--- /dev/null
+/*
+ * Copyright (c) 2015 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+ * Imported into CLIB by Eliot Dresselhaus from:
+ *
+ * This file is part of
+ * MakeIndex - A formatter and format independent index processor
+ *
+ * This file is public domain software donated by
+ * Nelson Beebe (beebe@science.utah.edu).
+ *
+ * modifications copyright (c) 2003 Cisco Systems, Inc.
+ */
+
+#include <vppinfra/clib.h>
+
+/*
+ * 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 */
+
+typedef struct
+{
+ word qsz; /* size of each record */
+ word thresh; /* THRESHold in chars */
+ word mthresh; /* MTHRESHold in chars */
+ int (*qcmp) (const void *, const void *); /* the comparison routine */
+} qst_t;
+
+static void qst (qst_t * q, char *base, char *max);
+
+/*
+ * qqsort: 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...
+ */
+
+void
+qsort (void *base, uword n, uword size,
+ int (*compar) (const void *, const void *))
+{
+ char *i;
+ char *j;
+ char *lo;
+ char *hi;
+ char *min;
+ char c;
+ char *max;
+ qst_t _q, *q = &_q;
+
+ if (n <= 1)
+ return;
+
+ q->qsz = size;
+ q->qcmp = compar;
+ q->thresh = q->qsz * THRESH;
+ q->mthresh = q->qsz * MTHRESH;
+ max = base + n * q->qsz;
+ if (n >= THRESH)
+ {
+ qst (q, base, max);
+ hi = base + q->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 += q->qsz) < hi;)
+ {
+ if ((*compar) (j, lo) > 0)
+ j = lo;
+ }
+ if (j != base)
+ { /* swap j into place */
+ for (i = base, hi = base + q->qsz; 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 += q->qsz) < max;)
+ {
+ while ((*q->qcmp) (hi -= q->qsz, min) > 0);
+ if ((hi += q->qsz) != min)
+ {
+ for (lo = min + q->qsz; --lo >= min;)
+ {
+ c = *lo;
+ for (i = j = lo; (j -= q->qsz) >= hi; i = j)
+ *i = *j;
+ *i = c;
+ }
+ }
+ }
+}
+
+
+
+/*
+ * 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 (qst_t * q, char *base, char *max)
+{
+ char *i;
+ char *j;
+ char *jj;
+ char *mid;
+ int ii;
+ char c;
+ char *tmp;
+ int lo;
+ int hi;
+ int qsz = q->qsz;
+
+ lo = (int) (max - base); /* number of elements as chars */
+ do
+ {
+ /*
+ * 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.
+ */
+ mid = i = base + qsz * ((unsigned) (lo / qsz) >> 1);
+ if (lo >= q->mthresh)
+ {
+ j = ((*q->qcmp) ((jj = base), i) > 0 ? jj : i);
+ if ((*q->qcmp) (j, (tmp = max - qsz)) > 0)
+ {
+ /* switch to first loser */
+ j = (j == jj ? i : jj);
+ if ((*q->qcmp) (j, tmp) < 0)
+ j = tmp;
+ }
+ if (j != i)
+ {
+ ii = qsz;
+ do
+ {
+ c = *i;
+ *i++ = *j;
+ *j++ = c;
+ }
+ while (--ii);
+ }
+ }
+ /* Semi-standard quicksort partitioning/swapping */
+ for (i = base, j = max - qsz;;)
+ {
+ while (i < mid && (*q->qcmp) (i, mid) <= 0)
+ i += qsz;
+ while (j > mid)
+ {
+ if ((*q->qcmp) (mid, j) <= 0)
+ {
+ j -= qsz;
+ continue;
+ }
+ tmp = i + qsz; /* value of i after swap */
+ if (i == mid)
+ { /* j <-> mid, new mid is j */
+ mid = jj = j;
+ }
+ else
+ { /* i <-> j */
+ jj = j;
+ j -= qsz;
+ }
+ goto swap;
+ }
+ if (i == mid)
+ {
+ break;
+ }
+ else
+ { /* i <-> mid, new mid is i */
+ jj = mid;
+ tmp = mid = i; /* value of i after swap */
+ j -= qsz;
+ }
+ swap:
+ ii = qsz;
+ 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) + qsz;
+ if ((lo = (int) (j - base)) <= (hi = (int) (max - i)))
+ {
+ if (lo >= q->thresh)
+ qst (q, base, j);
+ base = i;
+ lo = hi;
+ }
+ else
+ {
+ if (hi >= q->thresh)
+ qst (q, i, max);
+ max = j;
+ }
+ }
+ while (lo >= q->thresh);
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
Code Review / vpp.git / blobdiff