From: Martin Wilck <mwilck@xxxxxxxx> glibc's msort.c contains a stable sort algorithm based on mergesort. This will be useful for us, as qsort(3) is not necessarily stable. The added code is under LGPL-2.1. Signed-off-by: Martin Wilck <mwilck@xxxxxxxx> --- libmultipath/msort.c | 309 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 309 insertions(+) create mode 100644 libmultipath/msort.c diff --git a/libmultipath/msort.c b/libmultipath/msort.c new file mode 100644 index 0000000..cbe9a4a --- /dev/null +++ b/libmultipath/msort.c @@ -0,0 +1,309 @@ +/* An alternative to qsort, with an identical interface. + This file is part of the GNU C Library. + Copyright (C) 1992-2022 Free Software Foundation, Inc. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <alloca.h> +#include <stdint.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <memcopy.h> +#include <errno.h> +#include <atomic.h> + +struct msort_param +{ + size_t s; + size_t var; + __compar_d_fn_t cmp; + void *arg; + char *t; +}; +static void msort_with_tmp (const struct msort_param *p, void *b, size_t n); + +static void +msort_with_tmp (const struct msort_param *p, void *b, size_t n) +{ + char *b1, *b2; + size_t n1, n2; + + if (n <= 1) + return; + + n1 = n / 2; + n2 = n - n1; + b1 = b; + b2 = (char *) b + (n1 * p->s); + + msort_with_tmp (p, b1, n1); + msort_with_tmp (p, b2, n2); + + char *tmp = p->t; + const size_t s = p->s; + __compar_d_fn_t cmp = p->cmp; + void *arg = p->arg; + switch (p->var) + { + case 0: + while (n1 > 0 && n2 > 0) + { + if ((*cmp) (b1, b2, arg) <= 0) + { + *(uint32_t *) tmp = *(uint32_t *) b1; + b1 += sizeof (uint32_t); + --n1; + } + else + { + *(uint32_t *) tmp = *(uint32_t *) b2; + b2 += sizeof (uint32_t); + --n2; + } + tmp += sizeof (uint32_t); + } + break; + case 1: + while (n1 > 0 && n2 > 0) + { + if ((*cmp) (b1, b2, arg) <= 0) + { + *(uint64_t *) tmp = *(uint64_t *) b1; + b1 += sizeof (uint64_t); + --n1; + } + else + { + *(uint64_t *) tmp = *(uint64_t *) b2; + b2 += sizeof (uint64_t); + --n2; + } + tmp += sizeof (uint64_t); + } + break; + case 2: + while (n1 > 0 && n2 > 0) + { + unsigned long *tmpl = (unsigned long *) tmp; + unsigned long *bl; + + tmp += s; + if ((*cmp) (b1, b2, arg) <= 0) + { + bl = (unsigned long *) b1; + b1 += s; + --n1; + } + else + { + bl = (unsigned long *) b2; + b2 += s; + --n2; + } + while (tmpl < (unsigned long *) tmp) + *tmpl++ = *bl++; + } + break; + case 3: + while (n1 > 0 && n2 > 0) + { + if ((*cmp) (*(const void **) b1, *(const void **) b2, arg) <= 0) + { + *(void **) tmp = *(void **) b1; + b1 += sizeof (void *); + --n1; + } + else + { + *(void **) tmp = *(void **) b2; + b2 += sizeof (void *); + --n2; + } + tmp += sizeof (void *); + } + break; + default: + while (n1 > 0 && n2 > 0) + { + if ((*cmp) (b1, b2, arg) <= 0) + { + tmp = (char *) __mempcpy (tmp, b1, s); + b1 += s; + --n1; + } + else + { + tmp = (char *) __mempcpy (tmp, b2, s); + b2 += s; + --n2; + } + } + break; + } + + if (n1 > 0) + memcpy (tmp, b1, n1 * s); + memcpy (b, p->t, (n - n2) * s); +} + + +void +__qsort_r (void *b, size_t n, size_t s, __compar_d_fn_t cmp, void *arg) +{ + size_t size = n * s; + char *tmp = NULL; + struct msort_param p; + + /* For large object sizes use indirect sorting. */ + if (s > 32) + size = 2 * n * sizeof (void *) + s; + + if (size < 1024) + /* The temporary array is small, so put it on the stack. */ + p.t = __alloca (size); + else + { + /* We should avoid allocating too much memory since this might + have to be backed up by swap space. */ + static long int phys_pages; + static int pagesize; + + if (pagesize == 0) + { + phys_pages = __sysconf (_SC_PHYS_PAGES); + + if (phys_pages == -1) + /* Error while determining the memory size. So let's + assume there is enough memory. Otherwise the + implementer should provide a complete implementation of + the `sysconf' function. */ + phys_pages = (long int) (~0ul >> 1); + + /* The following determines that we will never use more than + a quarter of the physical memory. */ + phys_pages /= 4; + + /* Make sure phys_pages is written to memory. */ + atomic_write_barrier (); + + pagesize = __sysconf (_SC_PAGESIZE); + } + + /* Just a comment here. We cannot compute + phys_pages * pagesize + and compare the needed amount of memory against this value. + The problem is that some systems might have more physical + memory then can be represented with a `size_t' value (when + measured in bytes. */ + + /* If the memory requirements are too high don't allocate memory. */ + if (size / pagesize > (size_t) phys_pages) + { + _quicksort (b, n, s, cmp, arg); + return; + } + + /* It's somewhat large, so malloc it. */ + int save = errno; + tmp = malloc (size); + __set_errno (save); + if (tmp == NULL) + { + /* Couldn't get space, so use the slower algorithm + that doesn't need a temporary array. */ + _quicksort (b, n, s, cmp, arg); + return; + } + p.t = tmp; + } + + p.s = s; + p.var = 4; + p.cmp = cmp; + p.arg = arg; + + if (s > 32) + { + /* Indirect sorting. */ + char *ip = (char *) b; + void **tp = (void **) (p.t + n * sizeof (void *)); + void **t = tp; + void *tmp_storage = (void *) (tp + n); + + while ((void *) t < tmp_storage) + { + *t++ = ip; + ip += s; + } + p.s = sizeof (void *); + p.var = 3; + msort_with_tmp (&p, p.t + n * sizeof (void *), n); + + /* tp[0] .. tp[n - 1] is now sorted, copy around entries of + the original array. Knuth vol. 3 (2nd ed.) exercise 5.2-10. */ + char *kp; + size_t i; + for (i = 0, ip = (char *) b; i < n; i++, ip += s) + if ((kp = tp[i]) != ip) + { + size_t j = i; + char *jp = ip; + memcpy (tmp_storage, ip, s); + + do + { + size_t k = (kp - (char *) b) / s; + tp[j] = jp; + memcpy (jp, kp, s); + j = k; + jp = kp; + kp = tp[k]; + } + while (kp != ip); + + tp[j] = jp; + memcpy (jp, tmp_storage, s); + } + } + else + { + if ((s & (sizeof (uint32_t) - 1)) == 0 + && ((char *) b - (char *) 0) % __alignof__ (uint32_t) == 0) + { + if (s == sizeof (uint32_t)) + p.var = 0; + else if (s == sizeof (uint64_t) + && ((char *) b - (char *) 0) % __alignof__ (uint64_t) == 0) + p.var = 1; + else if ((s & (sizeof (unsigned long) - 1)) == 0 + && ((char *) b - (char *) 0) + % __alignof__ (unsigned long) == 0) + p.var = 2; + } + msort_with_tmp (&p, b, n); + } + free (tmp); +} +libc_hidden_def (__qsort_r) +weak_alias (__qsort_r, qsort_r) + + +void +qsort (void *b, size_t n, size_t s, __compar_fn_t cmp) +{ + return __qsort_r (b, n, s, (__compar_d_fn_t) cmp, NULL); +} +libc_hidden_def (qsort) -- 2.37.1 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
