/// <summary>
/// Generic marshalling function to retrieve structs from libvlc by reading from unmanaged memory with offsets
/// This supports uint libvlc signatures.
/// </summary>
/// <typeparam name="T">Internal struct type</typeparam>
/// <typeparam name="TU">publicly facing struct type</typeparam>
/// <param name="nativeRef">native reference of the parent</param>
/// <param name="getRef">Native libvlc call: retrieve collection start pointer from parent reference</param>
/// <param name="retrieve">Retrieve the internal struct by marshalling the native pointer</param>
/// <param name="create">Create a publicly facing struct from the internal struct values</param>
/// <param name="releaseRef">Native libvlc call: release the array allocated with the getRef call with the given element count</param>
/// <returns>An array of publicly facing struct types</returns>
internal static TU[] Retrieve <T, TU>(IntPtr nativeRef, ArrayOut getRef, Func <IntPtr, T> retrieve,
Func <T, TU> create, Action <IntPtr, uint> releaseRef)
where T : struct
where TU : struct
{
var arrayPtr = IntPtr.Zero;
uint count = 0;
try
{
count = getRef(nativeRef, out arrayPtr);
if (count == 0)
{
#if NETSTANDARD1_1 || NET40
return(new TU[0]);
#else
return(Array.Empty <TU>());
#endif
}
var resultList = new List <TU>();
T structure;
for (var i = 0; i < count; i++)
{
var ptr = Marshal.ReadIntPtr(arrayPtr, i * IntPtr.Size);
structure = retrieve(ptr);
var managedStruct = create(structure);
resultList.Add(managedStruct);
}
return(resultList.ToArray());
}
finally
{
if (arrayPtr != IntPtr.Zero)
{
releaseRef(arrayPtr, count);
arrayPtr = IntPtr.Zero;
}
}
}
/// <summary>
/// Generic marshalling function to retrieve structs from libvlc by reading from unmanaged memory with offsets
/// This supports uint libvlc signatures. This is used for the new mediatrack type which became a class.
/// From libvlcsharp 4.0
/// </summary>
/// <typeparam name="T">publicly facing class type</typeparam>
/// <param name="nativeRef">native reference of the parent</param>
/// <param name="getRef">Native libvlc call: retrieve collection start pointer from parent reference</param>
/// <param name="create">Create a publicly facing class from the ptr/internal struct values</param>
/// <param name="releaseRef">Native libvlc call: release the array allocated with the getRef call with the given element count</param>
/// <returns>An array of publicly facing class types</returns>
internal static T[] Retrieve <T>(IntPtr nativeRef, ArrayOut getRef, Func <IntPtr, T> create, Action <IntPtr, uint> releaseRef)
where T : class
{
var arrayPtr = IntPtr.Zero;
uint count = 0;
try
{
count = getRef(nativeRef, out arrayPtr);
if (count == 0)
{
#if NETSTANDARD1_1 || NET45
return(new T[0]);
#else
return(Array.Empty <T>());
#endif
}
var resultList = new List <T>();
T type;
for (var i = 0; i < count; i++)
{
var ptr = Marshal.ReadIntPtr(arrayPtr, i * IntPtr.Size);
type = create(ptr);
resultList.Add(type);
}
return(resultList.ToArray());
}
finally
{
if (arrayPtr != IntPtr.Zero)
{
releaseRef(arrayPtr, count);
arrayPtr = IntPtr.Zero;
}
}
}