--- /dev/null
+/* Plug-compatible replacement for UNIX qsort.
+ Copyright (C) 1989 Free Software Foundation, Inc.
+ Written by Douglas C. Schmidt (schmidt@ics.uci.edu)
+
+This file is part of GNU CC.
+
+GNU QSORT is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU QSORT 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU QSORT; see the file COPYING. If not, write to
+the Free the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+Boston, MA 02111-1307, USA. */
+
+/* Synched up with: FSF 19.28. */
+
+#ifdef sparc
+#include <alloca.h>
+#endif
+
+/* Invoke the comparison function, returns either 0, < 0, or > 0. */
+#define CMP(A,B) ((*cmp)((A),(B)))
+
+/* Byte-wise swap two items of size SIZE. */
+#define SWAP(A,B,SIZE) do {int sz = (SIZE); char *a = (A); char *b = (B); \
+ do { char _temp = *a;*a++ = *b;*b++ = _temp;} while (--sz);} while (0)
+
+/* Copy SIZE bytes from item B to item A. */
+#define COPY(A,B,SIZE) {int sz = (SIZE); do { *(A)++ = *(B)++; } while (--sz); }
+
+/* This should be replaced by a standard ANSI macro. */
+#define BYTES_PER_WORD 8
+
+/* The next 4 #defines implement a very fast in-line stack abstraction. */
+#define STACK_SIZE (BYTES_PER_WORD * sizeof (long))
+#define PUSH(LOW,HIGH) do {top->lo = LOW;top++->hi = HIGH;} while (0)
+#define POP(LOW,HIGH) do {LOW = (--top)->lo;HIGH = top->hi;} while (0)
+#define STACK_NOT_EMPTY (stack < top)
+
+/* Discontinue quicksort algorithm when partition gets below this size.
+ This particular magic number was chosen to work best on a Sun 4/260. */
+#define MAX_THRESH 4
+
+/* Stack node declarations used to store unfulfilled partition obligations. */
+typedef struct
+{
+ char *lo;
+ char *hi;
+} stack_node;
+
+/* Order size using quicksort. This implementation incorporates
+ four optimizations discussed in Sedgewick:
+
+ 1. Non-recursive, using an explicit stack of pointer that store the
+ next array partition to sort. To save time, this maximum amount
+ of space required to store an array of MAX_INT is allocated on the
+ stack. Assuming a 32-bit integer, this needs only 32 *
+ sizeof (stack_node) == 136 bits. Pretty cheap, actually.
+
+ 2. Chose the pivot element using a median-of-three decision tree.
+ This reduces the probability of selecting a bad pivot value and
+ eliminates certain extraneous comparisons.
+
+ 3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
+ insertion sort to order the MAX_THRESH items within each partition.
+ This is a big win, since insertion sort is faster for small, mostly
+ sorted array segments.
+
+ 4. The larger of the two sub-partitions is always pushed onto the
+ stack first, with the algorithm then concentrating on the
+ smaller partition. This *guarantees* no more than log (n)
+ stack size is needed (actually O(1) in this case)! */
+
+int
+qsort (base_ptr, total_elems, size, cmp)
+ char *base_ptr;
+ int total_elems;
+ int size;
+ int (*cmp)();
+{
+ /* Allocating SIZE bytes for a pivot buffer facilitates a better
+ algorithm below since we can do comparisons directly on the pivot. */
+ char *pivot_buffer = (char *) alloca (size);
+ int max_thresh = MAX_THRESH * size;
+
+ if (total_elems > MAX_THRESH)
+ {
+ char *lo = base_ptr;
+ char *hi = lo + size * (total_elems - 1);
+ stack_node stack[STACK_SIZE]; /* Largest size needed for 32-bit int!!! */
+ stack_node *top = stack + 1;
+
+ while (STACK_NOT_EMPTY)
+ {
+ char *left_ptr;
+ char *right_ptr;
+ {
+ char *pivot = pivot_buffer;
+ {
+ /* Select median value from among LO, MID, and HI. Rearrange
+ LO and HI so the three values are sorted. This lowers the
+ probability of picking a pathological pivot value and
+ skips a comparison for both the LEFT_PTR and RIGHT_PTR. */
+
+ char *mid = lo + size * ((hi - lo) / size >> 1);
+
+ if (CMP (mid, lo) < 0)
+ SWAP (mid, lo, size);
+ if (CMP (hi, mid) < 0)
+ SWAP (mid, hi, size);
+ else
+ goto jump_over;
+ if (CMP (mid, lo) < 0)
+ SWAP (mid, lo, size);
+ jump_over:
+ COPY (pivot, mid, size);
+ pivot = pivot_buffer;
+ }
+ left_ptr = lo + size;
+ right_ptr = hi - size;
+
+ /* Here's the famous ``collapse the walls'' section of quicksort.
