basedisktable.java

开源的axion的数据库代码

                return true;
            }
        }
        return true;
    }

    protected void parseMetaFile(File file) throws AxionException {
        ObjectInputStream in = null;
        try {
            in = new ObjectInputStream(new BufferedInputStream(new FileInputStream(file)));
            // read version number
            int ver = in.readInt();
            if(ver != 0) {
                throw new AxionException("Can't parse meta file " + file + " for table " + getName() + ", unrecognized meta file version " + ver);
            } else { 
                // read number of columns
                int I = in.readInt();
                for(int i=0;i<I;i++) {
                    // read column name
                    String name = in.readUTF();
                    // read data type class name
                    String dtypename = in.readUTF();
                    // create instance of datatype
                    DataType type = null;
                    try {
                        Class clazz = Class.forName(dtypename);
                        type = (DataType)(clazz.newInstance());
                    } catch(ClassNotFoundException e) {
                        throw new AxionException("Can't load table " + getName() + ", data type " + dtypename + " not found.",e);
                    } catch(ClassCastException e) {
                        throw new AxionException("Can't load table " + getName() + ", data type " + dtypename + " not a DataType.",e);
                    } catch(InstantiationException e) {
                        throw new AxionException("Can't load table " + getName() + ", data type " + dtypename + " can't be instantiated.",e);
                    } catch(IllegalAccessException e) {
                        throw new AxionException("Can't load table " + getName() + ", data type " + dtypename + " can't be instantiated.",e);
                    }
                    addColumn(new Column(name,type),false);
                }
            }
        } catch(IOException e) {
            throw new AxionException("Unable to parse meta file " + file + " for table " + getName(),e);
        } finally {
            try { in.close(); } catch(Exception e) { }
        }
    }
  
    protected void writeMetaFile(File file) throws AxionException {
        ObjectOutputStream out = null;
        try {
            out = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
            // write version number
            out.writeInt(0);
            // write number of columns
            out.writeInt(getColumnCount());
            // for each column
            for(int i=0,I=getColumnCount();i<I;i++) {
                Column col = getColumn(i);                
                // write column name
                out.writeUTF(col.getName());
                // write data type class name
                out.writeUTF(col.getDataType().getClass().getName());
            }
            out.flush();
        } catch(IOException e) {
            throw new AxionException("Unable to write meta file " + file + " for table " + getName(),e);
        } finally {
            try { out.close(); } catch(Exception e) { }
        }
    }

    /**
     * Writes a list of <tt>int</tt> values to a file.
     * 
     * @param file the {@link File} to write to
     */
    protected void writeIntFile(String file, IntList list) throws AxionException {
        DataOutputStream out = null;
        try {
            out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
            for(int i=0;i<list.size();i++) {
                out.writeInt(list.get(i));
            }
            out.flush();
        } catch(IOException e) {
            throw new AxionException("Unable to write to " + file,e);
        } finally {
            try { out.close(); } catch(Exception t) { }
        }
    }
    /**
     * Writes a list of <tt>long</tt> values to a file.
     * 
     * @param file the {@link File} to write to
     */
    protected void writeLongFile(String file, LongList list) throws AxionException {
        DataOutputStream out = null;
        try {
            out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));
            for(int i=0;i<list.size();i++) {
                out.writeLong(list.get(i));
            }
            out.flush();
        } catch(IOException e) {
            throw new AxionException("Unable to write to " + file,e);
        } finally {
            try { out.close(); } catch(Exception t) { }
        }
    }

    /**
     * Appends a long value to a file.
     * 
     * @param file the {@link File} to append to
     * @param value the value to write
     */
    protected void appendLongFile(String file, long value) throws AxionException {
        DataOutputStream out = null;
        try {
            out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file, true)));
            out.writeLong(value);
        } catch(IOException e) {
            throw new AxionException("Unable to write to " + file,e);
        } finally {
            try { out.close(); } catch(Exception t) { }
        }
    }


    /**
     * Appends several long values to a file.
     * 
     * @param file the {@link File} to append to
     * @param values the values to write
     */
    protected void appendLongFile(String file, LongList value) throws AxionException {
        DataOutputStream out = null;
        try {
            out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file, true)));
            for(LongIterator iter = value.iterator();iter.hasNext();) {
                out.writeLong(iter.next());
            }
        } catch(IOException e) {
            throw new AxionException("Unable to write to " + file,e);
        } finally {
            try { out.close(); } catch(Exception t) { }
        }
    }

    /**
     * Reads a list of long values from a file.
     * 
     * @param file the {@link File} to read from
     */
    protected LongList parseLongFile(File file) throws AxionException {
        int count = (int)(file.length()/8L);
        LongList list = new ArrayUnsignedIntList(count);
        DataInputStream in = null;
        try {
            in = new DataInputStream(new BufferedInputStream(new FileInputStream(file),8192));
            for(int i=0;i<count;i++) {
                list.add(in.readLong());
            }
            return list;
        } catch(IOException e) {
            throw new AxionException("Unable to parse " + file,e);
        } finally {
            try {
                in.close();
            } catch(Exception t) {
            }
        }
    }

    /**
     * Reads a list of int values from a file.
     * 
     * @param file the {@link File} to read from
     */
    protected IntList parseIntFile(File file) throws AxionException {
        int count = (int)(file.length()/4L);
        IntList list = new ArrayIntList(count);
        DataInputStream in = null;
        try {
            in = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
            for(int i=0;i<count;i++) {
                list.add(in.readInt());
            }
            return list;
        } catch(IOException e) {
            throw new AxionException("Unable to parse " + file,e);
        } finally {
            try {
                in.close();
            } catch(Exception t) {
            }
        }
    }

    //----------------------------------------------------------------- Private

    private File getMetaFile() {
        if(null == _metaFile) {
            _metaFile = new File(getRootDir(),getName() + ".meta");
        } 
        return _metaFile;
    }

    private void clearMetaFileReference() {
        _metaFile = null;
    }


    //--------------------------------------------------------------- Attributes

    private File _metaFile = null;
    private static Log _log = LogFactory.getLog(BaseDiskTable.class);
}