[PATCH 2/4] xen: Add generic implementation of binary search

[PATCH 2/4] xen: Add generic implementation of binary search

[Shanker Donthineni]

This patch adds the generic implementation of binary search algorithm
whcih is copied from Linux kernel v4.7-rc7. No functional changes.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
---
 xen/common/Makefile       |  1 +
 xen/common/bsearch.c      | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/bsearch.h |  9 +++++++++
 3 files changed, 61 insertions(+)
 create mode 100644 xen/common/bsearch.c
 create mode 100644 xen/include/xen/bsearch.h

diff --git a/xen/common/Makefile b/xen/common/Makefile
index dbf00c6..f8123c2 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -43,6 +43,7 @@ obj-y += schedule.o
 obj-y += shutdown.o
 obj-y += softirq.o
 obj-y += sort.o
+obj-y += bsearch.o
 obj-y += smp.o
 obj-y += spinlock.o
 obj-y += stop_machine.o
diff --git a/xen/common/bsearch.c b/xen/common/bsearch.c
new file mode 100644
index 0000000..3bcfd72
--- /dev/null
+++ b/xen/common/bsearch.c
@@ -0,0 +1,51 @@
+/*
+ * A generic implementation of binary search for the Linux kernel
+ *
+ * Copyright (C) 2008-2009 Ksplice, Inc.
+ * Author: Tim Abbott <tabbott@ksplice.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; version 2.
+ */
+
+#include <xen/bsearch.h>
+
+/*
+ * bsearch - binary search an array of elements
+ * @key: pointer to item being searched for
+ * @base: pointer to first element to search
+ * @num: number of elements
+ * @size: size of each element
+ * @cmp: pointer to comparison function
+ *
+ * This function does a binary search on the given array.  The
+ * contents of the array should already be in ascending sorted order
+ * under the provided comparison function.
+ *
+ * Note that the key need not have the same type as the elements in
+ * the array, e.g. key could be a string and the comparison function
+ * could compare the string with the struct's name field.  However, if
+ * the key and elements in the array are of the same type, you can use
+ * the same comparison function for both sort() and bsearch().
+ */
+void *bsearch(const void *key, const void *base, size_t num, size_t size,
+	      int (*cmp)(const void *key, const void *elt))
+{
+	size_t start = 0, end = num;
+	int result;
+
+	while (start < end) {
+		size_t mid = start + (end - start) / 2;
+
+		result = cmp(key, base + mid * size);
+		if (result < 0)
+			end = mid;
+		else if (result > 0)
+			start = mid + 1;
+		else
+			return (void *)base + mid * size;
+	}
+
+	return NULL;
+}
diff --git a/xen/include/xen/bsearch.h b/xen/include/xen/bsearch.h
new file mode 100644
index 0000000..07cf604
--- /dev/null
+++ b/xen/include/xen/bsearch.h
@@ -0,0 +1,9 @@
+#ifndef __XEN_BSEARCH_H__
+#define __XEN_BSEARCH_H__
+
+#include <xen/types.h>
+
+void *bsearch(const void *key, const void *base, size_t num, size_t size,
+	      int (*cmp)(const void *key, const void *elt));
+
+#endif /* __XEN_BSEARCH_H__ */
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of the Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.


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