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"""
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):
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):
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 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
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