1 files changed, 46 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/lbitops.c b/reference/C/CONTRIB/SNIP/lbitops.c
new file mode 100755
index 0000000..85040be
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/lbitops.c
@@ -0,0 +1,46 @@
+/*
+**  large bit array operations by Scott Dudley
+**  with modifications by Auke Reitsma and Bob Stout
+**
+**  Public domain
+*/
+
+#include <limits.h>
+
+/*
+**  The following macros assume CHAR_BIT is one of either 8, 16, or 32
+*/
+
+#define MASK  CHAR_BIT-1
+#define SHIFT ((CHAR_BIT==8)?3:(CHAR_BIT==16)?4:8)
+
+#define BitOff(a,x)  ((void)((a)[(x)>>SHIFT] &= ~(1 << ((x)&MASK))))
+#define BitOn(a,x)   ((void)((a)[(x)>>SHIFT] |=  (1 << ((x)&MASK))))
+#define BitFlip(a,x) ((void)((a)[(x)>>SHIFT] ^=  (1 << ((x)&MASK))))
+#define IsBit(a,x)   ((a)[(x)>>SHIFT]        &   (1 << ((x)&MASK)))
+
+#include <stdio.h>
+#include <string.h>
+
+int main(void)
+{
+      char array[64];
+
+      memset(array, '\0', sizeof(array));
+
+      BitOn(array, 5);
+      BitOn(array, 12);
+      BitOn(array, 500);
+
+      if (IsBit(array, 5) && IsBit(array, 12) && IsBit(array, 500))
+            puts("These functions seem to work!");
+      else  puts("Something's broken here!");
+
+      BitFlip(array, 12);
+      BitOff(array, 5);
+
+      if (!IsBit(array, 5) && !IsBit(array, 12) && IsBit(array, 500))
+            puts("These functions still seem to work!");
+      else  puts("Something's broken here!");
+      return 0;
+}