SboxSuperuser/Engine/Vendor/ImGui/ImHash.cs
Utility class providing FNV-1a hashing helpers used for ImGui IDs. It implements Str(string, seed) which hashes a string and resets when encountering "###", and Int(int, seed) which hashes a 32-bit integer while marking it distinct from equivalent byte sequences in strings.
Native Interop
// Vendored from zeljkovranjes/sbox-imgui; see LICENSE and PROVENANCE.md in this folder.
using Sandbox;
#pragma warning disable CS0649 // Upstream reserves fields for optional widgets and features.
namespace SboxSuperuser.Engine.Vendor.ImGui;
/// <summary>
/// ID hashing shared by the facade and the window state (moved out of the facade so Engine never calls it).
/// </summary>
internal static class ImHash
{
/// <summary>
/// FNV-1a hash of a string, seeded. Supports "###" to reset the hash so that only the part after "###" counts.
/// </summary>
internal static int Str( string str, int seed )
{
unchecked
{
uint crc = (uint)seed ^ 2166136261u;
uint seedU = crc;
if ( str is null )
return (int)crc;
for ( int i = 0; i < str.Length; i++ )
{
char c = str[i];
if ( c == '#' && i + 2 < str.Length && str[i + 1] == '#' && str[i + 2] == '#' )
crc = seedU;
crc ^= c;
crc *= 16777619u;
}
int result = (int)crc;
return result == 0 ? 1 : result;
}
}
internal static int Int( int value, int seed )
{
unchecked
{
uint crc = (uint)seed ^ 2166136261u;
for ( int i = 0; i < 4; i++ )
{
crc ^= (uint)((value >> (i * 8)) & 0xFF);
crc *= 16777619u;
}
// Distinguish int ids from string ids of the same bytes.
crc ^= 0x9E3779B9u;
crc *= 16777619u;
int result = (int)crc;
return result == 0 ? 1 : result;
}
}
}