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javadoc and branchless hilo

This commit is contained in:
Greg Wilkins 2013-06-20 11:23:18 +10:00
parent 53278e5121
commit 60828fe8a3
1 changed files with 24 additions and 6 deletions
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30
jetty-util/src/main/java/org/eclipse/jetty/util/ArrayTernaryTrie.java
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@ -26,6 +26,19 @@ import java.util.Set;
/* ------------------------------------------------------------ */
/** A Ternary Trie String lookup data structure.
* This Trie is of a fixed size and cannot grow (which can be a good thing with regards to DOS when used as a cache).
* <p>
* The Trie is stored in 3 arrays:<dl>
* <dt>char[] _tree</dt><dd>This is semantically 2 dimensional array flattened into a 1 dimensional char array. The second dimension
* is that every 4 sequential elements represents a row of: character; hi index; eq index; low index, used to build a
* ternary trie of key strings.</dd>
* <dt>String[] _key<dt><dd>An array of key values where each element matches a row in the _tree array. A non zero key element
* indicates that the _tree row is a complete key rather than an intermediate character of a longer key.</dd>
* <dt>V[] _value</dt><dd>An array of values corresponding to the _key array</dd>
* </dl>
* <p>The lookup of a value will iterate through the _tree array matching characters. If the equal tree branch is followed,
* then the _key array is looked up to see if this is a complete match. If a match is found then the _value array is looked up
* to return the matching value.
* </p>
* @param <V>
*/
public class ArrayTernaryTrie<V> extends AbstractTrie<V>
@ -59,7 +72,6 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
*/
private final Object[] _value;
/**
* The number of rows allocated
*/
@ -183,7 +195,7 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
break;
}
t=_tree[row+((diff<0)?LO:HI)];
t=_tree[row+hilo(diff)];
if (t==0)
return null;
}
@ -223,7 +235,7 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
break;
}
t=_tree[row+((diff<0)?LO:HI)];
t=_tree[row+hilo(diff)];
if (t==0)
return null;
}
@ -279,7 +291,7 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
break;
}
t=_tree[row+((diff<0)?LO:HI)];
t=_tree[row+hilo(diff)];
}
}
return null;
@ -328,7 +340,7 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
break;
}
t=_tree[row+((diff<0)?LO:HI)];
t=_tree[row+hilo(diff)];
}
}
return null;
@ -369,7 +381,7 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
break;
}
t=_tree[row+((diff<0)?LO:HI)];
t=_tree[row+hilo(diff)];
}
}
return null;
@ -418,6 +430,12 @@ public class ArrayTernaryTrie<V> extends AbstractTrie<V>
return _rows+1==_key.length;
}
public static int hilo(int diff)
{
// branchless equivalent to return ((diff<0)?LO:HI);
// return 3+2*((diff&Integer.MIN_VALUE)>>Integer.SIZE-1);
return 1+(diff|Integer.MAX_VALUE)/(Integer.MAX_VALUE/2);
}
public void dump()
{