QUuid: add support for creating UUID v7

Thanks to Thiago for the more efficient way of using 12 bits of
the sub-milliseconds part of the timestamp. Previously I used the method
described in the RFC (value of type double multiplied by 4096).

Add a private helper to check the version since now there is a gap in
the Version enum values (UUID v6 isn't supported).

Drive-by, document Version::Sha1 enumerator.

[ChangeLog][QtCore][QUuid] Added support for creating UUID v7 as
described in
https://datatracker.ietf.org/doc/html/rfc9562#name-uuid-version-7

Fixes: QTBUG-130672
Change-Id: Idfea9fbb12a7f28e25b27b56a3b402799afb4864
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/CMakeLists.txt

@@ -194,7 +194,7 @@ qt_internal_add_module(Core
         plugin/qfactoryloader.cpp plugin/qfactoryloader_p.h
         plugin/qplugin.h plugin/qplugin_p.h
         plugin/qpluginloader.cpp plugin/qpluginloader.h
-        plugin/quuid.cpp plugin/quuid.h
+        plugin/quuid.cpp plugin/quuid.h plugin/quuid_p.h
         serialization/qcborarray.h
         serialization/qcborcommon.cpp serialization/qcborcommon.h serialization/qcborcommon_p.h
         serialization/qcbordiagnostic.cpp

src/corelib/plugin/quuid.cpp

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "quuid.h"
+#include "quuid_p.h"
 
 #include "qcryptographichash.h"
 #include "qdatastream.h"
@@ -543,7 +544,7 @@ QUuid QUuid::fromString(QAnyStringView text) noexcept
   \note In Qt versions prior to 6.8, this function took QByteArray, not
   QByteArrayView.
 
-  \sa variant(), version(), createUuidV5()
+  \sa variant(), version(), createUuidV5(), createUuidV7()
 */
 
 /*!
@@ -553,7 +554,7 @@ QUuid QUuid::fromString(QAnyStringView text) noexcept
   This function returns a new UUID with variant QUuid::DCE and version QUuid::Md5.
   \a ns is the namespace and \a baseData is the basic data as described by RFC 4122.
 
-  \sa variant(), version(), createUuidV5()
+  \sa variant(), version(), createUuidV5(), createUuidV7()
 */
 
 /*!
@@ -590,6 +591,25 @@ QUuid QUuid::createUuidV5(QUuid ns, QByteArrayView baseData) noexcept
     return createFromName(ns, baseData, QCryptographicHash::Sha1, 5);
 }
 
+/*!
+    \since 6.9
+
+    This function returns a new UUID with variant QUuid::DCE and version
+    QUuid::UnixEpoch.
+
+    It uses a time-ordered value field derived from the number of milliseconds
+    since the UNIX Epoch as described by
+    \l {https://datatracker.ietf.org/doc/html/rfc9562#name-uuid-version-7}{RFC9562}.
+
+    \sa variant(), version(), createUuidV3(), createUuidV5()
+*/
+#ifndef QT_BOOTSTRAPPED
+QUuid QUuid::createUuidV7()
+{
+    return createUuidV7_internal(std::chrono::system_clock::now());
+}
+#endif // !defined(QT_BOOTSTRAPPED)
+
 /*!
   Creates a QUuid object from the binary representation of the UUID, as
   specified by RFC 4122 section 4.1.2. See toRfc4122() for a further
@@ -861,7 +881,9 @@ QDataStream &operator>>(QDataStream &s, QUuid &id)
     \value Name Name-based, by using values from a name for all sections
     \value Md5 Alias for Name
     \value Random Random-based, by using random numbers for all sections
-    \value Sha1
+    \value Sha1      Name-based version that uses SHA-1 hashing
+    \value UnixEpoch Time-based UUID using the number of milliseconds since
+                     the UNIX epoch
 */
 
 /*!

src/corelib/plugin/quuid.h

@@ -48,7 +48,8 @@ public:
         Md5                 = 3, // 0 0 1 1
         Name = Md5,
         Random                = 4,  // 0 1 0 0
-        Sha1                 = 5 // 0 1 0 1
+        Sha1            = 5, // 0 1 0 1
+        UnixEpoch       = 7, // 0 1 1 1
     };
 
     enum StringFormat {
@@ -277,6 +278,26 @@ public:
         return QUuid::createUuidV5(ns, qToByteArrayViewIgnoringNull(baseData.toUtf8()));
     }
 
+    static QUuid createUuidV7();
+
+private:
+    static constexpr bool isKnownVersion(Version v) noexcept
+    {
+        switch (v) {
+        case VerUnknown:
+            return false;
+        case Time:
+        case EmbeddedPOSIX:
+        case Md5:
+        case Random:
+        case Sha1:
+        case UnixEpoch:
+            return true;
+        }
+        return false;
+    }
+
+public:
 #if QT_CORE_REMOVED_SINCE(6, 9)
     QUuid::Variant variant() const noexcept;
     QUuid::Version version() const noexcept;
@@ -296,7 +317,7 @@ public:
         // Check the 4 MSB of data3
         const Version ver = Version(data3 >> 12);
         // Check that variant() == DCE and version is in a valid range
-        if (ver >= Time && ver <= Sha1 && (data4[0] & 0xC0) == 0x80)
+        if (isKnownVersion(ver) && (data4[0] & 0xC0) == 0x80)
             return ver;
         return VerUnknown;
     }

