first commit

lib/dtl/database_exporter.php

@@ -0,0 +1,165 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * General database export class
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Base class for database export operations. This class defines basic callbacks
+ * for export operations and implements the @see export_database and
+ * @export_table methods generic export processing. In general, subclasses will
+ * override callback methods to provide specific output and (optionally)
+ * @see export_database to add functionality.
+ * Between a single pair of calls to @see begin_database_export and
+ * @see finish_database_export, multiple non-overlapping pairs of calls may
+ * be made to @see begin_table_export and @see finish_database_export for
+ * different tables. Between one pair of calls to @see begin_table_export and
+ * @see finish_database_export multiple calls may be made to
+ * @see export_table_data for the same table.
+ */
+abstract class database_exporter {
+    /** @var moodle_database Connection to the source database (a @see moodle_database object). */
+    protected $mdb;
+    /** @var database_manager Database manager of the source database (a @see database_manager object). */
+    protected $manager;
+    /** @var xmldb_structure Source database schema in XMLDB format (a @see xmldb_structure object). */
+    protected $schema;
+    /**
+     * Boolean flag - whether or not to check that XML database schema matches
+     * the RDBMS database schema before exporting (used by
+     * @see export_database).
+     * @var bool
+     */
+    protected $check_schema;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb Connection to the source database (a
+     * @see moodle_database object).
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before exporting (used by
+     * @see export_database).
+     */
+    public function __construct(moodle_database $mdb, $check_schema=true) {
+        $this->mdb          = $mdb;
+        $this->manager      = $mdb->get_manager();
+        $this->schema       = $this->manager->get_install_xml_schema();
+        $this->check_schema = $check_schema;
+    }
+
+    /**
+     * Callback function. Should be called only once database per export
+     * operation, before any other export operations. Subclasses should export
+     * basic database information (version and timestamp).
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $release moodle release info
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    abstract public function begin_database_export($version, $release, $timestamp, $description);
+
+    /**
+     * Callback function. Should be called only once per table export operation,
+     * before any other table export operations. Subclasses should export
+     * basic database information (name and schema's hash).
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    abstract public function begin_table_export(xmldb_table $table);
+
+    /**
+     * Callback function. Should be called only once per table export operation,
+     * after all other table export operations.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     */
+    abstract public function finish_table_export(xmldb_table $table);
+
+    /**
+     * Callback function. Should be called only once database per export
+     * operation, after all database export operations.
+     */
+    abstract public function finish_database_export();
+
+    /**
+     * Callback function. Should be called only once per record export operation,
+     * only between @see begin_table_export and @see finish_table_export calls.
+     * It will insert table data. Subclasses should export basic record
+     * information (data values).
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data was retrieved
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    abstract public function export_table_data(xmldb_table $table, $data);
+
+    /**
+     * Generic method to export the database. It checks the schema (if
+     * @see $check_schema is true), queries the database and calls
+     * appropriate callbacks.
+     *
+     * @throws dbtransfer_exception if any checking (e.g. database schema) fails
+     *
+     * @param string $description a user description of the data.
+     */
+    public function export_database($description=null) {
+        global $CFG;
+
+        $options = [
+            'changedcolumns' => false, // Column types may be fixed by transfer.
+            'missingindexes' => false, // No need to worry about indexes for transfering data.
+            'extraindexes' => false
+        ];
+        if ($this->check_schema and $errors = $this->manager->check_database_schema($this->schema, $options)) {
+            $details = '';
+            foreach ($errors as $table=>$items) {
+                $details .= '<div>'.get_string('tablex', 'dbtransfer', $table);
+                $details .= '<ul>';
+                foreach ($items as $item) {
+                    $details .= '<li>'.$item.'</li>';
+                }
+                $details .= '</ul></div>';
+            }
+            throw new dbtransfer_exception('exportschemaexception', $details);
+        }
+        $tables = $this->schema->getTables();
+        $this->begin_database_export($CFG->version, $CFG->release, date('c'), $description);
+        foreach ($tables as $table) {
+            $rs = $this->mdb->export_table_recordset($table->getName());
+            if (!$rs) {
+                throw new ddl_table_missing_exception($table->getName());
+            }
+            $this->begin_table_export($table);
+            foreach ($rs as $row) {
+                $this->export_table_data($table, $row);
+            }
+            $this->finish_table_export($table);
+            $rs->close();
+        }
+        $this->finish_database_export();
+    }
+}

