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

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

diff --git a/src/nmutil/divmod.py b/src/nmutil/divmod.py
index 99e6847631b1b9621d80b5bd4878d038a848fff0..7c503e6199992462824c8646f1ef62d697d6a536 100644 (file)
--- a/src/nmutil/divmod.py
+++ b/src/nmutil/divmod.py
@@ -1,22 +1,46 @@
+# SPDX-License-Identifier: LGPL-3-or-later
+"""
+    This work is funded through NLnet under Grant 2019-02-012
+
+    License: LGPLv3+
+
+
+"""
+
+from copy import copy
 # this is a POWER ISA 3.0B compatible *signed* div function
 # however it is also the c, c++, rust, java *and* x86 way of doing things
+
+
 def trunc_divs(n, d):
-    abs_n = abs(n)
-    abs_d = abs(d)
+    abs_n = abs(n.to_signed_int())
+    abs_d = abs(d.to_signed_int())
+    print("trunc_div n", abs_n, n.to_signed_int())
+    print("trunc_div d", abs_d, d.to_signed_int())
     abs_q = abs_n // abs_d
-    print ("trunc_div", n.value, d.value,
-                        abs_n.value, abs_d.value, abs_q.value,
-                        n == abs_n, d == abs_d)
-    if (n == abs_n) == (d == abs_d):
-        return abs_q
-    return -abs_q
+    sign_n = n.value & (1 << (n.bits - 1)) != 0
+    sign_d = d.value & (1 << (d.bits - 1)) != 0
+    print("trunc_div", hex(n.value), hex(d.value),
+          hex(abs_n), hex(abs_d), hex(abs_q),
+          sign_n, sign_d)
+    res = copy(n)
+    if (sign_n == sign_d):
+        res.value = abs_q
+        if res.value & (1 << (res.bits - 1)) != 0:
+            # result should be positive but is negative
+            raise OverflowError()
+        return res
+    mask = (1 << res.bits) - 1
+    res.value = (-abs_q) & mask
+
+    return res
 
 
 # this is a POWER ISA 3.0B compatible *signed* mod / remainder function
 # however it is also the c, c++, rust, java *and* x86 way of doing things
 def trunc_rems(n, d):
     m = d * trunc_divs(n, d)
-    m.bits = n.bits # cheat - really shouldn't do this. mul returns full length
-    return n - m
-
 
+    # cheat - really shouldn't do this. mul returns full length
+    m.bits = n.bits
+    return n - m