+ Gotta like those tight inner loops! They are the main reason
+ that this algorithm runs much faster than others. */
+ do
+ {
+ while (CMP (left_ptr, pivot) < 0)
+ left_ptr += size;
+
+ while (CMP (pivot, right_ptr) < 0)
+ right_ptr -= size;
+
+ if (left_ptr < right_ptr)
+ {
+ SWAP (left_ptr, right_ptr, size);
+ left_ptr += size;
+ right_ptr -= size;
+ }
+ else if (left_ptr == right_ptr)
+ {
+ left_ptr += size;
+ right_ptr -= size;
+ break;
+ }
+ }
+ while (left_ptr <= right_ptr);
+
+ }
+
+ /* Set up pointers for next iteration. First determine whether
+ left and right partitions are below the threshold size. If so,
+ ignore one or both. Otherwise, push the larger partition's
+ bounds on the stack and continue sorting the smaller one. */
+
+ if ((right_ptr - lo) <= max_thresh)
+ {
+ if ((hi - left_ptr) <= max_thresh) /* Ignore both small partitions. */
+ POP (lo, hi);
+ else /* Ignore small left partition. */
+ lo = left_ptr;
+ }
+ else if ((hi - left_ptr) <= max_thresh) /* Ignore small right partition. */
+ hi = right_ptr;
+ else if ((right_ptr - lo) > (hi - left_ptr)) /* Push larger left partition indices. */
+ {
+ PUSH (lo, right_ptr);
+ lo = left_ptr;
+ }
+ else /* Push larger right partition indices. */
+ {
+ PUSH (left_ptr, hi);
+ hi = right_ptr;
+ }
+ }
+ }
+
+ /* Once the BASE_PTR array is partially sorted by quicksort the rest
+ is completely sorted using insertion sort, since this is efficient
+ for partitions below MAX_THRESH size. BASE_PTR points to the beginning
+ of the array to sort, and END_PTR points at the very last element in
+ the array (*not* one beyond it!). */
+
+#define MIN(X,Y) ((X) < (Y) ? (X) : (Y))
+
+ {
+ char *end_ptr = base_ptr + size * (total_elems - 1);
+ char *run_ptr;
+ char *tmp_ptr = base_ptr;
+ char *thresh = MIN (end_ptr, base_ptr + max_thresh);
+
+ /* Find smallest element in first threshold and place it at the
+ array's beginning. This is the smallest array element,
+ and the operation speeds up insertion sort's inner loop. */
+
+ for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
+ if (CMP (run_ptr, tmp_ptr) < 0)
+ tmp_ptr = run_ptr;
+
+ if (tmp_ptr != base_ptr)
+ SWAP (tmp_ptr, base_ptr, size);
+
+ /* Insertion sort, running from left-hand-side up to `right-hand-side.'
+ Pretty much straight out of the original GNU qsort routine. */
+
+ for (run_ptr = base_ptr + size; (tmp_ptr = run_ptr += size) <= end_ptr; )
+ {
+
+ while (CMP (run_ptr, tmp_ptr -= size) < 0)
+ ;
+
+ if ((tmp_ptr += size) != run_ptr)
+ {
+ char *trav;
+
+ for (trav = run_ptr + size; --trav >= run_ptr;)
+ {
+ char c = *trav;
+ char *hi, *lo;
+
+ for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
+ *hi = *lo;
+ *hi = c;
+ }
+ }
+
+ }
+ }
+ return 1;
+}
+
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