btree.java

这个是perst-269.zip下面的SOURCECODE,和大家分享了。

    public IPersistent[] toPersistentArray(IPersistent[] arr) {
        if (arr.length < nElems) { 
            arr = (IPersistent[])Array.newInstance(arr.getClass().getComponentType(), nElems);
        }
        if (root != 0) { 
            BtreePage.traverseForward((StorageImpl)getStorage(), root, type, height, arr, 0);
        }
        if (arr.length > nElems) { 
            arr[nElems] = null;
        }
        return arr;
    }

    public void deallocate() { 
        if (root != 0) { 
            BtreePage.purge((StorageImpl)getStorage(), root, type, height);
        }
        super.deallocate();
    }

    public int markTree() 
    { 
        if (root != 0) { 
            return BtreePage.markPage((StorageImpl)getStorage(), root, type, height);
        }
        return 0;
    }        

    public void export(XMLExporter exporter) throws java.io.IOException 
    { 
        if (root != 0) { 
            BtreePage.exportPage((StorageImpl)getStorage(), exporter, root, type, height);
        }
    }        

    static class BtreeEntry implements Map.Entry {
        public Object getKey() { 
            return key;
        }

        public Object getValue() { 
            return db.lookupObject(oid, null);
        }

        public Object setValue(Object value) { 
            throw new UnsupportedOperationException();
        }

        public boolean equals(Object o) {
            if (!(o instanceof Map.Entry)) {
                return false;
            }
            Map.Entry e = (Map.Entry)o;
            return (getKey()==null 
                    ? e.getKey()==null : getKey().equals(e.getKey())) 
                && (getValue()==null 
                    ? getValue()==null : getValue().equals(e.getValue()));
        }

        BtreeEntry(StorageImpl db, Object key, int oid) {
            this.db = db;
            this.key = key;
            this.oid = oid;
        }

        private Object      key;
        private StorageImpl db;
        private int         oid;
    }

    Object unpackKey(StorageImpl db, Page pg, int pos) { 
        byte[] data = pg.data;
        int offs =  BtreePage.firstKeyOffs + pos*ClassDescriptor.sizeof[type];
        switch (type) { 
          case ClassDescriptor.tpBoolean:
            return Boolean.valueOf(data[offs] != 0);
          case ClassDescriptor.tpByte:
            return new Byte(data[offs]);
          case ClassDescriptor.tpShort:
            return new Short(Bytes.unpack2(data, offs));
          case ClassDescriptor.tpChar:
            return new Character((char)Bytes.unpack2(data, offs));
          case ClassDescriptor.tpInt:
            return new Integer(Bytes.unpack4(data, offs));
          case ClassDescriptor.tpObject:
            return db.lookupObject(Bytes.unpack4(data, offs), null);
          case ClassDescriptor.tpLong:
            return new Long(Bytes.unpack8(data, offs));
          case ClassDescriptor.tpDate:
            return new Date(Bytes.unpack8(data, offs));
          case ClassDescriptor.tpFloat:
            return new Float(Float.intBitsToFloat(Bytes.unpack4(data, offs)));
          case ClassDescriptor.tpDouble:
            return new Double(Double.longBitsToDouble(Bytes.unpack8(data, offs)));
          case ClassDescriptor.tpString:
            return unpackStrKey(pg, pos);
          case ClassDescriptor.tpArrayOfByte:
            return unpackByteArrayKey(pg, pos);
          default:
            Assert.failed("Invalid type");
        }
        return null;
    }
    
    static String unpackStrKey(Page pg, int pos) {
        int len = BtreePage.getKeyStrSize(pg, pos);
        int offs = BtreePage.firstKeyOffs + BtreePage.getKeyStrOffs(pg, pos);
        byte[] data = pg.data;
        char[] sval = new char[len];
        for (int j = 0; j < len; j++) { 
            sval[j] = (char)Bytes.unpack2(data, offs);
            offs += 2;
        }
        return new String(sval);
    }
            
    Object unpackByteArrayKey(Page pg, int pos) {
        int len = BtreePage.getKeyStrSize(pg, pos);
        int offs = BtreePage.firstKeyOffs + BtreePage.getKeyStrOffs(pg, pos);
        byte[] val = new byte[len];
        System.arraycopy(pg.data, offs, val, 0, len);
        return val;
    }
            
              
    public Iterator iterator() { 
        return iterator(null, null, ASCENT_ORDER);
    }

    public Iterator entryIterator() { 
        return entryIterator(null, null, ASCENT_ORDER);
    }


    final int compareByteArrays(Key key, Page pg, int i) { 
        return compareByteArrays((byte[])key.oval, 
                                 pg.data, 
                                 BtreePage.getKeyStrOffs(pg, i) + BtreePage.firstKeyOffs, 
                                 BtreePage.getKeyStrSize(pg, i));
    }


    class BtreeSelectionIterator implements PersistentIterator { 
        BtreeSelectionIterator(Key from, Key till, int order) { 
            this.from = from;
            this.till = till;
            this.order = order;
            reset();
        }

