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/*
** Find out if a FILE * is valid
**
** public domain demo by Bob Stout
*/
#include <stdio.h>
#ifdef __TURBOC__
#define STREAM_BUF _streams
#define FCNT FOPEN_MAX
#define FLAG flags
#else /* MSC, ZTC++ */
#define STREAM_BUF _iob
#define FCNT _NFILE
#define FLAG _flag
#endif
typedef enum {FALSE, TRUE} LOGICAL;
int isfopen(FILE *fp)
{
int i;
for (i = 0; i < FCNT; ++i)
{
if (0 != STREAM_BUF[i].FLAG && fp == &STREAM_BUF[i])
return TRUE;
}
return FALSE;
}
#ifdef TEST
void main(void)
{
printf("stdout is%s valid\n", isfopen(stdout) ? "":" not");
printf("buffer #10 is%s valid\n", isfopen(&STREAM_BUF[9]) ? "":" not");
}
#endif /*TEST */
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