lib/dtl/database_importer.php

@@ -0,0 +1,218 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * General database importer class
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * Base class for database import operations. This class implements
+ * basic callbacks for import operations and defines the @see import_database
+ * method as a common method for all importers. In general, subclasses will
+ * override import_database and call other methods in appropriate moments.
+ * Between a single pair of calls to @see begin_database_import and
+ * @see finish_database_import, multiple non-overlapping pairs of calls may
+ * be made to @see begin_table_import and @see finish_database_import for
+ * different tables.
+ * Between one pair of calls to @see begin_table_import and
+ * @see finish_database_import multiple calls may be made to
+ * @see import_table_data for the same table.
+ * This class can be used directly, if the standard control flow (defined above)
+ * is respected.
+ */
+class database_importer {
+    /** @var moodle_database Connection to the target database (a @see moodle_database object). */
+    protected $mdb;
+    /** @var database_manager Database manager of the target database (a @see database_manager object). */
+    protected $manager;
+    /** @var xmldb_structure Target database schema in XMLDB format (a @see xmldb_structure object). */
+    protected $schema;
+    /**
+     * Boolean flag - whether or not to check that XML database schema matches
+     * the RDBMS database schema before importing (used by
+     * @see begin_database_import).
+     * @var bool
+     */
+    protected $check_schema;
+    /** @var string How to use transactions. */
+    protected $transactionmode = 'allinone';
+    /** @var moodle_transaction Transaction object */
+    protected $transaction;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb Connection to the target database (a
+     * @see moodle_database object). Use null to use the current $DB connection.
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before importing (inside
+     * @see begin_database_import).
+     */
+    public function __construct(moodle_database $mdb, $check_schema=true) {
+        $this->mdb          = $mdb;
+        $this->manager      = $mdb->get_manager();
+        $this->schema       = $this->manager->get_install_xml_schema();
+        $this->check_schema = $check_schema;
+    }
+
+    /**
+     * How to use transactions during the import.
+     * @param string $mode 'pertable', 'allinone' or 'none'.
+     */
+    public function set_transaction_mode($mode) {
+        if (!in_array($mode, array('pertable', 'allinone', 'none'))) {
+            throw new coding_exception('Unknown transaction mode', $mode);
+        }
+        $this->transactionmode = $mode;
+    }
+
+    /**
+     * Callback function. Should be called only once database per import
+     * operation, before any database changes are made. It will check the database
+     * schema if @see check_schema is true
+     *
+     * @throws dbtransfer_exception if any checking (e.g. database schema, Moodle
+     * version) fails
+     *
+     * @param float $version the version of the system which generated the data
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @return void
+     */
+    public function begin_database_import($version, $timestamp) {
+        global $CFG;
+
+        if (!$this->mdb->get_tables()) {
+            // No tables present yet, time to create all tables.
+            $this->manager->install_from_xmldb_structure($this->schema);
+        }
+
+        if (round($version, 2) !== round($CFG->version, 2)) { // version might be in decimal format too
+            $a = (object)array('schemaver'=>$version, 'currentver'=>$CFG->version);
+            throw new dbtransfer_exception('importversionmismatchexception', $a);
+        }
+
+        $options = [
+            'changedcolumns' => false, // Column types may be fixed by transfer.
+            'missingindexes' => false, // No need to worry about indexes for transfering data.
+            'extraindexes' => false
+        ];
+        if ($this->check_schema and $errors = $this->manager->check_database_schema($this->schema, $options)) {
+            $details = '';
+            foreach ($errors as $table=>$items) {
+                $details .= '<div>'.get_string('table').' '.$table.':';
+                $details .= '<ul>';
+                foreach ($items as $item) {
+                    $details .= '<li>'.$item.'</li>';
+                }
+                $details .= '</ul></div>';
+            }
+            throw new dbtransfer_exception('importschemaexception', $details);
+        }
+        if ($this->transactionmode == 'allinone') {
+            $this->transaction = $this->mdb->start_delegated_transaction();
+        }
+    }
+
+    /**
+     * Callback function. Should be called only once per table import operation,
+     * before any table changes are made. It will delete all table data.
+     *
+     * @throws dbtransfer_exception an unknown table import is attempted
+     * @throws ddl_table_missing_exception if the table is missing
+     *
+     * @param string $tablename - the name of the table that will be imported
+     * @param string $schemaHash - the hash of the xmldb_table schema of the table
+     * @return void
+     */
+    public function begin_table_import($tablename, $schemaHash) {
+        if ($this->transactionmode == 'pertable') {
+            $this->transaction = $this->mdb->start_delegated_transaction();
+        }
+        if (!$table = $this->schema->getTable($tablename)) {
+            throw new dbtransfer_exception('unknowntableexception', $tablename);
+        }
+        if ($schemaHash != $table->getHash()) {
+            throw new dbtransfer_exception('differenttableexception', $tablename);
+        }
+        // this should not happen, unless someone drops tables after import started
+        if (!$this->manager->table_exists($table)) {
+            throw new ddl_table_missing_exception($tablename);
+        }
+        $this->mdb->delete_records($tablename);
+    }
+
+    /**
+     * Callback function. Should be called only once per table import operation,
+     * after all table changes are made. It will reset table sequences if any.
+     * @param string $tablename
+     * @return void
+     */
+    public function finish_table_import($tablename) {
+        $table  = $this->schema->getTable($tablename);
+        $fields = $table->getFields();
+        foreach ($fields as $field) {
+            if ($field->getSequence()) {
+                $this->manager->reset_sequence($tablename);
+                return;
+            }
+        }
+        if ($this->transactionmode == 'pertable') {
+            $this->transaction->allow_commit();
+        }
+    }
+
+    /**
+     * Callback function. Should be called only once database per import
+     * operation, after all database changes are made. It will commit changes.
+     * @return void
+     */
+    public function finish_database_import() {
+        if ($this->transactionmode == 'allinone') {
+            $this->transaction->allow_commit();
+        }
+    }
+
+    /**
+     * Callback function. Should be called only once per record import operation, only
+     * between @see begin_table_import and @see finish_table_import calls.
+     * It will insert table data.
+     *
+     * @throws dml_exception if data insert operation failed
+     *
+     * @param string $tablename - the name of the table in which data will be
+     * imported
+     * @param object $data - data object (fields and values will be inserted
+     * into table)
+     * @return void
+     */
+    public function import_table_data($tablename, $data) {
+        $this->mdb->import_record($tablename, $data);
+    }
+
+    /**
+     * Common import method
+     * @return void
+     */
+    public function import_database() {
+        // implement in subclasses
+    }
+}

