Have the binascii module use zlib's optimized crc32() function when available

to reduce our code size (1k data table and tiny bit of code).  It falls back
to its own without zlib.

2 files changed, 41 insertions, 3 deletions

diff --git a/Modules/binascii.c b/Modules/binascii.c
index 659e08c..dfc3b7a 100644
--- a/Modules/binascii.c
+++ b/Modules/binascii.c
@@ -56,6 +56,9 @@
 #define PY_SSIZE_T_CLEAN
 
 #include "Python.h"
+#ifdef USE_ZLIB_CRC32
+#include "zlib.h"
+#endif
 
 static PyObject *Error;
 static PyObject *Incomplete;
@@ -748,6 +751,26 @@ binascii_crc_hqx(PyObject *self, PyObject *args)
 PyDoc_STRVAR(doc_crc32,
 "(data, oldcrc = 0) -> newcrc. Compute CRC-32 incrementally");
 
+#ifdef USE_ZLIB_CRC32
+/* This was taken from zlibmodule.c PyZlib_crc32 (but is PY_SSIZE_T_CLEAN) */
+static PyObject *
+binascii_crc32(PyObject *self, PyObject *args)
+{
+    uLong crc32val = 0;  /* crc32(0L, Z_NULL, 0) */
+    Byte *buf;
+    Py_ssize_t len;
+    int signed_val;
+
+    if (!PyArg_ParseTuple(args, "s#|k:crc32", &buf, &len, &crc32val))
+	return NULL;
+    /* 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);
+}
+#else  /* USE_ZLIB_CRC32 */
 /*  Crc - 32 BIT ANSI X3.66 CRC checksum files
     Also known as: ISO 3307
 **********************************************************************|
@@ -898,6 +921,7 @@ binascii_crc32(PyObject *self, PyObject *args)
 #endif
 	return PyInt_FromLong(result);
 }
+#endif  /* USE_ZLIB_CRC32 */
 
 
 static PyObject *
diff --git a/setup.py b/setup.py
index c28d839..20a3e9b 100644
--- a/setup.py
+++ b/setup.py
@@ -486,9 +486,6 @@ class PyBuildExt(build_ext):
         # select(2); not on ancient System V
         exts.append( Extension('select', ['selectmodule.c']) )
 
-        # Helper module for various ascii-encoders
-        exts.append( Extension('binascii', ['binascii.c']) )
-
         # Fred Drake's interface to the Python parser
         exts.append( Extension('parser', ['parsermodule.c']) )
 
@@ -1069,6 +1066,7 @@ class PyBuildExt(build_ext):
         # You can upgrade zlib to version 1.1.4 yourself by going to
         # http://www.gzip.org/zlib/
         zlib_inc = find_file('zlib.h', [], inc_dirs)
+        have_zlib = False
         if zlib_inc is not None:
             zlib_h = zlib_inc[0] + '/zlib.h'
             version = '"0.0.0"'
@@ -1090,6 +1088,7 @@ class PyBuildExt(build_ext):
                     exts.append( Extension('zlib', ['zlibmodule.c'],
                                            libraries = ['z'],
                                            extra_link_args = zlib_extra_link_args))
+                    have_zlib = True
                 else:
                     missing.append('zlib')
             else:
@@ -1097,6 +1096,21 @@ class PyBuildExt(build_ext):
         else:
             missing.append('zlib')
 
+        # Helper module for various ascii-encoders.  Uses zlib for an optimized
+        # crc32 if we have it.  Otherwise binascii uses its own.
+        if have_zlib:
+            extra_compile_args = ['-DUSE_ZLIB_CRC32']
+            libraries = ['z']
+            extra_link_args = zlib_extra_link_args
+        else:
+            extra_compile_args = []
+            libraries = []
+            extra_link_args = []
+        exts.append( Extension('binascii', ['binascii.c'],
+                               extra_compile_args = extra_compile_args,
+                               libraries = libraries,
+                               extra_link_args = extra_link_args) )
+
         # Gustavo Niemeyer's bz2 module.
         if (self.compiler.find_library_file(lib_dirs, 'bz2')):
             if sys.platform == "darwin":