libc: minimal: add qsort to the minimal libc
This change implements qsort() for the minimal libc via Heapsort. Heapsort time complexity is O(n log(n)) in the best, average, and worst cases. It is O(1) in space complexity (i.e. sorts in-place) and is iterative rather than recursive. Heapsort is not stable (i.e. does not preserve order of identical elements). On cortex-m0, this implementation occupies ~240 bytes. Fixes #28896 Signed-off-by: Christopher Friedt <chrisfriedt@gmail.com>
This commit is contained in:
Christopher Friedt
parent
bbe8f182c7
commit
bd83df1552
6 changed files with 122 additions and 203 deletions
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@ -257,6 +257,29 @@ static inline void bytecpy(void *dst, const void *src, size_t size)
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}
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}
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/**
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* @brief byte by byte swap.
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*
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* Swap @a size bytes between memory regions @a a and @a b. This is
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* guaranteed to be done byte by byte.
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*
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* @param a Pointer to the the first memory region.
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* @param b Pointer to the the second memory region.
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* @param size The number of bytes to swap.
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*/
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static inline void byteswp(void *a, void *b, size_t size)
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{
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uint8_t t;
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uint8_t *aa = (uint8_t *)a;
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uint8_t *bb = (uint8_t *)b;
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for (; size > 0; --size) {
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t = *aa;
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*aa++ = *bb;
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*bb++ = t;
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}
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}
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/**
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* @brief Convert a single character into a hexadecimal nibble.
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*
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@ -11,6 +11,7 @@ zephyr_library_sources(
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source/stdlib/malloc.c
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source/stdlib/bsearch.c
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source/stdlib/exit.c
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source/stdlib/qsort.c
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source/string/strncasecmp.c
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source/string/strstr.c
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source/string/string.c
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@ -30,6 +30,9 @@ void *bsearch(const void *key, const void *array,
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size_t count, size_t size,
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int (*cmp)(const void *key, const void *element));
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void qsort_r(void *base, size_t nmemb, size_t size,
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int (*compar)(const void *, const void *, void *), void *arg);
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#define EXIT_SUCCESS 0
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#define EXIT_FAILURE 1
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void _exit(int status);
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@ -60,6 +63,14 @@ static inline long long llabs(long long __n)
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return (__n < 0LL) ? -__n : __n;
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}
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static inline void qsort(void *base, size_t nmemb, size_t size,
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int (*compar)(const void *, const void *))
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{
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typedef int (*compar3)(const void *, const void *, void *);
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qsort_r(base, nmemb, size, (compar3)compar, NULL);
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}
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#ifdef __cplusplus
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}
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#endif
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86
lib/libc/minimal/source/stdlib/qsort.c
Normal file
86
lib/libc/minimal/source/stdlib/qsort.c
Normal file
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@ -0,0 +1,86 @@
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/*
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* Copyright (c) 2021 Friedt Professional Engineering Services, Inc
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include <sys/types.h>
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#include <sys/util.h>
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typedef int (*comp3_t)(const void *, const void *, void *);
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/*
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* Normally parent is defined parent(k) = floor((k-1) / 2) but we can avoid a
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* divide by noticing that floor((k-1) / 2) = ((k - 1) >> 1).
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*/
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#define parent(k) (((k) - 1) >> 1)
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/*
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* Normally left is defined left(k) = (2 * k + 1) but we can avoid a
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* multiply by noticing that (2 * k + 1) = ((k << 1) + 1).
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*/
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#define left(k) (((k) << 1) + 1)
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/*
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* Normally right is defined right(k) = (2 * k + 2) but we can avoid a
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* multiply by noticing that right(k) = left(k) + 1
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*/
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#define right(k) (left(k) + 1)
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#define A(k) ((uint8_t *)base + size * (k))
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static void sift_down(void *base, int start, int end, size_t size, comp3_t comp, void *comp_arg)
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{
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int root;
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int child;
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int swap;
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for (swap = start, root = swap; left(root) < end; root = swap) {
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child = left(root);
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/* if root < left */
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if (comp(A(swap), A(child), comp_arg) < 0) {
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swap = child;
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}
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/* right exists and min(A(root),A(left)) < A(right) */
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if (right(root) < end && comp(A(swap), A(right(root)), comp_arg) < 0) {
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swap = right(root);
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}
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if (swap == root) {
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return;
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}
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byteswp(A(root), A(swap), size);
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}
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}
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static void heapify(void *base, int nmemb, size_t size, comp3_t comp, void *comp_arg)
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{
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int start;
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for (start = parent(nmemb - 1); start >= 0; --start) {
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sift_down(base, start, nmemb, size, comp, comp_arg);
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}
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}
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static void heap_sort(void *base, int nmemb, size_t size, comp3_t comp, void *comp_arg)
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{
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int end;
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heapify(base, nmemb, size, comp, comp_arg);
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for (end = nmemb - 1; end > 0; --end) {
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byteswp(A(end), A(0), size);
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sift_down(base, 0, end, size, comp, comp_arg);
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}
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}
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void qsort_r(void *base, size_t nmemb, size_t size, comp3_t comp, void *arg)
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{
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heap_sort(base, nmemb, size, comp, arg);
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}
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@ -5,5 +5,5 @@ find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
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project(shell_module)
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target_sources(app PRIVATE src/main.c src/test_module.c)
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target_sources_ifdef(CONFIG_SHELL_DYNAMIC_CMDS app PRIVATE src/dynamic_cmd.c src/qsort.c)
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target_sources_ifdef(CONFIG_SHELL_DYNAMIC_CMDS app PRIVATE src/dynamic_cmd.c)
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target_sources_ifdef(CONFIG_SHELL_BACKEND_SERIAL app PRIVATE src/uart_reinit.c)
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@ -1,202 +0,0 @@
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/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static const char sccsid[] = "@(#)qsort.c 8.1 (Berkeley) 6/4/93";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.h>
