| CALL_EXTERNAL and IDL_STRING [message #22931] |
Fri, 22 December 2000 08:05  |
Frederique Soulard
Messages: 1
Registered: December 2000
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Junior Member |
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We are trying to use the CALL_EXTERNAL function in order to get strings from
a C routine. The variables are defined as IDL_STRING and have to be
modifyable into the C routine. Our C routine reads strings from a binary
file into C string variables. Then we are trying to copy the C strings into
the IDL_STRING pointers (copy byte after byte). We encounter problems while
doing this (memory overlaping probably). Does someone has any advice to give
in order to solve our problems (no question to re-develop the reading in IDL
routine) ? Is a ByteArr method a solution ?
Thanks.
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| Re: CALL_EXTERNAL and IDL_STRING [message #23116 is a reply to message #22931] |
Thu, 04 January 2001 02:55  |
Nigel Wade
Messages: 286
Registered: March 1998
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Senior Member |
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Mark Rivers wrote:
>
> Frederique Soulard wrote in message
> <91vttb$tpn$1@s1.read.news.oleane.net>...
>> We are trying to use the CALL_EXTERNAL function in order to get strings
> from
>> a C routine. The variables are defined as IDL_STRING and have to be
>> modifyable into the C routine. Our C routine reads strings from a binary
>> file into C string variables. Then we are trying to copy the C strings into
>> the IDL_STRING pointers (copy byte after byte). We encounter problems while
>> doing this (memory overlaping probably). Does someone has any advice to
> give
>> in order to solve our problems (no question to re-develop the reading in
> IDL
>> routine) ? Is a ByteArr method a solution ?
>
> Yes, I always use byte arrays for this. In IDL dimension your byte arrays
> so that the dimension
> which is the string length is greater than it will ever need to be in the C
> code. Have the C code
> fill in the byte array with trailing NULLs. On return to IDL convert to a
> string or string array using the string() function.
>
> Mark Rivers
Please pass the length of the IDL string to the C routine and make sure
you don't copy more than the string can hold. Todays huge string is
tomorrows
buffer overrun. I don't use CALL_EXTERNAL so I don't really know much
about it,
but if you have an IDL_STRING pointer can you use IDL_StrStore to put
your
string into the IDL variable?
The alternative would be to write a "system routine" (i.e. using
LINKIMAGE
or a DLM). System routines can create IDL variables of any type.
--
-----------------------------------------------------------
Nigel Wade, System Administrator, Space Plasma Physics Group,
University of Leicester, Leicester, LE1 7RH, UK
E-mail : nmw@ion.le.ac.uk
Phone : +44 (0)116 2523568, Fax : +44 (0)116 2523555
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| Re: CALL_EXTERNAL and IDL_STRING [message #23119 is a reply to message #22931] |
Wed, 03 January 2001 21:00 |
Mark Rivers
Messages: 49
Registered: February 2000
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Member |
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Frederique Soulard wrote in message
<91vttb$tpn$1@s1.read.news.oleane.net>...
> We are trying to use the CALL_EXTERNAL function in order to get strings
from
> a C routine. The variables are defined as IDL_STRING and have to be
> modifyable into the C routine. Our C routine reads strings from a binary
> file into C string variables. Then we are trying to copy the C strings into
> the IDL_STRING pointers (copy byte after byte). We encounter problems while
> doing this (memory overlaping probably). Does someone has any advice to
give
> in order to solve our problems (no question to re-develop the reading in
IDL
> routine) ? Is a ByteArr method a solution ?
Yes, I always use byte arrays for this. In IDL dimension your byte arrays
so that the dimension
which is the string length is greater than it will ever need to be in the C
code. Have the C code
fill in the byte array with trailing NULLs. On return to IDL convert to a
string or string array using the string() function.
Mark Rivers
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