Create a branch for cmake bringup.

svn path=/branches/cmake-bringup/; revision=48236

lib/sdk/crt/stdlib/qsort.c

@@ -0,0 +1,242 @@
+/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
+
+#include <stdlib.h>
+#include <search.h>
+
+/*-
+ * Copyright (c) 1980, 1983 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that: (1) source distributions retain this entire copyright
+ * notice and comment, and (2) distributions including binaries display
+ * the following acknowledgement:  ``This product includes software
+ * developed by the University of California, Berkeley and its contributors''
+ * in the documentation or other materials provided with the distribution
+ * and in all advertising materials mentioning features or use of this
+ * software. Neither the name of the University nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ */
+
+/*
+ * qsort.c:
+ * Our own version of the system qsort routine which is faster by an average
+ * of 25%, with lows and highs of 10% and 50%.
+ * The THRESHold below is the insertion sort threshold, and has been adjusted
+ * for records of size 48 bytes.
+ * The MTHREShold is where we stop finding a better median.
+ */
+
+#define		THRESH		4		/* threshold for insertion */
+#define		MTHRESH		6		/* threshold for median */
+
+/*
+ * qst:
+ * Do a quicksort
+ * First, find the median element, and put that one in the first place as the
+ * discriminator.  (This "median" is just the median of the first, last and
+ * middle elements).  (Using this median instead of the first element is a big
+ * win).  Then, the usual partitioning/swapping, followed by moving the
+ * discriminator into the right place.  Then, figure out the sizes of the two
+ * partions, do the smaller one recursively and the larger one via a repeat of
+ * this code.  Stopping when there are less than THRESH elements in a partition
+ * and cleaning up with an insertion sort (in our caller) is a huge win.
+ * All data swaps are done in-line, which is space-losing but time-saving.
+ * (And there are only three places where this is done).
+ */
+
+static void
+qst(size_t size, int (__cdecl *compar)(const void*, const void*), char *base, char *max)
+{
+  char c, *i, *j, *jj;
+  int ii;
+  char *mid, *tmp;
+  int lo, hi;
+  size_t thresh;
+  size_t mthresh;
+
+  thresh = size * THRESH;
+  mthresh = size * MTHRESH;
+
+  /*
+   * At the top here, lo is the number of characters of elements in the
+   * current partition.  (Which should be max - base).
+   * Find the median of the first, last, and middle element and make
+   * that the middle element.  Set j to largest of first and middle.
+   * If max is larger than that guy, then it's that guy, else compare
+   * max with loser of first and take larger.  Things are set up to
+   * prefer the middle, then the first in case of ties.
+   */
+  lo = max - base;		/* number of elements as chars */
+  do	{
+    mid = i = base + size * ((lo / size) >> 1);
+    if (lo >= mthresh)
+    {
+      j = (compar((jj = base), i) > 0 ? jj : i);
+      if (compar(j, (tmp = max - size)) > 0)
+      {
+	/* switch to first loser */
+	j = (j == jj ? i : jj);
+	if (compar(j, tmp) < 0)
+	  j = tmp;
+      }
+      if (j != i)
+      {
+	ii = size;
+	do	{
+	  c = *i;
+	  *i++ = *j;
+	  *j++ = c;
+	} while (--ii);
+      }
+    }
+    /*
+     * Semi-standard quicksort partitioning/swapping
+     */
+    for (i = base, j = max - size; ; )
+    {
+      while (i < mid && compar(i, mid) <= 0)
+	i += size;
+      while (j > mid)
+      {
+	if (compar(mid, j) <= 0)
+	{
+	  j -= size;
+	  continue;
+	}
+	tmp = i + size;	/* value of i after swap */
+	if (i == mid)
+	{
+	  /* j <-> mid, new mid is j */
+	  mid = jj = j;
+	}
+	else
+	{
+	  /* i <-> j */
+	  jj = j;
+	  j -= size;
+	}
+	goto swap;
+      }
+      if (i == mid)
+      {
+	break;
+      }
+      else
+      {
+	/* i <-> mid, new mid is i */
+	jj = mid;
+	tmp = mid = i;		/* value of i after swap */
+	j -= size;
+      }
+    swap:
+      ii = size;
+      do	{
+	c = *i;
+	*i++ = *jj;
+	*jj++ = c;
+      } while (--ii);
+      i = tmp;
+    }
+    /*
+     * Look at sizes of the two partitions, do the smaller
+     * one first by recursion, then do the larger one by
+     * making sure lo is its size, base and max are update
+     * correctly, and branching back.  But only repeat
+     * (recursively or by branching) if the partition is
+     * of at least size THRESH.
+     */
+    i = (j = mid) + size;
+    if ((lo = j - base) <= (hi = max - i))
+    {
+      if (lo >= thresh)
+	qst(size, compar, base, j);
+      base = i;
+      lo = hi;
+    }
+    else
+    {
+      if (hi >= thresh)
+	qst(size, compar, i, max);
+      max = j;
+    }
+  } while (lo >= thresh);
+}
+
+/*
+ * qsort:
+ * First, set up some global parameters for qst to share.  Then, quicksort
+ * with qst(), and then a cleanup insertion sort ourselves.  Sound simple?
+ * It's not...
+ *
+ * @implemented
+ */
+void
+qsort(void *base0, size_t n, size_t size, int (__cdecl *compar)(const void*, const void*))
+{
+  char *base = (char *)base0;
+  char c, *i, *j, *lo, *hi;
+  char *min, *max;
+  size_t thresh;
+
+  if (n <= 1)
+    return;
+
+  size = size;
+  compar = compar;
+  thresh = size * THRESH;
+  max = base + n * size;
+  if (n >= THRESH)
+  {
+    qst(size, compar, base, max);
+    hi = base + thresh;
+  }
+  else
+  {
+    hi = max;
+  }
+  /*
+   * First put smallest element, which must be in the first THRESH, in
+   * the first position as a sentinel.  This is done just by searching
+   * the first THRESH elements (or the first n if n < THRESH), finding
+   * the min, and swapping it into the first position.
+   */
+  for (j = lo = base; (lo += size) < hi; )
+    if (compar(j, lo) > 0)
+      j = lo;
+  if (j != base)
+  {
+    /* swap j into place */
+    for (i = base, hi = base + size; i < hi; )
+    {
+      c = *j;
+      *j++ = *i;
+      *i++ = c;
+    }
+  }
+  /*
+   * With our sentinel in place, we now run the following hyper-fast
+   * insertion sort.  For each remaining element, min, from [1] to [n-1],
+   * set hi to the index of the element AFTER which this one goes.
+   * Then, do the standard insertion sort shift on a character at a time
+   * basis for each element in the frob.
+   */
+  for (min = base; (hi = min += size) < max; )
+  {
+    while (compar(hi -= size, min) > 0)
+      /* void */;
+    if ((hi += size) != min) {
+      for (lo = min + size; --lo >= min; )
+      {
+	c = *lo;
+	for (i = j = lo; (j -= size) >= hi; i = j)
+	  *i = *j;
+	*i = c;
+      }
+    }
+  }
+}