        void reset() { 
            int i, l, r;
            
            sp = 0;
            counter = updateCounter;
            if (height == 0) { 
                return;
            }
            int pageId = root;
            StorageImpl db = (StorageImpl)getStorage();
            if (db == null) {             
                throw new StorageError(StorageError.DELETED_OBJECT);
            }
            int h = height;
            
            pageStack = new int[h];
            posStack =  new int[h];
            
            if (type == ClassDescriptor.tpString) { 
                if (order == ASCENT_ORDER) { 
                    if (from == null) { 
                        while (--h >= 0) { 
                            posStack[sp] = 0;
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            pageId = BtreePage.getKeyStrOid(pg, 0);
                            end = BtreePage.getnItems(pg);
                            db.pool.unfix(pg);
                            sp += 1;
                        }
                    } else { 
                        while (--h > 0) { 
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            l = 0;
                            r = BtreePage.getnItems(pg);
                            while (l < r)  {
                                i = (l+r) >> 1;
                                if (BtreePage.compareStr(from, pg, i) >= from.inclusion) {
                                    l = i + 1; 
                                } else { 
                                    r = i;
                                }
                            }
                            Assert.that(r == l); 
                            posStack[sp] = r;
                            pageId = BtreePage.getKeyStrOid(pg, r);
                            db.pool.unfix(pg);
                            sp += 1;
                        }
                        pageStack[sp] = pageId;
                        Page pg = db.getPage(pageId);
                        l = 0;
                        end = r = BtreePage.getnItems(pg);
                        while (l < r)  {
                            i = (l+r) >> 1;
                            if (BtreePage.compareStr(from, pg, i) >= from.inclusion) {
                                l = i + 1; 
                            } else { 
                                r = i;
                            }
                        }
                        Assert.that(r == l); 
                        if (r == end) {
                            sp += 1;
                            gotoNextItem(pg, r-1);
                        } else { 
                            posStack[sp++] = r;
                            db.pool.unfix(pg);
                        }
                    }
                    if (sp != 0 && till != null) { 
                        Page pg = db.getPage(pageStack[sp-1]);
                        if (-BtreePage.compareStr(till, pg, posStack[sp-1]) >= till.inclusion) { 
                            sp = 0;
                        }
                        db.pool.unfix(pg);
                    }
                } else { // descent order
                    if (till == null) { 
                        while (--h > 0) { 
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            posStack[sp] = BtreePage.getnItems(pg);
                            pageId = BtreePage.getKeyStrOid(pg, posStack[sp]);
                            db.pool.unfix(pg);
                            sp += 1;
                        }
                        pageStack[sp] = pageId;
                        Page pg = db.getPage(pageId);
                        posStack[sp++] = BtreePage.getnItems(pg)-1;
                        db.pool.unfix(pg);
                    } else {
                        while (--h > 0) { 
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            l = 0;
                            r = BtreePage.getnItems(pg);
                            while (l < r)  {
                                i = (l+r) >> 1;
                                if (BtreePage.compareStr(till, pg, i) >= 1-till.inclusion) {
                                    l = i + 1; 
                                } else { 
                                    r = i;
                                }
                            }
                            Assert.that(r == l); 
                            posStack[sp] = r;
                            pageId = BtreePage.getKeyStrOid(pg, r);
                            db.pool.unfix(pg);
                            sp += 1;
                        }
                        pageStack[sp] = pageId;
                        Page pg = db.getPage(pageId);
                        l = 0;
                        r = BtreePage.getnItems(pg);
                        while (l < r)  {
                            i = (l+r) >> 1;
                            if (BtreePage.compareStr(till, pg, i) >= 1-till.inclusion) {
                                l = i + 1; 
                            } else { 
                                r = i;
                            }
                        }
                        Assert.that(r == l); 
                        if (r == 0) {
                            sp += 1;
                            gotoNextItem(pg, r);
                        } else { 
                            posStack[sp++] = r-1;
                            db.pool.unfix(pg);
                        }
                    }
                    if (sp != 0 && from != null) { 
                        Page pg = db.getPage(pageStack[sp-1]);
                        if (BtreePage.compareStr(from, pg, posStack[sp-1]) >= from.inclusion) { 
                            sp = 0;
                        }
                        db.pool.unfix(pg);
                    }
                }
            } else if (type == ClassDescriptor.tpArrayOfByte) { 
                if (order == ASCENT_ORDER) { 
                    if (from == null) { 
                        while (--h >= 0) { 
                            posStack[sp] = 0;
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            pageId = BtreePage.getKeyStrOid(pg, 0);
                            end = BtreePage.getnItems(pg);
                            db.pool.unfix(pg);
                            sp += 1;
                        }
                    } else { 
                        while (--h > 0) { 
                            pageStack[sp] = pageId;
                            Page pg = db.getPage(pageId);
                            l = 0;
                            r = BtreePage.getnItems(pg);
                            while (l < r)  {
                                i = (l+r) >> 1;