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Diffstat (limited to 'cpukit/libc/search/qsort.c')
| -rw-r--r-- | cpukit/libc/search/qsort.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/cpukit/libc/search/qsort.c b/cpukit/libc/search/qsort.c new file mode 100644 index 0000000000..b53400aa8e --- /dev/null +++ b/cpukit/libc/search/qsort.c @@ -0,0 +1,345 @@ +/* +FUNCTION +<<qsort>>---sort an array + +INDEX + qsort + +SYNOPSIS + #include <stdlib.h> + void qsort(void *<[base]>, size_t <[nmemb]>, size_t <[size]>, + int (*<[compar]>)(const void *, const void *) ); + +DESCRIPTION +<<qsort>> sorts an array (beginning at <[base]>) of <[nmemb]> objects. +<[size]> describes the size of each element of the array. + +You must supply a pointer to a comparison function, using the argument +shown as <[compar]>. (This permits sorting objects of unknown +properties.) Define the comparison function to accept two arguments, +each a pointer to an element of the array starting at <[base]>. The +result of <<(*<[compar]>)>> must be negative if the first argument is +less than the second, zero if the two arguments match, and positive if +the first argument is greater than the second (where ``less than'' and +``greater than'' refer to whatever arbitrary ordering is appropriate). + +The array is sorted in place; that is, when <<qsort>> returns, the +array elements beginning at <[base]> have been reordered. + +RETURNS +<<qsort>> does not return a result. + +PORTABILITY +<<qsort>> is required by ANSI (without specifying the sorting algorithm). +*/ + +/*- + * 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. + * 3. 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 <_ansi.h> +#include <sys/cdefs.h> +#include <stdlib.h> + +#ifndef __GNUC__ +#define inline +#endif + +#if defined(I_AM_QSORT_R) +typedef int cmp_t(void *, const void *, const void *); +#elif defined(I_AM_GNU_QSORT_R) +typedef int cmp_t(const void *, const void *, void *); +#else +typedef int cmp_t(const void *, const void *); +#endif +static inline char *med3 (char *, char *, char *, cmp_t *, void *); +static inline void swapfunc (char *, char *, int, int); + +#define min(a, b) (a) < (b) ? a : b + +/* + * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function". + */ +#define swapcode(TYPE, parmi, parmj, n) { \ + long 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 = ((char *)a - (char *)0) % sizeof(long) || \ + es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1; + +static inline void +swapfunc (char *a, + char *b, + int n, + int swaptype) +{ + if(swaptype <= 1) + swapcode(long, a, b, n) + else + swapcode(char, a, b, n) +} + +#define swap(a, b) \ + if (swaptype == 0) { \ + long t = *(long *)(a); \ + *(long *)(a) = *(long *)(b); \ + *(long *)(b) = t; \ + } else \ + swapfunc(a, b, es, swaptype) + +#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype) + +#if defined(I_AM_QSORT_R) +#define CMP(t, x, y) (cmp((t), (x), (y))) +#elif defined(I_AM_GNU_QSORT_R) +#define CMP(t, x, y) (cmp((x), (y), (t))) +#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 +#if !defined(I_AM_QSORT_R) && !defined(I_AM_GNU_QSORT_R) +__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 )); +} + +/* + * Classical function call recursion wastes a lot of stack space. Each + * recursion level requires a full stack frame comprising all local variables + * and additional space as dictated by the processor calling convention. + * + * This implementation instead stores the variables that are unique for each + * recursion level in a parameter stack array, and uses iteration to emulate + * recursion. Function call recursion is not used until the array is full. + * + * To ensure the stack consumption isn't worsened by this design, the size of + * the parameter stack array is chosen to be similar to the stack frame + * excluding the array. Each function call recursion level can handle this + * number of iterative recursion levels. + */ +#define PARAMETER_STACK_LEVELS 8u + +#if defined(I_AM_QSORT_R) +void +__bsd_qsort_r (void *a, + size_t n, + size_t es, + void *thunk, + cmp_t *cmp) +#elif defined(I_AM_GNU_QSORT_R) +void +qsort_r (void *a, + size_t n, + size_t