Re: [ctypes-users] Null terminators..

[John S. <ga...@ga...>]

Well, after some much hacking, I came up with the following solution to my
non-null-terminated string problem... Below is some sample code.. Not sure
if I totally like the idea, but it works.. Is there a way to get the size
of a field (to eliminate the seperate storing of the lengths) ??

from ctypes import *

def create__setattr__():
    def s( self, key, value ):
        # bizzare stuff for string that are not null terminated
        if type( value ) is str:
            # figure out the offset.
            tempP = addressof( self )

            # add in the offsets..
            for field in self._fields_:
                if field[ 0 ] == key:
                    fieldsize = self.lengths[key]
                    break
                tempP = tempP + self.lengths[key]

            # field[1] has the data type for what I need..
            tempBuff = field[1].from_address( tempP )

            tempValue = c_char_p( value )

            cdll.msvcrt.memcpy( byref(tempBuff),
                                tempValue,
                                self.lengths[key] )
        else:
            Structure.__setattr__( self, key, value )

    return s


fields = [ ( "test1", c_char * 6 ), ( "test2", c_int ) ]
fieldLen = {"test1":6, "test2":4 }

recObject = type( "RECORD", (Structure,),
                    {'_fields_':fields,
                     'lengths':fieldLen,
                     '__setattr__':create__setattr__()
                    } )

rec = recObject()

rec.test1 = "AAAAAB"
rec.test2 = 7

print rec.test1
print rec.test2

rec.test1 = "BBBBBC"

print rec.test1
print rec.test2


> "John Sutherland" <ga...@ga...> writes:
>
>> A new question..
>>
>> In that struct that was dynamicly generated, I have character strings
>> that
>> are -not- null terminated (based on some 1985 programming, they wanted
>> to
>> save memory.. Hey, it still works :) )..
>>
>> More of less, the structure looks like this:
>>
>> struct
>> {
>>   char field1[2];
>>   char field2[4];
>> }
>>
>> So if I put "11" into field1 and "2222" into field2, I should get
>> something in memory like:
>>
>> "112222"
>>
>> ctypes seems to read this ok.. But when I try to field1 = "JS", it tells
>> me that its too long.. I assume that it expects a null terminator.. Is
>> there any way to handle this type of situation?
>
> It doesn't seem so, at the moment. It is currently discussed in other
> threads.
>
> Thomas
>
>
>
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--John