--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/contrib/gis/geos/prototypes/errcheck.py	Tue Oct 14 16:00:59 2008 +0000
@@ -0,0 +1,76 @@
+"""
+ Error checking functions for GEOS ctypes prototype functions.
+"""
+import os
+from ctypes import string_at, CDLL
+from ctypes.util import find_library
+from django.contrib.gis.geos.error import GEOSException
+
+# Getting the C library, needed to free the string pointers
+# returned from GEOS.
+if os.name == 'nt':
+    libc_name = 'msvcrt'
+else:
+    libc_name = 'libc'
+libc = CDLL(find_library(libc_name))
+
+### ctypes error checking routines ###
+def last_arg_byref(args):
+    "Returns the last C argument's by reference value."
+    return args[-1]._obj.value
+        
+def check_dbl(result, func, cargs):
+    "Checks the status code and returns the double value passed in by reference."
+    # Checking the status code
+    if result != 1: return None
+    # Double passed in by reference, return its value.
+    return last_arg_byref(cargs)
+
+def check_geom(result, func, cargs):
+    "Error checking on routines that return Geometries."
+    if not result: 
+        raise GEOSException('Error encountered checking Geometry returned from GEOS C function "%s".' % func.__name__)
+    return result
+
+def check_minus_one(result, func, cargs):
+    "Error checking on routines that should not return -1."
+    if result == -1:
+        raise GEOSException('Error encountered in GEOS C function "%s".' % func.__name__)
+    else:
+        return result
+
+def check_predicate(result, func, cargs):
+    "Error checking for unary/binary predicate functions."
+    val = ord(result) # getting the ordinal from the character
+    if val == 1: return True
+    elif val == 0: return False
+    else:
+        raise GEOSException('Error encountered on GEOS C predicate function "%s".' % func.__name__)
+
+def check_sized_string(result, func, cargs):
+    "Error checking for routines that return explicitly sized strings."
+    if not result:
+        raise GEOSException('Invalid string pointer returned by GEOS C function "%s"' % func.__name__)
+    # A c_size_t object is passed in by reference for the second
+    # argument on these routines, and its needed to determine the
+    # correct size.
+    s = string_at(result, last_arg_byref(cargs))
+    libc.free(result)
+    return s
+
+def check_string(result, func, cargs):
+    "Error checking for routines that return strings."
+    if not result: raise GEOSException('Error encountered checking string return value in GEOS C function "%s".' % func.__name__)
+    # Getting the string value at the pointer address.
+    s = string_at(result)
+    # Freeing the memory allocated by the GEOS library.
+    libc.free(result)
+    return s
+
+def check_zero(result, func, cargs):
+    "Error checking on routines that should not return 0."
+    if result == 0:
+        raise GEOSException('Error encountered in GEOS C function "%s".' % func.__name__)
+    else:
+        return result
+