private static IEnumerable <WritePackage> CreateWritePackages(SiemensPlcProtocolContext s7Context, IEnumerable <WriteItem> vars)
{
var result = new List <WritePackage>();
foreach (var item in vars.OrderByDescending(x => x.NumberOfItems).ToList())
{
var currentPackage = result.FirstOrDefault(package => package.TryAdd(item));
if (currentPackage == null)
{
if (item.NumberOfItems > s7Context.WriteItemMaxLength)
{
var bytesToWrite = item.NumberOfItems;
ushort processed = 0;
while (bytesToWrite > 0)
{
var slice = Math.Min(s7Context.WriteItemMaxLength, bytesToWrite);
var child = WriteItem.CreateChild(item, (ushort)(item.Offset + processed), slice);
if (slice < s7Context.WriteItemMaxLength)
{
currentPackage = result.FirstOrDefault(package => package.TryAdd(child));
}
if (currentPackage == null)
{
currentPackage = new WritePackage(s7Context.PduSize);
if (currentPackage.TryAdd(child))
{
if (currentPackage.Full)
{
yield return(currentPackage.Return());
if (currentPackage.Handled)
{
currentPackage = null;
}
}
else
{
result.Add(currentPackage);
}
}
else
{
ThrowHelper.ThrowCouldNotAddPackageException(nameof(WritePackage));
}
}
processed += slice;
bytesToWrite -= slice;
}
}
else
{
currentPackage = new WritePackage(s7Context.PduSize);
result.Add(currentPackage);
if (!currentPackage.TryAdd(item))
{
ThrowHelper.ThrowCouldNotAddPackageException(nameof(WritePackage));
}
}
}
if (currentPackage != null)
{
if (currentPackage.Full)
{
yield return(currentPackage.Return());
}
if (currentPackage.Handled)
{
result.Remove(currentPackage);
}
}
}
foreach (var package in result)
{
yield return(package.Return());
}
}
