comp.lang.idl-pvwave archive: archive » Null terminated strings

Home » Public Forums » archive » Null terminated strings

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Null terminated strings [message #28759 is a reply to message #28677]

Tue, 08 January 2002 09:17

thompson
Messages: 584
Registered: August 1991

Senior Member

James Kuyper <kuyper@gscmail.gsfc.nasa.gov> writes:

> Craig Markwardt wrote:

>> James Kuyper <kuyper@gscmail.gsfc.nasa.gov> writes:
>>
>>
>>> I'm reading a string-valued file attribute from an HDF file that was
>>> created using C code. As seems quite reasonable for C programs, the
>>> attribute was written with a length that includes a terminating null
>>> character. When I read it in using IDL, that null character got included
>>> as well. This causes a number of bizarre effects, most notably:
>>>
>>> IDL> print,date
>>> 2001-10-07
>>> IDL> print,date+'T12:00:00'
>>> 2001-10-07'T12:00:0
>>>
>>> I can handle this particular case by using strmid(date,0,10), but in
>>> general a file attribute might contain multiple null-delimited strings,
>>> of unknown length. Is there an efficient way of converting such a string
>>> into an IDL string array?
>>
>>
>> What happens when you swizzle it through a STRING-BYTE-STRING
>> transformation?
>>
>> I.e.,
>>
>> date = string(byte(date))
>>
>> I believe that STRING will ignore any trailing 0-bytes, hence this may
>> solve your problem exactly, at the expense of some extra CPU.

> Thanks - that worked. It only solves the single-string case, but that's
> the case I am currently facing. It saves me the trouble of figuring out
> how long the string is, and it does the right thing, whether or not the
> string is null-terminated.

> I'm still wonder how to best convert a null-delimited list of strings
> into an IDL string array (it's just curiousity, I don't have any
> immediate need for that ability). My best solution so far is to convert
> it to a byte array, find the null delimiting characters with where(),
> and then write a loop to convert each subarray into a seperate IDL
> string. This should work, but I'm always suspicious of the efficiency of
> any solution for an IDL problem that involves an explicit loop.

As far as I can determine, that should work equally as well with arrays as
with strings. For example,

IDL> test = ['This','is','a','test']
IDL> btest=byte(test)
IDL> print,btest
84 104 105 115
105 115 0 0
97 0 0 0
116 101 115 116
IDL> stest = string(btest)
IDL> help,stest
STEST STRING = Array[4]
IDL> print,strlen(stest)
4 2 1 4
IDL> print,stest
This is a test

You shouldn't have to use a loop.

Bill Thompson

Report message to a moderator

[Message index]

		Null terminated strings By: James Kuyper on Mon, 07 January 2002 10:11
		Re: Null terminated strings By: Craig Markwardt on Wed, 09 January 2002 15:43
		Re: Null terminated strings By: James Kuyper on Wed, 09 January 2002 06:19
		Re: Null terminated strings By: Struan Gray on Thu, 10 January 2002 06:57
		Re: Null terminated strings By: Malcolm Walters on Wed, 09 January 2002 02:26
		Re: Null terminated strings By: Struan Gray on Wed, 09 January 2002 00:29
		Re: Null terminated strings By: James Kuyper on Tue, 08 January 2002 12:58
		Re: Null terminated strings By: Craig Markwardt on Tue, 08 January 2002 11:51
		Re: Null terminated strings By: thompson on Tue, 08 January 2002 09:17
		Re: Null terminated strings By: Jaco van Gorkom on Tue, 08 January 2002 08:17

Previous Topic:	Re: WIDGET REALIZATION BUG in 5.5 ?
Next Topic:	Re: Spherical Contour Plotting

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 00:17:41 PDT 2025

Total time taken to generate the page: 0.64405 seconds