libc: minimal: add qsort to the minimal libc

include/sys/util.h

@@ -257,6 +257,29 @@ static inline void bytecpy(void *dst, const void *src, size_t size)
 	}
 }
 
+/**
+ * @brief byte by byte swap.
+ *
+ * Swap @a size bytes between memory regions @a a and @a b. This is
+ * guaranteed to be done byte by byte.
+ *
+ * @param a Pointer to the the first memory region.
+ * @param b Pointer to the the second memory region.
+ * @param size The number of bytes to swap.
+ */
+static inline void byteswp(void *a, void *b, size_t size)
+{
+	uint8_t t;
+	uint8_t *aa = (uint8_t *)a;
+	uint8_t *bb = (uint8_t *)b;
+
+	for (; size > 0; --size) {
+		t = *aa;
+		*aa++ = *bb;
+		*bb++ = t;
+	}
+}
+
 /**
  * @brief      Convert a single character into a hexadecimal nibble.
  *

lib/libc/minimal/CMakeLists.txt

@@ -11,6 +11,7 @@ zephyr_library_sources(
   source/stdlib/malloc.c
   source/stdlib/bsearch.c
   source/stdlib/exit.c
+  source/stdlib/qsort.c
   source/string/strncasecmp.c
   source/string/strstr.c
   source/string/string.c

lib/libc/minimal/include/stdlib.h

@@ -30,6 +30,9 @@ void *bsearch(const void *key, const void *array,
 	      size_t count, size_t size,
 	      int (*cmp)(const void *key, const void *element));
 
+void qsort_r(void *base, size_t nmemb, size_t size,
+	     int (*compar)(const void *, const void *, void *), void *arg);
+
 #define EXIT_SUCCESS 0
 #define EXIT_FAILURE 1
 void _exit(int status);
@@ -60,6 +63,14 @@ static inline long long llabs(long long __n)
 	return (__n < 0LL) ? -__n : __n;
 }
 
+static inline void qsort(void *base, size_t nmemb, size_t size,
+	int (*compar)(const void *, const void *))
+{
+	typedef int (*compar3)(const void *, const void *, void *);
+
+	qsort_r(base, nmemb, size, (compar3)compar, NULL);
+}
+
 #ifdef __cplusplus
 }
 #endif

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

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2021 Friedt Professional Engineering Services, Inc
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/util.h>
+
+typedef int (*comp3_t)(const void *, const void *, void *);
+
+/*
+ * Normally parent is defined parent(k) = floor((k-1) / 2) but we can avoid a
+ * divide by noticing that floor((k-1) / 2) = ((k - 1) >> 1).
+ */
+
+#define parent(k) (((k) - 1) >> 1)
+/*
+ * Normally left is defined left(k) = (2 * k + 1) but we can avoid a
+ * multiply by noticing that (2 * k + 1) = ((k << 1) + 1).
+ */
+
+#define left(k) (((k) << 1) + 1)
+
+/*
+ * Normally right is defined right(k) = (2 * k + 2) but we can avoid a
+ * multiply by noticing that right(k) = left(k) + 1
+ */
+#define right(k) (left(k) + 1)
+
+#define A(k) ((uint8_t *)base + size * (k))
+
+static void sift_down(void *base, int start, int end, size_t size, comp3_t comp, void *comp_arg)
+{
+	int root;
+	int child;
+	int swap;
+
+	for (swap = start, root = swap; left(root) < end; root = swap) {
+		child = left(root);
+
+		/* if root < left */
+		if (comp(A(swap), A(child), comp_arg) < 0) {
+			swap = child;
+		}
+
+		/* right exists and min(A(root),A(left)) < A(right) */
+		if (right(root) < end && comp(A(swap), A(right(root)), comp_arg) < 0) {
+			swap = right(root);
+		}
+
+		if (swap == root) {
+			return;
+		}
+
+		byteswp(A(root), A(swap), size);
+	}
+}
+
+static void heapify(void *base, int nmemb, size_t size, comp3_t comp, void *comp_arg)
+{
+	int start;
+
+	for (start = parent(nmemb - 1); start >= 0; --start) {
+		sift_down(base, start, nmemb, size, comp, comp_arg);
+	}
+}
+
+static void heap_sort(void *base, int nmemb, size_t size, comp3_t comp, void *comp_arg)
+{
+	int end;
+
+	heapify(base, nmemb, size, comp, comp_arg);
+
+	for (end = nmemb - 1; end > 0; --end) {
+		byteswp(A(end), A(0), size);
+		sift_down(base, 0, end, size, comp, comp_arg);
+	}
+}
+
+void qsort_r(void *base, size_t nmemb, size_t size, comp3_t comp, void *arg)
+{
+	heap_sort(base, nmemb, size, comp, arg);
+}

samples/subsys/shell/shell_module/CMakeLists.txt

@@ -5,5 +5,5 @@ find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
 project(shell_module)
 
 target_sources(app PRIVATE src/main.c src/test_module.c)
-target_sources_ifdef(CONFIG_SHELL_DYNAMIC_CMDS app PRIVATE src/dynamic_cmd.c src/qsort.c)
+target_sources_ifdef(CONFIG_SHELL_DYNAMIC_CMDS app PRIVATE src/dynamic_cmd.c)
 target_sources_ifdef(CONFIG_SHELL_BACKEND_SERIAL app PRIVATE src/uart_reinit.c)

tests/lib/c_lib/src/main.c

@@ -1041,6 +1041,14 @@ void test_exit(void)
 	zassert_equal(a, 0, "exit failed");
 }
 
+/**
+ *
+ * @brief Test qsort function
+ *
+ * @see qsort()
+ */
+extern void test_qsort(void);
+
 /**
  * @}
  */
@@ -1079,7 +1087,8 @@ void test_main(void)
 			 ztest_unit_test(test_exit),
 			 ztest_unit_test(test_str_operate),
 			 ztest_unit_test(test_tolower_toupper),
-			 ztest_unit_test(test_strtok_r)
+			 ztest_unit_test(test_strtok_r),
+			 ztest_unit_test(test_qsort)
 			 );
 	ztest_run_test_suite(test_c_lib);
 }