/src/libunistring/lib/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: 2023-03-26 08:33

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