[pyassimp] Fix py3.3 + 64bits issues

64-bit Compatibility:

The first four characters of a String material property would be cut
off. A String's length is defined in structs.py as a c_size_t
variable, which is 8 bytes wide on 64-bit Python. However, when an
aiString is used as an aiMaterial property in C/C++, the length is
truncated down to a 4-byte value on 64-bit machines (see
MaterialSystem.cpp aiMaterial::AddProperty() for details). A new
struct was declared in structs.py (MaterialPropertyString) and used
in core._get_properties().

Python 3.3 Compatibility:

The built-in function hasattr() changed in Python 3.2 to not
trap exceptions, which means a NULL pointer ValueException now
escaped when checking if a pointer was valid (hasattr(obj,
'contents') in core.call_init()) (see
http://bugs.python.org/issue9666 for details). A new helper
function was defined that preserves the legacy functionality of
trapping the exceptions (helper.hasattr_silent()) and used
throughout the code as a replacement for hasattr().

String objects would import as "bytes" rather than as a
string. This was most noticeable in the key names for
material properties, where the trailing ' of a bytes object
would remain after it was converted to a string. The
solution was to call decode() on the bytes object using
utf-8 decoding. This applies to various parts of core.py.

Closes #35

port/PyAssimp/pyassimp/core.py

@@ -59,12 +59,12 @@ def make_tuple(ai_obj, type = None):
 
 def call_init(obj, caller = None):
         # init children
-        if hasattr(obj, '_init'):
+        if helper.hasattr_silent(obj, '_init'):
             obj._init(parent = caller)
 
         # pointers
-        elif hasattr(obj, 'contents'):
+        elif helper.hasattr_silent(obj, 'contents'):
-            if hasattr(obj.contents, '_init'):
+            if helper.hasattr_silent(obj.contents, '_init'):
                 obj.contents._init(target = obj, parent = caller)
 
 
@@ -76,7 +76,7 @@ def _init(self, target = None, parent = None):
     :param target: set the object which receive the added methods. Useful when manipulating
     pointers, to skip the intermediate 'contents' deferencing.
     """
-    if hasattr(self, '_is_init'):
+    if helper.hasattr_silent(self, '_is_init'):
         return self
     self._is_init = True
     
@@ -108,7 +108,7 @@ def _init(self, target = None, parent = None):
 
 
         if isinstance(obj, structs.String):
-            setattr(target, 'name', str(obj.data))
+            setattr(target, 'name', obj.data.decode("utf-8"))
             setattr(target.__class__, '__repr__', lambda x: str(x.__class__) + "(" + x.name + ")")
             setattr(target.__class__, '__str__', lambda x: x.name)
             continue
@@ -121,7 +121,7 @@ def _init(self, target = None, parent = None):
                 logger.debug("Added a parent as self." + name)
                 continue
 
-            if hasattr(self, 'mNum' + m[1:]):
+            if helper.hasattr_silent(self, 'mNum' + m[1:]):
 
                 length =  getattr(self, 'mNum' + m[1:])
     
@@ -346,7 +346,7 @@ def _get_properties(properties, length):
     for p in [properties[i] for i in range(length)]:
         #the name
         p = p.contents
-        key = str(p.mKey.data).split('.')[1]
+        key = str(p.mKey.data.decode("utf-8")).split('.')[1]
 
         #the data
         from ctypes import POINTER, cast, c_int, c_float, sizeof
@@ -354,7 +354,7 @@ def _get_properties(properties, length):
             arr = cast(p.mData, POINTER(c_float * int(p.mDataLength/sizeof(c_float)) )).contents
             value = [x for x in arr]
         elif p.mType == 3: #string can't be an array
-            value = cast(p.mData, POINTER(structs.String)).contents.data
+            value = cast(p.mData, POINTER(structs.MaterialPropertyString)).contents.data.decode("utf-8")
         elif p.mType == 4:
             arr = cast(p.mData, POINTER(c_int * int(p.mDataLength/sizeof(c_int)) )).contents
             value = [x for x in arr]

port/PyAssimp/pyassimp/helper.py

@@ -154,5 +154,15 @@ def search_library():
         # XXX: take version postfix of the .so on linux?
         return res[1:]
 
+def hasattr_silent(object, name):
+    """
+        Calls hasttr() with the given parameters and preserves the legacy (pre-Python 3.2)
+        functionality of silently catching exceptions.
         
+        Returns the result of hasatter() or False if an exception was raised.
+    """
     
+    try:
+        return hasattr(object, name)
+    except:
+        return False

port/PyAssimp/pyassimp/structs.py

@@ -1,6 +1,6 @@
 #-*- coding: UTF-8 -*-
 
-from ctypes import POINTER, c_void_p, c_int, c_uint, c_char, c_float, Structure, c_char_p, c_double, c_ubyte, c_size_t
+from ctypes import POINTER, c_void_p, c_int, c_uint, c_char, c_float, Structure, c_char_p, c_double, c_ubyte, c_size_t, c_uint32
 
 
 class Vector2D(Structure):
@@ -82,6 +82,26 @@ class String(Structure):
             ("data", c_char*MAXLEN),
         ]
 
+class MaterialPropertyString(Structure):
+    """
+    See 'aiTypes.h' for details.
+    
+    The size of length is truncated to 4 bytes on 64-bit platforms when used as a
+    material property (see MaterialSystem.cpp aiMaterial::AddProperty() for details).
+    """
+
+    MAXLEN = 1024
+
+    _fields_ = [
+            # Binary length of the string excluding the terminal 0. This is NOT the
+            #  logical length of strings containing UTF-8 multibyte sequences! It's
+            #  the number of bytes from the beginning of the string to its end.
+            ("length", c_uint32),
+            
+            # String buffer. Size limit is MAXLEN
+            ("data", c_char*MAXLEN),
+        ]
+
 class MemoryInfo(Structure):
     """
     See 'aiTypes.h' for details.