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/** @file
Convert 128 bit unique identifier between GUID and UUID format.
Copyright (c) 2024, Arm Limited. All rights reserved.<BR>
Copyright (c) Microsoft Corporation.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include "BaseLibInternals.h"
/*******************************************************************************
UUID (Universally Unique IDentifier), as defined in RFC4122
(https://datatracker.ietf.org/doc/html/rfc4122#section-4.1), is a 128-bit number
used to uniquely identify information in computer systems.
UUIDs contains 5 fields:
- time_low: 32 bits
- time_mid: 16 bits
- time_hi_and_version: 16 bits
- clock_seq_hi_and_reserved: 8 bits
- clock_seq_low: 8 bits
- node: 8 bits * 6
Each field encoded with the Most Significant Byte first (known as network byte
order, or big-endian).
GUID (Globally Unique Identifier), on the other hand, is a 128-bit number used
in UEFI environments, which is similar to UUID but has a different byte order
in memory. See https://uefi.org/specs/UEFI/2.11/Apx_A_GUID_and_Time_Formats.html
GUID also contains 5 fields:
- TimeLow: 32 bits
- TimeMid: 16 bits
- TimeHiAndVersion: 16 bits
- ClockSeqHighAndReserved: 16 bits
- ClockSeqLow: 8 bits
- Node: 8 bits * 6
TimeLow, TimeMid, TimeHighAndVersion fields in the EFI are encoded with the Least
Significant Byte first (also known as little-endian).
Example:
Consider the same string representation/registry format for MM communication v2:
"378daedc-f06b-4446-8314-40ab933c87a3"
In UUID format, it is represented as:
- Data fields:
- time_low: 0x37 0x8d 0xae 0xdc (0x378daedc in big-endian)
- time_mid: 0xf0 0x6b (0xf06b in big-endian)
- time_hi_and_version: 0x44 0x46 (0x4446 in big-endian)
- clock_seq_hi_and_reserved: 0x83
- clock_seq_low: 0x14
- node: 0x00, 0xab, 0x93, 0x3c, 0x87, 0xa3
- Byte representation in memory:
- 37 8d ae dc f0 6b 44 46 83 14 40 ab 93 3c 87 a3
However, in GUID format, it is represented as:
- Data fields:
- TimeLow: 0xdc 0xae 0x8d 0x37 (0x378daedc in little-endian)
- TimeMid: 0x6b 0xf0 (0xf06b in little-endian)
- TimeHiAndVersion: 0x46 0x44 (0x4446 in little-endian)
- ClockSeqHighAndReserved: 0x83
- ClockSeqLow: 0x14
- Node: 0x00, 0xab, 0x93, 0x3c, 0x87, 0xa3
- Byte representation in memory:
- dc ae 8d 37 6b f0 46 44 83 14 40 ab 93 3c 87 a3
*******************************************************************************/
/**
This function converts a GUID in UEFI format to a UUID in RFC4122 format.
The conversion is done by swapping the byte order of the TimeLow, TimeMid, and
TimeHiAndVersion fields, while keeping the ClockSeq and Node fields unchanged.
@param [in] FromGuid GUID in format to be converted to UUID RFC4122 format.
@param [out] ToUuid Pointer to a GUID structure that will hold the converted
UUID in RFC4122 format.
**/
VOID
EFIAPI
ConvertGuidToUuid (
IN GUID *FromGuid,
OUT GUID *ToUuid
)
{
ASSERT (ToUuid != NULL);
ASSERT (FromGuid != NULL);
CopyGuid (ToUuid, FromGuid);
ToUuid->Data1 = SwapBytes32 (ToUuid->Data1);
ToUuid->Data2 = SwapBytes16 (ToUuid->Data2);
ToUuid->Data3 = SwapBytes16 (ToUuid->Data3);
}
/**
This function converts a UUID in RFC4122 format to a GUID in UEFI format.
The conversion is done by swapping the byte order of the time_low, time_mid, and
time_hi_and_version fields, while keeping the ClockSeq and Node fields unchanged.
This function is symmetric to ConvertGuidToUuid.
@param [in] FromUuid UUID in RFC4122 format to be converted to GUID in UEFI format.
@param [out] ToGuid Pointer to a GUID structure that will hold the converted
GUID in UEFI format.
**/
VOID
EFIAPI
ConvertUuidToGuid (
IN GUID *FromUuid,
OUT GUID *ToGuid
)
{
// The conversion is symmetric, so we can use the same function.
// The only difference is the order of the parameters.
ConvertGuidToUuid (
FromUuid,
ToGuid
);
}
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