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json.cpp
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json.cpp
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/** @file json.cpp JSON parser and composer.
*
* Parses JSON and outputs a QVariant with the data.
*
* @authors Copyright © 2012-2016 Jaakko Keränen <jaakko.keranen@iki.fi>
*
* @par License
* LGPL: http://www.gnu.org/licenses/lgpl.html
*
* <small>This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser 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 Lesser
* General Public License for more details. You should have received a copy of
* the GNU Lesser General Public License along with this program; if not, see:
* http://www.gnu.org/licenses</small>
*/
#include "de/data/json.h"
#include <QVarLengthArray>
#include <de/Block>
#include <de/Error>
#include <de/Log>
#include <de/Record>
#include <de/NoneValue>
#include <de/NumberValue>
#include <de/RecordValue>
#include <de/DictionaryValue>
#include <de/ArrayValue>
#include <QTextStream>
#include <QDebug>
namespace de {
namespace internal {
/**
* @internal Not exposed outside this source file; use parseJSON() instead.
*/
class JSONParser
{
QString const &source;
int pos;
public:
JSONParser(QString const &s) : source(s), pos(0)
{
skipWhite();
}
void advance()
{
pos++;
skipWhite();
}
void skipWhite()
{
while (!atEnd() && source[pos].isSpace()) pos++;
}
bool atEnd() const
{
return pos >= source.size();
}
QChar peek() const
{
if (atEnd()) return 0;
return source[pos];
}
QChar next()
{
if (atEnd()) return 0;
QChar c = source[pos];
advance();
return c;
}
QChar nextNoSkip()
{
if (atEnd()) return 0;
return source[pos++];
}
DENG2_NORETURN void error(QString const &message)
{
throw de::Error("JSONParser", de::String("Error at position %1 (%2^%3): %4")
.arg(pos).arg(source.mid(pos - 4, 4)).arg(source.mid(pos, 4)).arg(message));
}
QVariant parse()
{
LOG_AS("JSONParser");
if (atEnd()) return QVariant();
QChar c = peek();
if (c == '{')
{
return parseObject();
}
else if (c == '[')
{
return parseArray();
}
else if (c == '\"')
{
return parseString();
}
else if (c == '-' || c.isDigit())
{
return parseNumber();
}
else
{
return parseKeyword();
}
}
QVariant parseObject()
{
QVariantMap result;
QChar c = next();
DENG2_ASSERT(c == '{');
forever
{
QString name = parseString().toString();
c = next();
if (c != ':') error("object keys and values must be separated by a colon");
QVariant value = parse();
// Add to the result.
result.insert(name, value);
// Move forward.
skipWhite();
c = next();
if (c == '}')
{
// End of object.
break;
}
else if (c != ',')
{
LOG_DEBUG(de::String("got %1 instead of ,").arg(c));
error("key/value pairs must be separated by comma");
}
}
return result;
}
QVariant parseArray()
{
QVariantList result;
QChar c = next();
DENG2_ASSERT(c == '[');
if (peek() == ']')
{
// Empty list.
next();
return result;
}
forever
{
result << parse();
c = next();
if (c == ']')
{
// End of array.
break;
}
else if (c != ',')
{
// What?
error("array items must be separated by comma");
}
}
return result;
}
QVariant parseString()
{
QVarLengthArray<QChar, 1024> result;
QChar c = next();
DENG2_ASSERT(c == '\"');
forever
{
c = nextNoSkip();
if (c == '\\')
{
// Escape.
c = nextNoSkip();
if (c == '\"' || c == '\\' || c == '/')
result.append(c);
else if (c == 'b')
result.append('\b');
else if (c == 'f')
result.append('\f');
else if (c == 'n')
result.append('\n');
else if (c == 'r')
result.append('\r');
else if (c == 't')
result.append('\t');
else if (c == 'u')
{
QString code = source.mid(pos, 4);
pos += 4;
result.append(QChar(ushort(code.toLong(0, 16))));
}
else error("unknown escape sequence in string");
}
else if (c == '\"')
{
// End of string.
break;
}
else
{
result.append(c);
}
}
skipWhite();
return QString(result.constData(), result.size());
}
QVariant parseNumber()
{
QVarLengthArray<QChar> str;
QChar c = next();
if (c == '-')
{
str.append(c);
c = nextNoSkip();
}
for (; c.isDigit(); c = nextNoSkip())
{
str.append(c);
}
bool hasDecimal = false;
if (c == '.')
