// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
 
namespace System.Reflection.Metadata
{
    public static partial class AssemblyExtensions
    {
        [LibraryImport(RuntimeHelpers.QCall, EntryPoint = "AssemblyNative_InternalTryGetRawMetadata")]
        [return: MarshalAs(UnmanagedType.Bool)]
        private static unsafe partial bool InternalTryGetRawMetadata(QCallAssembly assembly, ref byte* blob, ref int length);
 
        /// <summary>
        /// Retrieves the metadata section of the assembly, for use with <see cref="T:System.Reflection.Metadata.MetadataReader" />.
        /// </summary>
        /// <param name="assembly">The assembly from which to retrieve the metadata.</param>
        /// <param name="blob">When this method returns, contains the pointer to the metadata section blob.</param>
        /// <param name="length">When this method returns, contains the length of the metadata section blob.</param>
        /// <returns>
        /// <see langword="true" /> if the metadata is retrieved successfully; <see langword="false" /> upon failure.
        /// The metadata might not be available for some assemblies, such as <see cref="Emit.AssemblyBuilder" />, AOT images, etc.
        /// </returns>
        /// <remarks>
        /// <para>Callers should not write to the metadata blob.</para>
        /// <para>The metadata blob pointer will remain valid as long as the assembly is alive.</para>
        /// <para>The caller is responsible for keeping the assembly object alive while accessing the metadata blob.</para>
        /// </remarks>
        [CLSCompliant(false)] // out byte* blob
        public static unsafe bool TryGetRawMetadata(this Assembly assembly, out byte* blob, out int length)
        {
            ArgumentNullException.ThrowIfNull(assembly);
 
            blob = null;
            length = 0;
 
            var runtimeAssembly = assembly as RuntimeAssembly;
            if (runtimeAssembly == null)
            {
                return false;
            }
 
            RuntimeAssembly rtAsm = runtimeAssembly;
 
            return InternalTryGetRawMetadata(new QCallAssembly(ref rtAsm), ref blob, ref length);
        }
    }
}