es, + cmp_t *cmp, + void *thunk) +#else +#define thunk NULL +void +qsort (void *a, + size_t n, + size_t es, + cmp_t *cmp) +#endif +{ + char *pa, *pb, *pc, *pd, *pl, *pm, *pn; + size_t d, r; + int cmp_result; + int swaptype, swap_cnt; + size_t recursion_level = 0; + struct { void *a; size_t n; } parameter_stack[PARAMETER_STACK_LEVELS]; + + SWAPINIT(a, es); +loop: swap_cnt = 0; + if (n < 7) { + /* Short arrays are insertion sorted. */ + 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); + goto pop; + } + + /* Select a pivot element, move it to the left. */ + 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, pm); + + /* + * Sort the array relative the pivot in four ranges as follows: + * { elems == pivot, elems < pivot, elems > pivot, elems == pivot } + */ + pa = pb = (char *) a + es; + pc = pd = (char *) a + (n - 1) * es; + for (;;) { + /* Scan left to right stopping at first element > pivot. */ + while (pb <= pc && (cmp_result = CMP(thunk, pb, a)) <= 0) { + /* Move elements == pivot to the left (to pa) */ + if (cmp_result == 0) { + swap_cnt = 1; + swap(pa, pb); + pa += es; + } + pb += es; + } + /* Scan right to left stopping at first element < pivot. */ + while (pb <= pc && (cmp_result = CMP(thunk, pc, a)) >= 0) { + /* Move elements == pivot to the right (to pd) */ + if (cmp_result == 0) { + swap_cnt = 1; + swap(pc, pd); + pd -= es; + } + pc -= es; + } + if (pb > pc) + break; + /* The scan has found two elements to swap with each other. */ + swap(pb, pc); + swap_cnt = 1; + pb += es; + pc -= es; + } + if (swap_cnt == 0) { /* Switch to insertion sort */ + 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); + goto pop; + } + + /* + * Rearrange the array in three parts sorted like this: + * { elements < pivot, elements == pivot, elements > pivot } + */ + pn = (char *) a + n * es; + r = min(pa - (char *)a, pb - pa); + vecswap(a, pb - r, r); + r = min(pd - pc, pn - pd - es); + vecswap(pb, pn - r, r); + d = pb - pa; /* d = Size of left part. */ + r = pd - pc; /* r = Size of right part. */ + pn -= r; /* pn = Base of right part. */ + + /* + * Check which of the left and right parts are larger. + * Set (a, n) to (base, size) of the larger part. + * Set (pa, r) to (base, size) of the smaller part. + */ + if (r > d) { /* Right part is the larger part */ + pa = a; + a = pn; + n = r; + r = d; + } + else { /* Left part is the larger part, or both are equal. */ + pa = pn; + n = d; + } + + /* + * The left and right parts each need further sorting if they + * contain two elements or more. If both need sorting we use + * recursion to sort the smaller part and save the larger part + * to be sorted by iteration after the recursion. + * Using recursion only for the smaller part guarantees a + * recursion depth that is bounded to be less than (log2(n)). + */ + if (r > es) { /* Smaller part > 1 element. Both parts need sorting. */ + if (recursion_level < PARAMETER_STACK_LEVELS) { + /* + * The smaller part needs to be recursively sorted + * before the larger part is sorted. To avoid function + * call recursion the parameters for the larger part + * are pushed on the parameter_stack array. The smaller + * part is sorted using iteration and the larger part + * will be sorted when the parameter_stack is popped + * after the smaller part has been sorted. + */ + parameter_stack[recursion_level].a = a; + parameter_stack[recursion_level].n = n / es; + recursion_level++; + a = pa; + n = r / es; + goto loop; + } + else { + /* + * The parameter_stack array is full. The smaller part + * is sorted using function call recursion. The larger + * part will be sorted after the function call returns. + */ +#if defined(I_AM_QSORT_R) + __bsd_qsort_r(pa, r / es, es, thunk, cmp); +#elif defined(I_AM_GNU_QSORT_R) + qsort_r(pa, r / es, es, cmp, thunk); +#else + qsort(pa, r / es, es, cmp); +#endif + } + } + if (n > es) { /* The larger part needs sorting. Iterate to sort. */ + n = n / es; + goto loop; + } + /* Both left and right parts are one element or less - level done. */ +pop: + if (recursion_level != 0) { + recursion_level--; + a = parameter_stack[recursion_level].a; + n = parameter_stack[recursion_level].n; + goto loop; + } +} |