ternarytree.java

iText是一个能够快速产生PDF文件的java类库。iText的java类对于那些要产生包含文本

        hi = na;
        na = new char[newsize];
        System.arraycopy(eq, 0, na, 0, len);
        eq = na;
        na = new char[newsize];
        System.arraycopy(sc, 0, na, 0, len);
        sc = na;
    }

    public int size() {
        return length;
    }

    public Object clone() {
        TernaryTree t = new TernaryTree();
        t.lo = (char[])this.lo.clone();
        t.hi = (char[])this.hi.clone();
        t.eq = (char[])this.eq.clone();
        t.sc = (char[])this.sc.clone();
        t.kv = (CharVector)this.kv.clone();
        t.root = this.root;
        t.freenode = this.freenode;
        t.length = this.length;

        return t;
    }

    /**
     * Recursively insert the median first and then the median of the
     * lower and upper halves, and so on in order to get a balanced
     * tree. The array of keys is assumed to be sorted in ascending
     * order.
     */
    protected void insertBalanced(String[] k, char[] v, int offset, int n) {
        int m;
        if (n < 1) {
            return;
        }
        m = n >> 1;

        insert(k[m + offset], v[m + offset]);
        insertBalanced(k, v, offset, m);

        insertBalanced(k, v, offset + m + 1, n - m - 1);
    }


    /**
     * Balance the tree for best search performance
     */
    public void balance() {
        // System.out.print("Before root splitchar = "); System.out.println(sc[root]);

        int i = 0, n = length;
        String[] k = new String[n];
        char[] v = new char[n];
        Iterator iter = new Iterator();
        while (iter.hasMoreElements()) {
            v[i] = iter.getValue();
            k[i++] = (String)iter.nextElement();
        }
        init();
        insertBalanced(k, v, 0, n);

        // With uniform letter distribution sc[root] should be around 'm'
        // System.out.print("After root splitchar = "); System.out.println(sc[root]);
    }

    /**
     * Each node stores a character (splitchar) which is part of
     * some key(s). In a compressed branch (one that only contain
     * a single string key) the trailer of the key which is not
     * already in nodes is stored  externally in the kv array.
     * As items are inserted, key substrings decrease.
     * Some substrings may completely  disappear when the whole
     * branch is totally decompressed.
     * The tree is traversed to find the key substrings actually
     * used. In addition, duplicate substrings are removed using
     * a map (implemented with a TernaryTree!).
     *
     */
    public void trimToSize() {
        // first balance the tree for best performance
        balance();

        // redimension the node arrays
        redimNodeArrays(freenode);

        // ok, compact kv array
        CharVector kx = new CharVector();
        kx.alloc(1);
        TernaryTree map = new TernaryTree();
        compact(kx, map, root);
        kv = kx;
        kv.trimToSize();
    }

    private void compact(CharVector kx, TernaryTree map, char p) {
        int k;
        if (p == 0) {
            return;
        }
        if (sc[p] == 0xFFFF) {
            k = map.find(kv.getArray(), lo[p]);
            if (k < 0) {
                k = kx.alloc(strlen(kv.getArray(), lo[p]) + 1);
                strcpy(kx.getArray(), k, kv.getArray(), lo[p]);
                map.insert(kx.getArray(), k, (char)k);
            }
            lo[p] = (char)k;
        } else {
            compact(kx, map, lo[p]);
            if (sc[p] != 0) {
                compact(kx, map, eq[p]);
            }
            compact(kx, map, hi[p]);
        }
    }


    public Enumeration keys() {
        return new Iterator();
    }

    public class Iterator implements Enumeration {

        /**
         * current node index
         */
        int cur;

        /**
         * current key
         */
        String curkey;

        private class Item implements Cloneable {
            char parent;
            char child;

            public Item() {
                parent = 0;
                child = 0;
            }

            public Item(char p, char c) {
                parent = p;
                child = c;
            }

            public Object clone() {
                return new Item(parent, child);
            }

