// Use as a regular unit from Delphi, or run as a console app from FreePascal

unit uuidv7;

interface

uses

SysUtils, DateUtils;

function GenerateUUIDv7: TGUID;

implementation

function GenerateUUIDv7: TGUID;

var

timestamp: Int64;

randomBytes: array[0..9] of Byte;

uuid: TGUID;

i: Integer;

begin

FillChar(uuid, SizeOf(uuid), 0);

{$IFDEF FPC}

timestamp := DateTimeToUnix(Now) * 1000; // seconds accuracy

{$ELSE}

timestamp := DateTimeToMilliseconds(Now) - Int64(UnixDateDelta DateDelta) * MSecsPerDay; // millisecond accuracy

{$ENDIF}

// Generate 10 random bytes

for i := 0 to 9 do

randomBytes[i] := Random($FF);

// Populate the TGUID fields

uuid.D1 := (timestamp shr 16) and $FFFFFFFF; // Top 32 bits of the 48-bit timestamp

uuid.D2 := ((timestamp shr 4) and $0FFF) or $7000; // Next 12 bits of the timestamp and version 7

uuid.D3 := ((timestamp and $0000000F) shl 12) or // the last 4 bits of timestamp

(randomBytes[0] and $F0); // the top 4 bits of randomBytes[0]

uuid.D4[0] := (randomBytes[0] and $0F) or $80; // Set the variant to 10xx

Move(randomBytes[1], uuid.D4[1], 7); // Remaining 7 bytes

Result := uuid;

end;

// Optionally remove this to make a regular unit for FPC too

{$IFDEF FPC}

var i: Integer;

begin

Randomize;

for i := 0 to 30 do

writeln(GUIDToString(GenerateUUIDv7).ToLower);

readln;

{$ELSE}

initialization

Randomize;

{$ENDIF}

end.