internal static GifPropertyItem[] ConvertFromMemory(IntPtr propdata, int count)
{
var props = new GifPropertyItem[count];
for (var i = 0; i < count; i++)
{
GifPropertyItemInternal propcopy = null;
try
{
propcopy = (GifPropertyItemInternal)ExternDllHelper.PtrToStructure(propdata,
typeof(GifPropertyItemInternal));
props[i] = new GifPropertyItem
{
Id = propcopy.id,
Len = propcopy.len,
Type = propcopy.type,
Value = propcopy.Value
};
// this calls Marshal.Copy and creates a copy of the original memory into a byte array.
propcopy.value = IntPtr.Zero; // we dont actually own this memory so dont free it.
}
finally
{
propcopy?.Dispose();
}
propdata = (IntPtr)((long)propdata + Marshal.SizeOf(typeof(GifPropertyItemInternal)));
}
return(props);
}
internal GifPropertyItem GetPropertyItem(int propid)
{
GifPropertyItem propitem;
var status = ExternDllHelper.Gdip.GdipGetPropertyItemSize(new HandleRef(this, NativeImage), propid, out var size);
if (status != ExternDllHelper.Gdip.Ok)
{
throw ExternDllHelper.Gdip.StatusException(status);
}
if (size == 0)
{
return(null);
}
var propdata = Marshal.AllocHGlobal(size);
if (propdata == IntPtr.Zero)
{
throw ExternDllHelper.Gdip.StatusException(ExternDllHelper.Gdip.OutOfMemory);
}
status = ExternDllHelper.Gdip.GdipGetPropertyItem(new HandleRef(this, NativeImage), propid, size, propdata);
try
{
if (status != ExternDllHelper.Gdip.Ok)
{
throw ExternDllHelper.Gdip.StatusException(status);
}
propitem = GifPropertyItemInternal.ConvertFromMemory(propdata, 1)[0];
}
finally
{
Marshal.FreeHGlobal(propdata);
}
return(propitem);
}
internal static GifPropertyItemInternal ConvertFromPropertyItem(GifPropertyItem propItem)
{
var propItemInternal = new GifPropertyItemInternal
{
id = propItem.Id,
len = 0,
type = propItem.Type
};
var propItemValue = propItem.Value;
if (propItemValue != null)
{
var length = propItemValue.Length;
propItemInternal.len = length;
propItemInternal.value = Marshal.AllocHGlobal(length);
Marshal.Copy(propItemValue, 0, propItemInternal.value, length);
}
return(propItemInternal);
}