Restore compatibility to python 3.0 to 3.4

Author: Byron

doc/source/changes.rst

@@ -2,6 +2,11 @@
 Changelog
 #########
 
+**********
+v0.8.5
+**********
+- Fixed Python 3.0-3.3 regression, which also causes smmap to become about 3 times slower depending on the code path. It's related to this bug (http://bugs.python.org/issue15958), which was fixed in python 3.4
+
 **********
 v0.8.4
 **********

smmap/__init__.py

@@ -3,7 +3,7 @@
 __author__ = "Sebastian Thiel"
 __contact__ = "[email protected]"
 __homepage__ = "https://github.com/Byron/smmap"
-version_info = (0, 8, 4)
+version_info = (0, 8, 5)
 __version__ = '.'.join(str(i) for i in version_info)
 
 # make everything available in root package for convenience

smmap/buf.py

@@ -3,6 +3,8 @@
 
 __all__ = ["SlidingWindowMapBuffer"]
 
+import sys
+
 try:
     bytes
 except NameError:
@@ -79,16 +81,31 @@ def __getslice__(self, i, j):
             ofs = i
             # It's fastest to keep tokens and join later, especially in py3, which was 7 times slower
             # in the previous iteration of this code
-            md = list()
-            while l:
-                c.use_region(ofs, l)
-                assert c.is_valid()
-                d = c.buffer()[:l]
-                ofs += len(d)
-                l -= len(d)
-                md.append(d)
-            # END while there are bytes to read
-            return bytes().join(md)
+            pyvers = sys.version_info[:2]
+            if (3, 0) <= pyvers <= (3, 3):
+                # Memory view cannot be joined below python 3.4 ... 
+                out = bytes()
+                while l:
+                    c.use_region(ofs, l)
+                    assert c.is_valid()
+                    d = c.buffer()[:l]
+                    ofs += len(d)
+                    l -= len(d)
+                    # This is slower than the join ... but what can we do ... 
+                    out += d
+                # END while there are bytes to read
+                return out
+            else:
+                md = list()
+                while l:
+                    c.use_region(ofs, l)
+                    assert c.is_valid()
+                    d = c.buffer()[:l]
+                    ofs += len(d)
+                    l -= len(d)
+                    md.append(d)
+                # END while there are bytes to read
+                return bytes().join(md)
         # END fast or slow path
     #{ Interface