[Python-checkins] r81082 - in python/branches/release31-maint: Modules/audioop.c

[mark.dickinson]

Author: mark.dickinson
Date: Tue May 11 15:11:12 2010
New Revision: 81082

Log:
Merged revisions 81081 via svnmerge from 
svn+ssh://pythondev@svn.python.org/python/branches/py3k

................
  r81081 | mark.dickinson | 2010-05-11 14:09:58 +0100 (Tue, 11 May 2010) | 9 lines
  
  Merged revisions 81079 via svnmerge from 
  svn+ssh://pythondev@svn.python.org/python/trunk
  
  ........
    r81079 | mark.dickinson | 2010-05-11 14:05:30 +0100 (Tue, 11 May 2010) | 1 line
    
    Issue #8674: fix another bogus overflow check in audioop module.
  ........
................


Modified:
   python/branches/release31-maint/   (props changed)
   python/branches/release31-maint/Modules/audioop.c

Modified: python/branches/release31-maint/Modules/audioop.c
==============================================================================
--- python/branches/release31-maint/Modules/audioop.c	(original)
+++ python/branches/release31-maint/Modules/audioop.c	Tue May 11 15:11:12 2010
@@ -1160,25 +1160,16 @@
            ceiling(len*outrate/inrate) output frames, and each frame
            requires bytes_per_frame bytes.  Computing this
            without spurious overflow is the challenge; we can
-           settle for a reasonable upper bound, though. */
-        int ceiling;   /* the number of output frames */
-        int nbytes;    /* the number of output bytes needed */
-        int q = len / inrate;
-        /* Now len = q * inrate + r exactly (with r = len % inrate),
-           and this is less than q * inrate + inrate = (q+1)*inrate.
-           So a reasonable upper bound on len*outrate/inrate is
-           ((q+1)*inrate)*outrate/inrate =
-           (q+1)*outrate.
-        */
-        ceiling = (q+1) * outrate;
-        nbytes = ceiling * bytes_per_frame;
-        /* See whether anything overflowed; if not, get the space. */
-        if (q+1 < 0 ||
-            ceiling / outrate != q+1 ||
-            nbytes / bytes_per_frame != ceiling)
+           settle for a reasonable upper bound, though, in this
+           case ceiling(len/inrate) * outrate. */
+
+        /* compute ceiling(len/inrate) without overflow */
+        int q = len > 0 ? 1 + (len - 1) / inrate : 0;
+        if (outrate > INT_MAX / q / bytes_per_frame)
             str = NULL;
         else
-            str = PyBytes_FromStringAndSize(NULL, nbytes);
+            str = PyBytes_FromStringAndSize(NULL,
+                                            q * outrate * bytes_per_frame);
 
         if (str == NULL) {
             PyErr_SetString(PyExc_MemoryError,