/src/libunistring/lib/array-mergesort.h

Source (jump to first uncovered line)
/* Stable-sorting of an array using mergesort.
   Copyright (C) 2009-2024 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2009.

   This file 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.

   This file 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 this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* This file implements stable sorting of an array, using the mergesort
   algorithm.
   Worst-case running time for an array of length N is O(N log N).
   Unlike the mpsort module, the algorithm here attempts to minimize not
   only the number of comparisons, but also the number of copying operations.

   Before including this file, you need to define
     ELEMENT      The type of every array element.
     COMPARE      A two-argument macro that takes two 'const ELEMENT *'
                  pointers and returns a negative, zero, or positive 'int'
                  value if the element pointed to by the first argument is,
                  respectively, less, equal, or greater than the element
                  pointed to by the second argument.
     STATIC       The storage class of the functions being defined.
     STATIC_FROMTO  (Optional.) Overrides STATIC for the 'merge_sort_fromto'
                    function.
   Before including this file, you also need to include:
     #include <stddef.h>
 */

/* Merge the sorted arrays src1[0..n1-1] and src2[0..n2-1] into
   dst[0..n1+n2-1].  In case of ambiguity, put the elements of src1
   before the elements of src2.
   n1 and n2 must be > 0.
   The arrays src1 and src2 must not overlap the dst array, except that
   src1 may be dst[n2..n1+n2-1], or src2 may be dst[n1..n1+n2-1].  */
static void
merge (const ELEMENT *src1, size_t n1,
       const ELEMENT *src2, size_t n2,
       ELEMENT *dst)
{
  for (;;) /* while (n1 > 0 && n2 > 0) */
    {
      if (COMPARE (src1, src2) <= 0)
        {
          *dst++ = *src1++;
          n1--;
          if (n1 == 0)
            break;
        }
      else
        {
          *dst++ = *src2++;
          n2--;
          if (n2 == 0)
            break;
        }
    }
  /* Here n1 == 0 || n2 == 0 but also n1 > 0 || n2 > 0.  */
  if (n1 > 0)
    {
      if (dst != src1)
        do
          {
            *dst++ = *src1++;
            n1--;
          }
        while (n1 > 0);
    }
  else /* n2 > 0 */
    {
      if (dst != src2)
        do
          {
            *dst++ = *src2++;
            n2--;
          }
        while (n2 > 0);
    }
}

/* Sort src[0..n-1] into dst[0..n-1], using tmp[0..n/2-1] as temporary
   (scratch) storage.
   The arrays src, dst, tmp must not overlap.  */
#ifdef STATIC_FROMTO
STATIC_FROMTO
#else
STATIC
#endif
void
merge_sort_fromto (const ELEMENT *src, ELEMENT *dst, size_t n, ELEMENT *tmp)
{
  switch (n)
    {
    case 0:
      return;
    case 1:
      /* Nothing to do.  */
      dst[0] = src[0];
      return;
    case 2:
      /* Trivial case.  */
      if (COMPARE (&src[0], &src[1]) <= 0)
        {
          /* src[0] <= src[1] */
          dst[0] = src[0];
          dst[1] = src[1];
        }
      else
        {
          dst[0] = src[1];
          dst[1] = src[0];
        }
      break;
    case 3:
      /* Simple case.  */
      if (COMPARE (&src[0], &src[1]) <= 0)
        {
          if (COMPARE (&src[1], &src[2]) <= 0)
            {
              /* src[0] <= src[1] <= src[2] */
              dst[0] = src[0];
              dst[1] = src[1];
              dst[2] = src[2];
            }
          else if (COMPARE (&src[0], &src[2]) <= 0)
            {
              /* src[0] <= src[2] < src[1] */
              dst[0] = src[0];
              dst[1] = src[2];
              dst[2] = src[1];
            }
          else
            {
              /* src[2] < src[0] <= src[1] */
              dst[0] = src[2];
              dst[1] = src[0];
              dst[2] = src[1];
            }
        }
      else
        {
          if (COMPARE (&src[0], &src[2]) <= 0)
            {
              /* src[1] < src[0] <= src[2] */
              dst[0] = src[1];
              dst[1] = src[0];
              dst[2] = src[2];
            }
          else if (COMPARE (&src[1], &src[2]) <= 0)
            {
              /* src[1] <= src[2] < src[0] */
              dst[0] = src[1];
              dst[1] = src[2];
              dst[2] = src[0];
            }
          else
            {
              /* src[2] < src[1] < src[0] */
              dst[0] = src[2];
              dst[1] = src[1];
              dst[2] = src[0];
            }
        }
      break;
    default:
      {
        size_t n1 = n / 2;
        size_t n2 = (n + 1) / 2;
        /* Note: n1 + n2 = n, n1 <= n2.  */
        /* Sort src[n1..n-1] into dst[n1..n-1], scratching tmp[0..n2/2-1].  */
        merge_sort_fromto (src + n1, dst + n1, n2, tmp);
        /* Sort src[0..n1-1] into tmp[0..n1-1], scratching dst[0..n1-1].  */
        merge_sort_fromto (src, tmp, n1, dst);
        /* Merge the two half results.  */
        merge (tmp, n1, dst + n1, n2, dst);
      }
      break;
    }
}

