started to implement xml parser as part of a very generic parser framework which can be used for all Ousia format parsers

2 files changed, 197 insertions, 0 deletions

diff --git a/src/core/parser/XmlParser.cpp b/src/core/parser/XmlParser.cpp
new file mode 100644
index 0000000..f9bb43e
--- /dev/null
+++ b/src/core/parser/XmlParser.cpp
@@ -0,0 +1,134 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program 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.
+
+    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <expat.h>
+
+#include "XmlParser.hpp"
+
+namespace ousia {
+
+/**
+ * The XmlParserData struct holds all information relevant to the expat callback
+ * functions.
+ */
+struct XmlParserData {
+	Rooted<Node> context;
+	Logger &logger;
+
+	XmlParserData(Handle<Node> context, Logger &logger)
+	    : context(context), logger(logger)
+	{
+	}
+};
+
+/**
+ * Wrapper class around the XML_Parser pointer which safely frees it whenever
+ * the scope is left (e.g. because an exception was thrown).
+ */
+class ScopedExpatXmlParser {
+private:
+	/**
+	 * Internal pointer to the XML_Parser instance.
+	 */
+	XML_Parser parser;
+
+public:
+	/**
+	 * Constructor of the ScopedExpatXmlParser class. Calls XML_ParserCreateNS
+	 * from the expat library. Throws a parser exception if the XML parser
+	 * cannot be initialized.
+	 *
+	 * @param encoding is the protocol-defined encoding passed to expat (or
+	 * nullptr if expat should determine the encoding by itself).
+	 * @param namespaceSeparator is the separator used to separate the namespace
+	 * components in the node name given by expat.
+	 */
+	ScopedExpatXmlParser(const XML_Char *encoding, XML_Char namespaceSeparator)
+	    : parser(nullptr)
+	{
+		parser = XML_ParserCreateNS("UTF-8", ':');
+		if (!parser) {
+			throw ParserException{
+			    "Internal error: Could not create expat XML parser!"};
+		}
+	}
+
+	/**
+	 * Destuctor of the ScopedExpatXmlParser, frees the XML parser instance.
+	 */
+	~ScopedExpatXmlParser()
+	{
+		if (parser) {
+			XML_ParserFree(parser);
+			parser = nullptr;
+		}
+	}
+
+	/**
+	 * Returns the XML_Parser pointer.
+	 */
+	XML_Parser operator&() { return parser; }
+};
+
+std::set<std::string> XmlParser::mimetypes()
+{
+	return std::set<std::string>{{"text/vnd.ousia.oxm", "text/vnd.ousia.oxd"}};
+}
+
+Rooted<Node> XmlParser::parse(std::istream &is, Handle<Node> context,
+                              Logger &logger)
+{
+	// Create the parser object
+	ScopedExpatXmlParser p{"UTF-8", ':'};
+
+	// Set the callback functions, provide a pointer to a XmlParserData instance
+	// as user data.
+	XmlParserData ctx{context, logger};
+
+	// Feed data into expat while there is data to process
+	const std::streamsize BUFFER_SIZE = 4096;  // TODO: Move to own header?
+	while (true) {
+		// Fetch a buffer from expat for the input data
+		char *buf = static_cast<char *>(XML_GetBuffer(&p, BUFFER_SIZE));
+		if (!buf) {
+			throw ParserException{"Internal error: XML parser out of memory!"};
+		}
+
+		// Read the input data from the stream
+		const std::streamsize bytesRead = is.read(buf, BUFFER_SIZE).gcount();
+
+		// Parse the data and handle any XML error
+		if (!XML_ParseBuffer(&p, bytesRead, bytesRead == 0)) {
+			const int line = XML_GetCurrentLineNumber(&p);
+			const int column = XML_GetCurrentColumnNumber(&p);
+			const XML_Error code = XML_GetErrorCode(&p);
+			const std::string msg = std::string{XML_ErrorString(code)};
+			logger.error("XML: " + msg, line, column);
+			break;
+		}
+
+		// Abort once there are no more bytes in the stream
+		if (bytesRead == 0) {
+			break;
+		}
+	}
+
+	return nullptr;
+}
+}
+
diff --git a/src/core/parser/XmlParser.hpp b/src/core/parser/XmlParser.hpp
new file mode 100644
index 0000000..f6fb060
--- /dev/null
+++ b/src/core/parser/XmlParser.hpp
@@ -0,0 +1,63 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program 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.
+
+    This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file XmlParser.hpp
+ *
+ * Contains the parser responsible for reading Ousía XML Documents (extension
+ * oxd) and Ousía XML Modules (extension oxm).
+ *
+ * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
+ */
+
+#ifndef _OUSIA_XML_PARSER_HPP_
+#define _OUSIA_XML_PARSER_HPP_
+
+#include <core/Parser.hpp>
+
+namespace ousia {
+
+/**
+ * The XmlParser class implements parsing the various types of Ousía XML
+ * documents using the expat stream XML parser.
+ */
+class XmlParser : public Parser {
+public:
+	/**
+	 * Returns the mimetype supported by the XmlParser which is
+	 * "text/vnd.ousia.oxm" and "text/vnd.ousia.oxd".
+	 *
+	 * @return a list containing the mimetype supported by Ousía.
+	 */
+	std::set<std::string> mimetypes() override;
+
+	/**
+	 * Parses the given input stream as XML file and returns the parsed
+	 * top-level node. Throws
+	 *
+	 * @param is is the input stream that will be parsed.
+	 */
+	Rooted<Node> parse(std::istream &is, Handle<Node> context,
+	                   Logger &logger) override;
+
+	using Parser::parse;
+};
+}
+
+#endif /* _OUSIA_XML_PARSER_HPP_ */
+