Fix PLC setter functions for memoryview compatibility

[LuTiFlekSSer]

Some setter functions in snap7.util fail when writing to a memoryview.
Added conversion of tuples returned by struct.unpack into bytes.
Also replaced some loops with slice assignments.

[gijzelaerr]

can you update this pr with the changes in master? i've fixed the test suite.

[LuTiFlekSSer]

done

[gijzelaerr]

Code Review

I took a deep look at this PR. Here's my analysis:

The Good

The core change is valid and improves code quality. The old pattern was unnecessarily convoluted:

# Old: pack to bytes, unpack to tuple, assign (converts back to bytes)
_bytes = struct.unpack("2B", struct.pack(">H", _int))
bytearray_[byte_index : byte_index + 2] = _bytes

# New: just pack to bytes and assign directly
bytearray_[byte_index : byte_index + 2] = struct.pack(">H", _int)

The memoryview claim is also verified - tuples don't implement the buffer protocol, so the old code fails with memoryview while the new code works:

mv = memoryview(bytearray(4))
mv[0:2] = (255, 255)    # TypeError: a bytes-like object is required
mv[0:2] = b'\xff\xff'   # Works

Issue to Fix

In set_time, there's a redundant bytes() wrapper:

bytes_array = time_int.to_bytes(4, byteorder="big", signed=True)
bytearray_[byte_index : byte_index + 4] = bytes(bytes_array)  # bytes() is unnecessary

int.to_bytes() already returns bytes, so this just creates an unnecessary copy. Please remove the bytes() wrapper.

Summary

• ✅ Code simplification is genuine and welcome
• ✅ Memoryview compatibility fix is valid
• ❌ Remove redundant bytes() in set_time

Once that's fixed, this is good to merge.