1 files changed, 41 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/isfopen.c b/reference/C/CONTRIB/SNIP/isfopen.c
new file mode 100755
index 0000000..4a88f1d
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/isfopen.c
@@ -0,0 +1,41 @@
+/*
+**  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 */