lib/dtl/database_mover.php

@@ -0,0 +1,122 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * General database mover class
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+class database_mover extends database_exporter {
+    /** @var database_importer Importer object used to transfer data. */
+    protected $importer;
+    /** @var progress_trace Progress tracing object */
+    protected $feedback;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb_source Connection to the source database (a
+     * @see moodle_database object).
+     * @param moodle_database $mdb_target Connection to the target database (a
+     * @see moodle_database object).
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before exporting (used by
+     * @param progress_trace $feedback Progress tracing object
+     * @see export_database).
+     */
+    public function __construct(moodle_database $mdb_source, moodle_database $mdb_target,
+            $check_schema = true, progress_trace $feedback = null) {
+        if (empty($feedback)) {
+            $this->feedback = new null_progress_trace();
+        } else {
+            $this->feedback = $feedback;
+        }
+        if ($check_schema) {
+            $this->feedback->output(get_string('checkingsourcetables', 'core_dbtransfer'));
+        }
+        parent::__construct($mdb_source, $check_schema);
+        $this->feedback->output(get_string('creatingtargettables', 'core_dbtransfer'));
+        $this->importer = new database_importer($mdb_target, $check_schema);
+    }
+
+    /**
+     * How to use transactions during the transfer.
+     * @param string $mode 'pertable', 'allinone' or 'none'.
+     */
+    public function set_transaction_mode($mode) {
+        $this->importer->set_transaction_mode($mode);
+    }
+
+    /**
+     * Callback function. Calls importer's begin_database_import callback method.
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $release moodle release info
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function begin_database_export($version, $release, $timestamp, $description) {
+        $this->feedback->output(get_string('copyingtables', 'core_dbtransfer'));
+        $this->importer->begin_database_import($version, $timestamp, $description);
+    }
+
+    /**
+     * Callback function. Calls importer's begin_table_import callback method.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function begin_table_export(xmldb_table $table) {
+        $this->feedback->output(get_string('copyingtable', 'core_dbtransfer', $table->getName()), 1);
+        $this->importer->begin_table_import($table->getName(), $table->getHash());
+    }
+
+    /**
+     * Callback function. Calls importer's import_table_data callback method.
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data
+     * was retrieved
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    public function export_table_data(xmldb_table $table, $data) {
+        $this->importer->import_table_data($table->getName(), $data);
+    }
+
+    /**
+     * Callback function. Calls importer's finish_table_import callback method.
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function finish_table_export(xmldb_table $table) {
+        $this->feedback->output(get_string('done', 'core_dbtransfer', $table->getName()), 2);
+        $this->importer->finish_table_import($table->getName());
+    }
+
+    /**
+     * Callback function. Calls importer's finish_database_import callback method.
+     * @return void
+     */
+    public function finish_database_export() {
+        $this->importer->finish_database_import();
+    }
+}

