[PATCH 09/22] lib: Add generic binary search function

[Sascha Hauer]

Add generic binary search function based on Linux-6.5-rc3.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 include/linux/bsearch.h | 33 +++++++++++++++++++++++++++++++++
 include/linux/types.h   |  2 ++
 lib/Makefile            |  1 +
 lib/bsearch.c           | 34 ++++++++++++++++++++++++++++++++++
 4 files changed, 70 insertions(+)
 create mode 100644 include/linux/bsearch.h
 create mode 100644 lib/bsearch.c

diff --git a/include/linux/bsearch.h b/include/linux/bsearch.h
new file mode 100644
index 0000000000..26f6bd1f70
--- /dev/null
+++ b/include/linux/bsearch.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_BSEARCH_H
+#define _LINUX_BSEARCH_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+
+static __always_inline
+void *__inline_bsearch(const void *key, const void *base, size_t num, size_t size, cmp_func_t cmp)
+{
+	const char *pivot;
+	int result;
+
+	while (num > 0) {
+		pivot = base + (num >> 1) * size;
+		result = cmp(key, pivot);
+
+		if (result == 0)
+			return (void *)pivot;
+
+		if (result > 0) {
+			base = pivot + size;
+			num--;
+		}
+		num >>= 1;
+	}
+
+	return NULL;
+}
+
+extern void *bsearch(const void *key, const void *base, size_t num, size_t size, cmp_func_t cmp);
+
+#endif /* _LINUX_BSEARCH_H */
diff --git a/include/linux/types.h b/include/linux/types.h
index 5872bd8e38..aee9dfa87e 100644
--- a/include/linux/types.h
+++ b/include/linux/types.h
@@ -216,5 +216,7 @@ struct hlist_node {
 	struct hlist_node *next, **pprev;
 };
 
+typedef int (*cmp_func_t)(const void *a, const void *b);
+
 #endif
 #endif /* _LINUX_TYPES_H */
diff --git a/lib/Makefile b/lib/Makefile
index 921e5eedf4..7f308598cb 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -63,6 +63,7 @@ obj-y			+= wchar.o
 obj-y			+= libfile.o
 obj-y			+= bitmap.o
 obj-y			+= gcd.o
+obj-y			+= bsearch.o
 obj-pbl-y		+= hexdump.o
 obj-$(CONFIG_FONTS)	+= fonts/
 obj-$(CONFIG_BAREBOX_LOGO)     += logo/
diff --git a/lib/bsearch.c b/lib/bsearch.c
new file mode 100644
index 0000000000..0ddf304dae
--- /dev/null
+++ b/lib/bsearch.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * A generic implementation of binary search for the Linux kernel
+ *
+ * Copyright (C) 2008-2009 Ksplice, Inc.
+ * Author: Tim Abbott <tabbott at ksplice.com>
+ */
+
+#include <linux/export.h>
+#include <linux/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, cmp_func_t cmp)
+{
+	return __inline_bsearch(key, base, num, size, cmp);
+}
+EXPORT_SYMBOL(bsearch);
-- 
2.39.2