src/corelib/plugin/quuid_p.h

@@ -0,0 +1,61 @@
+// Copyright (C) 2020 The Qt Company Ltd.
+// Copyright (C) 2021 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QUUID_P_H
+#define QUUID_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists for the convenience
+// of the QLibrary class.  This header file may change from
+// version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "quuid.h"
+
+#include <QtCore/qrandom.h>
+
+#include <chrono>
+
+QT_BEGIN_NAMESPACE
+
+#ifndef QT_BOOTSTRAPPED
+static inline QUuid createUuidV7_internal(
+    std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds> tp)
+{
+    QUuid result;
+
+    using namespace std::chrono;
+    const nanoseconds nsecSinceEpoch = tp.time_since_epoch();
+    const auto msecSinceEpoch = floor<milliseconds>(nsecSinceEpoch);
+    const quint64 frac = (nsecSinceEpoch - msecSinceEpoch).count();
+    // Lower 48 bits of the timestamp
+    const quint64 msecs = quint64(msecSinceEpoch.count()) & 0xffffffffffff;
+    result.data1 = uint(msecs >> 16);
+    result.data2 = ushort(msecs);
+    // rand_a: use a 12-bit sub-millisecond timestamp for additional monotonicity
+    // https://datatracker.ietf.org/doc/html/rfc9562#monotonicity_counters (Method 3)
+
+    // "frac" is a number between 0 and 999,999, so the lowest 20 bits
+    // should be roughly random. Use the high 12 of those for additional
+    // monotonicity.
+    result.data3 = frac >> 8;
+    result.data3 &= 0x0FFF;
+    result.data3 |= ushort(7) << 12;
+
+    // rand_b: 62 bits of random data (64 - 2 bits for the variant)
+    const quint64 random = QRandomGenerator::system()->generate64();
+    memcpy(result.data4, &random, sizeof(quint64));
+    result.data4[0] = (result.data4[0] & 0x3F) | 0x80; // UV_DCE
+    return result;
+}
+#endif
+
+QT_END_NAMESPACE
+
+#endif // QUUID_P_H

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

@@ -11,11 +11,15 @@
 
 #include <qcoreapplication.h>
 #include <quuid.h>
+#include <QtCore/private/quuid_p.h>
 
 #ifdef Q_OS_ANDROID
 #include <QStandardPaths>
 #endif
 
+using namespace std::chrono_literals;
+using namespace Qt::StringLiterals;
+
 class tst_QUuid : public QObject
 {
     Q_OBJECT
@@ -35,6 +39,9 @@ private slots:
     void id128();
     void uint128();
     void createUuidV3OrV5();
+    void createUuidV7_unique();
+    void createUuidV7_data();
+    void createUuidV7();
     void check_QDataStream();
     void isNull();
     void equal();
@@ -323,6 +330,51 @@ void tst_QUuid::createUuidV3OrV5()
     QT_TEST_EQUALITY_OPS(uuidD, QUuid::createUuidV5(uuidNS, QString("www.widgets.com")), true);
 }
 
+void tst_QUuid::createUuidV7_unique()
+{
+    const int count = 1000;
+    std::vector<QUuid> vec;
+    vec.reserve(count);
+    for (int i = 0; i < count; ++i) {
+        auto id = QUuid::createUuidV7();
+        QCOMPARE(id.version(), QUuid::UnixEpoch);
+        QCOMPARE(id.variant(), QUuid::DCE);
+        vec.push_back(id);
+    }
+
+    QVERIFY(std::unique(vec.begin(), vec.end()) == vec.end());
+}
+
+void tst_QUuid::createUuidV7_data()
+{
+    QTest::addColumn<QDateTime>("dt");
+    QTest::addColumn<QUuid>("expected");
+
+    // February 22, 2022 2:22:22.00 PM GMT-05:00, example from:
+    // https://datatracker.ietf.org/doc/html/rfc9562#name-example-of-a-uuidv7-value
+    QTest::newRow("feb2022")
+        << QDateTime::fromString("2022-02-22T14:22:22.00-05:00"_L1, Qt::ISODateWithMs)
+        << QUuid::fromString("017F22E2-79B0-7CC3-98C4-DC0C0C07398F"_L1);
+
+    QTest::newRow("jan2000")
+        << QDateTime::fromString("2000-01-02T14:22:22.00-05:00"_L1, Qt::ISODateWithMs)
+        << QUuid("00dc741e-35b0-7643-947d-0380e108ce80"_L1);
+}
+
+void tst_QUuid::createUuidV7()
+{
+    QFETCH(QDateTime, dt);
+    QFETCH(QUuid, expected);
+
+    QVERIFY(dt.isValid());
+
+    using namespace std::chrono;
+    auto extractTimestamp = [](const QUuid &id) { return (quint64(id.data1) << 16) | id.data2; };
+    const auto result =
+        createUuidV7_internal(time_point<system_clock, milliseconds>(dt.toMSecsSinceEpoch() * 1ms));
+    QCOMPARE_EQ(extractTimestamp(result), extractTimestamp(expected));
+}
+
 void tst_QUuid::check_QDataStream()
 {
     QUuid tmp;
@@ -618,8 +670,8 @@ void tst_QUuid::versions_data()
     QTest::newRow("DCE-inv-less-than-Time->unknown")
             << QUuid(0, 0, 0b0000'1101'0101'1011, 0b1000'0000, 0, 0, 0, 0, 0, 0, 0)
             << QUuid::VerUnknown;
-    QTest::newRow("DCE-inv-greater-than-Sha1->unknown")
+    QTest::newRow("DCE-inv-greater-than-UnixEpoch->unknown")
-            << QUuid(0, 0, 0b0111'1101'0101'1011, 0b1000'0000, 0, 0, 0, 0, 0, 0, 0)
+            << QUuid(0, 0, 0b1000'1101'0101'1011, 0b1000'0000, 0, 0, 0, 0, 0, 0, 0)
             << QUuid::VerUnknown;
     QTest::newRow("NCS-Time->unknown")
             << QUuid(0, 0, 0b0001'0000'0000'0000, 0b0100'0000, 0, 0, 0, 0, 0, 0, 0)