lib/dtl/dbdata.xsd

@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
+    <xs:element name="moodle_database" type="databaseType" />
+    <xs:complexType name="databaseType">
+        <xs:sequence>
+            <xs:element maxOccurs="unbounded" name="table"
+                type="tableType" />
+        </xs:sequence>
+        <xs:attribute name="version" type="xs:float" use="required" />
+        <xs:attribute name="release" type="xs:string"></xs:attribute>
+        <xs:attribute name="timestamp" type="xs:dateTime"
+            use="required" />
+        <xs:attribute name="comment" type="xs:string" />
+    </xs:complexType>
+    <xs:complexType name="tableType">
+        <xs:sequence>
+            <xs:element maxOccurs="unbounded" name="record" type="recordType" />
+        </xs:sequence>
+        <xs:attribute name="name" type="xs:NCName" use="required" />
+        <xs:attribute name="schemaHash" type="xs:string" use="required" />
+    </xs:complexType>
+    <xs:complexType name="recordType">
+        <xs:sequence>
+            <xs:element maxOccurs="unbounded" name="field" type="fieldType" />
+        </xs:sequence>
+    </xs:complexType>
+    <xs:complexType name="fieldType">
+        <xs:simpleContent>
+            <xs:extension base="xs:string">
+                <xs:attribute name="name" type="xs:string" use="required" />
+                <xs:attribute default="content" name="value" use="optional">
+                    <xs:simpleType>
+                    <xs:restriction base="xs:string">
+                        <xs:enumeration value="content" />
+                        <xs:enumeration value="null" />
+                    </xs:restriction>
+                    </xs:simpleType>
+                </xs:attribute>
+            </xs:extension>
+        </xs:simpleContent>
+    </xs:complexType>
+</xs:schema>

lib/dtl/file_xml_database_exporter.php

@@ -0,0 +1,75 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format exporter class to file storage
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format exporter class to file storage.
+ */
+class file_xml_database_exporter extends xml_database_exporter {
+    /** @var string Path to the XML data file. */
+    protected $filepath;
+    /** @var resource File descriptor for the output file. */
+    protected $file;
+
+    /**
+     * Object constructor.
+     *
+     * @param string $filepath - path to the XML data file. Use 'php://output' for PHP
+     * output stream.
+     * @param moodle_database $mdb Connection to the source database
+     * @see xml_database_exporter::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_exporter::__construct()
+     */
+    public function __construct($filepath, moodle_database $mdb, $check_schema=true) {
+        parent::__construct($mdb, $check_schema);
+        $this->filepath = $filepath;
+    }
+
+    /**
+     * Specific output method for the file XML sink.
+     * @param string $text
+     */
+    protected function output($text) {
+        fwrite($this->file, $text);
+    }
+
+    /**
+     * Specific implementation for file exporting the database: it opens output stream, calls
+     * superclass @see database_exporter::export_database() and closes output stream.
+     *
+     * @throws dbtransfer_exception if any checking (e.g. database schema) fails
+     *
+     * @param string $description a user description of the data.
+     */
+    public function export_database($description=null) {
+        global $CFG;
+        // TODO: add exception if file creation fails
+        $this->file = fopen($this->filepath, 'wb');
+        parent::export_database($description);
+        fclose($this->file);
+        @chmod($this->filepath, $CFG->filepermissions);
+    }
+}

