Utils_p: Add functions to generate random QByteArray

Co-authored-by: Melvin Keskin <melvo@olomono.de>

1 files changed, 67 insertions, 0 deletions

diff --git a/src/base/QXmppUtils.cpp b/src/base/QXmppUtils.cpp
index 1d99a87f..462d19fb 100644
--- a/src/base/QXmppUtils.cpp
+++ b/src/base/QXmppUtils.cpp
@@ -6,6 +6,7 @@
 #include "QXmppUtils.h"
 
 #include "QXmppLogger.h"
+#include "QXmppUtils_p.h"
 
 #include <QBuffer>
 #include <QByteArray>
@@ -322,3 +323,69 @@ void helperToXmlAddTextElement(QXmlStreamWriter *stream, const QString &name,
     else
         stream->writeEmptyElement(name);
 }
+
+/// \cond
+
+//
+// Generates a random count of random bytes.
+//
+// \param minimumByteCount minimum count of bytes to generate
+// \param maximumByteCount maximum count of bytes to generate
+//
+// \return the generated bytes
+//
+QByteArray QXmpp::Private::generateRandomBytes(uint32_t minimumByteCount, uint32_t maximumByteCount)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
+    const auto byteCount = QRandomGenerator::system()->bounded(minimumByteCount, maximumByteCount);
+#else
+    const auto byteCount = (qrand() % (maximumByteCount - minimumByteCount)) + minimumByteCount;
+#endif
+    QByteArray bytes;
+    bytes.resize(byteCount);
+    generateRandomBytes(reinterpret_cast<uint8_t *>(bytes.data()), byteCount);
+
+    return bytes;
+}
+
+//
+// Generates random bytes.
+//
+// \param bytes generated bytes
+// \param byteCount count of bytes to generate
+//
+void QXmpp::Private::generateRandomBytes(uint8_t *bytes, uint32_t byteCount)
+{
+    // QRandomGenerator does not provide a random generation of single bytes. Thus, this approach
+    // fills an array with unsigned integers until no additional integer fits into the array. If
+    // byteCount is no multiple of intSize, the remaining bytes need to be filled separately.
+    constexpr uint32_t intSize = sizeof(uint32_t);
+    auto intCount = byteCount / intSize;
+
+#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
+    auto *randomGenerator = QRandomGenerator::system();
+
+    // Fill the space with intCount unsigned integers.
+    if (intCount) {
+        randomGenerator->fillRange(reinterpret_cast<uint32_t *>(bytes), intCount);
+    }
+
+    // Fill the remaining space with single bytes.
+    for (size_t i = byteCount - byteCount % intSize; i < byteCount; i++) {
+        bytes[i] = randomGenerator->bounded(std::numeric_limits<uint8_t>::max() + 1);
+    }
+#else
+    // Fill the range with intCount unsigned integers.
+    for (size_t i = 0; i < intCount; i++) {
+        reinterpret_cast<int *>(bytes)[i] = qrand();
+    }
+
+    // Fill the remaining space with single bytes.
+    for (size_t i = byteCount - byteCount % intSize; i < byteCount; i++) {
+        auto rand = qrand();
+        bytes[i] = *reinterpret_cast<uint *>(&rand) % (std::numeric_limits<uint8_t>::max() + 1);
+    }
+#endif
+}
+
+/// \endcond