| Re: dlm creating an array? [message #24491] |
Wed, 04 April 2001 01:22 |
Randall Skelton
Messages: 169
Registered: October 2000
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Senior Member |
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Thanks for the help JD and Jim! That was WAY easier than I thought it
would be :)
Randall
> Two ways. Here is the better:
>
> void test_array(int argc, IDL_VPTR argv[])
> {
> float *test;
> int i;
> IDL_MEMINT dim[2];
> IDL_VPTR tmp;
>
> dim[0]=dim[1]=10;
> /* Make Sure we can write to it, free anything already associated */
> IDL_StoreScalarZero(argv[0], IDL_TYP_LONG);
>
> test=(float *)IDL_MakeTempArray(IDL_TYP_FLOAT,
> 2,dim,IDL_ARR_INI_NOP,&tmp);
> IDL_VarCopy(tmp,argv[0]); /* This is the key. Copy tmp to passed arg
> */
> for(i=0;i<100;i++) test[i]=i*i;
> }
>
> That is, you make a temporary array, and copy it over to the passed
> argument (no data is actually copied, since it's a temporary). The
> StoreScalarZero makes sure it's passed by reference.
>
> This method is easiest. Another way is to make your own data, and then
> use IDL_Import_Array to wrap an IDL_VPTR around it (also no copying
> performed). They are basically equivalent, but the typing is more up
> front with a the temporary variable method.
>
> Please note that I did not free the tmp VPTR with IDL_DelTmp(). Why?
> Because it was already reclaimed by IDL_VarCopy (which in this case is
> more of a renaming than a copy). Doing so twice is a no-no.
>
> What if you have an arbitrary number of dimensions (read from the file
> perhaps)? I'd simply declare dim[IDL_MAX_ARRAY_DIM] instead, and test
> to ensure this limit isn't surpassed.
>
> Good luck,
>
> JD
>
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| Re: dlm creating an array? [message #24501 is a reply to message #24491] |
Tue, 03 April 2001 12:49  |
John-David T. Smith
Messages: 384
Registered: January 2000
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Senior Member |
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Randall Skelton wrote:
>
> Hello all,
>
> Is there a way to make a dlm that creates an IDL array?
>
> i.e. I am writing a simple file reading dlm that reads a binary file and
> generates a 1 dimensional array (or vector) and I would like this array
> returned to IDL such that the function syntax is something like:
>
> IDL> return = file_reader("test.bin", a);
>
> where "return" is for error checking, "test.bin" is the file to read, and
> "a" is what I would like the *new* array to be called.
>
> Is there something like, "IDL_StoreArray" as opposed to "IDL_StoreScalar?"
>
> Any and all hints and suggestions are greatly appreciated!
Two ways. Here is the better:
void test_array(int argc, IDL_VPTR argv[])
{
float *test;
int i;
IDL_MEMINT dim[2];
IDL_VPTR tmp;
dim[0]=dim[1]=10;
/* Make Sure we can write to it, free anything already associated */
IDL_StoreScalarZero(argv[0], IDL_TYP_LONG);
test=(float *)IDL_MakeTempArray(IDL_TYP_FLOAT,
2,dim,IDL_ARR_INI_NOP,&tmp);
IDL_VarCopy(tmp,argv[0]); /* This is the key. Copy tmp to passed arg
*/
for(i=0;i<100;i++) test[i]=i*i;
}
That is, you make a temporary array, and copy it over to the passed
argument (no data is actually copied, since it's a temporary). The
StoreScalarZero makes sure it's passed by reference.
This method is easiest. Another way is to make your own data, and then
use IDL_Import_Array to wrap an IDL_VPTR around it (also no copying
performed). They are basically equivalent, but the typing is more up
front with a the temporary variable method.
Please note that I did not free the tmp VPTR with IDL_DelTmp(). Why?
Because it was already reclaimed by IDL_VarCopy (which in this case is
more of a renaming than a copy). Doing so twice is a no-no.
What if you have an arbitrary number of dimensions (read from the file
perhaps)? I'd simply declare dim[IDL_MAX_ARRAY_DIM] instead, and test
to ensure this limit isn't surpassed.
Good luck,
JD
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