1 files changed, 137 insertions, 0 deletions
diff --git a/src/plugins/utilities/uuid/UUIDGeneration.cpp b/src/plugins/utilities/uuid/UUIDGeneration.cpp
new file mode 100644
index 0000000..bb03fc6
--- /dev/null
+++ b/src/plugins/utilities/uuid/UUIDGeneration.cpp
@@ -0,0 +1,137 @@
+/*
+ * Copyright 2018-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *     http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+// This code is copied from https://github.com/alexa/avs-device-sdk/
+// Minor modifications are made to the original file.
+
+#include <random>
+#include <chrono>
+#include <sstream>
+#include <iomanip>
+#include <mutex>
+#include <climits>
+#include <algorithm>
+#include <functional>
+
+#include "utilities/uuid/UUIDGeneration.h"
+
+namespace vshl {
+namespace utilities {
+namespace uuid {
+
+/// String to identify log entries originating from this file.
+static const std::string TAG("UUIDGeneration");
+
+/// The UUID version (Version 4), shifted into the correct position in the byte.
+static const uint8_t UUID_VERSION_VALUE = 4 << 4;
+
+/// The UUID variant (Variant 1), shifted into the correct position in the byte.
+static const size_t UUID_VARIANT_VALUE = 2 << 6;
+
+/// Separator used between UUID fields.
+static const std::string SEPARATOR("-");
+
+/// Number of bits in the replacement value.
+static const size_t MAX_NUM_REPLACEMENT_BITS = CHAR_BIT;
+
+/// Number of bits in a hex digit.
+static const size_t BITS_IN_HEX_DIGIT = 4;
+
+/**
+ * Randomly generate a string of hex digits. Before the conversion of hex to string,
+ * the function allows replacement of the bits of the first two generated hex digits.
+ * Replacement happens starting at the most significant, to the least significant bit.
+ *
+ * @param ibe A random number generator.
+ * @param numDigits The number of hex digits [0-9],[a-f] to generate.
+ * @param replacementBits The replacement value for up to the first two digits generated.
+ * @param numReplacementBits The number of bits of @c replacementBits to use.
+ *
+ * @return A hex string of length @c numDigits.
+ */
+static const std::string generateHexWithReplacement(
+    std::independent_bits_engine<std::default_random_engine, CHAR_BIT, uint8_t>& ibe,
+    unsigned int numDigits,
+    uint8_t replacementBits,
+    unsigned short numReplacementBits) {
+    if (numReplacementBits > MAX_NUM_REPLACEMENT_BITS) {
+        return "";
+    }
+
+    if (numReplacementBits > (numDigits * BITS_IN_HEX_DIGIT)) {
+        return "";
+    }
+
+    // Makes assumption that 1 digit = 4 bits.
+    std::vector<uint8_t> bytes(ceil(numDigits / 2.0));
+    std::generate(bytes.begin(), bytes.end(), std::ref(ibe));
+
+    // Replace the specified number of bits from the first byte.
+    bytes.at(0) &= (0xff >> numReplacementBits);
+    replacementBits &= (0xff << (MAX_NUM_REPLACEMENT_BITS - numReplacementBits));
+    bytes.at(0) |= replacementBits;
+
+    std::ostringstream oss;
+    for (const auto& byte : bytes) {
+        oss << std::hex << std::setfill('0') << std::setw(2) << static_cast<int>(byte);
+    }
+
+    std::string bytesText = oss.str();
+    // Remove the last digit for odd numDigits case.
+    bytesText.resize(numDigits);
+
+    return bytesText;
+}
+
+/**
+ * Randomly generate a string of hex digits.
+ *
+ * @param ibe A random number generator.
+ * @param numDigits The number of hex digits [0-9],[a-f] to generate.
+ *
+ * @return A hex string of length @c numDigits.
+ */
+static const std::string generateHex(
+    std::independent_bits_engine<std::default_random_engine, CHAR_BIT, uint8_t>& ibe,
+    unsigned int numDigits) {
+    return generateHexWithReplacement(ibe, numDigits, 0, 0);
+}
+
+const std::string generateUUID() {
+    static bool seeded = false;
+    static std::independent_bits_engine<std::default_random_engine, CHAR_BIT, uint8_t> ibe;
+    static std::mutex mutex;
+    std::unique_lock<std::mutex> lock(mutex);
+    if (!seeded) {
+        std::random_device rd;
+        ibe.seed(
+            rd() +
+            std::chrono::duration_cast<std::chrono::nanoseconds>(std::chrono::steady_clock::now().time_since_epoch())
+                .count());
+        seeded = true;
+    }
+
+    std::ostringstream uuidText;
+    uuidText << generateHex(ibe, 8) << SEPARATOR << generateHex(ibe, 4) << SEPARATOR
+             << generateHexWithReplacement(ibe, 4, UUID_VERSION_VALUE, 4) << SEPARATOR
+             << generateHexWithReplacement(ibe, 4, UUID_VARIANT_VALUE, 2) << SEPARATOR << generateHex(ibe, 12);
+
+    lock.unlock();
+
+    return uuidText.str();
+}
+
+}  // namespace uuid
+}  // namespace utilities
+}  // namespace vshl