lossless bidirectional XML conversion of relational data
Both generate same data:
relpipe-in-cli demo | relpipe-out-xml | relpipe-in-xml | sha512sum
relpipe-in-cli demo | sha512sum
/**
* Relational pipes
* Copyright © 2019 František Kučera (Frantovo.cz, GlobalCode.info)
*
* 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/>.
*/
#pragma once
#include <cstdlib>
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <algorithm>
#include <xercesc/sax2/SAX2XMLReader.hpp>
#include <xercesc/sax2/XMLReaderFactory.hpp>
#include <xercesc/sax2/DefaultHandler.hpp>
#include <xercesc/sax2/Attributes.hpp>
#include <xercesc/util/XMLString.hpp>
#include <relpipe/writer/typedefs.h>
#include "StreamInputSource.h"
#include "XercesStringConvertor.h"
namespace relpipe {
namespace in {
namespace xml {
using namespace relpipe::writer;
using namespace xercesc;
class XMLCommand {
private:
class RelpipeSaxHandler : public xercesc::DefaultHandler {
private:
const wstring XMLNS = L"tag:globalcode.info,2018:relpipe";
unique_ptr<RelationalWriter> writer;
XercesStringConvertor xConvertor;
wstring currentRelationName;
vector<AttributeMetadata> currentAttributes;
wstringstream currentValue;
void resetCurrentValue() {
currentValue.str(L"");
currentValue.clear();
}
string_t getAttributeName(const Attributes& attrs, string_t uri, string_t localname) {
// TODO: less string conversions, better performance
XMLCh* xUri = xConvertor.toXercesString(uri);
XMLCh* xLocalName = xConvertor.toXercesString(localname);
string_t value = xConvertor.toString(attrs.getValue(xUri, xLocalName));
XMLString::release(&xUri);
XMLString::release(&xLocalName);
return value;
}
void startElement(const string_t uri, const string_t localname, const string_t qname, const Attributes& attrs) {
if (uri == XMLNS) {
if (localname == L"name") {
resetCurrentValue();
} else if (localname == L"attributes-metadata") {
currentAttributes.clear();
} else if (localname == L"attribute-metadata") {
AttributeMetadata am;
am.attributeName = getAttributeName(attrs, L"", L"name");
am.typeId = writer->toTypeId(getAttributeName(attrs, L"", L"type"));
currentAttributes.push_back(am);
} else if (localname == L"attribute") {
resetCurrentValue();
}
}
}
void endElement(const string_t uri, const string_t localname, const string_t qname) {
if (uri == XMLNS) {
if (localname == L"name") {
currentRelationName = currentValue.str();
} else if (localname == L"attributes-metadata") {
writer->startRelation(currentRelationName, currentAttributes, true);
} else if (localname == L"attribute") {
writer->writeAttribute(currentValue.str());
}
}
}
void characters(const string_t chars) {
currentValue << chars.c_str();
}
public:
RelpipeSaxHandler(std::ostream& output) : DefaultHandler(), writer(Factory::create(output)) {
}
virtual ~RelpipeSaxHandler() {
}
void startElement(const XMLCh * const uri, const XMLCh * const localname, const XMLCh * const qname, const Attributes& attrs) override {
startElement(xConvertor.toString(uri), xConvertor.toString(localname), xConvertor.toString(qname), attrs);
}
void endElement(const XMLCh * const uri, const XMLCh * const localname, const XMLCh * const qname) override {
endElement(xConvertor.toString(uri), xConvertor.toString(localname), xConvertor.toString(qname));
}
void characters(const XMLCh * const chars, const XMLSize_t length) override {
characters(xConvertor.toString(chars));
}
};
public:
void process(std::istream& input, std::ostream& output) {
XMLPlatformUtils::Initialize();
unique_ptr<SAX2XMLReader> parser(XMLReaderFactory::createXMLReader());
parser->setFeature(XMLUni::fgSAX2CoreValidation, true);
parser->setFeature(XMLUni::fgSAX2CoreNameSpaces, true);
// TODO: optional unbuffered mode for more fluent output?
// http://xerces.apache.org/xerces-c/program-sax2-3.html#SAX2Features
// parser->setProperty(XMLUni::fgXercesLowWaterMark, ...);
// parser->setInputBufferSize(...);
RelpipeSaxHandler saxHandler(output);
parser->setContentHandler(&saxHandler);
parser->setErrorHandler(&saxHandler);
StreamInputSource inputSource(input);
parser->parse(inputSource);
}
};
}
}
}