libc: minimal: Add bsearch function

This function implements generic binary-search.

Fixes #15159

Signed-off-by: Balaji Kulkarni <balaji.kulkarni92@gmail.com>

CODEOWNERS

@@ -237,6 +237,7 @@
 /lib/gui/                                 @vanwinkeljan
 /lib/os/                                  @andrewboie @andyross
 /lib/posix/                               @pfalcon
+/lib/libc/minimal/source/stdlib/bsearch.c @balajikulkarni
 /kernel/device.c                          @andrewboie @andyross @nashif
 /kernel/idle.c                            @andrewboie @andyross @nashif
 /samples/basic/servo_motor/*microbit*     @jhe

lib/libc/minimal/CMakeLists.txt

@@ -8,6 +8,7 @@ zephyr_library_sources(
   source/stdlib/strtol.c
   source/stdlib/strtoul.c
   source/stdlib/malloc.c
+  source/stdlib/bsearch.c
   source/string/strncasecmp.c
   source/string/strstr.c
   source/string/string.c

lib/libc/minimal/include/stdlib.h

@@ -24,6 +24,10 @@ void *calloc(size_t nmemb, size_t size);
 void *realloc(void *ptr, size_t size);
 void *reallocarray(void *ptr, size_t nmemb, size_t size);
 
+void *bsearch(const void *key, const void *array,
+	      size_t count, size_t size,
+	      int (*cmp)(const void *key, const void *element));
+
 int rand(void);
 
 #define abs(x) ((x) < 0 ? -(x) : (x))

lib/libc/minimal/source/stdlib/bsearch.c

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2019 Balaji Kulkarni
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+/**
+ * @brief Generic implementation of Binary Search
+ *
+ * @param key	pointer to first element to search
+ * @param array	pointer to item being searched for
+ * @param count	number of elements
+ * @param size	size of each element
+ * @param cmp	pointer to comparison function
+ *
+ * @return	pointer to key if present in the array, or NULL otherwise
+ */
+
+void *bsearch(const void *key, const void *array, size_t count, size_t size,
+	      int (*cmp)(const void *key, const void *element))
+{
+	size_t low = 0;
+	size_t high = count;
+	size_t index;
+	int result;
+	const char *pivot;
+
+	while (low < high) {
+		index = low + (high - low) / 2;
+		pivot = (const char *)array + index * size;
+		result = cmp(key, pivot);
+
+		if (result == 0) {
+			return (void *)pivot;
+		} else if (result > 0) {
+			low = index + 1;
+		} else {
+			high = index;
+
+		}
+	}
+	return NULL;
+}

tests/lib/c_lib/src/main.c

@@ -24,6 +24,7 @@
 #include <stddef.h>
 #include <zephyr/types.h>
 #include <string.h>
+#include <stdlib.h>
 
 /* Recent GCC's are issuing a warning for the truncated strncpy()
  * below (the static source string is longer than the locally-defined
@@ -254,6 +255,32 @@ void test_memcmp(void)
 	zassert_true((ret != 0), "memcmp 5");
 }
 
+/**
+ *
+ * @brief Test binary search function
+ *
+ */
+
+int cmp_func(const void *a, const void *b)
+{
+	return (*(int *)a - *(int *)b);
+}
+
+void test_bsearch(void)
+{
+	void *result = NULL;
+	int arr[5] = { 2, 5, 20, 50, 60 };
+	size_t size = ARRAY_SIZE(arr);
+	int key = 30;
+
+	result = (int *)bsearch(&key, arr, size, sizeof(int), cmp_func);
+	zassert_is_null(result, "bsearch -key not found");
+
+	key = 60;
+	result = (int *)bsearch(&key, arr, size, sizeof(int), cmp_func);
+	zassert_not_null(result, "bsearch -key found");
+}
+
 void test_main(void)
 {
 	ztest_test_suite(test_c_lib,
@@ -267,7 +294,8 @@ void test_main(void)
 			 ztest_unit_test(test_strncpy),
 			 ztest_unit_test(test_memset),
 			 ztest_unit_test(test_strlen),
-			 ztest_unit_test(test_strcmp)
+			 ztest_unit_test(test_strcmp),
+			 ztest_unit_test(test_bsearch)
 			 );
 	ztest_run_test_suite(test_c_lib);
 }