From 6348de873724fc613446c46b5accfabab7afaaea Mon Sep 17 00:00:00 2001 From: "Darryl L. Miles" Date: Sun, 10 Feb 2013 09:02:00 +0000 Subject: Json writer, emit full precision for floating point Number types Previously Qt JSON writer would only emit 6 digits of precision as this is the default with the formatter. However with testing against NodeJS JSON.stringify() this behavior is inconsistent with the defacto standard JSON implementation and conveys a loss of precision. Change-Id: Ie1845a6e0ee0b4c05f63ec0062f372e891855f0b Reviewed-by: Thiago Macieira --- src/corelib/json/qjson_p.h | 1 + src/corelib/json/qjsonwriter.cpp | 4 +-- tests/auto/corelib/json/tst_qtjson.cpp | 52 ++++++++++++++++++++++++++++++++++ 3 files changed, 55 insertions(+), 2 deletions(-) diff --git a/src/corelib/json/qjson_p.h b/src/corelib/json/qjson_p.h index 8d6735273c..96a11cd40e 100644 --- a/src/corelib/json/qjson_p.h +++ b/src/corelib/json/qjson_p.h @@ -63,6 +63,7 @@ #include #include +#include QT_BEGIN_NAMESPACE diff --git a/src/corelib/json/qjsonwriter.cpp b/src/corelib/json/qjsonwriter.cpp index c284f76cbb..8426b351f6 100644 --- a/src/corelib/json/qjsonwriter.cpp +++ b/src/corelib/json/qjsonwriter.cpp @@ -171,8 +171,8 @@ static void valueToJson(const QJsonPrivate::Base *b, const QJsonPrivate::Value & break; case QJsonValue::Double: { const double d = v.toDouble(b); - if (qIsFinite(d)) - json += QByteArray::number(d); + if (qIsFinite(d)) // +2 to format to ensure the expected precision + json += QByteArray::number(d, 'g', std::numeric_limits::digits10 + 2); // ::digits10 is 15 else json += "null"; // +INF || -INF || NaN (see RFC4627#section2.4) break; diff --git a/tests/auto/corelib/json/tst_qtjson.cpp b/tests/auto/corelib/json/tst_qtjson.cpp index 7cdf6deb87..bbc137d688 100644 --- a/tests/auto/corelib/json/tst_qtjson.cpp +++ b/tests/auto/corelib/json/tst_qtjson.cpp @@ -96,6 +96,7 @@ private Q_SLOTS: void toJson(); void toJsonSillyNumericValues(); + void toJsonLargeNumericValues(); void fromJson(); void fromJsonErrors(); void fromBinary(); @@ -1110,6 +1111,57 @@ void tst_QtJson::toJsonSillyNumericValues() QCOMPARE(json, expected); } +void tst_QtJson::toJsonLargeNumericValues() +{ + QJsonObject object; + QJsonArray array; + array.append(QJsonValue(1.234567)); // actual precision bug in Qt 5.0.0 + array.append(QJsonValue(1.7976931348623157e+308)); // JS Number.MAX_VALUE + array.append(QJsonValue(5e-324)); // JS Number.MIN_VALUE + array.append(QJsonValue(std::numeric_limits::min())); + array.append(QJsonValue(std::numeric_limits::max())); + array.append(QJsonValue(std::numeric_limits::epsilon())); + array.append(QJsonValue(std::numeric_limits::denorm_min())); + array.append(QJsonValue(0.0)); + array.append(QJsonValue(-std::numeric_limits::min())); + array.append(QJsonValue(-std::numeric_limits::max())); + array.append(QJsonValue(-std::numeric_limits::epsilon())); + array.append(QJsonValue(-std::numeric_limits::denorm_min())); + array.append(QJsonValue(-0.0)); + object.insert("Array", array); + + QByteArray json = QJsonDocument(object).toJson(); + + QByteArray expected = + "{\n" + " \"Array\": [\n" + " 1.234567,\n" + " 1.7976931348623157e+308,\n" + // ((4.9406564584124654e-324 == 5e-324) == true) + // I can only think JavaScript has a special formatter to + // emit this value for this IEEE754 bit pattern. + " 4.9406564584124654e-324,\n" + " 2.2250738585072014e-308,\n" + " 1.7976931348623157e+308,\n" + " 2.2204460492503131e-16,\n" + " 4.9406564584124654e-324,\n" + " 0,\n" + " -2.2250738585072014e-308,\n" + " -1.7976931348623157e+308,\n" + " -2.2204460492503131e-16,\n" + " -4.9406564584124654e-324,\n" + " 0\n" + " ]\n" + "}\n"; + + QCOMPARE(json, expected); + + QJsonDocument doc; + doc.setObject(object); + json = doc.toJson(); + QCOMPARE(json, expected); +} + void tst_QtJson::fromJson() { { -- cgit v1.2.3