| Re: Binary file created with IDL strings [message #57272 is a reply to message #57239] |
Wed, 05 December 2007 13:46   |
Vince Hradil
Messages: 574
Registered: December 1999
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Senior Member |
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On Dec 5, 3:12 pm, peajai.all.the....@gmail.com wrote:
> On Dec 5, 12:12 pm, Vince Hradil <hrad...@yahoo.com> wrote:
>
>
>
>> On Dec 5, 11:00 am, peajai.all.the....@gmail.com wrote:
>
>>> On Dec 5, 11:36 am, Vince Hradil <hrad...@yahoo.com> wrote:
>
>>>> On Dec 5, 10:32 am, peajai.all.the....@gmail.com wrote:
>
>>>> > I am trying to read in a IDL created binary file in C++. The file
>>>> > contains floats, ints, doubles, and strings. I am able to read the
>>>> > floats and ints (shorts in C++) with no problem, but once I get to the
>>>> > section of the file containing strings, I cannot seem to read in the
>>>> > correct number of bytes. I am not concerned with the contents on the
>>>> > strings, but there is more data in floats after the strings that I
>>>> > need to be able to read properly. If possible, I could seek forward
>>>> > however many bytes just to get to the location of the data after the
>>>> > strings. Does anyone know how many bytes each character in an IDL
>>>> > string is? There are 22 strings, each 20 characters long. How many
>>>> > bytes would this be?
>
>>>> Each character is a byte.
>
>>> Do I need to account for an extra byte at the end of each string for a
>>> null terminator?
>
>> I should have guessed you were going to ask that 8) I avoided it
>> because I'm not 100% sure, but I think IDL does NOT write the null
>> terminator like C. Pretty easy to test...- Hide quoted text -
>
>> - Show quoted text -
>
> Easy in theory but not in practice, this problem has been vexing me
> for 2 days. I tried skipping forward 440 bytes (20char*22strings) and
> 462 bytes ((20char*22strings)+22nulls) and still did not end up in the
> right place in the file to correctly read the floats follow. The first
> string seemed to start 8 characters later than I expected it to, and I
> cannot tell if I need to add 8 extra characters for each string or if
> something is just weird at the beginning of strings. Mind you, I have
> IDL code that reads this same file perfectly so I know the file isn't
> bad and I am following the same order that the IDL code follows to
> read the data in.
>
> The IDL code actually just calls readu once and passes it all of the
> arrays it is expecting to populate and this includes one string array
> of 22 elements with 20 chars each. If this file was created in IDL and
> initialized with an array of strings, should there be extra bytes for
> the array? Or for each string? How would I be able to tell? Would an
> array of strings take up more bytes than just simply a set of
> contiguous strings?
Are you sure all the strings are 20 characters? Have you looked at
the file in a hex editor?
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