Initial Contribution
diff --git a/libc/kernel/common/linux/circ_buf.h b/libc/kernel/common/linux/circ_buf.h
new file mode 100644
index 0000000..438250c
--- /dev/null
+++ b/libc/kernel/common/linux/circ_buf.h
@@ -0,0 +1,29 @@
+/****************************************************************************
+ ****************************************************************************
+ ***
+ *** This header was automatically generated from a Linux kernel header
+ *** of the same name, to make information necessary for userspace to
+ *** call into the kernel available to libc. It contains only constants,
+ *** structures, and macros generated from the original header, and thus,
+ *** contains no copyrightable information.
+ ***
+ ****************************************************************************
+ ****************************************************************************/
+#ifndef _LINUX_CIRC_BUF_H
+#define _LINUX_CIRC_BUF_H 1
+
+struct circ_buf {
+ char *buf;
+ int head;
+ int tail;
+};
+
+#define CIRC_CNT(head,tail,size) (((head) - (tail)) & ((size)-1))
+
+#define CIRC_SPACE(head,tail,size) CIRC_CNT((tail),((head)+1),(size))
+
+#define CIRC_CNT_TO_END(head,tail,size) ({int end = (size) - (tail); int n = ((head) + end) & ((size)-1); n < end ? n : end;})
+
+#define CIRC_SPACE_TO_END(head,tail,size) ({int end = (size) - 1 - (head); int n = (end + (tail)) & ((size)-1); n <= end ? n : end+1;})
+
+#endif