lib/dtl/file_xml_database_importer.php

@@ -0,0 +1,65 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format importer class from file storage
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format importer class from file storage.
+ */
+class file_xml_database_importer extends xml_database_importer {
+    /** @var string Path to the XML data file. */
+    protected $filepath;
+
+    /**
+     * Object constructor.
+     *
+     * @param string $filepath - path to the XML data file. Use 'php://input' for PHP
+     * input stream.
+     * @param moodle_database $mdb Connection to the target database
+     * @see xml_database_importer::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_importer::__construct()
+     */
+    public function __construct($filepath, moodle_database $mdb, $check_schema=true) {
+        $this->filepath = $filepath;
+        parent::__construct($mdb, $check_schema);
+    }
+
+    /**
+     * Common import method: it opens the file storage, creates the parser, feeds
+     * the XML parser with data, releases the parser and closes the file storage.
+     * @return void
+     */
+    public function import_database() {
+        $file = fopen($this->filepath, 'r');
+        $parser = $this->get_parser();
+        while ($data = fread($file, 65536)) {
+            if (!xml_parse($parser, $data, feof($file))) {
+                throw new dbtransfer_exception('malformedxmlexception');
+            }
+        }
+        xml_parser_free($parser);
+        fclose($file);
+    }
+}

lib/dtl/string_xml_database_exporter.php

@@ -0,0 +1,62 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format exporter class to memory storage
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format exporter class to memory storage (i.e. a string).
+ */
+class string_xml_database_exporter extends xml_database_exporter {
+    /** @var string String with XML data. */
+    protected $data;
+
+    /**
+     * Specific output method for the memory XML sink.
+     * @param string $text
+     */
+    protected function output($text) {
+        $this->data .= $text;
+    }
+
+    /**
+     * Returns the output of the exporters
+     * @return string XML data from exporter
+     */
+    public function get_output() {
+        return $this->data;
+    }
+
+    /**
+     * Specific implementation for memory exporting the database: it clear the buffer
+     * and calls superclass @see database_exporter::export_database().
+     *
+     * @throws dbtransfer_exception if any checking (e.g. database schema) fails
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function export_database($description=null) {
+        $this->data = '';
+        parent::export_database($description);
+    }
+}

lib/dtl/string_xml_database_importer.php

@@ -0,0 +1,60 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format importer class from memory storage
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format importer class from memory storage (i.e. string).
+ */
+class string_xml_database_importer extends xml_database_importer {
+    /** @var string String with XML data. */
+    protected $data;
+
+    /**
+     * Object constructor.
+     *
+     * @param string $data - string with XML data
+     * @param moodle_database $mdb Connection to the target database
+     * @see xml_database_importer::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_importer::__construct()
+     */
+    public function __construct($data, moodle_database $mdb, $check_schema=true) {
+        parent::__construct($mdb, $check_schema);
+        $this->data = $data;
+    }
+
+    /**
+     * Common import method: it creates the parser, feeds the XML parser with
+     * data, releases the parser.
+     * @return void
+     */
+    public function import_database() {
+        $parser = $this->get_parser();
+        if (!xml_parse($parser, $this->data, true)) {
+            throw new dbtransfer_exception('malformedxmlexception');
+        }
+        xml_parser_free($parser);
+    }
+}

lib/dtl/xml_database_exporter.php

@@ -0,0 +1,98 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format exporter class
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format exporter class.
+ * Provides logic for writing XML tags and data inside appropriate callbacks.
+ * Subclasses should define XML data sinks.
+ */
+abstract class xml_database_exporter extends database_exporter {
+    /**
+     * Generic output method. Subclasses should implement it with code specific
+     * to the target XML sink.
+     */
+    abstract protected function output($text);
+
+    /**
+     * Callback function. Outputs open XML PI and moodle_database opening tag.
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $release moodle release info
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function begin_database_export($version, $release, $timestamp, $description) {
+        $this->output('<?xml version="1.0" encoding="utf-8"?>');
+        //TODO add xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" and schema information
+        $this->output('<moodle_database version="'.$version.'" release="'.$release.'" timestamp="'.$timestamp.'"'.(empty ($description) ? '' : ' comment="'.htmlspecialchars($description, ENT_QUOTES, 'UTF-8').'"').'>');
+    }
+
+    /**
+     * Callback function. Outputs table opening tag.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function begin_table_export(xmldb_table $table) {
+        $this->output('<table name="'.$table->getName().'" schemaHash="'.$table->getHash().'">');
+    }
+
+    /**
+     * Callback function. Outputs table closing tag.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     */
+    public function finish_table_export(xmldb_table $table) {
+        $this->output('</table>');
+    }
+
+    /**
+     * Callback function. Outputs moodle_database closing tag.
+     */
+    public function finish_database_export() {
+        $this->output('</moodle_database>');
+    }
+
+    /**
+     * Callback function. Outputs record tag with field subtags and data.
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data was retrieved
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    public function export_table_data(xmldb_table $table, $data) {
+        $this->output('<record>');
+        foreach ($data as $key => $value) {
+            if (is_null($value)) {
+                $this->output('<field name="'.$key.'" value="null" />');
+            } else {
+                $this->output('<field name="'.$key.'">'.htmlspecialchars($value, ENT_NOQUOTES, 'UTF-8').'</field>');
+            }
+        }
+        $this->output('</record>');
+    }
+}

