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

Source (jump to first uncovered line)
/* Stable-sorting of an array using mergesort.
   Copyright (C) 2009-2023 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: 2023-06-07 07:18

Line	Count	Source (jump to first uncovered line)
1		/* Stable-sorting of an array using mergesort.
2		Copyright (C) 2009-2023 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	928k	{
49	928k	for (;;) /* while (n1 > 0 && n2 > 0) */
50	12.9M	{
51	12.9M	if (COMPARE (src1, src2) <= 0)
52	12.0M	{
53	12.0M	dst++ = src1++;
54	12.0M	n1--;
55	12.0M	if (n1 == 0)
56	920k	break;
57	12.0M	}
58	942k	else
59	942k	{
60	942k	dst++ = src2++;
61	942k	n2--;
62	942k	if (n2 == 0)
63	7.20k	break;
64	942k	}
65	12.9M	}
66		/* Here n1 == 0 \|\| n2 == 0 but also n1 > 0 \|\| n2 > 0. */
67	928k	if (n1 > 0)
68	7.20k	{
69	7.20k	if (dst != src1)
70	7.20k	do
71	22.3k	{
72	22.3k	dst++ = src1++;
73	22.3k	n1--;
74	22.3k	}
75	22.3k	while (n1 > 0);
76	7.20k	}
77	920k	else /* n2 > 0 */
78	920k	{
79	920k	if (dst != src2)
80	0	do
81	0	{
82	0	dst++ = src2++;
83	0	n2--;
84	0	}
85	0	while (n2 > 0);
86	920k	}
87	928k	}
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	1.81M	{
100	1.81M	switch (n)
101	1.81M	{
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	811k	case 2:
109		/* Trivial case. */
110	811k	if (COMPARE (&src[0], &src[1]) <= 0)
111	804k	{
112		/* src[0] <= src[1] */
113	804k	dst[0] = src[0];
114	804k	dst[1] = src[1];
115	804k	}
116	6.90k	else
117	6.90k	{
118	6.90k	dst[0] = src[1];
119	6.90k	dst[1] = src[0];
120	6.90k	}
121	811k	break;
122	116k	case 3:
123		/* Simple case. */
124	116k	if (COMPARE (&src[0], &src[1]) <= 0)
125	109k	{
126	109k	if (COMPARE (&src[1], &src[2]) <= 0)
127	104k	{
128		/* src[0] <= src[1] <= src[2] */
129	104k	dst[0] = src[0];
130	104k	dst[1] = src[1];
131	104k	dst[2] = src[2];
132	104k	}
133	5.42k	else if (COMPARE (&src[0], &src[2]) <= 0)
134	2.86k	{
135		/* src[0] <= src[2] < src[1] */
136	2.86k	dst[0] = src[0];
137	2.86k	dst[1] = src[2];
138	2.86k	dst[2] = src[1];
139	2.86k	}
140	2.56k	else
141	2.56k	{
142		/* src[2] < src[0] <= src[1] */
143	2.56k	dst[0] = src[2];
144	2.56k	dst[1] = src[0];
145	2.56k	dst[2] = src[1];
146	2.56k	}
147	109k	}
148	6.53k	else
149	6.53k	{
150	6.53k	if (COMPARE (&src[0], &src[2]) <= 0)
151	3.96k	{
152		/* src[1] < src[0] <= src[2] */
153	3.96k	dst[0] = src[1];
154	3.96k	dst[1] = src[0];
155	3.96k	dst[2] = src[2];
156	3.96k	}
157	2.56k	else if (COMPARE (&src[1], &src[2]) <= 0)
158	1.14k	{
159		/* src[1] <= src[2] < src[0] */
160	1.14k	dst[0] = src[1];
161	1.14k	dst[1] = src[2];
162	1.14k	dst[2] = src[0];
163	1.14k	}
164	1.41k	else
165	1.41k	{
166		/* src[2] < src[1] < src[0] */
167	1.41k	dst[0] = src[2];
168	1.41k	dst[1] = src[1];
169	1.41k	dst[2] = src[0];
170	1.41k	}
171	6.53k	}
172	116k	break;
173	890k	default:
174	890k	{
175	890k	size_t n1 = n / 2;
176	890k	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	890k	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	890k	merge_sort_fromto (src, tmp, n1, dst);
182		/* Merge the two half results. */
183	890k	merge (tmp, n1, dst + n1, n2, dst);
184	890k	}
185	890k	break;
186	1.81M	}
187	1.81M	}
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	2.10M	{
194	2.10M	switch (n)
195	2.10M	{
196	0	case 0:
197	0	case 1:
198		/* Nothing to do. */
199	0	return;
200	2.04M	case 2:
201		/* Trivial case. */
202	2.04M	if (COMPARE (&src[0], &src[1]) <= 0)
203	2.04M	{
204		/* src[0] <= src[1] */
205	2.04M	}
206	1.17k	else
207	1.17k	{
208	1.17k	ELEMENT t = src[0];
209	1.17k	src[0] = src[1];
210	1.17k	src[1] = t;
211	1.17k	}
212	2.04M	break;
213	19.7k	case 3:
214		/* Simple case. */
215	19.7k	if (COMPARE (&src[0], &src[1]) <= 0)
216	15.5k	{
217	15.5k	if (COMPARE (&src[1], &src[2]) <= 0)
218	13.4k	{
219		/* src[0] <= src[1] <= src[2] */
220	13.4k	}
221	2.12k	else if (COMPARE (&src[0], &src[2]) <= 0)
222	1.14k	{
223		/* src[0] <= src[2] < src[1] */
224	1.14k	ELEMENT t = src[1];
225	1.14k	src[1] = src[2];
226	1.14k	src[2] = t;
227	1.14k	}
228	977	else
229	977	{
230		/* src[2] < src[0] <= src[1] */
231	977	ELEMENT t = src[0];
232	977	src[0] = src[2];
233	977	src[2] = src[1];
234	977	src[1] = t;
235	977	}
236	15.5k	}
237	4.21k	else
238	4.21k	{
239	4.21k	if (COMPARE (&src[0], &src[2]) <= 0)
240	1.80k	{
241		/* src[1] < src[0] <= src[2] */
242	1.80k	ELEMENT t = src[0];
243	1.80k	src[0] = src[1];
244	1.80k	src[1] = t;
245	1.80k	}
246	2.40k	else if (COMPARE (&src[1], &src[2]) <= 0)
247	1.69k	{
248		/* src[1] <= src[2] < src[0] */
249	1.69k	ELEMENT t = src[0];
250	1.69k	src[0] = src[1];
251	1.69k	src[1] = src[2];
252	1.69k	src[2] = t;
253	1.69k	}
254	709	else
255	709	{
256		/* src[2] < src[1] < src[0] */
257	709	ELEMENT t = src[0];
258	709	src[0] = src[2];
259	709	src[2] = t;
260	709	}
261	4.21k	}
262	19.7k	break;
263	38.1k	default:
264	38.1k	{
265	38.1k	size_t n1 = n / 2;
266	38.1k	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	38.1k	merge_sort_inplace (src + n1, n2, tmp);
270		/* Sort src[0..n1-1] into tmp[0..n1-1], scratching tmp[n1..2n1-1]. /
271	38.1k	merge_sort_fromto (src, tmp, n1, tmp + n1);
272		/* Merge the two half results. */
273	38.1k	merge (tmp, n1, src + n1, n2, src);
274	38.1k	}
275	38.1k	break;
276	2.10M	}
277	2.10M	}
278
279		#undef ELEMENT
280		#undef COMPARE
281		#undef STATIC