Class NamePool
- All Implemented Interfaces:
Serializable
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 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
- See Also:
-
Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic class
Uncaught Exception raised when some limit in the design of the name pool is exceeded -
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
FP_MASK is a mask used to obtain a fingerprint from a nameCode.static final int
static final int
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionint
Allocate a name from the pool, or a new Name if there is not a matching one thereint
Allocate a name from the pool, or a new Name if there is not a matching one thereint
allocateClarkName
(String expandedName) Allocate a fingerprint given a Clark Nameshort
allocateCodeForURI
(String uri) Allocate the uri code for a given URI; create one if not foundint
allocateLexicalQName
(CharSequence qname, boolean useDefault, NamespaceResolver resolver, NameChecker checker) Get the nameCode for a lexical QName, given a namespace resolver.int
allocateNamespaceCode
(int namecode) Allocate a namespace code for the prefix/URI of a given namecodeint
allocateNamespaceCode
(String prefix, String uri) Allocate the namespace code for a namespace prefix/URI pair.void
Diagnostic print of the namepool contents.getClarkName
(int nameCode) Get the Clark form of a name, given its name code or fingerprintgetClientData
(Class key) Retrieve client data on behalf of a user of the namepoolshort
getCodeForPrefix
(String prefix) Get the prefix code for a given Prefixshort
getCodeForURI
(String uri) Get the uri code for a given URIstatic NamePool
Get the singular static NamePool.getDisplayName
(int nameCode) Get the display form of a name (the QName), given its name code or fingerprintint
getFingerprint
(String uri, String localName) Get a fingerprint for the name with a given uri and local name.getLocalName
(int nameCode) Get the local part of a name, given its name code or fingerprintint
getNamespaceCode
(int namecode) Allocate a namespace code for a given namecodeint
getNamespaceCode
(String prefix, String uri) Get the existing namespace code for a namespace prefix/URI pair.getPrefix
(int nameCode) Get the prefix part of a name, given its name codegetPrefixFromNamespaceCode
(int code) Get the namespace prefix from a namespace code.static int
getPrefixIndex
(int nameCode) Get the prefix index from a namecodegetURI
(int nameCode) Get the namespace-URI of a name, given its name code or fingerprintshort
getURICode
(int nameCode) Get the URI code of a name, given its name code or fingerprintgetURIFromNamespaceCode
(int code) Get the namespace URI from a namespace code.getURIFromURICode
(short code) Get the namespace URI from a URI code.static String[]
parseClarkName
(String expandedName) Parse a Clark-format expanded name, returning the URI and local namevoid
setClientData
(Class key, Object value) Save client data on behalf of a user of the namepoolstatic void
setDefaultNamePool
(NamePool pool) Set the default NamePool.void
Statistics summarizing the namepool contents.Suggest a prefix for a given URI.
-
Field Details
-
FP_MASK
public static final int FP_MASKFP_MASK is a mask used to obtain a fingerprint from a nameCode. Given a nameCode nc, the fingerprint isnc invalid input: '&' NamePool.FP_MASK
. (In practice, Saxon code often uses the literal constant 0xfffff, to extract the bottom 20 bits).The difference between a fingerprint and a nameCode is that a nameCode contains information about the prefix of a name, the fingerprint depends only on the namespace URI and local name. Note that the "null" nameCode (-1) does not produce the "null" fingerprint (also -1) when this mask is applied.
- See Also:
-
USER_DEFINED_MASK
public static final int USER_DEFINED_MASK- See Also:
-
MAX_PREFIXES_PER_URI
public static final int MAX_PREFIXES_PER_URI- See Also:
-
-
Constructor Details
-
NamePool
public NamePool()Create a NamePool
-
-
Method Details
-
getDefaultNamePool
Get the singular static NamePool. Until Saxon 8.9, all Configurations shared the same NamePool unless users explicitly allocated a different one. This is no longer the case (each Configuration now has its own NamePool), but the singular static NamePool remains available.- Returns:
- a singular NamePool, shared by all users of this Java VM instance.
