summaryrefslogtreecommitdiffstats
path: root/src/corelib/json
diff options
context:
space:
mode:
authorLars Knoll <lars.knoll@theqtcompany.com>2015-03-18 08:49:09 +0100
committerSimon Hausmann <simon.hausmann@theqtcompany.com>2016-02-18 07:38:37 +0000
commit4889269ff0fb37130b332863e82dd7c19564116c (patch)
treec3a7a27faf4c7de6b37c053862921e3c5f8b9481 /src/corelib/json
parent03f1a69e9cffe919597373471f7609521a465470 (diff)
Fix quadratic behavior when converting from QVariant
The old code called insert for each item, leading to constant reallocation of the data structure. Instead rely on the fact that a QVariantMap (as well as the variant list) is sorted, so we can convert to the QJson data structure in one go without lots of reallocations. Task-number: QTBUG-44737 Change-Id: Id2d38d278fb9afa5e062c7353b4d4215bdfb993c Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib/json')
-rw-r--r--src/corelib/json/qjsonarray.cpp41
-rw-r--r--src/corelib/json/qjsonobject.cpp51
2 files changed, 86 insertions, 6 deletions
diff --git a/src/corelib/json/qjsonarray.cpp b/src/corelib/json/qjsonarray.cpp
index e8d54b5b87..dc8851e8e7 100644
--- a/src/corelib/json/qjsonarray.cpp
+++ b/src/corelib/json/qjsonarray.cpp
@@ -256,8 +256,45 @@ QJsonArray QJsonArray::fromStringList(const QStringList &list)
QJsonArray QJsonArray::fromVariantList(const QVariantList &list)
{
QJsonArray array;
- for (QVariantList::const_iterator it = list.constBegin(); it != list.constEnd(); ++it)
- array.append(QJsonValue::fromVariant(*it));
+ if (list.isEmpty())
+ return array;
+
+ array.detach2(1024);
+
+ QVector<QJsonPrivate::Value> values;
+ values.resize(list.size());
+ QJsonPrivate::Value *valueData = values.data();
+ uint currentOffset = sizeof(QJsonPrivate::Base);
+
+ for (int i = 0; i < list.size(); ++i) {
+ QJsonValue val = QJsonValue::fromVariant(list.at(i));
+
+ bool latinOrIntValue;
+ int valueSize = QJsonPrivate::Value::requiredStorage(val, &latinOrIntValue);
+
+ if (!array.detach2(valueSize))
+ return QJsonArray();
+
+ QJsonPrivate::Value *v = valueData + i;
+ v->type = (val.t == QJsonValue::Undefined ? QJsonValue::Null : val.t);
+ v->latinOrIntValue = latinOrIntValue;
+ v->latinKey = false;
+ v->value = QJsonPrivate::Value::valueToStore(val, currentOffset);
+ if (valueSize)
+ QJsonPrivate::Value::copyData(val, (char *)array.a + currentOffset, latinOrIntValue);
+
+ currentOffset += valueSize;
+ array.a->size = currentOffset;
+ }
+
+ // write table
+ array.a->tableOffset = currentOffset;
+ if (!array.detach2(sizeof(QJsonPrivate::offset)*values.size()))
+ return QJsonArray();
+ memcpy(array.a->table(), values.constData(), values.size()*sizeof(uint));
+ array.a->length = values.size();
+ array.a->size = currentOffset + sizeof(QJsonPrivate::offset)*values.size();
+
return array;
}
diff --git a/src/corelib/json/qjsonobject.cpp b/src/corelib/json/qjsonobject.cpp
index 8b45dd196b..b83c8dd19a 100644
--- a/src/corelib/json/qjsonobject.cpp
+++ b/src/corelib/json/qjsonobject.cpp
@@ -197,11 +197,54 @@ QJsonObject &QJsonObject::operator =(const QJsonObject &other)
*/
QJsonObject QJsonObject::fromVariantMap(const QVariantMap &map)
{
- // ### this is implemented the trivial way, not the most efficient way
-
QJsonObject object;
- for (QVariantMap::const_iterator it = map.constBegin(); it != map.constEnd(); ++it)
- object.insert(it.key(), QJsonValue::fromVariant(it.value()));
+ if (map.isEmpty())
+ return object;
+
+ object.detach2(1024);
+
+ QVector<QJsonPrivate::offset> offsets;
+ QJsonPrivate::offset currentOffset;
+ currentOffset = sizeof(QJsonPrivate::Base);
+
+ // the map is already sorted, so we can simply append one entry after the other and
+ // write the offset table at the end
+ for (QVariantMap::const_iterator it = map.constBegin(); it != map.constEnd(); ++it) {
+ QString key = it.key();
+ QJsonValue val = QJsonValue::fromVariant(it.value());
+
+ bool latinOrIntValue;
+ int valueSize = QJsonPrivate::Value::requiredStorage(val, &latinOrIntValue);
+
+ bool latinKey = QJsonPrivate::useCompressed(key);
+ int valueOffset = sizeof(QJsonPrivate::Entry) + QJsonPrivate::qStringSize(key, latinKey);
+ int requiredSize = valueOffset + valueSize;
+
+ if (!object.detach2(requiredSize + sizeof(QJsonPrivate::offset))) // offset for the new index entry
+ return QJsonObject();
+
+ QJsonPrivate::Entry *e = reinterpret_cast<QJsonPrivate::Entry *>(reinterpret_cast<char *>(object.o) + currentOffset);
+ e->value.type = val.t;
+ e->value.latinKey = latinKey;
+ e->value.latinOrIntValue = latinOrIntValue;
+ e->value.value = QJsonPrivate::Value::valueToStore(val, (char *)e - (char *)object.o + valueOffset);
+ QJsonPrivate::copyString((char *)(e + 1), key, latinKey);
+ if (valueSize)
+ QJsonPrivate::Value::copyData(val, (char *)e + valueOffset, latinOrIntValue);
+
+ offsets << currentOffset;
+ currentOffset += requiredSize;
+ object.o->size = currentOffset;
+ }
+
+ // write table
+ object.o->tableOffset = currentOffset;
+ if (!object.detach2(sizeof(QJsonPrivate::offset)*offsets.size()))
+ return QJsonObject();
+ memcpy(object.o->table(), offsets.constData(), offsets.size()*sizeof(uint));
+ object.o->length = offsets.size();
+ object.o->size = currentOffset + sizeof(QJsonPrivate::offset)*offsets.size();
+
return object;
}