Class ArrayTrie<V>
- Type Parameters:
V
- the entry type
- All Implemented Interfaces:
Trie<V>
A Trie String lookup data structure using a fixed size array.
This implementation is always case insensitive and is optimal for a small number of fixed strings with few special characters. The Trie is stored in an array of lookup tables, each indexed by the next character of the key. Frequently used characters are directly indexed in each lookup table, whilst infrequently used characters must use a big character table.
This Trie is very space efficient if the key characters are from ' ', '+', '-', ':', ';', '.', 'A' to 'Z' or 'a' to 'z'. Other ISO-8859-1 characters can be used by the key, but less space efficiently.
This Trie is not Threadsafe and contains no mutual exclusion or deliberate memory barriers. It is intended for an ArrayTrie to be built by a single thread and then used concurrently by multiple threads and not mutated during that access. If concurrent mutations of the Trie is required external locks need to be applied.
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final int[]
The index lookup table, this maps a character as a byte (ISO-8859-1 or UTF8) to an index within a Trie rowprivate char[][]
A big index for each row.private final String[]
The key (if any) for a Trie row.private final char[]
The Trie rows in a single array which allows a lookup of row,character to the next row in the Trie.private char
The number of rows allocatedprivate final V[]
The value (if any) for a Trie row.private static final int
The Size of a Trie row is how many characters can be looked up directly without going to a big index.Fields inherited from class org.eclipse.jetty.util.AbstractTrie
_caseInsensitive
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
clear()
Get an exact match from a String keyget
(ByteBuffer b, int offset, int len) Get an exact match from a segment of a ByteBuufer as keygetBest
(byte[] b, int offset, int len) Get the best match from key in a byte array.private V
getBest
(int t, byte[] b, int offset, int len) private V
private V
getBest
(int t, ByteBuffer b, int offset, int len) Get the best match from key in a String.getBest
(ByteBuffer b, int offset, int len) Get the best match from key in a byte buffer.boolean
isFull()
keySet()
private void
boolean
Put an entry into the TrietoString()
private void
toString
(Appendable out, int t) Methods inherited from class org.eclipse.jetty.util.AbstractTrie
get, get, getBest, isCaseInsensitive, put, remove
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Field Details
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ROW_SIZE
private static final int ROW_SIZEThe Size of a Trie row is how many characters can be looked up directly without going to a big index. This is set at 32 to cover case insensitive alphabet and a few other common characters.- See Also:
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__lookup
private static final int[] __lookupThe index lookup table, this maps a character as a byte (ISO-8859-1 or UTF8) to an index within a Trie row -
_rowIndex
private final char[] _rowIndexThe Trie rows in a single array which allows a lookup of row,character to the next row in the Trie. This is actually a 2 dimensional array that has been flattened to achieve locality of reference. The first ROW_SIZE entries are for row 0, then next ROW_SIZE entries are for row 1 etc. So in general instead of using _rows[row][index], we use _rows[row*ROW_SIZE+index] to look up the next row for a given character. The array is of characters rather than integers to save space. -
_key
The key (if any) for a Trie row. A row may be a leaf, a node or both in the Trie tree. -
_value
The value (if any) for a Trie row. A row may be a leaf, a node or both in the Trie tree. -
_bigIndex
private char[][] _bigIndexA big index for each row. If a character outside of the lookup map is needed, then a big index will be created for the row, with 256 entries, one for each possible byte. -
_rows
private char _rowsThe number of rows allocated
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Constructor Details
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ArrayTrie
public ArrayTrie() -
ArrayTrie
public ArrayTrie(int capacity) - Parameters:
capacity
- The capacity of the trie, which at the worst case is the total number of characters of all keys stored in the Trie. The capacity needed is dependent of the shared prefixes of the keys. For example, a capacity of 6 nodes is required to store keys "foo" and "bar", but a capacity of only 4 is required to store "bar" and "bat".
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Method Details
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clear
public void clear() -
put
Description copied from interface:Trie
Put an entry into the Trie- Parameters:
s
- The key for the entryv
- The value of the entry- Returns:
- True if the Trie had capacity to add the field.
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get
Description copied from interface:Trie
Get an exact match from a String key- Parameters:
s
- The keyoffset
- The offset within the string of the keylen
- the length of the key- Returns:
- the value for the string / offset / length
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get
Description copied from interface:Trie
Get an exact match from a segment of a ByteBuufer as key- Parameters:
b
- The bufferoffset
- The offset within the buffer of the keylen
- the length of the key- Returns:
- The value or null if not found
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getBest
Description copied from interface:Trie
Get the best match from key in a byte array. The key is assumed to by ISO_8859_1 characters. -
getBest
Description copied from interface:Trie
Get the best match from key in a byte buffer. The key is assumed to by ISO_8859_1 characters.- Parameters:
b
- The bufferoffset
- The offset within the buffer of the keylen
- the length of the key- Returns:
- The value or null if not found
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getBest
Description copied from interface:Trie
Get the best match from key in a String.- Parameters:
s
- The stringoffset
- The offset within the string of the keylen
- the length of the key- Returns:
- The value or null if not found
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getBest
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getBest
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getBest
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toString
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toString
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keySet
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keySet
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isFull
public boolean isFull()
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