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#pragma once
#include <Core/Types.h>
/**
* Implementation Details
* ^^^^^^^^^^^^^^^^^^^^^^
* The underlying implementation for a UUID has it represented as a 128-bit unsigned integer. Underlying this, a wide
* integer with a 64-bit unsigned integer as its base is utilized. This wide integer can be interfaced with as an array
* to access different components of the base. For example, on a Little Endian platform, accessing at index 0 will give
* you the 8 higher bytes, and index 1 will give you the 8 lower bytes. On a Big Endian platform, this is reversed where
* index 0 will give you the 8 lower bytes, and index 1 will give you the 8 higher bytes.
*
* uuid.toUnderType().items[0]
*
* // uint64_t uint64_t
* // [xxxxxxxx] [ ]
*
* uuid.toUnderType().items[1]
*
* // uint64_t uint64_t
* // [ ] [xxxxxxxx]
*
* The way that data is stored in the underlying wide integer treats the data as two 64-bit chunks sequenced in the
* array. On a Little Endian platform, this results in the following layout
*
* // Suppose uuid contains 61f0c404-5cb3-11e7-907b-a6006ad3dba0
*
* uuid.toUnderType().items[0]
*
* // uint64_t as HEX
* // [E7 11 B3 5C 04 C4 F0 61] [A0 DB D3 6A 00 A6 7B 90]
* // ^^^^^^^^^^^^^^^^^^^^^^^
*
* uuid.toUnderType().items[1]
*
* // uint64_t as HEX
* // [E7 11 B3 5C 04 C4 F0 61] [A0 DB D3 6A 00 A6 7B 90]
* // ^^^^^^^^^^^^^^^^^^^^^^^
*
* while on a Big Endian platform this would be
*
* // Suppose uuid contains 61f0c404-5cb3-11e7-907b-a6006ad3dba0
*
* uuid.toUnderType().items[0]
*
* // uint64_t as HEX
* // [90 7B A6 00 6A D3 DB A0] [61 F0 C4 04 5C B3 11 E7]
* // ^^^^^^^^^^^^^^^^^^^^^^^
*
* uuid.toUnderType().items[1]
*
* // uint64_t as HEX
* // [90 7B A6 00 6A D3 DB A0] [61 F0 C4 04 5C B3 11 E7]
* // ^^^^^^^^^^^^^^^^^^^^^^^
*/
namespace DB
{
namespace UUIDHelpers
{
/// Generate random UUID.
UUID generateV4();
constexpr size_t HighBytes = (std::endian::native == std::endian::little) ? 0 : 1;
constexpr size_t LowBytes = (std::endian::native == std::endian::little) ? 1 : 0;
inline uint64_t getHighBytes(const UUID & uuid)
{
return uuid.toUnderType().items[HighBytes];
}
inline uint64_t & getHighBytes(UUID & uuid)
{
return uuid.toUnderType().items[HighBytes];
}
inline uint64_t getLowBytes(const UUID & uuid)
{
return uuid.toUnderType().items[LowBytes];
}
inline uint64_t & getLowBytes(UUID & uuid)
{
return uuid.toUnderType().items[LowBytes];
}
const UUID Nil{};
}
}
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