feat(libc): import qsort implementation

Import qsort implementation from FreeBSD[1] to libc.

[1]: https://cgit.freebsd.org/src/tree/lib/libc/stdlib/qsort.c

Change-Id: Ia0d8e2d1c40c679844c0746db1b669cda672a482
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>

include/lib/libc/cdefs.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2022, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2018-2025, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -36,4 +36,7 @@
 #define __STRING(x)	#x
 #define __XSTRING(x)	__STRING(x)
 
+#define __predict_true(exp)     (exp)
+#define __predict_false(exp)    (exp)
+
 #endif /* CDEFS_H */

include/lib/libc/stdlib.h

@@ -29,4 +29,6 @@ long strtol(const char *nptr, char **endptr, int base);
 unsigned long strtoul(const char *nptr, char **endptr, int base);
 long long strtoll(const char *nptr, char **endptr, int base);
 unsigned long long strtoull(const char *nptr, char **endptr, int base);
+void qsort(void *, size_t, size_t,
+           int (* _Nonnull)(const void *, const void *));
 #endif /* STDLIB_H */

lib/libc/libc_common.mk

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2024, Arm Limited and Contributors. All rights reserved.
+# Copyright (c) 2024-2025, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -17,6 +17,7 @@ LIBC_SRCS	:=	$(addprefix lib/libc/,		\
 			printf.c			\
 			putchar.c			\
 			puts.c				\
+			qsort.c				\
 			snprintf.c			\
 			strchr.c			\
 			strcmp.c			\