lib/dtl/xml_database_importer.php

@@ -0,0 +1,155 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * XML format importer class
+ *
+ * @package    core_dtl
+ * @copyright  2008 Andrei Bautu
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+defined('MOODLE_INTERNAL') || die();
+
+/**
+ * XML format importer class (uses SAX for speed and low memory footprint).
+ * Provides logic for parsing XML data and calling appropriate callbacks.
+ * Subclasses should define XML data sources.
+ */
+abstract class xml_database_importer extends database_importer {
+    protected $current_table;
+    protected $current_row;
+    protected $current_field;
+    protected $current_data;
+    protected $current_data_is_null;
+
+    /**
+     * Creates and setups a SAX parser. Subclasses should use this method to
+     * create the XML parser.
+     *
+     * @return resource XML parser resource.
+     */
+    protected function get_parser() {
+        $parser = xml_parser_create();
+        xml_set_object($parser, $this);
+        xml_set_element_handler($parser, 'tag_open', 'tag_close');
+        xml_set_character_data_handler($parser, 'cdata');
+        xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false);
+        return $parser;
+    }
+
+    /**
+     * Callback function. Called by the XML parser for opening tags processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $tag name of opening tag
+     * @param array $attributes set of opening tag XML attributes
+     * @return void
+     */
+    protected function tag_open($parser, $tag, $attributes) {
+        switch ($tag) {
+            case 'moodle_database' :
+                if (empty($attributes['version']) || empty($attributes['timestamp'])) {
+                    throw new dbtransfer_exception('malformedxmlexception');
+                }
+                $this->begin_database_import($attributes['version'], $attributes['timestamp']);
+                break;
+            case 'table' :
+                if (isset($this->current_table)) {
+                    throw new dbtransfer_exception('malformedxmlexception');
+                }
+                if (empty($attributes['name']) || empty($attributes['schemaHash'])) {
+                    throw new dbtransfer_exception('malformedxmlexception');
+                }
+                $this->current_table = $attributes['name'];
+                $this->begin_table_import($this->current_table, $attributes['schemaHash']);
+                break;
+            case 'record' :
+                if (isset($this->current_row) || !isset($this->current_table)) {
+                    throw new dbtransfer_exception('malformedxmlexception');
+                }
+                $this->current_row = new stdClass();
+                break;
+            case 'field' :
+                if (isset($this->current_field) || !isset($this->current_row)) {
+                    throw new dbtransfer_exception('malformedxmlexception');
+                }
+                $this->current_field = $attributes['name'];
+                $this->current_data = '';
+                if (isset($attributes['value']) and $attributes['value'] === 'null') {
+                    $this->current_data_is_null = true;
+                } else {
+                    $this->current_data_is_null = false;
+                }
+                break;
+            default :
+                throw new dbtransfer_exception('malformedxmlexception');
+        }
+    }
+
+    /**
+     * Callback function. Called by the XML parser for closing tags processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $tag name of opening tag
+     * @return void
+     */
+    protected function tag_close($parser, $tag) {
+        switch ($tag) {
+            case 'moodle_database' :
+                $this->finish_database_import();
+                break;
+
+            case 'table' :
+                $this->finish_table_import($this->current_table);
+                $this->current_table = null;
+                break;
+
+            case 'record' :
+                $this->import_table_data($this->current_table, $this->current_row);
+                $this->current_row = null;
+                break;
+
+            case 'field' :
+                $field = $this->current_field;
+                if ($this->current_data_is_null) {
+                    $this->current_row->$field = null;
+                } else {
+                    $this->current_row->$field = $this->current_data;
+                }
+                $this->current_field        = null;
+                $this->current_data         = null;
+                $this->current_data_is_null = null;
+                break;
+
+            default :
+                throw new dbtransfer_exception('malformedxmlexception');
+        }
+    }
+
+    /**
+     * Callback function. Called by the XML parser for character data processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $data character data to be processed
+     * @return void
+     */
+    protected function cdata($parser, $data) {
+        if (isset($this->current_field)) {
+            $this->current_data .= $data;
+        }
+    }
+}