-
setDefaultNamePool
Set the default NamePool. NOTE: although a "default" namepool still exists, it is actually no longer used by default. Since Saxon 8.9, when you create a new Configuration, a new NamePool specific to that configuration is created. The so-called "default" namepool is only used if you specifically ask for it.- Parameters:
pool
- the NamePool to be returned by calls ofgetDefaultNamePool()
-
allocateNamespaceCode
Allocate the namespace code for a namespace prefix/URI pair. Create it if not already present- Parameters:
prefix
- the namespace prefixuri
- the namespace URI- Returns:
- an integer code identifying the namespace. The namespace code identifies both the prefix and the URI.
-
getNamespaceCode
Get the existing namespace code for a namespace prefix/URI pair.- Parameters:
prefix
- the namespace prefix. May be "" for the default namespaceuri
- the namespace URI. May be "" for the "null namespace"- Returns:
- the integer namespace code that identifies this namespace binding; or -1 if this binding is not present in the name pool
-
getNamespaceCode
public int getNamespaceCode(int namecode) Allocate a namespace code for a given namecode- Parameters:
namecode
- a code identifying an expanded QName, e.g. of an element or attribute- Returns:
- a code identifying the namespace used in the given name. The namespace code identifies both the prefix and the URI. Return -1 if no namespace code has been allocated (in this case the caller should call allocateNamespaceCode() to get one).
-
getPrefixIndex
public static int getPrefixIndex(int nameCode) Get the prefix index from a namecode- Parameters:
nameCode
- the name code- Returns:
- the prefix index. A value of zero means the name is unprefixed (which in the case of an attribute, means that it is in the null namespace)
-
allocateCodeForURI
Allocate the uri code for a given URI; create one if not found- Parameters:
uri
- The namespace URI. Supply "" or null for the "null namespace"- Returns:
- an integer code that uniquely identifies this URI within the namepool.
-
getCodeForURI
Get the uri code for a given URI- Parameters:
uri
- the URI whose code is required- Returns:
- the associated integer URI code, or -1 if not present in the name pool
-
getCodeForPrefix
Get the prefix code for a given Prefix- Parameters:
prefix
- the prefix. Supply "" for the null prefix representing the default namespace.- Returns:
- a code uniquely identifying this prefix within the name pool, or -1 if not found
-
suggestPrefixForURI
Suggest a prefix for a given URI. If there are several, it's undefined which one is returned. If there are no prefixes registered for this URI, return null.- Parameters:
URI
- the namespace URI- Returns:
- a prefix that has previously been associated with this URI, if available; otherwise null
-
allocate
Allocate a name from the pool, or a new Name if there is not a matching one there- Parameters:
prefix
- the namespace prefix. Use "" for the null prefix, representing the absent namespaceuri
- the namespace URI. Use "" or null for the non-namespace.localName
- the local part of the name- Returns:
- an integer (the "namecode") identifying the name within the namepool. The Name itself may be retrieved using the getName(int) method
-
allocate
Allocate a name from the pool, or a new Name if there is not a matching one there- Parameters:
prefix
- - the namespace prefixuriCode
- - the code of the URIlocalName
- - the local part of the QName- Returns:
- an integer (the "namecode") identifying the name within the namepool.
-
allocateNamespaceCode
public int allocateNamespaceCode(int namecode) Allocate a namespace code for the prefix/URI of a given namecode- Parameters:
namecode
- a code identifying an expanded QName, e.g. of an element or attribute- Returns:
- a code identifying the namespace used in the given name. The namespace code identifies both the prefix and the URI.
-
getURI
Get the namespace-URI of a name, given its name code or fingerprint- Parameters:
nameCode
- the name code or fingerprint of a name- Returns:
- the namespace URI corresponding to this name code. Returns "" for the null namespace.
- Throws:
IllegalArgumentException
- if the nameCode is not known to the NamePool.
