QUuid: add the ability to specify the byte order for 128-bit IDs

Some more modern protocols like Bluetooth LE transmit data in little
endian. QtBluetooth will benefit from this.

Change-Id: Id8e48e8f498c4a029619fffd1728c94ddd444537
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/plugin/quuid.cpp

@@ -301,30 +301,33 @@ static QUuid createFromName(const QUuid &ns, const QByteArray &baseData, QCrypto
 */
 
 /*!
-    \fn QUuid::QUuid(Id128Bytes id128) noexcept
+    \fn QUuid::QUuid(Id128Bytes id128, QSysInfo::Endian order) noexcept
     \since 6.6
 
-    Creates a QUuid based on the integral \a id128 parameter.
+    Creates a QUuid based on the integral \a id128 parameter and respecting the
+    byte order \a order.
 
     \sa fromBytes(), toBytes(), toRfc4122()
 */
 
 /*!
-    \fn QUuid::Id128Bytes QUuid::toBytes() const noexcept
+    \fn QUuid::Id128Bytes QUuid::toBytes(QSysInfo::Endian order) const noexcept
     \since 6.6
 
-    Returns an 128-bit ID created from this QUuid. The binary content of this
-    function is the same as toRfc4122(). See that function for more details.
+    Returns an 128-bit ID created from this QUuid on the byte order specified
+    by \a order. The binary content of this function is the same as toRfc4122()
+    if the order is QSysInfo::BigEndian. See that function for more details.
 
     \sa toRfc4122(), fromBytes(), QUuid()
 */
 
 /*!
-    \fn QUuid QUuid::fromBytes(const void *bytes) noexcept
+    \fn QUuid QUuid::fromBytes(const void *bytes, QSysInfo::Endian order) noexcept
     \since 6.6
 
-    Reads 128 bits (16 bytes) from \a bytes and returns the QUuid corresponding
-    to those bytes. This function does the same as fromRfc4122().
+    Reads 128 bits (16 bytes) from \a bytes using byte order \a order and
+    returns the QUuid corresponding to those bytes. This function does the same
+    as fromRfc4122() if the byte order \a order is QSysInfo::BigEndian.
 
     \sa fromRfc4122()
 */
@@ -674,6 +677,9 @@ QDataStream &operator<<(QDataStream &s, const QUuid &id)
         bytes = QByteArray(16, Qt::Uninitialized);
         uchar *data = reinterpret_cast<uchar *>(bytes.data());
 
+        // for historical reasons, our little-endian serialization format
+        // stores each of the UUID fields in little endian, instead of storing
+        // a little endian Id128
         qToLittleEndian(id.data1, data);
         data += sizeof(quint32);
         qToLittleEndian(id.data2, data);

src/corelib/plugin/quuid.h

@@ -72,7 +72,7 @@ public:
     constexpr QUuid(uint l, ushort w1, ushort w2, uchar b1, uchar b2, uchar b3,
                            uchar b4, uchar b5, uchar b6, uchar b7, uchar b8) noexcept
         : data1(l), data2(w1), data3(w2), data4{b1, b2, b3, b4, b5, b6, b7, b8} {}
-    QUuid(Id128Bytes id128) noexcept;
+    QUuid(Id128Bytes id128, QSysInfo::Endian order = QSysInfo::BigEndian) noexcept;
 
     explicit QUuid(QAnyStringView string) noexcept
         : QUuid{fromString(string)} {}
@@ -86,10 +86,10 @@ public:
 #endif
     QString toString(StringFormat mode = WithBraces) const;
     QByteArray toByteArray(StringFormat mode = WithBraces) const;
-    Id128Bytes toBytes() const noexcept;
+    Id128Bytes toBytes(QSysInfo::Endian order = QSysInfo::BigEndian) const noexcept;
     QByteArray toRfc4122() const;
 
-    static QUuid fromBytes(const void *bytes) noexcept;
+    static QUuid fromBytes(const void *bytes, QSysInfo::Endian order = QSysInfo::BigEndian) noexcept;
 #if QT_CORE_REMOVED_SINCE(6, 3)
     static QUuid fromRfc4122(const QByteArray &);
 #endif
@@ -179,6 +179,16 @@ public:
     ushort  data2 = 0;
     ushort  data3 = 0;
     uchar   data4[8] = {};
+
+private:
+    static constexpr Id128Bytes bswap(Id128Bytes b)
+    {
+        // 128-bit byte swap
+        b.data64[0] = qbswap(b.data64[0]);
+        b.data64[1] = qbswap(b.data64[1]);
+        qSwap(b.data64[0], b.data64[1]);
+        return b;
+    }
 };
 
 Q_DECLARE_TYPEINFO(QUuid, Q_PRIMITIVE_TYPE);
@@ -194,29 +204,33 @@ Q_CORE_EXPORT QDebug operator<<(QDebug, const QUuid &);
 
 Q_CORE_EXPORT size_t qHash(const QUuid &uuid, size_t seed = 0) noexcept;
 
-inline QUuid::QUuid(Id128Bytes uuid) noexcept
+inline QUuid::QUuid(Id128Bytes uuid, QSysInfo::Endian order) noexcept
 {
+    if (order == QSysInfo::LittleEndian)
+        uuid = bswap(uuid);
     data1 = qFromBigEndian<quint32>(&uuid.data[0]);
     data2 = qFromBigEndian<quint16>(&uuid.data[4]);
     data3 = qFromBigEndian<quint16>(&uuid.data[6]);
     memcpy(data4, &uuid.data[8], sizeof(data4));
 }
 
-inline QUuid::Id128Bytes QUuid::toBytes() const noexcept
+inline QUuid::Id128Bytes QUuid::toBytes(QSysInfo::Endian order) const noexcept
 {
     Id128Bytes result = {};
     qToBigEndian(data1, &result.data[0]);
     qToBigEndian(data2, &result.data[4]);
     qToBigEndian(data3, &result.data[6]);
     memcpy(&result.data[8], data4, sizeof(data4));
+    if (order == QSysInfo::LittleEndian)
+        return bswap(result);
     return result;
 }
 
-inline QUuid QUuid::fromBytes(const void *bytes) noexcept
+inline QUuid QUuid::fromBytes(const void *bytes, QSysInfo::Endian order) noexcept
 {
     Id128Bytes result = {};
     memcpy(result.data, bytes, sizeof(result));
-    return QUuid(result);
+    return QUuid(result, order);
 }
 
 inline bool operator<=(const QUuid &lhs, const QUuid &rhs) noexcept

tests/auto/corelib/plugin/quuid/tst_quuid.cpp

@@ -237,6 +237,12 @@ void tst_QUuid::id128()
     QCOMPARE(QUuid(bytesB), uuidB);
     QVERIFY(memcmp(uuidA.toBytes().data, bytesA.data, sizeof(QUuid::Id128Bytes)) == 0);
     QVERIFY(memcmp(uuidB.toBytes().data, bytesB.data, sizeof(QUuid::Id128Bytes)) == 0);
+
+    QUuid::Id128Bytes leBytesA = {};
+    for (int i = 0; i < 16; i++)
+        leBytesA.data[15 - i] = bytesA.data[i];
+    QCOMPARE(QUuid(leBytesA, QSysInfo::LittleEndian), uuidA);
+    QVERIFY(memcmp(uuidA.toBytes(QSysInfo::LittleEndian).data, leBytesA.data, sizeof(leBytesA)) == 0);
 }
 
 void tst_QUuid::createUuidV3OrV5()