[pypy-svn] r10464 - in pypy/dist/pypy/tool: . test

[pedronis at codespeak.net]

Author: pedronis
Date: Fri Apr  8 20:46:22 2005
New Revision: 10464

Modified:
   pypy/dist/pypy/tool/rarithmetic.py
   pypy/dist/pypy/tool/test/test_rarithmetic.py
Log:
ovfcheck with tests.



Modified: pypy/dist/pypy/tool/rarithmetic.py
==============================================================================
--- pypy/dist/pypy/tool/rarithmetic.py	(original)
+++ pypy/dist/pypy/tool/rarithmetic.py	Fri Apr  8 20:46:22 2005
@@ -1,18 +1,23 @@
 """
-This file defines restricted integers.
+This file defines restricted arithmetic:
+
+classes and operations to express integer arithmetic,
+such that before and after translation semantics are
+consistent
+
+r_uint   an unsigned integer which has not overflow
+         checking. It is always positive and always
+         truncated to the internal machine word size.
+intmask  mask a possibly long value when running on CPython
+         back to a signed int value
+ovfcheck check on CPython whether the result of a signed
+         integer operation did overflow
+
+These are meant to be erased by translation, r_uint
+in the process should mark unsigned values, ovfcheck should
+mark where overflow checking is required.
 
-Purpose:
-Have an integer implementation that emulates
-restricted Python for CPython.
-
-r_int   an integer type which has overflow checking.
-        It doesn not automatically extend to long
-r_uint  an unsigned integer which has not overflow
-        checking. It is always positive and always
-        truncated to the internal machine word size.
 
-We try to keep the number of such internal types
-to a minimum.
 """
 
 class r_int(int):
@@ -159,6 +164,15 @@
 
 del _bits, _itest, _Ltest
 
+def ovfcheck(r):
+    # to be used as ovfcheck(x <op> y)
+    # raise OverflowError if the operation did overflow
+    assert not isinstance(r, r_uint), "unexpected ovf check on unsigned"
+    if isinstance(r, long):
+        raise OverflowError, "signed integer expression did overflow"
+    return r
+    
+
 class r_uint(long):
     """ fake unsigned integer implementation """
 

Modified: pypy/dist/pypy/tool/test/test_rarithmetic.py
==============================================================================
--- pypy/dist/pypy/tool/test/test_rarithmetic.py	(original)
+++ pypy/dist/pypy/tool/test/test_rarithmetic.py	Fri Apr  8 20:46:22 2005
@@ -12,7 +12,7 @@
     i *= 2
     l *= 2
     machbits += 1
-print machbits
+#print machbits
 
 
 objspacename = 'std'
@@ -150,5 +150,65 @@
     assert intmask(sys.maxint+1) == minint
     assert intmask(minint-1) == sys.maxint
 
-    
 
+def test_ovfcheck():
+    one = 1
+    x = sys.maxint
+    minusx = -sys.maxint
+    n = -sys.maxint-1
+    y = sys.maxint-1
+    # sanity
+    raises(AssertionError, ovfcheck, r_uint(0))
+
+    
+    # not overflowing
+    try:
+        ovfcheck(y+one)
+    except OverflowError:
+        assert False
+    else:
+        pass
+    try:
+        ovfcheck(minusx-one)
+    except OverflowError:
+        assert False
+    else:
+        pass
+    try:
+        ovfcheck(x-x)
+    except OverflowError:
+        assert False
+    else:
+        pass        
+    try:
+        ovfcheck(n-n)
+    except OverflowError:
+        assert False
+    else:
+        pass    
+
+    # overflowing
+    try:
+        ovfcheck(x+one)
+    except OverflowError:
+        pass
+    else:
+        assert False        
+    try:
+        ovfcheck(x+x)
+    except OverflowError:
+        pass
+    else:
+        assert False
+    try:
+        ovfcheck(n-one)
+    except OverflowError:
+        pass
+    else:
+        assert False
+    try:
+        ovfcheck(n-y)
+    except OverflowError:
+        pass
+    else:
+        assert False