Package com.ctc.wstx.util

Class ElementIdMap

java.lang.Object

com.ctc.wstx.util.ElementIdMap

public final class ElementIdMap
extends java.lang.Object

This class is a specialized type-safe linked hash map used for storing ElementId instances. ElementId instances represent both id definitions (values of element attributes that have type ID in DTD), and references (values of element attributes of type IDREF and IDREFS). These definitions and references are stored for the purpose of verifying that all referenced id values are defined, and that none are defined more than once.

Note: there are 2 somewhat distinct usage modes, by DTDValidator and by MSV-based validators. DTDs pass raw character arrays, whereas MSV-based validators operate on Strings. This is the main reason for 2 distinct sets of methods.

Field Summary

Fields

Modifier and Type	Field	Description
protected static int	DEFAULT_SIZE	Default initial table size; set so that usually it need not be expanded.
protected static int	FILL_PCT	Let's use 80% fill factor...
protected int	mHashSeed	Seed mixed into the per-character hash, to defend against collision attacks crafted from attribute values.
protected ElementId	mHead
protected static int	MIN_SIZE
protected int	mIndexMask	Mask used to get index from hash values; equal to mBuckets.length - 1, when mBuckets.length is a power of two.
protected int	mSize	Current size (number of entries); needed to know if and when rehash.
protected int	mSizeThreshold	Limit that indicates maximum size this instance can hold before it needs to be expanded and rehashed.
protected ElementId[]	mTable	Actual hash table area
protected ElementId	mTail

Constructor Summary

Constructors

Constructor	Description
ElementIdMap()
ElementIdMap(int initialSize)	This constructor is mainly used for testing, as it can be sized appropriately to test rehashing etc.

Method Summary

Modifier and Type	Method	Description
ElementId	addDefined(char[] buffer, int start, int len, int hash, javax.xml.stream.Location loc, PrefixedName elemName, PrefixedName attrName)	Method called when an id definition is encountered.
ElementId	addDefined(java.lang.String idStr, javax.xml.stream.Location loc, PrefixedName elemName, PrefixedName attrName)
ElementId	addReferenced(char[] buffer, int start, int len, int hash, javax.xml.stream.Location loc, PrefixedName elemName, PrefixedName attrName)	Method called when a reference to id is encountered.
ElementId	addReferenced(java.lang.String idStr, javax.xml.stream.Location loc, PrefixedName elemName, PrefixedName attrName)
static int	calcHash(char[] buffer, int start, int len)	Deprecated. since 7.2; retained for binary compatibility.
static int	calcHash(char[] buffer, int start, int len, int seed)	Implementation of a hashing method for variable length Strings.
static int	calcHash(java.lang.String key)	Deprecated. since 7.2; retained for binary compatibility.
static int	calcHash(java.lang.String key, int seed)
ElementId	getFirstUndefined()
int	getHashSeed()	Returns the random seed that callers must fold into per-character hash computation for keys looked up in this table.
private void	rehash()	Method called when size (number of entries) of symbol table grows so big that load factor is exceeded.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_SIZE

protected static final int DEFAULT_SIZE

Default initial table size; set so that usually it need not be expanded.

See Also:

Constant Field Values

MIN_SIZE

protected static final int MIN_SIZE

See Also:

Constant Field Values

FILL_PCT

protected static final int FILL_PCT

Let's use 80% fill factor...

See Also:

Constant Field Values

mTable

protected ElementId[] mTable

Actual hash table area

mSize

protected int mSize

Current size (number of entries); needed to know if and when rehash.

mSizeThreshold

protected int mSizeThreshold

Limit that indicates maximum size this instance can hold before it needs to be expanded and rehashed. Calculated using fill factor passed in to constructor.

mIndexMask

protected int mIndexMask

Mask used to get index from hash values; equal to mBuckets.length - 1, when mBuckets.length is a power of two.

mHead

protected ElementId mHead

mTail

protected ElementId mTail

mHashSeed

protected final int mHashSeed

Seed mixed into the per-character hash, to defend against collision attacks crafted from attribute values. See issue #12.

Constructor Detail

ElementIdMap

public ElementIdMap()

ElementIdMap

public ElementIdMap(int initialSize)

This constructor is mainly used for testing, as it can be sized appropriately to test rehashing etc.

Method Detail

getHashSeed

public int getHashSeed()

Returns the random seed that callers must fold into per-character hash computation for keys looked up in this table.

getFirstUndefined

public ElementId getFirstUndefined()

addReferenced

public ElementId addReferenced(char[] buffer,
                               int start,
                               int len,
                               int hash,
                               javax.xml.stream.Location loc,
                               PrefixedName elemName,
                               PrefixedName attrName)

Method called when a reference to id is encountered. If so, need to check if specified id entry (ref or definiton) exists; and if not, to add a reference marker.

addReferenced

public ElementId addReferenced(java.lang.String idStr,
                               javax.xml.stream.Location loc,
                               PrefixedName elemName,
                               PrefixedName attrName)

addDefined

public ElementId addDefined(char[] buffer,
                            int start,
                            int len,
                            int hash,
                            javax.xml.stream.Location loc,
                            PrefixedName elemName,
                            PrefixedName attrName)

Method called when an id definition is encountered. If so, need to check if specified id entry (ref or definiton) exists. If not, need to add the definition marker. If it does exist, need to 'upgrade it', if it was a reference marker; otherwise need to just return the old entry, and expect caller to check for dups and report the error.

addDefined

public ElementId addDefined(java.lang.String idStr,
                            javax.xml.stream.Location loc,
                            PrefixedName elemName,
                            PrefixedName attrName)

calcHash

public static int calcHash(char[] buffer,
                           int start,
                           int len,
                           int seed)

Implementation of a hashing method for variable length Strings. Most of the time intention is that this calculation is done by caller during parsing, not here; however, sometimes it needs to be done for parsed "String" too.

Seed and finalizer match SymbolTable.calcHash(char[], int, int, int), so attacker- chosen names cannot land in the same bucket without knowing the table's per-instance seed.

Parameters:

len - Length of String; has to be at least 1 (caller guarantees this pre-condition)

seed - Per-table seed obtained from getHashSeed()

calcHash

public static int calcHash(java.lang.String key,
                           int seed)

calcHash

@Deprecated
public static int calcHash(char[] buffer,
                           int start,
                           int len)

Deprecated.

since 7.2; retained for binary compatibility. Use calcHash(char[], int, int, int) with getHashSeed().

calcHash

@Deprecated
public static int calcHash(java.lang.String key)

Deprecated.

since 7.2; retained for binary compatibility. Use calcHash(String, int) with getHashSeed().

rehash

private void rehash()

Method called when size (number of entries) of symbol table grows so big that load factor is exceeded. Since size has to remain power of two, arrays will then always be doubled. Main work is really redistributing old entries into new String/Bucket entries.