int SLang_pop_fileptr (SLang_MMT_Type **mmt, FILE **fp)
Description
SLang_pop_fileptr pops a file pointer from the S-lang
run-time stack. It returns zero upon success, or -1 upon failure.
A S-lang file pointer (SLANG_FILEPTR_TYPE) is actually a memory
managed object. For this reason, SLang_pop_fileptr also
returns the memory managed object via the argument list. It is up
to the calling routine to call SLang_free_mmt to free the
object.
Example
The following example illustrates an application defined intrinsic
function that writes a user defined double precision number to a
file. Note the use of SLang_free_mmt:
int write_double (void)
{
double t;
SLang_MMT_Type *mmt;
FILE *fp;
int status;
if (-1 == SLang_pop_double (&d, NULL, NULL))
return -1;
if (-1 == SLang_pop_fileptr (&mmt, &fp))
return -1;
status = fwrite (&d, sizeof (double), 1, fp);
SLang_free_mmt (mmt);
return status;
}
This function can be used by a S-lang function as follows:
define write_some_values ()
{
variable fp, d;
fp = fopen ("myfile.dat", "wb");
if (fp == NULL)
error ("file failed to open");
for (d = 0; d < 10.0; d += 0.1)
{
if (-1 == write_double (fp, d))
error ("write failed");
}
if (-1 == fclose (fp))
error ("fclose failed");
}