lib/libc/qsort.c

@@ -0,0 +1,261 @@
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if defined(I_AM_QSORT_R)
+typedef int		 cmp_t(const void *, const void *, void *);
+#elif defined(I_AM_QSORT_R_COMPAT)
+typedef int		 cmp_t(void *, const void *, const void *);
+#elif defined(I_AM_QSORT_S)
+typedef int		 cmp_t(const void *, const void *, void *);
+#else
+typedef int		 cmp_t(const void *, const void *);
+#endif
+static inline char	*med3(char *, char *, char *, cmp_t *, void *);
+
+#define	MIN(a, b)	((a) < (b) ? a : b)
+
+/*
+ * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
+ */
+
+static inline void
+swapfunc(char *a, char *b, size_t es)
+{
+	char t;
+
+	do {
+		t = *a;
+		*a++ = *b;
+		*b++ = t;
+	} while (--es > 0);
+}
+
+#define	vecswap(a, b, n)				\
+	if ((n) > 0) swapfunc(a, b, n)
+
+#if defined(I_AM_QSORT_R)
+#define	CMP(t, x, y) (cmp((x), (y), (t)))
+#elif defined(I_AM_QSORT_R_COMPAT)
+#define	CMP(t, x, y) (cmp((t), (x), (y)))
+#elif defined(I_AM_QSORT_S)
+#define	CMP(t, x, y) (cmp((x), (y), (t)))
+#else
+#define	CMP(t, x, y) (cmp((x), (y)))
+#endif
+
+static inline char *
+med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk
+#if !defined(I_AM_QSORT_R) && !defined(I_AM_QSORT_R_COMPAT) && !defined(I_AM_QSORT_S)
+__unused
+#endif
+)
+{
+	return CMP(thunk, a, b) < 0 ?
+	       (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a ))
+	      :(CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c ));
+}
+
+/*
+ * The actual qsort() implementation is static to avoid preemptible calls when
+ * recursing. Also give them different names for improved debugging.
+ */
+#if defined(I_AM_QSORT_R)
+#define local_qsort local_qsort_r
+#elif defined(I_AM_QSORT_R_COMPAT)
+#define local_qsort local_qsort_r_compat
+#elif defined(I_AM_QSORT_S)
+#define local_qsort local_qsort_s
+#endif
+static void
+local_qsort(void *a, size_t n, size_t es, cmp_t *cmp, void *thunk)
+{
+	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
+	size_t d1, d2;
+	int cmp_result;
+	int swap_cnt;
+
+	/* if there are less than 2 elements, then sorting is not needed */
+	if (__predict_false(n < 2))
+		return;
+loop:
+	swap_cnt = 0;
+	if (n < 7) {
+		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
+			for (pl = pm;
+			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
+			     pl -= es)
+				swapfunc(pl, pl - es, es);
+		return;
+	}
+	pm = (char *)a + (n / 2) * es;
+	if (n > 7) {
+		pl = a;
+		pn = (char *)a + (n - 1) * es;
+		if (n > 40) {
+			size_t d = (n / 8) * es;
+
+			pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
+			pm = med3(pm - d, pm, pm + d, cmp, thunk);
+			pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
+		}
+		pm = med3(pl, pm, pn, cmp, thunk);
+	}
+	swapfunc(a, pm, es);
+	pa = pb = (char *)a + es;
+
+	pc = pd = (char *)a + (n - 1) * es;
+	for (;;) {
+		while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
+			if (cmp_result == 0) {
+				swap_cnt = 1;
+				swapfunc(pa, pb, es);
+				pa += es;
+			}
+			pb += es;
+		}
+		while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
+			if (cmp_result == 0) {
+				swap_cnt = 1;
+				swapfunc(pc, pd, es);
+				pd -= es;
+			}
+			pc -= es;
+		}
+		if (pb > pc)
+			break;
+		swapfunc(pb, pc, es);
+		swap_cnt = 1;
+		pb += es;
+		pc -= es;
+	}
+	if (swap_cnt == 0) {  /* Switch to insertion sort */
+		for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es)
+			for (pl = pm;
+			     pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
+			     pl -= es)
+				swapfunc(pl, pl - es, es);
+		return;
+	}
+
+	pn = (char *)a + n * es;
+	d1 = MIN(pa - (char *)a, pb - pa);
+	vecswap(a, pb - d1, d1);
+	/*
+	 * Cast es to preserve signedness of right-hand side of MIN()
+	 * expression, to avoid sign ambiguity in the implied comparison.  es
+	 * is safely within [0, SSIZE_MAX].
+	 */
+	d1 = MIN(pd - pc, pn - pd - (ssize_t)es);
+	vecswap(pb, pn - d1, d1);
+
+	d1 = pb - pa;
+	d2 = pd - pc;
+	if (d1 <= d2) {
+		/* Recurse on left partition, then iterate on right partition */
+		if (d1 > es) {
+			local_qsort(a, d1 / es, es, cmp, thunk);
+		}
+		if (d2 > es) {
+			/* Iterate rather than recurse to save stack space */
+			/* qsort(pn - d2, d2 / es, es, cmp); */
+			a = pn - d2;
+			n = d2 / es;
+			goto loop;
+		}
+	} else {
+		/* Recurse on right partition, then iterate on left partition */
+		if (d2 > es) {
+			local_qsort(pn - d2, d2 / es, es, cmp, thunk);
+		}
+		if (d1 > es) {
+			/* Iterate rather than recurse to save stack space */
+			/* qsort(a, d1 / es, es, cmp); */
+			n = d1 / es;
+			goto loop;
+		}
+	}
+}
+
+#if defined(I_AM_QSORT_R)
+void
+(qsort_r)(void *a, size_t n, size_t es, cmp_t *cmp, void *thunk)
+{
+	local_qsort_r(a, n, es, cmp, thunk);
+}
+#elif defined(I_AM_QSORT_R_COMPAT)
+void
+__qsort_r_compat(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
+{
+	local_qsort_r_compat(a, n, es, cmp, thunk);
+}
+#elif defined(I_AM_QSORT_S)
+errno_t
+qsort_s(void *a, rsize_t n, rsize_t es, cmp_t *cmp, void *thunk)
+{
+	if (n > RSIZE_MAX) {
+		__throw_constraint_handler_s("qsort_s : n > RSIZE_MAX", EINVAL);
+		return (EINVAL);
+	} else if (es > RSIZE_MAX) {
+		__throw_constraint_handler_s("qsort_s : es > RSIZE_MAX",
+		    EINVAL);
+		return (EINVAL);
+	} else if (n != 0) {
+		if (a == NULL) {
+			__throw_constraint_handler_s("qsort_s : a == NULL",
+			    EINVAL);
+			return (EINVAL);
+		} else if (cmp == NULL) {
+			__throw_constraint_handler_s("qsort_s : cmp == NULL",
+			    EINVAL);
+			return (EINVAL);
+		} else if (es <= 0) {
+			__throw_constraint_handler_s("qsort_s : es <= 0",
+			    EINVAL);
+			return (EINVAL);
+		}
+	}
+
+	local_qsort_s(a, n, es, cmp, thunk);
+	return (0);
+}
+#else
+void
+qsort(void *a, size_t n, size_t es, cmp_t *cmp)
+{
+	local_qsort(a, n, es, cmp, NULL);
+}
+#endif