dotnet-installer/scripts/dotnet-cli-build/Utils/BuildVersion.cs

namespace Microsoft.DotNet.Cli.Build
{
    public class BuildVersion
    {
        public int Major { get; set; }
        public int Minor { get; set; }
        public int Patch { get; set; }
        public int CommitCount { get; set; }
        public string CommitCountString => CommitCount.ToString("000000");
        public string ReleaseSuffix { get; set; }

        public string SimpleVersion => $"{Major}.{Minor}.{Patch}.{CommitCountString}";
        public string VersionSuffix => $"{ReleaseSuffix}-{CommitCountString}";
        public string NuGetVersion => $"{Major}.{Minor}.{Patch}-{VersionSuffix}";
        public string ProductionVersion => $"{Major}.{Minor}.{Patch}";

        public string GenerateMsiVersion()
        {
            // MSI versioning
            // Encode the CLI version to fit into the MSI versioning scheme - https://msdn.microsoft.com/en-us/library/windows/desktop/aa370859(v=vs.85).aspx
            // MSI versions are 3 part
            //                           major.minor.build
            // Size(bits) of each part     8     8    16
            // So we have 32 bits to encode the CLI version
            // Starting with most significant bit this how the CLI version is going to be encoded as MSI Version
            // CLI major  -> 6 bits
            // CLI minor  -> 6 bits
            // CLI patch  -> 6 bits
            // CLI commitcount -> 14 bits

            var major = Major << 26;
            var minor = Minor << 20;
            var patch = Patch << 14;
            var msiVersionNumber = major | minor | patch | CommitCount;

            var msiMajor = (msiVersionNumber >> 24) & 0xFF;
            var msiMinor = (msiVersionNumber >> 16) & 0xFF;
            var msiBuild = msiVersionNumber & 0xFFFF;

            return $"{msiMajor}.{msiMinor}.{msiBuild}";
        }
    }
}