        }

        /**
         * Node stack
         */
        Stack ns;

        /**
         * key stack implemented with a StringBuffer
         */
        StringBuffer ks;

        public Iterator() {
            cur = -1;
            ns = new Stack();
            ks = new StringBuffer();
            rewind();
        }

        public void rewind() {
            ns.removeAllElements();
            ks.setLength(0);
            cur = root;
            run();
        }

        public Object nextElement() {
            String res = curkey;
            cur = up();
            run();
            return res;
        }

        public char getValue() {
            if (cur >= 0) {
                return eq[cur];
            }
            return 0;
        }

        public boolean hasMoreElements() {
            return (cur != -1);
        }

        /**
         * traverse upwards
         */
        private int up() {
            Item i = new Item();
            int res = 0;

            if (ns.empty()) {
                return -1;
            }

            if (cur != 0 && sc[cur] == 0) {
                return lo[cur];
            }

            boolean climb = true;

            while (climb) {
                i = (Item)ns.pop();
                i.child++;
                switch (i.child) {
                case 1:
                    if (sc[i.parent] != 0) {
                        res = eq[i.parent];
                        ns.push(i.clone());
                        ks.append(sc[i.parent]);
                    } else {
                        i.child++;
                        ns.push(i.clone());
                        res = hi[i.parent];
                    }
                    climb = false;
                    break;

                case 2:
                    res = hi[i.parent];
                    ns.push(i.clone());
                    if (ks.length() > 0) {
                        ks.setLength(ks.length() - 1);    // pop
                    }
                    climb = false;
                    break;

                default:
                    if (ns.empty()) {
                        return -1;
                    }
                    climb = true;
                    break;
                }
            }
            return res;
        }

        /**
         * traverse the tree to find next key
         */
        private int run() {
            if (cur == -1) {
                return -1;
            }

            boolean leaf = false;
            while (true) {
                // first go down on low branch until leaf or compressed branch
                while (cur != 0) {
                    if (sc[cur] == 0xFFFF) {
                        leaf = true;
                        break;
                    }
                    ns.push(new Item((char)cur, '\u0000'));
                    if (sc[cur] == 0) {
                        leaf = true;
                        break;
                    }
                    cur = lo[cur];
                }
                if (leaf) {
                    break;
                }
                    // nothing found, go up one node and try again
                cur = up();
                if (cur == -1) {
                    return -1;
                }
            }
            // The current node should be a data node and
            // the key should be in the key stack (at least partially)
            StringBuffer buf = new StringBuffer(ks.toString());
            if (sc[cur] == 0xFFFF) {
                int p = lo[cur];
                while (kv.get(p) != 0) {
                    buf.append(kv.get(p++));
            }
            }
            curkey = buf.toString();
            return 0;
        }

    }

    public void printStats() {
        System.out.println("Number of keys = " + Integer.toString(length));
        System.out.println("Node count = " + Integer.toString(freenode));
        // System.out.println("Array length = " + Integer.toString(eq.length));
        System.out.println("Key Array length = "
                           + Integer.toString(kv.length()));

        /*
         * for(int i=0; i<kv.length(); i++)
         * if ( kv.get(i) != 0 )
         * System.out.print(kv.get(i));
         * else
         * System.out.println("");
         * System.out.println("Keys:");
         * for(Enumeration enum = keys(); enum.hasMoreElements(); )
         * System.out.println(enum.nextElement());
         */

    }

/*    public static void main(String[] args) throws Exception {
        TernaryTree tt = new TernaryTree();
        tt.insert("Carlos", 'C');
        tt.insert("Car", 'r');
        tt.insert("palos", 'l');
        tt.insert("pa", 'p');
        tt.trimToSize();
        System.out.println((char)tt.find("Car"));
        System.out.println((char)tt.find("Carlos"));
        System.out.println((char)tt.find("alto"));
        tt.printStats();
    }*/

}