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#include <stdlib.h>
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#ifdef I_AM_QSORT_R
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typedef int cmp_t(void *, const void *, const void *);
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#else
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typedef int cmp_t(const void *, const void *);
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#endif
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static inline char *med3(char *, char *, char *, cmp_t *, void *);
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#define MIN(a, b) ((a) < (b) ? a : b)
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/*
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* Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
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*/
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static inline void
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swapfunc(char *a, char *b, size_t es)
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{
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char t;
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do {
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t = *a;
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*a++ = *b;
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*b++ = t;
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} while (--es > 0);
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}
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#define vecswap(a, b, n) \
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do { \
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if ((n) > 0) { \
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swapfunc(a, b, n); \
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} \
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} while (0)
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#ifdef I_AM_QSORT_R
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#define CMP(t, x, y) (cmp((t), (x), (y)))
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#else
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#define CMP(t, x, y) (cmp((x), (y)))
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#endif
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static inline char *
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med3(char *a, char *b, char *c, cmp_t *cmp, void *thunk)
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{
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return CMP(thunk, a, b) < 0 ?
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(CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a))
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: (CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c));
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}
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#ifdef I_AM_QSORT_R
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void qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
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#else
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#define thunk NULL
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void qsort(void *a, size_t n, size_t es, cmp_t *cmp)
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#endif
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{
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char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
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size_t d1, d2;
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int cmp_result;
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int swap_cnt;
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loop:
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swap_cnt = 0;
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if (n < 7) {
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for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es) {
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for (pl = pm;
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pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
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pl -= es) {
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swapfunc(pl, pl - es, es);
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}
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}
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return;
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}
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pm = (char *)a + (n / 2) * es;
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if (n > 7) {
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pl = a;
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pn = (char *)a + (n - 1) * es;
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if (n > 40) {
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size_t d = (n / 8) * es;
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pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
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pm = med3(pm - d, pm, pm + d, cmp, thunk);
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pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
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}
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pm = med3(pl, pm, pn, cmp, thunk);
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}
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swapfunc(a, pm, es);
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pa = pb = (char *)a + es;
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pc = pd = (char *)a + (n - 1) * es;
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for (;;) {
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while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) {
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if (cmp_result == 0) {
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swap_cnt = 1;
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swapfunc(pa, pb, es);
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pa += es;
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}
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pb += es;
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}
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while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) {
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if (cmp_result == 0) {
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swap_cnt = 1;
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swapfunc(pc, pd, es);
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pd -= es;
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}
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pc -= es;
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}
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if (pb > pc) {
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break;
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}
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swapfunc(pb, pc, es);
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swap_cnt = 1;
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pb += es;
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pc -= es;
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}
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if (swap_cnt == 0) { /* Switch to insertion sort */
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for (pm = (char *)a + es; pm < (char *)a + n * es; pm += es) {
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for (pl = pm;
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pl > (char *)a && CMP(thunk, pl - es, pl) > 0;
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pl -= es) {
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swapfunc(pl, pl - es, es);
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}
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}
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return;
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}
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pn = (char *)a + n * es;
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d1 = MIN(pa - (char *)a, pb - pa);
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vecswap(a, pb - d1, d1);
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d1 = MIN(pd - pc, pn - pd - es);
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vecswap(pb, pn - d1, d1);
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d1 = pb - pa;
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d2 = pd - pc;
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if (d1 <= d2) {
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/* Recurse on left partition, then iterate on right partition */
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if (d1 > es) {
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#ifdef I_AM_QSORT_R
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qsort_r(a, d1 / es, es, thunk, cmp);
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#else
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qsort(a, d1 / es, es, cmp);
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#endif
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}
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if (d2 > es) {
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/* Iterate rather than recurse to save stack space */
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/* qsort(pn - d2, d2 / es, es, cmp); */
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a = pn - d2;
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n = d2 / es;
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goto loop;
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}
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} else {
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/* Recurse on right partition, then iterate on left partition */
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if (d2 > es) {
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#ifdef I_AM_QSORT_R
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qsort_r(pn - d2, d2 / es, es, thunk, cmp);
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#else
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qsort(pn - d2, d2 / es, es, cmp);
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#endif
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}
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if (d1 > es) {
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/* Iterate rather than recurse to save stack space */
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/* qsort(a, d1 / es, es, cmp); */
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n = d1 / es;
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goto loop;
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}
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}
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}
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