QUuid: add a trivial structure to support exactly 128 bits

This is inspired by QBluetoothUuid's quint128, but with a better
name. It also matches systemd's sd_id128.

Change-Id: Id8e48e8f498c4a029619fffd172893dc1545adda
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

3 files changed, 117 insertions, 40 deletions

diff --git a/src/corelib/plugin/quuid.cpp b/src/corelib/plugin/quuid.cpp
index 8613f96c21..a980c9a5ba 100644
--- a/src/corelib/plugin/quuid.cpp
+++ b/src/corelib/plugin/quuid.cpp
@@ -13,6 +13,9 @@
 
 QT_BEGIN_NAMESPACE
 
+// ensure QList of this is efficient
+static_assert(QTypeInfo<QUuid::Id128Bytes>::isRelocatable);
+
 // 16 bytes (a uint, two shorts and a uchar[8]), each represented by two hex
 // digits; plus four dashes and a pair of enclosing brace: 16*2 + 4 + 2 = 38.
 enum { MaxStringUuidLength = 38 };
@@ -287,6 +290,46 @@ static QUuid createFromName(const QUuid &ns, const QByteArray &baseData, QCrypto
 */
 
 /*!
+    \class QUuid::Id128Bytes
+    \inmodule QtCore
+    \since 6.6
+
+    This trivial structure is 128 bits (16 bytes) in size and holds the binary
+    representation of a UUID. Applications can \c{memcpy()} its contents to and
+    from many other libraries' UUID or GUID structures that take 128-bit
+    values.
+*/
+
+/*!
+    \fn QUuid::QUuid(Id128Bytes id128) noexcept
+    \since 6.6
+
+    Creates a QUuid based on the integral \a id128 parameter.
+
+    \sa fromBytes(), toBytes(), toRfc4122()
+*/
+
+/*!
+    \fn QUuid::Id128Bytes QUuid::toBytes() 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.
+
+    \sa toRfc4122(), fromBytes(), QUuid()
+*/
+
+/*!
+    \fn QUuid QUuid::fromBytes(const void *bytes) 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().
+
+    \sa fromRfc4122()
+*/
+
+/*!
     \fn QUuid::QUuid(const GUID &guid)
 
     Casts a Windows \a guid to a Qt QUuid.
@@ -468,32 +511,13 @@ QUuid QUuid::createUuidV5(const QUuid &ns, const QByteArray &baseData)
 
     \since 4.8
 
-    \sa toRfc4122(), QUuid()
+    \sa toRfc4122(), QUuid(), fromBytes()
 */
 QUuid QUuid::fromRfc4122(QByteArrayView bytes) noexcept
 {
     if (bytes.isEmpty() || bytes.size() != 16)
         return QUuid();
-
-    uint d1;
-    ushort d2, d3;
-    uchar d4[8];
-
-    const uchar *data = reinterpret_cast<const uchar *>(bytes.data());
-
-    d1 = qFromBigEndian<quint32>(data);
-    data += sizeof(quint32);
-    d2 = qFromBigEndian<quint16>(data);
-    data += sizeof(quint16);
-    d3 = qFromBigEndian<quint16>(data);
-    data += sizeof(quint16);
-
-    for (int i = 0; i < 8; ++i) {
-        d4[i] = *(data);
-        data++;
-    }
-
-    return QUuid(d1, d2, d3, d4[0], d4[1], d4[2], d4[3], d4[4], d4[5], d4[6], d4[7]);
+    return fromBytes(bytes.data());
 }
 
 /*!
@@ -623,27 +647,16 @@ QByteArray QUuid::toByteArray(QUuid::StringFormat mode) const
 
     \endtable
 
+    The bytes in the byte array returned by this function contains the same
+    binary content as toBytes().
+
+    \sa toBytes()
     \since 4.8
 */
 QByteArray QUuid::toRfc4122() const
 {
-    // we know how many bytes a UUID has, I hope :)
-    QByteArray bytes(16, Qt::Uninitialized);
-    uchar *data = reinterpret_cast<uchar *>(bytes.data());
-
-    qToBigEndian(data1, data);
-    data += sizeof(quint32);
-    qToBigEndian(data2, data);
-    data += sizeof(quint16);
-    qToBigEndian(data3, data);
-    data += sizeof(quint16);
-
-    for (int i = 0; i < 8; ++i) {
-        *(data) = data4[i];
-        data++;
-    }
-
-    return bytes;
+    Id128Bytes bytes = toBytes();
+    return QByteArrayView(bytes).toByteArray();
 }
 
 #ifndef QT_NO_DATASTREAM
diff --git a/src/corelib/plugin/quuid.h b/src/corelib/plugin/quuid.h
index bcd78d85e7..21833efe03 100644
--- a/src/corelib/plugin/quuid.h
+++ b/src/corelib/plugin/quuid.h
@@ -4,6 +4,7 @@
 #ifndef QUUID_H
 #define QUUID_H
 
