qsort.c

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/*-
 * Copyright (c) 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdlib.h>
#include <string.h>
#include <strings.h>

#ifdef I_AM_QSORT_R
typedef int cmp_t(void*, const void*, const void*);
#else
typedef int cmp_t(const void*, const void*);
#endif
static inline char* med3(char* a, char* b, char* c, cmp_t* cmd, void* thunk)
    __attribute__((always_inline));
static inline void swapfunc(char* a, char* b, size_t n, size_t swaptype)
    __attribute__((always_inline));

#define min(a, b) (a) < (b) ? a : b

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) \
    {                                   \
        size_t i = (n) / sizeof(TYPE);  \
        TYPE* pi = (TYPE*)(parmi);      \
        TYPE* pj = (TYPE*)(parmj);      \
        do                              \
        {                               \
            TYPE t = *pi;               \
            *pi++ = *pj;                \
            *pj++ = t;                  \
        } while(--i > 0);               \
    }

#define SWAPINIT(a, es) \
    swaptype = (uintptr_t)a % sizeof(long) || es % sizeof(long) ? 2 : es == sizeof(long) ? 0 : 1;

static inline void swapfunc(char* a, char* b, size_t n, size_t swaptype)
{
    if(swaptype == 0)
    {
        long t = *(long*)(void*)(a);
        *(long*)(void*)(a) = *(long*)(void*)(b);
        *(long*)(void*)(b) = t;
    }
    else if(swaptype == 1)
    {
        swapcode(long, (void*)a, (void*)b, n)
    }
    else
    {
        swapcode(char, a, b, n)
    }
}

#define swap(a, b) swapfunc(a, b, (size_t)es, (size_t)swaptype)

// this switch exists because we needed to clean up
// the swap() macro, and vecswap has a different 0 meaning.
// To force the right swapfunc behavior we force it to 1 if it's
#define vecswap(a, b, n) \
    if((n) > 0)          \
    swapfunc(a, b, n, swaptype ? (size_t)swaptype : 1)

#ifdef I_AM_QSORT_R
#define CMP(t, x, y) (cmp((t), (x), (y)))
#else
#define CMP(t, x, y) (cmp((x), (y)))
#endif

static inline char* med3(char* a, char* b, char* c, cmp_t* cmp,
                         void* thunk
#ifndef I_AM_QSORT_R
                         __attribute__((unused))
#endif
)
{
    return CMP(thunk, a, b) < 0 ? (CMP(thunk, b, c) < 0 ? b : (CMP(thunk, a, c) < 0 ? c : a))
                                : (CMP(thunk, b, c) > 0 ? b : (CMP(thunk, a, c) < 0 ? a : c));
}

#ifdef __LP64__
#define DEPTH(x) (2 * (flsl((long)(x)) - 1))
#else /* !__LP64__ */
#define DEPTH(x) (2 * (fls((int)(x)) - 1))
#endif /* __LP64__ */

static void _qsort(void* a, size_t n, size_t es,
#ifdef I_AM_QSORT_R
                   void* thunk,
#else
#define thunk NULL
#endif
                   cmp_t* cmp, int depth_limit)
{
    char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
    size_t d, r, swap_cnt;
    int cmp_result;
    int swaptype;

loop:
    if(depth_limit-- <= 0)
    {
#ifdef I_AM_QSORT_R
        heapsort_r(a, n, es, thunk, cmp);
#else
        heapsort(a, n, es, cmp);
#endif
        return;
    }
    SWAPINIT(a, es);
    swap_cnt = 0;
    if(n < 7)
    {
        for(pm = (char*)a + es; pm < (char*)a + n * es; pm += es)
        {
            for(pl = pm; pl > (char*)a && CMP(thunk, pl - es, pl) > 0; pl -= es)
            {
                swap(pl, pl - es);
            }
        }
        return;
    }
    pm = (char*)a + (n / 2) * es;
    if(n > 7)
    {
        pl = a;
        pn = (char*)a + (n - 1) * es;
        if(n > 40)
        {
            d = (n / 8) * es;
            pl = med3(pl, pl + d, pl + 2 * d, cmp, thunk);
            pm = med3(pm - d, pm, pm + d, cmp, thunk);
            pn = med3(pn - 2 * d, pn - d, pn, cmp, thunk);
        }
        pm = med3(pl, pm, pn, cmp, thunk);
    }
    swap(a, (void*)pm);
    pa = pb = (char*)a + es;

    pc = pd = (char*)a + (n - 1) * es;
    for(;;)
    {
        while(pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0)
        {
            if(cmp_result == 0)
            {
                swap_cnt = 1;
                swap(pa, pb);
                pa += es;
            }
            pb += es;
        }
        while(pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0)
        {
            if(cmp_result == 0)
            {
                swap_cnt = 1;
                swap(pc, pd);
                pd -= es;
            }
            pc -= es;
        }
        if(pb > pc)
        {
            break;
        }
        swap(pb, pc);
        swap_cnt = 1;
        pb += es;
        pc -= es;
    }

    pn = (char*)a + n * es;
    r = min((uintptr_t)pa - (uintptr_t)a, (uintptr_t)pb - (uintptr_t)pa);
    vecswap(a, pb - r, r);
    r = min((uintptr_t)pd - (uintptr_t)pc, (uintptr_t)pn - (uintptr_t)pd - (uintptr_t)es);
    vecswap(pb, pn - r, r);

    if(swap_cnt == 0)
    { /* Switch to insertion sort */
        r = 1 + n / 4; /* n >= 7, so r >= 2 */
        for(pm = (char*)a + es; pm < (char*)a + n * es; pm += es)
        {
            for(pl = pm; pl > (char*)a && CMP(thunk, pl - es, pl) > 0; pl -= es)
            {
                swap(pl, pl - es);
                if(++swap_cnt > r)
                {
                    goto nevermind;
                }
            }
        }
        return;
    }

nevermind:
    if((r = (uintptr_t)pb - (uintptr_t)pa) > es)
    {
#ifdef I_AM_QSORT_R
        _qsort(a, r / es, es, thunk, cmp, depth_limit);
#else
        _qsort(a, r / es, es, cmp, depth_limit);
#endif
    }
    if((r = (uintptr_t)pd - (uintptr_t)pc) > es)
    {
        /* Iterate rather than recurse to save stack space */
        a = pn - r;
        n = r / es;
        goto loop;
    }
    /*      qsort(pn - r, r / es, es, cmp);*/
}

void
#ifdef I_AM_QSORT_R
qsort_r(void *a, size_t n, size_t es, void *thunk, cmp_t *cmp)
#else
qsort(void *a, size_t n, size_t es, cmp_t *cmp)
#endif
{
    _qsort(a, n, es,
#ifdef I_AM_QSORT_R
           thunk,
#endif
           cmp, DEPTH(n));
}