Force zlib.crc32 and zlib.adler32 to return a signed integer on all platforms

regardless of the native sizeof(long) used in the integer object.

This somewhat odd behavior of returning a signed is maintained in 2.x for
compatibility reasons of always returning an integer rather than a long object.

Fixes Issue1202 for Python 2.6

1 files changed, 17 insertions, 8 deletions

diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index ef00cca..384399d 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -884,37 +884,46 @@ PyDoc_STRVAR(adler32__doc__,
 "adler32(string[, start]) -- Compute an Adler-32 checksum of string.\n"
 "\n"
 "An optional starting value can be specified.  The returned checksum is\n"
-"an integer.");
+"a signed integer.");
 
 static PyObject *
 PyZlib_adler32(PyObject *self, PyObject *args)
 {
     uLong adler32val = adler32(0L, Z_NULL, 0);
     Byte *buf;
-    int len;
+    int len, signed_val;
 
     if (!PyArg_ParseTuple(args, "s#|k:adler32", &buf, &len, &adler32val))
 	return NULL;
-    adler32val = adler32(adler32val, buf, len);
-    return PyInt_FromLong(adler32val);
+    /* In Python 2.x we return a signed integer regardless of native platform
+     * long size (the 32bit unsigned long is treated as 32-bit signed and sign
+     * extended into a 64-bit long inside the integer object).  3.0 does the
+     * right thing and returns unsigned. http://bugs.python.org/issue1202 */
+    signed_val = adler32(adler32val, buf, len);
+    return PyInt_FromLong(signed_val);
 }
 
 PyDoc_STRVAR(crc32__doc__,
 "crc32(string[, start]) -- Compute a CRC-32 checksum of string.\n"
 "\n"
 "An optional starting value can be specified.  The returned checksum is\n"
-"an integer.");
+"a signed integer.");
 
 static PyObject *
 PyZlib_crc32(PyObject *self, PyObject *args)
 {
     uLong crc32val = crc32(0L, Z_NULL, 0);
     Byte *buf;
-    int len;
+    int len, signed_val;
+
     if (!PyArg_ParseTuple(args, "s#|k:crc32", &buf, &len, &crc32val))
 	return NULL;
-    crc32val = crc32(crc32val, buf, len);
-    return PyInt_FromLong(crc32val);
+    /* In Python 2.x we return a signed integer regardless of native platform
+     * long size (the 32bit unsigned long is treated as 32-bit signed and sign
+     * extended into a 64-bit long inside the integer object).  3.0 does the
+     * right thing and returns unsigned. http://bugs.python.org/issue1202 */
+    signed_val = crc32(crc32val, buf, len);
+    return PyInt_FromLong(signed_val);
 }