{
str.append(c);
hasDecimal = true;
c = nextNoSkip();
for (; c.isDigit(); c = nextNoSkip())
{
str.append(c);
}
}
if (c == 'e' || c == 'E')
{
// Exponent.
str.append(c);
c = nextNoSkip();
if (c == '+' || c == '-')
{
str.append(c);
c = nextNoSkip();
}
for (; c.isDigit(); c = nextNoSkip())
{
str.append(c);
}
}
// Rewind one char (the loop was broken when a non-digit was read).
pos--;
skipWhite();
double value = QString(str.constData(), str.size()).toDouble();
if (hasDecimal)
{
return QVariant(value);
}
else
{
return QVariant(int(value));
}
}
QVariant parseKeyword()
{
if (source.mid(pos, 4) == "true")
{
pos += 4;
skipWhite();
return QVariant(true);
}
else if (source.mid(pos, 5) == "false")
{
pos += 5;
skipWhite();
return QVariant(false);
}
else if (source.mid(pos, 4) == "null")
{
pos += 4;
skipWhite();
return QVariant();
}
else
{
error("unknown keyword");
}
return QVariant();
}
};
//---------------------------------------------------------------------------------------
static Block recordToJSON(Record const &rec);
static Block valueToJSON(Value const &value);
static Block valueToJSONWithTabNewlines(Value const &value)
{
Block json = valueToJSON(value);
json.replace('\n', "\n\t");
return json;
}
static Block valueToJSON(Value const &value)
{
if (value.is<NoneValue>())
{
return "null";
}
if (auto const *rec = value.maybeAs<RecordValue>())
{
return recordToJSON(rec->dereference());
}
if (auto const *dict = value.maybeAs<DictionaryValue>())
{
Block out = "{";
auto const &elems = dict->elements();
for (auto i = elems.begin(); i != elems.end(); ++i)
{
if (i != elems.begin())
{
out += ",";
}
out += "\n\t" + valueToJSON(*i->first.value) + ": " +
valueToJSONWithTabNewlines(*i->second);
}
return out + "\n}";
}
if (auto const *array = value.maybeAs<ArrayValue>())
{
Block out = "[";
auto const &elems = array->elements();
for (auto i = elems.begin(); i != elems.end(); ++i)
{
if (i != elems.begin())
{
out += ",";
}
out += "\n\t" + valueToJSONWithTabNewlines(**i);
}
return out + "\n]";
}
if (auto const *num = value.maybeAs<NumberValue>())
{
if (num->semanticHints().testFlag(NumberValue::Boolean))
{
return num->isTrue()? "true" : "false";
}
return num->asText().toUtf8();
}
// Text string.
String text = value.asText();
text.replace("\\", "\\\\")
.replace("\"", "\\\"")
.replace("\b", "\\b")
.replace("\f", "\\f")
.replace("\n", "\\n")
.replace("\r", "\\r")
.replace("\t", "\\t");
return "\"" + text.toUtf8() + "\"";
}
static Block recordToJSON(Record const &rec)
{
Block out = "{\n\t\"__obj__\": \"Record\"";
rec.forMembers([&out] (String const &name, Variable const &var)
{
out += ",\n\t\"" + name.toUtf8() + "\": " + valueToJSONWithTabNewlines(var.value());
return LoopContinue;
});
return out + "\n}";
}
} // internal
QVariant parseJSON(String const &jsonText)
{
try
{
return internal::JSONParser(jsonText).parse();
}
catch (de::Error const &er)
{
LOG_WARNING(er.asText());
return QVariant(); // invalid
}
}
Block composeJSON(Record const &rec)
{
return internal::recordToJSON(rec) + "\n";
}
} // de