public static void FlipSerializedGuidEndianness(this HelpersContainerClasses.Guid container, byte[] bytes)
{
// Some encryption tools (e.g. MP4Box) use GUIDs with different byte orders from .NET.
// Two variants exist: "big endian" and "little endian", with the latter as the defualt for .NET.
// A GUID consists of 5 groups of bytes, of which only the first 3 are byte order dependent.
Array.Reverse(bytes, 0, 4);
Array.Reverse(bytes, 4, 2);
Array.Reverse(bytes, 6, 2);
}
/// <summary>
/// Deserializes a GUID from a byte array that uses the big endian format for all components.
/// This format is often used by non-Microsoft tooling.
/// </summary>
public static Guid FromBigEndianByteArray(this HelpersContainerClasses.Guid container, byte[] bytes)
{
Helpers.Argument.ValidateIsNotNull(bytes, "bytes");
if (!BitConverter.IsLittleEndian)
{
throw new InvalidOperationException("This method has not been tested on big endian machines and likely would not operate correctly.");
}
var bytesCopy = bytes.ToArray(); // Copy, to ensure that input is not modified.
Helpers.Guid.FlipSerializedGuidEndianness(bytesCopy);
return(new Guid(bytesCopy));
}
/// <summary>
/// Generates a GUID that is in timestamp-sotrable order in SQL server.
/// Use this for generating row IDs that index well.
/// </summary>
public static Guid NewCombGuid(this HelpersContainerClasses.Guid container)
{
byte[] destinationArray = Guid.NewGuid().ToByteArray();
DateTime time = new DateTime(0x76c, 1, 1);
DateTime now = DateTime.UtcNow;
TimeSpan span = new TimeSpan(now.Ticks - time.Ticks);
TimeSpan timeOfDay = now.TimeOfDay;
byte[] bytes = BitConverter.GetBytes(span.Days);
byte[] array = BitConverter.GetBytes((long)(timeOfDay.TotalMilliseconds / 3.333333));
Array.Reverse(bytes);
Array.Reverse(array);
Array.Copy(bytes, bytes.Length - 2, destinationArray, destinationArray.Length - 6, 2);
Array.Copy(array, array.Length - 4, destinationArray, destinationArray.Length - 4, 4);
return(new Guid(destinationArray));
}
/// <summary>
/// Returns a new cryptographically secure GUID. The returned GUID shall be GUID v4 compatible.
/// </summary>
public static Guid NewCryptographicallySecureGuid(this HelpersContainerClasses.Guid container)
{
var guidBytes = new byte[16];
using (var randomGenerator = new RNGCryptoServiceProvider())
randomGenerator.GetBytes(guidBytes);
// The 16 bytes in guidBytes might not conform to GUIDv4 format.
// In order to achieve that, the 8th and 9th byte need to be modified
// to be in the form of 0x4Y and 0x[8-B]Y respectively where Y stays intact.
guidBytes[7] &= 0x0F; // Clear the 4 high bits of the 8th byte.
guidBytes[7] |= 0x40; // Set the 7th bit.
guidBytes[8] &= 0x3F; // Clear the 2 high bits of the 9th byte.
guidBytes[8] |= 0x80; // Set the 8th bit.
return(new Guid(guidBytes));
}
