alef 0.19.8

Opinionated polyglot binding generator for Rust libraries
Documentation 
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/// <summary>
/// Manages the FFI vtable and delegates for a {{ trait_pascal }} implementation
/// </summary>
public sealed class {{ trait_pascal }}Bridge : IDisposable {

    private readonly I{{ trait_pascal }} _impl;
    private readonly GCHandle _implHandle;
    internal IntPtr _vtable;
    private bool _disposed;
    private readonly object[] _delegates;

    // Vtable slot delegates ({{ num_vtable_fields }})
{% if has_super_trait %}

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate int NameFn(IntPtr userData, out IntPtr outName);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate int VersionFn(IntPtr userData, out IntPtr outVersion);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate int InitializeFn(IntPtr userData, out IntPtr outError);

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate int ShutdownFn(IntPtr userData, out IntPtr outError);
{% endif %}
{% for method in methods %}

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
{% if method.params_empty %}
{% if is_options_field %}
    private delegate int {{ method.pascal_name }}Fn(IntPtr userData, out IntPtr outResult);
{% else %}
    private delegate int {{ method.pascal_name }}Fn(IntPtr userData, out IntPtr outResult, out IntPtr outError);
{% endif %}
{% else %}
{% if is_options_field %}
    private delegate int {{ method.pascal_name }}Fn(IntPtr userData, {{ method.unmanaged_params }}, out IntPtr outResult);
{% else %}
    private delegate int {{ method.pascal_name }}Fn(IntPtr userData, {{ method.unmanaged_params }}, out IntPtr outResult, out IntPtr outError);
{% endif %}
{% endif %}
{% endfor %}

    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    private delegate void FreeUserDataFn(IntPtr userData);

    public {{ trait_pascal }}Bridge(I{{ trait_pascal }} impl) {
        _impl = impl ?? throw new ArgumentNullException(nameof(impl));
        _implHandle = GCHandle.Alloc(impl, GCHandleType.Normal);
        _vtable = IntPtr.Zero;
        _disposed = false;
        _delegates = new object[{{ num_vtable_fields }}];
        BuildVtable();
    }

    private void BuildVtable() {
        // Allocate unmanaged vtable struct (array of function pointers)
        _vtable = global::System.Runtime.InteropServices.Marshal.AllocHGlobal(IntPtr.Size * {{ num_vtable_fields }});

{{ vtable_slots }}
    }

    private static string ToJsonString<T>(T value) {
        return JsonSerializer.Serialize(value);
    }
{% if has_bytes_param %}

    private static byte[] MarshalBytesFromIntPtr(IntPtr ptr) {
        if (ptr == IntPtr.Zero) return Array.Empty<byte>();
        var json = global::System.Runtime.InteropServices.Marshal.PtrToStringUTF8(ptr) ?? "[]";
        return JsonSerializer.Deserialize<byte[]>(json) ?? Array.Empty<byte>();
    }
{% endif %}

{{ callbacks }}

    public void Dispose() {
        if (_disposed) return;
        _disposed = true;

        if (_vtable != IntPtr.Zero) {
            global::System.Runtime.InteropServices.Marshal.FreeHGlobal(_vtable);
            _vtable = IntPtr.Zero;
        }

        if (_implHandle.IsAllocated) {
            _implHandle.Free();
        }
    }
}