add first cut at PartitionedSignal "Cat"

[ieee754fpu.git] / src / ieee754 / part_mul_add / partpoints.py

diff --git a/src/ieee754/part_mul_add/partpoints.py b/src/ieee754/part_mul_add/partpoints.py
index f7fbd2cb5017eaa734c01bc3014c1666a5e97191..887372af62cef7bb7b213cd63e98dbb10aae85ce 100644 (file)
--- a/src/ieee754/part_mul_add/partpoints.py
+++ b/src/ieee754/part_mul_add/partpoints.py
@@ -4,6 +4,7 @@
 
 from nmigen import Signal, Value, Cat, C
 
+
 def make_partition(mask, width):
     """ from a mask and a bitwidth, create partition points.
         note that the assumption is that the mask indicates the
@@ -25,6 +26,28 @@ def make_partition(mask, width):
     return ppoints
 
 
+def make_partition2(mask, width):
+    """ from a mask and a bitwidth, create partition points.
+        note that the assumption is that the mask indicates the
+        breakpoints in regular intervals, and that the last bit (MSB)
+        of the mask is therefore *ignored*.
+        mask len = 4, width == 16 will return:
+            {4: mask[0], 8: mask[1], 12: mask[2]}
+        mask len = 8, width == 64 will return:
+            {8: mask[0], 16: mask[1], 24: mask[2], .... 56: mask[6]}
+    """
+    mlen = len(mask)
+    jumpsize = width // mlen # amount to jump by (size of each partition)
+    ppoints = {}
+    ppos = jumpsize
+    midx = 0
+    while ppos < width and midx < mlen: # -1, ignore last bit
+        ppoints[ppos] = mask[midx]
+        ppos += jumpsize
+        midx += 1
+    return ppoints
+
+
 class PartitionPoints(dict):
     """Partition points and corresponding ``Value``s.