/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: 2024-03-08 06:32

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	66.4k	{
49	66.4k	for (;;) /* while (n1 > 0 && n2 > 0) */
50	391k	{
51	391k	if (COMPARE (src1, src2) <= 0)
52	332k	{
53	332k	dst++ = src1++;
54	332k	n1--;
55	332k	if (n1 == 0)
56	62.8k	break;
57	332k	}
58	58.5k	else
59	58.5k	{
60	58.5k	dst++ = src2++;
61	58.5k	n2--;
62	58.5k	if (n2 == 0)
63	3.62k	break;
64	58.5k	}
65	391k	}
66		/* Here n1 == 0 \|\| n2 == 0 but also n1 > 0 \|\| n2 > 0. */
67	66.4k	if (n1 > 0)
68	3.62k	{
69	3.62k	if (dst != src1)
70	3.62k	do
71	6.27k	{
72	6.27k	dst++ = src1++;
73	6.27k	n1--;
74	6.27k	}
75	6.27k	while (n1 > 0);
76	3.62k	}
77	62.8k	else /* n2 > 0 */
78	62.8k	{
79	62.8k	if (dst != src2)
80	0	do
81	0	{
82	0	dst++ = src2++;
83	0	n2--;
84	0	}
85	0	while (n2 > 0);
86	62.8k	}
87	66.4k	}
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	113k	{
100	113k	switch (n)
101	113k	{
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	55.4k	case 2:
109		/* Trivial case. */
110	55.4k	if (COMPARE (&src[0], &src[1]) <= 0)
111	51.3k	{
112		/* src[0] <= src[1] */
113	51.3k	dst[0] = src[0];
114	51.3k	dst[1] = src[1];
115	51.3k	}
116	4.12k	else
117	4.12k	{
118	4.12k	dst[0] = src[1];
119	4.12k	dst[1] = src[0];
120	4.12k	}
121	55.4k	break;
122	11.0k	case 3:
123		/* Simple case. */
124	11.0k	if (COMPARE (&src[0], &src[1]) <= 0)
125	8.21k	{
126	8.21k	if (COMPARE (&src[1], &src[2]) <= 0)
127	5.36k	{
128		/* src[0] <= src[1] <= src[2] */
129	5.36k	dst[0] = src[0];
130	5.36k	dst[1] = src[1];
131	5.36k	dst[2] = src[2];
132	5.36k	}
133	2.84k	else if (COMPARE (&src[0], &src[2]) <= 0)
134	1.92k	{
135		/* src[0] <= src[2] < src[1] */
136	1.92k	dst[0] = src[0];
137	1.92k	dst[1] = src[2];
138	1.92k	dst[2] = src[1];
139	1.92k	}
140	919	else
141	919	{
142		/* src[2] < src[0] <= src[1] */
143	919	dst[0] = src[2];
144	919	dst[1] = src[0];
145	919	dst[2] = src[1];
146	919	}
147	8.21k	}
148	2.83k	else
149	2.83k	{
150	2.83k	if (COMPARE (&src[0], &src[2]) <= 0)
151	1.21k	{
152		/* src[1] < src[0] <= src[2] */
153	1.21k	dst[0] = src[1];
154	1.21k	dst[1] = src[0];
155	1.21k	dst[2] = src[2];
156	1.21k	}
157	1.61k	else if (COMPARE (&src[1], &src[2]) <= 0)
158	936	{
159		/* src[1] <= src[2] < src[0] */
160	936	dst[0] = src[1];
161	936	dst[1] = src[2];
162	936	dst[2] = src[0];
163	936	}
164	678	else
165	678	{
166		/* src[2] < src[1] < src[0] */
167	678	dst[0] = src[2];
168	678	dst[1] = src[1];
169	678	dst[2] = src[0];
170	678	}
171	2.83k	}
172	11.0k	break;
173	47.0k	default:
174	47.0k	{
175	47.0k	size_t n1 = n / 2;
176	47.0k	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	47.0k	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	47.0k	merge_sort_fromto (src, tmp, n1, dst);
182		/* Merge the two half results. */
183	47.0k	merge (tmp, n1, dst + n1, n2, dst);
184	47.0k	}
185	47.0k	break;
186	113k	}
187	113k	}
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	102k	{
194	102k	switch (n)
195	102k	{
196	0	case 0:
197	0	case 1:
198		/* Nothing to do. */
199	0	return;
200	84.9k	case 2:
201		/* Trivial case. */
202	84.9k	if (COMPARE (&src[0], &src[1]) <= 0)
203	84.2k	{
204		/* src[0] <= src[1] */
205	84.2k	}
206	687	else
207	687	{
208	687	ELEMENT t = src[0];
209	687	src[0] = src[1];
210	687	src[1] = t;
211	687	}
212	84.9k	break;
213	6.73k	case 3:
214		/* Simple case. */
215	6.73k	if (COMPARE (&src[0], &src[1]) <= 0)
216	4.90k	{
217	4.90k	if (COMPARE (&src[1], &src[2]) <= 0)
218	3.90k	{
219		/* src[0] <= src[1] <= src[2] */
220	3.90k	}
221	1.00k	else if (COMPARE (&src[0], &src[2]) <= 0)
222	520	{
223		/* src[0] <= src[2] < src[1] */
224	520	ELEMENT t = src[1];
225	520	src[1] = src[2];
226	520	src[2] = t;
227	520	}
228	486	else
229	486	{
230		/* src[2] < src[0] <= src[1] */
231	486	ELEMENT t = src[0];
232	486	src[0] = src[2];
233	486	src[2] = src[1];
234	486	src[1] = t;
235	486	}
236	4.90k	}
237	1.82k	else
238	1.82k	{
239	1.82k	if (COMPARE (&src[0], &src[2]) <= 0)
240	729	{
241		/* src[1] < src[0] <= src[2] */
242	729	ELEMENT t = src[0];
243	729	src[0] = src[1];
244	729	src[1] = t;
245	729	}
246	1.09k	else if (COMPARE (&src[1], &src[2]) <= 0)
247	652	{
248		/* src[1] <= src[2] < src[0] */
249	652	ELEMENT t = src[0];
250	652	src[0] = src[1];
251	652	src[1] = src[2];
252	652	src[2] = t;
253	652	}
254	445	else
255	445	{
256		/* src[2] < src[1] < src[0] */
257	445	ELEMENT t = src[0];
258	445	src[0] = src[2];
259	445	src[2] = t;
260	445	}
261	1.82k	}
262	6.73k	break;
263	10.6k	default:
264	10.6k	{
265	10.6k	size_t n1 = n / 2;
266	10.6k	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	10.6k	merge_sort_inplace (src + n1, n2, tmp);
270		/* Sort src[0..n1-1] into tmp[0..n1-1], scratching tmp[n1..2n1-1]. /
271	10.6k	merge_sort_fromto (src, tmp, n1, tmp + n1);
272		/* Merge the two half results. */
273	10.6k	merge (tmp, n1, src + n1, n2, src);
274	10.6k	}
275	10.6k	break;
276	102k	}
277	102k	}
278
279		#undef ELEMENT
280		#undef COMPARE
281		#undef STATIC