fix saveraw

wrapper/xgboost.py

@@ -91,7 +91,14 @@ def ctypes2numpy(cptr, length, dtype):
         raise RuntimeError('memmove failed')
     return res
 
-
+def ctypes2buffer(cptr, length):
+    if not isinstance(cptr, ctypes.POINTER(ctypes.c_char)):
+        raise RuntimeError('expected char pointer')
+    res = np.zeros(length, dtype='uint8')
+    if not ctypes.memmove(res.ctypes.data, cptr, length * res.strides[0]):
+        raise RuntimeError('memmove failed')
+    return res
+        
 def c_str(string):
     return ctypes.c_char_p(string.encode('utf-8'))
 
@@ -470,19 +477,26 @@ class Booster(object):
 
         Parameters
         ----------
-        fname : string or file handle
-            Output file name or handle. If a handle is given must be a BytesIO
-            object or a file opened for writing in binary format.
+        fname : string
+            Output file name or handle
         """
         if isinstance(fname, string_types):  # assume file name
             xglib.XGBoosterSaveModel(self.handle, c_str(fname))
         else:
-            length = ctypes.c_ulong()
-            cptr = xglib.XGBoosterGetModelRaw(self.handle,
-                                              ctypes.byref(length))
-            address = ctypes.addressof(cptr.contents)
-            buf = (ctypes.c_char * length.value).from_address(address)
-            fname.write(buf)
+            raise Exception("fname must be a string")
+
+    def save_raw(self):
+        """
+        Save the model to a in memory buffer represetation
+        
+        Returns
+        -------
+        a in memory buffer represetation of the model
+        """
+        length = ctypes.c_ulong()
+        cptr = xglib.XGBoosterGetModelRaw(self.handle,
+                                          ctypes.byref(length))
+        return ctypes2buffer(cptr, length.value)
 
     def load_model(self, fname):
         """
@@ -491,14 +505,14 @@ class Booster(object):
         Parameters
         ----------
         fname : string of file handle
-            Input file name or file handle object.
+            Input file name or memory buffer(see also save_raw)
         """
-        if isinstance(fname, string_types):  # assume file name
+        if isinstance(fname, str):  # assume file name
             xglib.XGBoosterLoadModel(self.handle, c_str(fname))
         else:
-            buf = fname.getbuffer()
-            length = ctypes.c_ulong(buf.nbytes)
-            ptr = ctypes.byref(ctypes.c_void_p.from_buffer(buf))
+            buf = fname
+            length = ctypes.c_ulong(len(buf))
+            ptr = (ctypes.c_char * len(buf)).from_buffer(buf)
             xglib.XGBoosterLoadModelFromBuffer(self.handle, ptr, length)
 
     def dump_model(self, fo, fmap='', with_stats=False):
@@ -861,12 +875,9 @@ class XGBModel(XGBModelBase):
         # can't pickle ctypes pointers so put _Booster in a BytesIO obj
 
         this = self.__dict__.copy()  # don't modify in place
-
-        tmp = BytesIO()
-        this["_Booster"].save_model(tmp)
-        tmp.seek(0)
-        this["_Booster"] = tmp
-
+        raw = this["_Booster"].save_raw()
+        this["_Booster"] = raw
+        
         return this
 
     def __setstate__(self, state):