From a5b9e2c1063046421ce01dcf5ddd7ec12567f3e1 Mon Sep 17 00:00:00 2001
From: Andi Kleen <andi@firstfloor.org>
Date: Fri, 15 Jan 2010 17:01:16 -0800
Subject: [PATCH] kfifo: add kfifo_out_peek
In some upcoming code it's useful to peek into a FIFO without permanentely
removing data. This patch implements a new kfifo_out_peek() to do this.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Stefani Seibold <stefani@seibold.net>
Cc: Roland Dreier <rdreier@cisco.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Andy Walls <awalls@radix.net>
Cc: Vikram Dhillon <dhillonv10@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/kfifo.h | 3 +++
kernel/kfifo.c | 21 +++++++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index 86ad50a900c8a..7ad6d32dd673d 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -113,6 +113,9 @@ extern unsigned int kfifo_in(struct kfifo *fifo,
const void *from, unsigned int len);
extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
void *to, unsigned int len);
+extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
+ void *to, unsigned int len, unsigned offset);
+
/**
* kfifo_reset - removes the entire FIFO contents
diff --git a/kernel/kfifo.c b/kernel/kfifo.c
index b50bb622e8b08..7384f120be876 100644
--- a/kernel/kfifo.c
+++ b/kernel/kfifo.c
@@ -302,6 +302,27 @@ unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len)
}
EXPORT_SYMBOL(kfifo_out);
+/**
+ * kfifo_out_peek - copy some data from the FIFO, but do not remove it
+ * @fifo: the fifo to be used.
+ * @to: where the data must be copied.
+ * @len: the size of the destination buffer.
+ * @offset: offset into the fifo
+ *
+ * This function copies at most @len bytes at @offset from the FIFO
+ * into the @to buffer and returns the number of copied bytes.
+ * The data is not removed from the FIFO.
+ */
+unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
+ unsigned offset)
+{
+ len = min(kfifo_len(fifo), len + offset);
+
+ __kfifo_out_data(fifo, to, len, offset);
+ return len;
+}
+EXPORT_SYMBOL(kfifo_out_peek);
+
unsigned int __kfifo_out_generic(struct kfifo *fifo,
void *to, unsigned int len, unsigned int recsize,
unsigned int *total)
--
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