Source/WTF/wtf/UUID.cpp

/*
* Copyright (C) 2010 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
*     * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#include "config.h"
#include <wtf/UUID.h>

#include <mutex>
#include <wtf/CryptographicallyRandomNumber.h>
#include <wtf/HexNumber.h>
#include <wtf/text/StringBuilder.h>

#if OS(DARWIN)
#include <sys/sysctl.h>
#endif

namespace WTF {

String createCanonicalUUIDString()
{
    unsigned randomData[4];
    cryptographicallyRandomValues(reinterpret_cast<unsigned char*>(randomData), sizeof(randomData));

    // Format as Version 4 UUID.
    StringBuilder builder;
    builder.reserveCapacity(36);
    appendUnsignedAsHexFixedSize(randomData[0], builder, 8, Lowercase);
    builder.append('-');
    appendUnsignedAsHexFixedSize(randomData[1] >> 16, builder, 4, Lowercase);
    builder.appendLiteral("-4");
    appendUnsignedAsHexFixedSize(randomData[1] & 0x00000fff, builder, 3, Lowercase);
    builder.append('-');
    appendUnsignedAsHexFixedSize((randomData[2] >> 30) | 0x8, builder, 1, Lowercase);
    appendUnsignedAsHexFixedSize((randomData[2] >> 16) & 0x00000fff, builder, 3, Lowercase);
    builder.append('-');
    appendUnsignedAsHexFixedSize(randomData[2] & 0x0000ffff, builder, 4, Lowercase);
    appendUnsignedAsHexFixedSize(randomData[3], builder, 8, Lowercase);
    return builder.toString();
}

String bootSessionUUIDString()
{
#if OS(DARWIN)
    static LazyNeverDestroyed<String> bootSessionUUID;
    static std::once_flag onceKey;
    std::call_once(onceKey, [] {
        size_t uuidLength = 37;
        char uuid[uuidLength];
        if (sysctlbyname("kern.bootsessionuuid", uuid, &uuidLength, nullptr, 0))
            return;
        bootSessionUUID.construct(static_cast<const char*>(uuid), uuidLength - 1);
    });
    return bootSessionUUID;
#else
    return String();
#endif
}

} // namespace WTF