==0) && !useDefault) {
            return "";
        } else if ("xml".equals(prefix)) {
            return NamespaceConstant.XML;
        } else {
            short prefixCode = pool.getCodeForPrefix(prefix);
            short uriCode = getURICode(prefixCode);
            if (uriCode == -1) {
                return null;
            }
            return pool.getURIFromURICode(uriCode);
        }
    }

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     * Get an iterator over all the prefixes declared in this namespace context. This will include
     * the default namespace (prefix="") and the XML namespace where appropriate
     */


    public Iterator iteratePrefixes() {
        NamePool pool = getNamePool();
        List prefixes = new ArrayList(namespacesSize);
        for (int i=namespacesSize-1; i>=0; i--) {
            String prefix = pool.getPrefixFromNamespaceCode(namespaces[i]);
            if (!prefixes.contains(prefix)) {
                prefixes.add(prefix);
            }
        }
        prefixes.add("xml");

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net.sf.saxon.dom.DocumentWrapper

net.sf.saxon.dom.DOMSender

net.sf.saxon.event.ContentHandlerProxy

net.sf.saxon.event.MetaTagAdjuster

net.sf.saxon.event.NamespaceReducer

net.sf.saxon.event.ResultWrapper

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net.sf.saxon.event.XHTMLEmitter

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Examples of net.sf.saxon.om.NamePool

Internal organization of the NamePool

Related Classes of net.sf.saxon.om.NamePool