/* Sort src[0..n-1], using tmp[0..n-1] as temporary (scratch) storage.
   The arrays src, tmp must not overlap. */
STATIC void
merge_sort_inplace (ELEMENT *src, size_t n, ELEMENT *tmp)
{
  switch (n)
    {
    case 0:
    case 1:
      /* Nothing to do.  */
      return;
    case 2:
      /* Trivial case.  */
      if (COMPARE (&src[0], &src[1]) <= 0)
        {
          /* src[0] <= src[1] */
        }
      else
        {
          ELEMENT t = src[0];
          src[0] = src[1];
          src[1] = t;
        }
      break;
    case 3:
      /* Simple case.  */
      if (COMPARE (&src[0], &src[1]) <= 0)
        {
          if (COMPARE (&src[1], &src[2]) <= 0)
            {
              /* src[0] <= src[1] <= src[2] */
            }
          else if (COMPARE (&src[0], &src[2]) <= 0)
            {
              /* src[0] <= src[2] < src[1] */
              ELEMENT t = src[1];
              src[1] = src[2];
              src[2] = t;
            }
          else
            {
              /* src[2] < src[0] <= src[1] */
              ELEMENT t = src[0];
              src[0] = src[2];
              src[2] = src[1];
              src[1] = t;
            }
        }
      else
        {
          if (COMPARE (&src[0], &src[2]) <= 0)
            {
              /* src[1] < src[0] <= src[2] */
              ELEMENT t = src[0];
              src[0] = src[1];
              src[1] = t;
            }
          else if (COMPARE (&src[1], &src[2]) <= 0)
            {
              /* src[1] <= src[2] < src[0] */
              ELEMENT t = src[0];
              src[0] = src[1];
              src[1] = src[2];
              src[2] = t;
            }
          else
            {
              /* src[2] < src[1] < src[0] */
              ELEMENT t = src[0];
              src[0] = src[2];
              src[2] = t;
            }
        }
      break;
    default:
      {
        size_t n1 = n / 2;
        size_t n2 = (n + 1) / 2;
        /* Note: n1 + n2 = n, n1 <= n2.  */
        /* Sort src[n1..n-1], scratching tmp[0..n2-1].  */
        merge_sort_inplace (src + n1, n2, tmp);
        /* Sort src[0..n1-1] into tmp[0..n1-1], scratching tmp[n1..2*n1-1].  */
        merge_sort_fromto (src, tmp, n1, tmp + n1);
        /* Merge the two half results.  */
        merge (tmp, n1, src + n1, n2, src);
      }
      break;
    }
}