-
getURICode
public short getURICode(int nameCode) Get the URI code of a name, given its name code or fingerprint- Parameters:
nameCode
- the name code or fingerprint of a name in the name pool- Returns:
- the integer code identifying the namespace URI part of the name
-
getLocalName
Get the local part of a name, given its name code or fingerprint- Parameters:
nameCode
- the integer name code or fingerprint of the name- Returns:
- the local part of the name represented by this name code or fingerprint
-
getPrefix
Get the prefix part of a name, given its name code- Parameters:
nameCode
- the integer name code of a name in the name pool- Returns:
- the prefix of this name. Note that if a fingerprint rather than a full name code is supplied the returned prefix will be ""
-
getDisplayName
Get the display form of a name (the QName), given its name code or fingerprint- Parameters:
nameCode
- the integer name code or fingerprint of a name in the name pool- Returns:
- the corresponding lexical QName (if a fingerprint was supplied, this will simply be the local name)
-
getClarkName
Get the Clark form of a name, given its name code or fingerprint- Parameters:
nameCode
- the integer name code or fingerprint of a name in the name pool- Returns:
- the local name if the name is in the null namespace, or "{uri}local" otherwise. The name is always interned.
-
allocateClarkName
Allocate a fingerprint given a Clark Name- Parameters:
expandedName
- the name in Clark notation, that is "localname" or "{uri}localName"- Returns:
- the fingerprint of the name, which need not previously exist in the name pool
-
parseClarkName
Parse a Clark-format expanded name, returning the URI and local name- Parameters:
expandedName
- the name in Clark notation, that is "localname" or "{uri}localName"- Returns:
- an array of two strings, the URI and the local name respectively
-
getFingerprint
Get a fingerprint for the name with a given uri and local name. These must be present in the NamePool. The fingerprint has the property that if two fingerprint are the same, the names are the same (ie. same local name and same URI).- Parameters:
uri
- the namespace URI of the required QNamelocalName
- the local part of the required QName- Returns:
- the integer fingerprint, or -1 if this is not found in the name pool
-
getURIFromNamespaceCode
Get the namespace URI from a namespace code.- Parameters:
code
- a namespace code, representing the binding of a prefix to a namespace URI- Returns:
- the namespace URI represented by this namespace binding
-
getURIFromURICode
Get the namespace URI from a URI code.- Parameters:
code
- a code that identifies the URI within the name pool- Returns:
- the URI represented by this code
-
getPrefixFromNamespaceCode
Get the namespace prefix from a namespace code.- Parameters:
code
- a namespace code representing the binding of a prefix to a URI)- Returns:
- the prefix represented by this namespace binding
-
allocateLexicalQName
public int allocateLexicalQName(CharSequence qname, boolean useDefault, NamespaceResolver resolver, NameChecker checker) throws XPathException Get the nameCode for a lexical QName, given a namespace resolver.- Parameters:
qname
- the lexical QName (with leading and trailing whitespace allowed).useDefault
- if true, an absent prefix is resolved by the NamespaceResolver to the namespace URI assigned to the prefix "". If false, an absent prefix is interpreted as meaning the name is in no namespace.resolver
- NamespaceResolver used to resolve the namespace prefix to a namespace URIchecker
- NameChecker used to check names against the XML 1.0 or 1.1 specification- Returns:
- the corresponding nameCode
- Throws:
XPathException
- if the string is not a valid lexical QName or if the namespace prefix has not been declared
-
setClientData
Save client data on behalf of a user of the namepool- Parameters:
key
- the class that is maintaining private data in the name poolvalue
- the private data maintained in the name pool on behalf of this class
-
getClientData
Retrieve client data on behalf of a user of the namepool- Parameters:
key
- the class that is maintaining private data in the name pool- Returns:
- the private data maintained in the name pool on behalf of this class
-
diagnosticDump
public void diagnosticDump()Diagnostic print of the namepool contents. -
statistics
public void statistics()Statistics summarizing the namepool contents. This method outputs summary statistical information to System.err
-