texttable.java

hsql是很有名的嵌入式数据库

/* Copyright (c) 2001-2005, The HSQL Development Group
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 * modification, are permitted provided that the following conditions are met:
 *
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 *
 * Redistributions in binary form must reproduce the above copyright notice,
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 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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package org.hsqldb;

import org.hsqldb.lib.FileUtil;
import org.hsqldb.lib.StringConverter;
import org.hsqldb.persist.TextCache;

// tony_lai@users 20020820 - patch 595099 - user define PK name

/**
 * Subclass of Table to handle TEXT data source. <p>
 *
 * Extends Table to provide the notion of an SQL base table object whose
 * data is read from and written to a text format data file.
 *
 * @author sqlbob@users (RMP)
 * @version    1.8.0
 */
class TextTable extends org.hsqldb.Table {

    private String  dataSource = "";
    private boolean isReversed = false;

    /**
     *  Constructs a new TextTable from the given arguments.
     *
     * @param  db the owning database
     * @param  name the table's HsqlName
     * @param  type (normal or temp text table)
     * @param  sessionid the id of the owning session (for temp table)
     * @exception  HsqlException  Description of the Exception
     */
    TextTable(Database db, HsqlNameManager.HsqlName name,
              int type) throws HsqlException {
        super(db, name, type);
    }

    /**
     * This method does some of the work involved with managing the creation
     * and openning of the cache, the rest is done in Log.java and
     * TextCache.java.
     *
     * Better clarification of the role of the methods is needed.
     */
    private void openCache(String dataSourceNew, boolean isReversedNew,
                           boolean isReadOnlyNew) throws HsqlException {

        if (dataSourceNew == null) {
            dataSourceNew = "";
        }

        // Close old cache:
        database.logger.closeTextCache(this);

        cache = null;

        clearAllRows(null);

        // Open new cache:
        if (dataSourceNew.length() > 0) {
            try {
                cache = database.logger.openTextCache(this, dataSourceNew,
                                                      isReadOnlyNew,
                                                      isReversedNew);

                // read and insert all the rows from the source file
                CachedRow row     = null;
                int       nextpos = 0;

                while (true) {
                    row = (CachedRow) rowStore.get(nextpos);

                    if (row == null) {
                        break;
                    }

                    nextpos = row.getPos() + row.getStorageSize();

                    row.setNewNodes();
                    insertFromTextSource(row);
                }
            } catch (HsqlException e) {
                int linenumber = cache == null ? 0
                                               : ((TextCache) cache)
                                                   .getLineNumber();

                if (!dataSource.equals(dataSourceNew)
                        || isReversedNew != isReversed
                        || isReadOnlyNew != isReadOnly) {

                    // Restore old cache.
                    // fredt - todo - recursion works - but code is not clear
                    openCache(dataSource, isReversed, isReadOnly);
                } else {
                    if (cache != null) {
                        cache.close(false);
                    }

                    //fredt added
                    cache      = null;
                    dataSource = "";
                    isReversed = false;
                }

                // everything is in order here.
                // At this point table should either have a valid (old) data
                // source and cache or have an empty source and null cache.
                throw Trace.error(Trace.TEXT_FILE, new Object[] {
                    new Integer(linenumber), e.getMessage()
                });
            }
        }

        dataSource = dataSourceNew;
        isReversed = (isReversedNew && dataSourceNew.length() > 0);
    }

    /**
     * High level command to assign a data source to the table definition.
     * Reassigns only if the data source or direction has changed.
     */
    protected void setDataSource(Session s, String dataSourceNew,
                                 boolean isReversedNew,
                                 boolean newFile) throws HsqlException {

        if (getTableType() == Table.TEMP_TEXT_TABLE) {
            ;
        } else {
            s.checkAdmin();
        }

        dataSourceNew = dataSourceNew.trim();

        if (newFile && FileUtil.exists(dataSourceNew)) {
            throw Trace.error(Trace.TEXT_SOURCE_EXISTS, dataSourceNew);
        }

        //-- Open if descending, direction changed, or file changed.
        if (isReversedNew || (isReversedNew != isReversed)
                ||!dataSource.equals(dataSourceNew)) {
            openCache(dataSourceNew, isReversedNew, isReadOnly);
        }

        if (isReversed) {
            isReadOnly = true;
        }
    }

    protected String getDataSource() {
        return dataSource;
    }

    protected boolean isDescDataSource() {
        return isReversed;
    }

    public void setHeader(String header) throws HsqlException {

        if (cache != null && ((TextCache) cache).ignoreFirst) {
            ((TextCache) cache).setHeader(header);

            return;
        }

        throw Trace.error(Trace.TEXT_TABLE_HEADER);
    }

    public String getHeader() {

        String header = cache == null ? null
                                      : ((TextCache) cache).getHeader();

        return header == null ? null
                              : StringConverter.toQuotedString(header, '\"',
                              true);
    }

    /**
     * Used by INSERT, DELETE, UPDATE operations. This class will return
     * a more appropriate message when there is no data source.
     */
    void checkDataReadOnly() throws HsqlException {

        if (dataSource.length() == 0) {
            throw Trace.error(Trace.UNKNOWN_DATA_SOURCE);
        }

        if (isReadOnly) {
            throw Trace.error(Trace.DATA_IS_READONLY);
        }
    }

    void setDataReadOnly(boolean value) throws HsqlException {

        if (isReversed && value == true) {
            throw Trace.error(Trace.DATA_IS_READONLY);
        }

        openCache(dataSource, isReversed, value);

        isReadOnly = value;
    }

    boolean isIndexCached() {
        return false;
    }

    protected Table duplicate() throws HsqlException {
        return new TextTable(database, tableName, getTableType());
    }

    void drop() throws HsqlException {
        openCache("", false, false);
    }

    void setIndexRoots(String s) throws HsqlException {

        // do nothing
    }
}