speed up ==, hash, <, >, <=, and >= for plain_data

[nmutil.git] / src / nmutil / byterev.py

diff --git a/src/nmutil/byterev.py b/src/nmutil/byterev.py
index 5c40e4104ec3499e739a5f37abd04dd648d282cb..a7f0a68aeacc1fd78609dcc9b60734c79e105381 100644 (file)
--- a/src/nmutil/byterev.py
+++ b/src/nmutil/byterev.py
@@ -1,15 +1,27 @@
+# SPDX-License-Identifier: LGPL-3-or-later
+"""
+    This work is funded through NLnet under Grant 2019-02-012
+
+    License: LGPLv3+
+"""
+
 from nmigen import Signal, Cat
 
-# TODO: turn this into a module
+# TODO: turn this into a module?
+
+
 def byte_reverse(m, name, data, length):
     """byte_reverse: unlike nmigen word_select this takes a dynamic length
 
     nmigen Signal.word_select may only take a fixed length.  we need
     bigendian byte-reverse, half-word reverse, word and dword reverse.
+
+    This only outputs the first `length` bytes, higher bytes are zeroed.
     """
     comb = m.d.comb
     data_r = Signal.like(data, name=name)
 
+    # if length is a static integer, we do not require a Case statement
     if isinstance(length, int):
         j = length
         rev = []
@@ -19,13 +31,12 @@ def byte_reverse(m, name, data, length):
         comb += data_r.eq(Cat(*rev))
         return data_r
 
+    # Switch statement needed: dynamic length had better be = 1,2,4 or 8
     with m.Switch(length):
-        for j in [1,2,4,8]:
+        for j in [1, 2, 4, 8]:
             with m.Case(j):
                 rev = []
                 for i in range(j):
                     rev.append(data.word_select(j-1-i, 8))
                 comb += data_r.eq(Cat(*rev))
     return data_r
-
-