xen: Add generic implementation of binary search

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

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Julien Grall <julien.grall@arm.com>

diff --git a/xen/common/Makefile b/xen/common/Makefile
index dbf00c639dace10138d974a52fd11867c5d06efd..f8123c27deaf0496176ee668ba3036ee806a5e42 100644 (file)
--- 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 (file)
index 0000000..7090930
--- /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/lib.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/lib.h b/xen/include/xen/lib.h
index b1b0fb2c1704635687d4b79f8870c07f4705d593..5272cc3a7ef80a961df5d3594839a72e56a65e1d 100644 (file)
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -153,4 +153,7 @@ void dump_execstate(struct cpu_user_regs *);
 
 void init_constructors(void);
 
+void *bsearch(const void *key, const void *base, size_t num, size_t size,
+              int (*cmp)(const void *key, const void *elt));
+
 #endif /* __LIB_H__ */