+#include <QtCore/qendian.h>
 #include <QtCore/qstring.h>
 
 #if defined(Q_OS_WIN) || defined(Q_QDOC)
@@ -26,7 +27,6 @@ Q_FORWARD_DECLARE_OBJC_CLASS(NSUUID);
 
 QT_BEGIN_NAMESPACE
 
-
 class Q_CORE_EXPORT QUuid
 {
     QUuid(Qt::Initialization) {}
@@ -55,11 +55,24 @@ public:
         Id128           = 3
     };
 
+    union Id128Bytes {
+        quint8 data[16];
+        quint16 data16[8];
+        quint32 data32[4];
+        quint64 data64[2];
+
+        constexpr explicit operator QByteArrayView() const noexcept
+        {
+            return QByteArrayView(data, sizeof(data));
+        }
+    };
+
     constexpr QUuid() noexcept {}
 
     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;
 
     explicit QUuid(QAnyStringView string) noexcept
         : QUuid{fromString(string)} {}
@@ -73,11 +86,15 @@ public:
 #endif
     QString toString(StringFormat mode = WithBraces) const;
     QByteArray toByteArray(StringFormat mode = WithBraces) const;
+    Id128Bytes toBytes() const noexcept;
     QByteArray toRfc4122() const;
+
+    static QUuid fromBytes(const void *bytes) noexcept;
 #if QT_CORE_REMOVED_SINCE(6, 3)
     static QUuid fromRfc4122(const QByteArray &);
 #endif
     static QUuid fromRfc4122(QByteArrayView) noexcept;
+
     bool isNull() const noexcept;
 
     constexpr bool operator==(const QUuid &orig) const noexcept
@@ -177,6 +194,31 @@ 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
+{
+    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
+{
+    Id128Bytes result = {};
+    qToBigEndian(data1, &result.data[0]);
+    qToBigEndian(data2, &result.data[4]);
+    qToBigEndian(data3, &result.data[6]);
+    memcpy(&result.data[8], data4, sizeof(data4));
+    return result;
+}
+
+inline QUuid QUuid::fromBytes(const void *bytes) noexcept
+{
+    Id128Bytes result = {};
+    memcpy(result.data, bytes, sizeof(result));
+    return QUuid(result);
+}
+
 inline bool operator<=(const QUuid &lhs, const QUuid &rhs) noexcept
 { return !(rhs < lhs); }
 inline bool operator>=(const QUuid &lhs, const QUuid &rhs) noexcept
diff --git a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
index 6b1e6003b8..b2eb4c420e 100644
--- a/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
+++ b/tests/auto/corelib/plugin/quuid/tst_quuid.cpp
@@ -25,6 +25,7 @@ private slots:
     void fromByteArray();
     void toRfc4122();
     void fromRfc4122();
+    void id128();
     void createUuidV3OrV5();
     void check_QDataStream();
     void isNull();
@@ -98,7 +99,7 @@ void tst_QUuid::fromChar()
     QCOMPARE(QUuid(), QUuid("fc69b59e-cc34-"));
     QCOMPARE(QUuid(), QUuid("fc69b59e-cc34"));
     QCOMPARE(QUuid(), QUuid("cc34"));
-    QCOMPARE(QUuid(), QUuid(NULL));
+    QCOMPARE(QUuid(), QUuid(nullptr));
 
     QCOMPARE(uuidB, QUuid(QString("{1ab6e93a-b1cb-4a87-ba47-ec7e99039a7b}")));
 }
@@ -217,6 +218,27 @@ void tst_QUuid::fromRfc4122()
     QCOMPARE(uuidB, QUuid::fromRfc4122(QByteArray::fromHex("1ab6e93ab1cb4a87ba47ec7e99039a7b")));
 }
 
+void tst_QUuid::id128()
+{
+    constexpr QUuid::Id128Bytes bytesA = { {
+        0xfc, 0x69, 0xb5, 0x9e,
+        0xcc, 0x34,
+        0x44, 0x36,
+        0xa4, 0x3c, 0xee, 0x95, 0xd1, 0x28, 0xb8, 0xc5,
+    } };
+    constexpr QUuid::Id128Bytes bytesB = { {
+        0x1a, 0xb6, 0xe9, 0x3a,
+        0xb1, 0xcb,
+        0x4a, 0x87,
+        0xba, 0x47, 0xec, 0x7e, 0x99, 0x03, 0x9a, 0x7b,
+    } };
+
+    QCOMPARE(QUuid(bytesA), uuidA);
+    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);
+}
+
 void tst_QUuid::createUuidV3OrV5()
 {
     //"www.widgets.com" is also from RFC4122