// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Reflection.Metadata;

namespace Microsoft.Diagnostics.DataContractReader.Legacy;

/// <summary>
/// Shared helpers for resolving MethodDesc signature information.
/// </summary>
internal static class MethodSignatureHelpers
{
    /// <summary>
    /// Parses raw signature bytes to determine the signature header and argument count.
    /// </summary>
    public static unsafe void GetSignatureInfo(ReadOnlySpan<byte> signature, out SignatureHeader header, out uint numArgs)
    {
        fixed (byte* pSig = signature)
        {
            BlobReader blobReader = new BlobReader(pSig, signature.Length);
            header = blobReader.ReadSignatureHeader();
            if (header.Kind != SignatureKind.Method)
                throw new BadImageFormatException();
            if (header.IsGeneric)
                blobReader.ReadCompressedInteger(); // skip generic arity
            uint paramCount = (uint)blobReader.ReadCompressedInteger();
            numArgs = paramCount + (header.IsInstance ? 1u : 0u);
        }
    }
}