quicksort.cpp

Torus 3D Engine is an open-source OpenGL ES 3D Engine for creating your own games in BREW environmen

//////////////////////////////////////////////////////////////////////
//
// QUICKSORT REPLACEMENT (not available on Brew v2.0)
//
// Vander Nunes, 2005.
//
//////////////////////////////////////////////////////////////////////

#include "../vfs_defs.h"
#include "Quicksort.h"


void quicksort(void *base, unsigned int num, unsigned int width, int (*comp)(const void *, const void *))
{
  char *lo, *hi;
  char *mid;
  char *loguy, *higuy;
  unsigned int size;
  char *lostk[30], *histk[30];
  int stkptr;

  if (num < 2 || width == 0) return;
  stkptr = 0;

  lo = (char*)base;
  hi = (char *) base + width * (num - 1);

recurse:
  size = (hi - lo) / width + 1;

  if (size <= QUICK_CUTOFF) 
  {
    shortsort(lo, hi, width, comp);
  }
  else 
  {
    mid = lo + (size / 2) * width;
    swap(mid, lo, width);

    loguy = lo;
    higuy = hi + width;

    for (;;) 
    {
      do { loguy += width; } while (loguy <= hi && comp(loguy, lo) <= 0);
      do { higuy -= width; } while (higuy > lo && comp(higuy, lo) >= 0);
      if (higuy < loguy) break;
      swap(loguy, higuy, width);
    }

    swap(lo, higuy, width);

    if (higuy - 1 - lo >= hi - loguy) 
    {
      if (lo + width < higuy) 
      {
        lostk[stkptr] = lo;
        histk[stkptr] = higuy - width;
        ++stkptr;
      }

      if (loguy < hi) 
      {
        lo = loguy;
        goto recurse;
      }
    }
    else
    {
      if (loguy < hi) 
      {
        lostk[stkptr] = loguy;
        histk[stkptr] = hi;
        ++stkptr;
      }

      if (lo + width < higuy) 
      {
        hi = higuy - width;
        goto recurse;
      }
    }
  }

  --stkptr;
  if (stkptr >= 0) 
  {
    lo = lostk[stkptr];
    hi = histk[stkptr];
    goto recurse;
  }
  else
    return;
}

static void shortsort(char *lo, char *hi, unsigned int width, int (*comp)(const void *, const void *))
{
  char *p, *max;

  while (hi > lo) 
  {
    max = lo;
    for (p = lo+width; p <= hi; p += width) if (comp(p, max) > 0) swap(max, hi, width);
    hi -= width;
  }
}

static void swap(char *a, char *b, unsigned int width)
{
  char tmp;

  if (a != b)
  {
    while (width--) 
    {
      tmp = *a;
      *a++ = *b;
      *b++ = tmp;
    }
  }
}

int exp_cmp(const void *a, const void *b)
{
	return(API_STRNCMP((char *) a, (char *) b, 2));
}