QFactoryLoader: rewrite parse() using the new iterateInPluginMetaData()

This doesn't simplify the actual parsing or make it any faster, but does
merge the validation code so we only have it in one place.

Change-Id: I8bd6bb457b9c42218247fffd1797543bec9cfbec
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

src/corelib/plugin/qfactoryloader.cpp

@@ -62,7 +62,8 @@ struct QFactoryLoaderIidSearch
 {
     QLatin1StringView iid;
     bool matchesIid = false;
-    QFactoryLoaderIidSearch(QLatin1StringView iid) : iid(iid) {}
+    QFactoryLoaderIidSearch(QLatin1StringView iid) : iid(iid)
+    { Q_ASSERT(!iid.isEmpty()); }
 
     static QString readString(QCborStreamReader &reader)
     {
@@ -93,7 +94,7 @@ struct QFactoryLoaderIidSearch
         matchesIid = (readString(reader) == iid);
         return IterationResult::FinishedSearch;
     }
-    IterationResult::Result operator()(const QCborValue &, QCborStreamReader &reader)
+    IterationResult::Result operator()(const QString &, QCborStreamReader &reader)
     {
         return skip(reader);
     }
@@ -129,11 +130,13 @@ template <typename F> static IterationResult iterateInPluginMetaData(QByteArrayV
             if (!reader.next())
                 return reader.lastError();
             r = f(key, reader);
-        } else {
-            QCborValue key = QCborValue::fromCbor(reader);
-            if (key.isInvalid())
+        } else if (reader.isString()) {
+            QString key = readString(reader);
+            if (key.isNull())
                 return reader.lastError();
             r = f(key, reader);
+        } else {
+            return IterationResult::InvalidTopLevelItem;
         }
 
         if (QCborError e = reader.lastError())
@@ -156,24 +159,35 @@ static bool isIidMatch(QByteArrayView raw, QLatin1StringView iid)
 
 bool QPluginParsedMetaData::parse(QByteArrayView raw)
 {
-    QPluginMetaData::Header header;
-    Q_ASSERT(raw.size() >= qsizetype(sizeof(header)));
-    memcpy(&header, raw.data(), sizeof(header));
-    if (Q_UNLIKELY(header.version > QPluginMetaData::CurrentMetaDataVersion))
-        return setError(QFactoryLoader::tr("Invalid metadata version"));
+    QCborMap map;
+    auto r = iterateInPluginMetaData(raw, [&](const auto &key, QCborStreamReader &reader) {
+        QCborValue item = QCborValue::fromCbor(reader);
+        if (item.isInvalid())
+            return IterationResult::ParsingError;
+        if constexpr (std::is_enum_v<std::decay_t<decltype(key)>>)
+            map[int(key)] = item;
+        else
+            map[key] = item;
+        return IterationResult::ContinueSearch;
+    });
 
-    // use fromRawData to keep QCborStreamReader from copying
-    raw = raw.sliced(sizeof(header));
-    QByteArray ba = QByteArray::fromRawData(raw.data(), raw.size());
-    QCborParserError err;
-    QCborValue metadata = QCborValue::fromCbor(ba, &err);
+    switch (r.result) {
+    case IterationResult::FinishedSearch:
+    case IterationResult::ContinueSearch:
+        break;
 
-    if (err.error != QCborError::NoError)
-        return setError(QFactoryLoader::tr("Metadata parsing error: %1").arg(err.error.toString()));
-    if (!metadata.isMap())
+    // parse errors
+    case IterationResult::ParsingError:
+        return setError(QFactoryLoader::tr("Metadata parsing error: %1").arg(r.error.toString()));
+    case IterationResult::InvalidMetaDataVersion:
+        return setError(QFactoryLoader::tr("Invalid metadata version"));
+    case IterationResult::InvalidTopLevelItem:
+    case IterationResult::InvalidHeaderItem:
         return setError(QFactoryLoader::tr("Unexpected metadata contents"));
-    QCborMap map = metadata.toMap();
-    metadata = {};
+    }
+
+    // header was validated
+    auto header = qFromUnaligned<QPluginMetaData::Header>(raw.data());
 
     DecodedArchRequirements archReq =
             header.version == 0 ? decodeVersion0ArchRequirements(header.plugin_arch_requirements)