xpcom/ds/nsQuickSort.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2
   3 /*-
   4  * Copyright (c) 1992, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 /* We need this because Solaris' version of qsort is broken and
  33  * causes array bounds reads.
  34  */
  35
  36 #include <stdlib.h>
  37 #include "nsAlgorithm.h"
  38 #include "nsQuickSort.h"
  39
  40 extern "C" {
  41
  42 #if !defined(DEBUG) && (defined(__cplusplus) || defined(__gcc))
  43 #  ifndef INLINE
  44 #    define INLINE inline
  45 #  endif
  46 #else
  47 #  define INLINE
  48 #endif
  49
  50 typedef int cmp_t(const void*, const void*, void*);
  51 static INLINE char* med3(char*, char*, char*, cmp_t*, void*);
  52 static INLINE void swapfunc(char*, char*, int, int);
  53
  54 /*
  55  * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
  56  */
  57 #define swapcode(TYPE, parmi, parmj, n) \
  58   {                                     \
  59     long i = (n) / sizeof(TYPE);        \
  60     TYPE* pi = (TYPE*)(parmi);          \
  61     TYPE* pj = (TYPE*)(parmj);          \
  62     do {                                \
  63       TYPE t = *pi;                     \
  64       *pi++ = *pj;                      \
  65       *pj++ = t;                        \
  66     } while (--i > 0);                  \
  67   }
  68
  69 #define SWAPINIT(a, es)                                                    \
  70   swaptype = ((char*)a - (char*)0) % sizeof(long) || es % sizeof(long) ? 2 \
  71              : es == sizeof(long)                                      ? 0 \
  72                                                                        : 1;
  73
  74 static INLINE void swapfunc(char* a, char* b, int n, int swaptype) {
  75   if (swaptype <= 1) swapcode(long, a, b, n) else swapcode(char, a, b, n)
  76 }
  77
  78 #define swap(a, b)             \
  79   if (swaptype == 0) {         \
  80     long t = *(long*)(a);      \
  81     *(long*)(a) = *(long*)(b); \
  82     *(long*)(b) = t;           \
  83   } else                       \
  84     swapfunc((char*)a, (char*)b, (int)es, swaptype)
  85
  86 #define vecswap(a, b, n) \
  87   if ((n) > 0) swapfunc((char*)a, (char*)b, (int)n, swaptype)
  88
  89 static INLINE char* med3(char* a, char* b, char* c, cmp_t* cmp, void* data) {
  90   return cmp(a, b, data) < 0
  91              ? (cmp(b, c, data) < 0 ? b : (cmp(a, c, data) < 0 ? c : a))
  92              : (cmp(b, c, data) > 0 ? b : (cmp(a, c, data) < 0 ? a : c));
  93 }
  94
  95 void NS_QuickSort(void* a, unsigned int n, unsigned int es, cmp_t* cmp,
  96                   void* data) {
  97   char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
  98   int d, r, swaptype;
  99
 100 loop:
 101   SWAPINIT(a, es);
 102   /* Use insertion sort when input is small */
 103   if (n < 7) {
 104     for (pm = (char*)a + es; pm < (char*)a + n * es; pm += es)
 105       for (pl = pm; pl > (char*)a && cmp(pl - es, pl, data) > 0; pl -= es)
 106         swap(pl, pl - es);
 107     return;
 108   }
 109   /* Choose pivot */
 110   pm = (char*)a + (n / 2) * es;
 111   if (n > 7) {
 112     pl = (char*)a;
 113     pn = (char*)a + (n - 1) * es;
 114     if (n > 40) {
 115       d = (n / 8) * es;
 116       pl = med3(pl, pl + d, pl + 2 * d, cmp, data);
 117       pm = med3(pm - d, pm, pm + d, cmp, data);
 118       pn = med3(pn - 2 * d, pn - d, pn, cmp, data);
 119     }
 120     pm = med3(pl, pm, pn, cmp, data);
 121   }
 122   swap(a, pm);
 123   pa = pb = (char*)a + es;
 124
 125   pc = pd = (char*)a + (n - 1) * es;
 126   /* loop invariants:
 127    * [a, pa) = pivot
 128    * [pa, pb) < pivot
 129    * [pb, pc + es) unprocessed
 130    * [pc + es, pd + es) > pivot
 131    * [pd + es, pn) = pivot
 132    */
 133   for (;;) {
 134     while (pb <= pc && (r = cmp(pb, a, data)) <= 0) {
 135       if (r == 0) {
 136         swap(pa, pb);
 137         pa += es;
 138       }
 139       pb += es;
 140     }
 141     while (pb <= pc && (r = cmp(pc, a, data)) >= 0) {
 142       if (r == 0) {
 143         swap(pc, pd);
 144         pd -= es;
 145       }
 146       pc -= es;
 147     }
 148     if (pb > pc) break;
 149     swap(pb, pc);
 150     pb += es;
 151     pc -= es;
 152   }
 153   /* Move pivot values */
 154   pn = (char*)a + n * es;
 155   r = XPCOM_MIN(pa - (char*)a, pb - pa);
 156   vecswap(a, pb - r, r);
 157   r = XPCOM_MIN<size_t>(pd - pc, pn - pd - es);
 158   vecswap(pb, pn - r, r);
 159   /* Recursively process partitioned items */
 160   if ((r = pb - pa) > (int)es) NS_QuickSort(a, r / es, es, cmp, data);
 161   if ((r = pd - pc) > (int)es) {
 162     /* Iterate rather than recurse to save stack space */
 163     a = pn - r;
 164     n = r / es;
 165     goto loop;
 166   }
 167   /*            NS_QuickSort(pn - r, r / es, es, cmp, data);*/
 168 }
 169 }
 170
 171 #undef INLINE
 172 #undef swapcode
 173 #undef SWAPINIT
 174 #undef swap
 175 #undef vecswap