#undef ELEMENT
#undef COMPARE
#undef STATIC

Coverage Report

Created: 2024-10-06 07:21

Line	Count	Source (jump to first uncovered line)
1		/* Stable-sorting of an array using mergesort.
2		Copyright (C) 2009-2024 Free Software Foundation, Inc.
3		Written by Bruno Haible <bruno@clisp.org>, 2009.
4
5		This file is free software: you can redistribute it and/or modify
6		it under the terms of the GNU Lesser General Public License as
7		published by the Free Software Foundation; either version 2.1 of the
8		License, or (at your option) any later version.
9
10		This file is distributed in the hope that it will be useful,
11		but WITHOUT ANY WARRANTY; without even the implied warranty of
12		MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13		GNU Lesser General Public License for more details.
14
15		You should have received a copy of the GNU Lesser General Public License
16		along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18		/* This file implements stable sorting of an array, using the mergesort
19		algorithm.
20		Worst-case running time for an array of length N is O(N log N).
21		Unlike the mpsort module, the algorithm here attempts to minimize not
22		only the number of comparisons, but also the number of copying operations.
23
24		Before including this file, you need to define
25		ELEMENT The type of every array element.
26		COMPARE A two-argument macro that takes two 'const ELEMENT *'
27		pointers and returns a negative, zero, or positive 'int'
28		value if the element pointed to by the first argument is,
29		respectively, less, equal, or greater than the element
30		pointed to by the second argument.
31		STATIC The storage class of the functions being defined.
32		STATIC_FROMTO (Optional.) Overrides STATIC for the 'merge_sort_fromto'
33		function.
34		Before including this file, you also need to include:
35		#include <stddef.h>
36		*/
37
38		/* Merge the sorted arrays src1[0..n1-1] and src2[0..n2-1] into
39		dst[0..n1+n2-1]. In case of ambiguity, put the elements of src1
40		before the elements of src2.
41		n1 and n2 must be > 0.
42		The arrays src1 and src2 must not overlap the dst array, except that
43		src1 may be dst[n2..n1+n2-1], or src2 may be dst[n1..n1+n2-1]. */
44		static void
45		merge (const ELEMENT *src1, size_t n1,
46		const ELEMENT *src2, size_t n2,
47		ELEMENT *dst)
48	580k	{
49	580k	for (;;) /* while (n1 > 0 && n2 > 0) */
50	8.31M	{
51	8.31M	if (COMPARE (src1, src2) <= 0)
52	7.47M	{
53	7.47M	dst++ = src1++;
54	7.47M	n1--;
55	7.47M	if (n1 == 0)
56	576k	break;
57	7.47M	}
58	845k	else
59	845k	{
60	845k	dst++ = src2++;
61	845k	n2--;
62	845k	if (n2 == 0)
63	3.64k	break;
64	845k	}
65	8.31M	}
66		/* Here n1 == 0 \|\| n2 == 0 but also n1 > 0 \|\| n2 > 0. */
67	580k	if (n1 > 0)
68	3.64k	{
69	3.64k	if (dst != src1)
70	3.64k	do
71	8.76k	{
72	8.76k	dst++ = src1++;
73	8.76k	n1--;
74	8.76k	}
75	8.76k	while (n1 > 0);
76	3.64k	}
77	576k	else /* n2 > 0 */
78	576k	{
79	576k	if (dst != src2)
80	0	do
81	0	{
82	0	dst++ = src2++;
83	0	n2--;
84	0	}
85	0	while (n2 > 0);
86	576k	}
87	580k	}
88
89		/* Sort src[0..n-1] into dst[0..n-1], using tmp[0..n/2-1] as temporary
90		(scratch) storage.
91		The arrays src, dst, tmp must not overlap. */
92		#ifdef STATIC_FROMTO
93		STATIC_FROMTO
94		#else
95		STATIC
96		#endif
97		void
98		merge_sort_fromto (const ELEMENT src, ELEMENT dst, size_t n, ELEMENT *tmp)
99	1.13M	{
100	1.13M	switch (n)
101	1.13M	{
102	0	case 0:
103	0	return;
104	0	case 1:
105		/* Nothing to do. */
106	0	dst[0] = src[0];
107	0	return;
108	549k	case 2:
109		/* Trivial case. */
110	549k	if (COMPARE (&src[0], &src[1]) <= 0)
111	547k	{
112		/* src[0] <= src[1] */
113	547k	dst[0] = src[0];
114	547k	dst[1] = src[1];
115	547k	}
116	2.01k	else
117	2.01k	{
118	2.01k	dst[0] = src[1];
119	2.01k	dst[1] = src[0];
120	2.01k	}
121	549k	break;
122	30.8k	case 3:
123		/* Simple case. */
124	30.8k	if (COMPARE (&src[0], &src[1]) <= 0)
125	28.5k	{
