/src/libidn2/unistring/array-mergesort.h

Source (jump to first uncovered line)
/* Stable-sorting of an array using mergesort.
   Copyright (C) 2009-2022 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: 2022-11-21 06:06

Line	Count	Source (jump to first uncovered line)
1		/* Stable-sorting of an array using mergesort.
2		Copyright (C) 2009-2022 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	47.0k	{
49	47.0k	for (;;) /* while (n1 > 0 && n2 > 0) */
50	294k	{
51	294k	if (COMPARE (src1, src2) <= 0)
52	252k	{
53	252k	dst++ = src1++;
54	252k	n1--;
55	252k	if (n1 == 0)
56	44.9k	break;
57	252k	}
58	41.6k	else
59	41.6k	{
60	41.6k	dst++ = src2++;
61	41.6k	n2--;
62	41.6k	if (n2 == 0)
63	2.19k	break;
64	41.6k	}
65	294k	}
66		/* Here n1 == 0 \|\| n2 == 0 but also n1 > 0 \|\| n2 > 0. */
67	47.0k	if (n1 > 0)
68	2.19k	{
69	2.19k	if (dst != src1)
70	2.19k	do
71	6.03k	{
72	6.03k	dst++ = src1++;
73	6.03k	n1--;
74	6.03k	}
75	6.03k	while (n1 > 0);
76	2.19k	}
77	44.9k	else /* n2 > 0 */
78	44.9k	{
79	44.9k	if (dst != src2)
80	0	do
81	0	{
82	0	dst++ = src2++;
83	0	n2--;
84	0	}
85	0	while (n2 > 0);
86	44.9k	}
87	47.0k	}
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	82.0k	{
100	82.0k	switch (n)
101	82.0k	{
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	39.7k	case 2:
109		/* Trivial case. */
110	39.7k	if (COMPARE (&src[0], &src[1]) <= 0)
111	37.0k	{
112		/* src[0] <= src[1] */
113	37.0k	dst[0] = src[0];
114	37.0k	dst[1] = src[1];
115	37.0k	}
116	2.64k	else
117	2.64k	{
118	2.64k	dst[0] = src[1];
119	2.64k	dst[1] = src[0];
120	2.64k	}
121	39.7k	break;
122	7.37k	case 3:
123		/* Simple case. */
124	7.37k	if (COMPARE (&src[0], &src[1]) <= 0)
125	6.17k	{
126	6.17k	if (COMPARE (&src[1], &src[2]) <= 0)
127	4.85k	{
128		/* src[0] <= src[1] <= src[2] */
129	4.85k	dst[0] = src[0];
130	4.85k	dst[1] = src[1];
131	4.85k	dst[2] = src[2];
132	4.85k	}
133	1.32k	else if (COMPARE (&src[0], &src[2]) <= 0)
134	981	{
135		/* src[0] <= src[2] < src[1] */
136	981	dst[0] = src[0];
137	981	dst[1] = src[2];
138	981	dst[2] = src[1];
139	981	}
140	343	else
141	343	{
142		/* src[2] < src[0] <= src[1] */
143	343	dst[0] = src[2];
144	343	dst[1] = src[0];
145	343	dst[2] = src[1];
146	343	}
147	6.17k	}
148	1.19k	else
149	1.19k	{
150	1.19k	if (COMPARE (&src[0], &src[2]) <= 0)
151	526	{
152		/* src[1] < src[0] <= src[2] */
153	526	dst[0] = src[1];
154	526	dst[1] = src[0];
155	526	dst[2] = src[2];
156	526	}
157	668	else if (COMPARE (&src[1], &src[2]) <= 0)
158	373	{
159		/* src[1] <= src[2] < src[0] */
160	373	dst[0] = src[1];
161	373	dst[1] = src[2];
162	373	dst[2] = src[0];
163	373	}
164	295	else
165	295	{
166		/* src[2] < src[1] < src[0] */
167	295	dst[0] = src[2];
168	295	dst[1] = src[1];
169	295	dst[2] = src[0];
170	295	}
171	1.19k	}
172	7.37k	break;
173	34.9k	default:
174	34.9k	{
175	34.9k	size_t n1 = n / 2;
176	34.9k	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	34.9k	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	34.9k	merge_sort_fromto (src, tmp, n1, dst);
182		/* Merge the two half results. */
183	34.9k	merge (tmp, n1, dst + n1, n2, dst);
184	34.9k	}
185	34.9k	break;
186	82.0k	}
187	82.0k	}
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	38.0k	{
194	38.0k	switch (n)
195	38.0k	{
196	0	case 0:
197	0	case 1:
198		/* Nothing to do. */
199	0	return;
200	18.5k	case 2:
201		/* Trivial case. */
202	18.5k	if (COMPARE (&src[0], &src[1]) <= 0)
203	17.9k	{
204		/* src[0] <= src[1] */
205	17.9k	}
206	671	else
207	671	{
208	671	ELEMENT t = src[0];
209	671	src[0] = src[1];
210	671	src[1] = t;
211	671	}
212	18.5k	break;
213	7.40k	case 3:
214		/* Simple case. */
215	7.40k	if (COMPARE (&src[0], &src[1]) <= 0)
216	6.21k	{
217	6.21k	if (COMPARE (&src[1], &src[2]) <= 0)
218	5.38k	{
219		/* src[0] <= src[1] <= src[2] */
220	5.38k	}
221	826	else if (COMPARE (&src[0], &src[2]) <= 0)
222	474	{
223		/* src[0] <= src[2] < src[1] */
224	474	ELEMENT t = src[1];
225	474	src[1] = src[2];
226	474	src[2] = t;
227	474	}
228	352	else
229	352	{
230		/* src[2] < src[0] <= src[1] */
231	352	ELEMENT t = src[0];
232	352	src[0] = src[2];
233	352	src[2] = src[1];
234	352	src[1] = t;
235	352	}
236	6.21k	}
237	1.19k	else
238	1.19k	{
239	1.19k	if (COMPARE (&src[0], &src[2]) <= 0)
240	427	{
241		/* src[1] < src[0] <= src[2] */
242	427	ELEMENT t = src[0];
243	427	src[0] = src[1];
244	427	src[1] = t;
245	427	}
246	768	else if (COMPARE (&src[1], &src[2]) <= 0)
247	466	{
248		/* src[1] <= src[2] < src[0] */
249	466	ELEMENT t = src[0];
250	466	src[0] = src[1];
251	466	src[1] = src[2];
252	466	src[2] = t;
253	466	}
254	302	else
255	302	{
256		/* src[2] < src[1] < src[0] */
257	302	ELEMENT t = src[0];
258	302	src[0] = src[2];
259	302	src[2] = t;
260	302	}
261	1.19k	}
262	7.40k	break;
263	12.1k	default:
264	12.1k	{
265	12.1k	size_t n1 = n / 2;
266	12.1k	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	12.1k	merge_sort_inplace (src + n1, n2, tmp);
270		/* Sort src[0..n1-1] into tmp[0..n1-1], scratching tmp[n1..2n1-1]. /
271	12.1k	merge_sort_fromto (src, tmp, n1, tmp + n1);
272		/* Merge the two half results. */
273	12.1k	merge (tmp, n1, src + n1, n2, src);
274	12.1k	}
275	12.1k	break;
276	38.0k	}
277	38.0k	}
278
279		#undef ELEMENT
280		#undef COMPARE
281		#undef STATIC