/django/contrib/gis/gdal/prototypes/errcheck.py
Python | 127 lines | 71 code | 14 blank | 42 comment | 16 complexity | 64b0a2a98d8309ecfec9ecbbef2d4a50 MD5 | raw file
Possible License(s): BSD-3-Clause
- """
- This module houses the error-checking routines used by the GDAL
- ctypes prototypes.
- """
- from ctypes import c_void_p, string_at
- from django.contrib.gis.gdal.error import check_err, OGRException, SRSException
- from django.contrib.gis.gdal.libgdal import lgdal
- # Helper routines for retrieving pointers and/or values from
- # arguments passed in by reference.
- def arg_byref(args, offset=-1):
- "Returns the pointer argument's by-refernece value."
- return args[offset]._obj.value
- def ptr_byref(args, offset=-1):
- "Returns the pointer argument passed in by-reference."
- return args[offset]._obj
- def check_bool(result, func, cargs):
- "Returns the boolean evaluation of the value."
- if bool(result): return True
- else: return False
- ### String checking Routines ###
- def check_const_string(result, func, cargs, offset=None):
- """
- Similar functionality to `check_string`, but does not free the pointer.
- """
- if offset:
- check_err(result)
- ptr = ptr_byref(cargs, offset)
- return ptr.value
- else:
- return result
- def check_string(result, func, cargs, offset=-1, str_result=False):
- """
- Checks the string output returned from the given function, and frees
- the string pointer allocated by OGR. The `str_result` keyword
- may be used when the result is the string pointer, otherwise
- the OGR error code is assumed. The `offset` keyword may be used
- to extract the string pointer passed in by-reference at the given
- slice offset in the function arguments.
- """
- if str_result:
- # For routines that return a string.
- ptr = result
- if not ptr: s = None
- else: s = string_at(result)
- else:
- # Error-code return specified.
- check_err(result)
- ptr = ptr_byref(cargs, offset)
- # Getting the string value
- s = ptr.value
- # Correctly freeing the allocated memory beind GDAL pointer
- # w/the VSIFree routine.
- if ptr: lgdal.VSIFree(ptr)
- return s
- ### DataSource, Layer error-checking ###
- ### Envelope checking ###
- def check_envelope(result, func, cargs, offset=-1):
- "Checks a function that returns an OGR Envelope by reference."
- env = ptr_byref(cargs, offset)
- return env
- ### Geometry error-checking routines ###
- def check_geom(result, func, cargs):
- "Checks a function that returns a geometry."
- # OGR_G_Clone may return an integer, even though the
- # restype is set to c_void_p
- if isinstance(result, (int, long)):
- result = c_void_p(result)
- if not result:
- raise OGRException('Invalid geometry pointer returned from "%s".' % func.__name__)
- return result
- def check_geom_offset(result, func, cargs, offset=-1):
- "Chcks the geometry at the given offset in the C parameter list."
- check_err(result)
- geom = ptr_byref(cargs, offset=offset)
- return check_geom(geom, func, cargs)
- ### Spatial Reference error-checking routines ###
- def check_srs(result, func, cargs):
- if isinstance(result, (int, long)):
- result = c_void_p(result)
- if not result:
- raise SRSException('Invalid spatial reference pointer returned from "%s".' % func.__name__)
- return result
- ### Other error-checking routines ###
- def check_arg_errcode(result, func, cargs):
- """
- The error code is returned in the last argument, by reference.
- Check its value with `check_err` before returning the result.
- """
- check_err(arg_byref(cargs))
- return result
- def check_errcode(result, func, cargs):
- """
- Check the error code returned (c_int).
- """
- check_err(result)
- return
- def check_pointer(result, func, cargs):
- "Makes sure the result pointer is valid."
- if isinstance(result, (int, long)):
- result = c_void_p(result)
- if bool(result):
- return result
- else:
- raise OGRException('Invalid pointer returned from "%s"' % func.__name__)
- def check_str_arg(result, func, cargs):
- """
- This is for the OSRGet[Angular|Linear]Units functions, which
- require that the returned string pointer not be freed. This
- returns both the double and tring values.
- """
- dbl = result
- ptr = cargs[-1]._obj
- return dbl, ptr.value