126	28.5k	if (COMPARE (&src[1], &src[2]) <= 0)
127	26.7k	{
128		/* src[0] <= src[1] <= src[2] */
129	26.7k	dst[0] = src[0];
130	26.7k	dst[1] = src[1];
131	26.7k	dst[2] = src[2];
132	26.7k	}
133	1.82k	else if (COMPARE (&src[0], &src[2]) <= 0)
134	1.11k	{
135		/* src[0] <= src[2] < src[1] */
136	1.11k	dst[0] = src[0];
137	1.11k	dst[1] = src[2];
138	1.11k	dst[2] = src[1];
139	1.11k	}
140	701	else
141	701	{
142		/* src[2] < src[0] <= src[1] */
143	701	dst[0] = src[2];
144	701	dst[1] = src[0];
145	701	dst[2] = src[1];
146	701	}
147	28.5k	}
148	2.25k	else
149	2.25k	{
150	2.25k	if (COMPARE (&src[0], &src[2]) <= 0)
151	810	{
152		/* src[1] < src[0] <= src[2] */
153	810	dst[0] = src[1];
154	810	dst[1] = src[0];
155	810	dst[2] = src[2];
156	810	}
157	1.44k	else if (COMPARE (&src[1], &src[2]) <= 0)
158	773	{
159		/* src[1] <= src[2] < src[0] */
160	773	dst[0] = src[1];
161	773	dst[1] = src[2];
162	773	dst[2] = src[0];
163	773	}
164	673	else
165	673	{
166		/* src[2] < src[1] < src[0] */
167	673	dst[0] = src[2];
168	673	dst[1] = src[1];
169	673	dst[2] = src[0];
170	673	}
171	2.25k	}
172	30.8k	break;
173	559k	default:
174	559k	{
175	559k	size_t n1 = n / 2;
176	559k	size_t n2 = (n + 1) / 2;
177		/* Note: n1 + n2 = n, n1 <= n2. */
178		/* Sort src[n1..n-1] into dst[n1..n-1], scratching tmp[0..n2/2-1]. */
179	559k	merge_sort_fromto (src + n1, dst + n1, n2, tmp);
180		/* Sort src[0..n1-1] into tmp[0..n1-1], scratching dst[0..n1-1]. */
181	559k	merge_sort_fromto (src, tmp, n1, dst);
182		/* Merge the two half results. */
183	559k	merge (tmp, n1, dst + n1, n2, dst);
184	559k	}
185	559k	break;
186	1.13M	}
187	1.13M	}
188
189		/* Sort src[0..n-1], using tmp[0..n-1] as temporary (scratch) storage.
190		The arrays src, tmp must not overlap. */
191		STATIC void
192		merge_sort_inplace (ELEMENT src, size_t n, ELEMENT tmp)
193	1.45M	{
194	1.45M	switch (n)
195	1.45M	{
196	0	case 0:
197	0	case 1:
198		/* Nothing to do. */
199	0	return;
200	1.41M	case 2:
201		/* Trivial case. */
202	1.41M	if (COMPARE (&src[0], &src[1]) <= 0)
203	1.41M	{
204		/* src[0] <= src[1] */
205	1.41M	}
206	844	else
207	844	{
208	844	ELEMENT t = src[0];
209	844	src[0] = src[1];
210	844	src[1] = t;
211	844	}
212	1.41M	break;
213	18.0k	case 3:
214		/* Simple case. */
215	18.0k	if (COMPARE (&src[0], &src[1]) <= 0)
216	13.6k	{
217	13.6k	if (COMPARE (&src[1], &src[2]) <= 0)
218	12.0k	{
219		/* src[0] <= src[1] <= src[2] */
220	12.0k	}
221	1.67k	else if (COMPARE (&src[0], &src[2]) <= 0)
222	817	{
223		/* src[0] <= src[2] < src[1] */
224	817	ELEMENT t = src[1];
225	817	src[1] = src[2];
226	817	src[2] = t;
227	817	}
228	859	else
229	859	{
230		/* src[2] < src[0] <= src[1] */
231	859	ELEMENT t = src[0];
232	859	src[0] = src[2];
233	859	src[2] = src[1];
234	859	src[1] = t;
235	859	}
236	13.6k	}
237	4.35k	else
238	4.35k	{
239	4.35k	if (COMPARE (&src[0], &src[2]) <= 0)
240	687	{
241		/* src[1] < src[0] <= src[2] */
242	687	ELEMENT t = src[0];
243	687	src[0] = src[1];
244	687	src[1] = t;
245	687	}
246	3.66k	else if (COMPARE (&src[1], &src[2]) <= 0)
247	2.40k	{
248		/* src[1] <= src[2] < src[0] */
249	2.40k	ELEMENT t = src[0];
250	2.40k	src[0] = src[1];
251	2.40k	src[1] = src[2];
252	2.40k	src[2] = t;
253	2.40k	}
254	1.26k	else
255	1.26k	{
256		/* src[2] < src[1] < src[0] */
257	1.26k	ELEMENT t = src[0];
258	1.26k	src[0] = src[2];
259	1.26k	src[2] = t;
260	1.26k	}
261	4.35k	}
262	18.0k	break;
263	20.5k	default:
264	20.5k	{
265	20.5k	size_t n1 = n / 2;
266	20.5k	size_t n2 = (n + 1) / 2;
267		/* Note: n1 + n2 = n, n1 <= n2. */
268		/* Sort src[n1..n-1], scratching tmp[0..n2-1]. */
269	20.5k	merge_sort_inplace (src + n1, n2, tmp);
270		/* Sort src[0..n1-1] into tmp[0..n1-1], scratching tmp[n1..2n1-1]. /
271	20.5k	merge_sort_fromto (src, tmp, n1, tmp + n1);
272		/* Merge the two half results. */
273	20.5k	merge (tmp, n1, src + n1, n2, src);
274	20.5k	}
275	20.5k	break;
276	1.45M	}
277	1.45M	}
278
279		#undef ELEMENT
280		#undef COMPARE
281		#undef STATIC