--- /dev/null
+/* Isaac Turner 29 April 2014 Public Domain */
+#ifndef SORT_R_H_
+#define SORT_R_H_
+
+#include <stdlib.h>
+#include <string.h>
+
+/*
+
+sort_r function to be exported.
+
+Parameters:
+ base is the array to be sorted
+ nel is the number of elements in the array
+ width is the size in bytes of each element of the array
+ compar is the comparison function
+ arg is a pointer to be passed to the comparison function
+
+void sort_r(void *base, size_t nel, size_t width,
+ int (*compar)(const void *_a, const void *_b, void *_arg),
+ void *arg);
+
+*/
+
+#define _SORT_R_INLINE inline
+
+#if (defined __APPLE__ || defined __MACH__ || defined __DARWIN__ || \
+ defined __FreeBSD__ || defined __DragonFly__)
+# define _SORT_R_BSD
+#elif (defined _GNU_SOURCE || defined __gnu_hurd__ || defined __GNU__ || \
+ defined __linux__ || defined __MINGW32__ || defined __GLIBC__)
+# define _SORT_R_LINUX
+#elif (defined _WIN32 || defined _WIN64 || defined __WINDOWS__)
+# define _SORT_R_WINDOWS
+# undef _SORT_R_INLINE
+# define _SORT_R_INLINE __inline
+#else
+ /* Using our own recursive quicksort sort_r_simple() */
+#endif
+
+#if (defined NESTED_QSORT && NESTED_QSORT == 0)
+# undef NESTED_QSORT
+#endif
+
+#define SORT_R_SWAP(a,b,tmp) ((tmp) = (a), (a) = (b), (b) = (tmp))
+
+/* swap a and b */
+/* a and b must not be equal! */
+static _SORT_R_INLINE void sort_r_swap(char *__restrict a, char *__restrict b,
+ size_t w)
+{
+ char tmp, *end = a+w;
+ for(; a < end; a++, b++) { SORT_R_SWAP(*a, *b, tmp); }
+}
+
+/* swap a, b iff a>b */
+/* a and b must not be equal! */
+/* __restrict is same as restrict but better support on old machines */
+static _SORT_R_INLINE int sort_r_cmpswap(char *__restrict a,
+ char *__restrict b, size_t w,
+ int (*compar)(const void *_a,
+ const void *_b,
+ void *_arg),
+ void *arg)
+{
+ if(compar(a, b, arg) > 0) {
+ sort_r_swap(a, b, w);
+ return 1;
+ }
+ return 0;
+}
+
+/*
+Swap consecutive blocks of bytes of size na and nb starting at memory addr ptr,
+with the smallest swap so that the blocks are in the opposite order. Blocks may
+be internally re-ordered e.g.
+
+ 12345ab -> ab34512
+ 123abc -> abc123
+ 12abcde -> deabc12
+*/
+static _SORT_R_INLINE void sort_r_swap_blocks(char *ptr, size_t na, size_t nb)
+{
+ if(na > 0 && nb > 0) {
+ if(na > nb) { sort_r_swap(ptr, ptr+na, nb); }
+ else { sort_r_swap(ptr, ptr+nb, na); }
+ }
+}
+
+/* Implement recursive quicksort ourselves */
+/* Note: quicksort is not stable, equivalent values may be swapped */
+static _SORT_R_INLINE void sort_r_simple(void *base, size_t nel, size_t w,
+ int (*compar)(const void *_a,
+ const void *_b,
+ void *_arg),
+ void *arg)
+{
+ char *b = (char *)base, *end = b + nel*w;
+
+ /* for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
+ printf("\n"); */
+
+ if(nel < 10) {
+ /* Insertion sort for arbitrarily small inputs */
+ char *pi, *pj;
+ for(pi = b+w; pi < end; pi += w) {
+ for(pj = pi; pj > b && sort_r_cmpswap(pj-w,pj,w,compar,arg); pj -= w) {}
+ }
+ }
+ else
+ {
+ /* nel > 6; Quicksort */
+
+ int cmp;
+ char *pl, *ple, *pr, *pre, *pivot;
+ char *last = b+w*(nel-1), *tmp;
+
+ /*
+ Use median of second, middle and second-last items as pivot.
+ First and last may have been swapped with pivot and therefore be extreme
+ */
+ char *l[3];
+ l[0] = b + w;
+ l[1] = b+w*(nel/2);
+ l[2] = last - w;
+
+ /* printf("pivots: %i, %i, %i\n", *(int*)l[0], *(int*)l[1], *(int*)l[2]); */
+
+ if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
+ if(compar(l[1],l[2],arg) > 0) {
+ SORT_R_SWAP(l[1], l[2], tmp);
+ if(compar(l[0],l[1],arg) > 0) { SORT_R_SWAP(l[0], l[1], tmp); }
+ }
+
+ /* swap mid value (l[1]), and last element to put pivot as last element */
+ if(l[1] != last) { sort_r_swap(l[1], last, w); }
+
+ /*
+ pl is the next item on the left to be compared to the pivot
+ pr is the last item on the right that was compared to the pivot
+ ple is the left position to put the next item that equals the pivot
+ ple is the last right position where we put an item that equals the pivot
+
+ v- end (beyond the array)
+ EEEEEELLLLLLLLuuuuuuuuGGGGGGGEEEEEEEE.
+ ^- b ^- ple ^- pl ^- pr ^- pre ^- last (where the pivot is)
+
+ Pivot comparison key:
+ E = equal, L = less than, u = unknown, G = greater than, E = equal
+ */
+ pivot = last;
+ ple = pl = b;
+ pre = pr = last;
+
+ /*
+ Strategy:
+ Loop into the list from the left and right at the same time to find:
+ - an item on the left that is greater than the pivot
+ - an item on the right that is less than the pivot
+ Once found, they are swapped and the loop continues.
+ Meanwhile items that are equal to the pivot are moved to the edges of the
+ array.
+ */
+ while(pl < pr) {
+ /* Move left hand items which are equal to the pivot to the far left.
+ break when we find an item that is greater than the pivot */
+ for(; pl < pr; pl += w) {
+ cmp = compar(pl, pivot, arg);
+ if(cmp > 0) { break; }
+ else if(cmp == 0) {
+ if(ple < pl) { sort_r_swap(ple, pl, w); }
+ ple += w;
+ }
+ }
+ /* break if last batch of left hand items were equal to pivot */
+ if(pl >= pr) { break; }
+ /* Move right hand items which are equal to the pivot to the far right.
+ break when we find an item that is less than the pivot */
+ for(; pl < pr; ) {
+ pr -= w; /* Move right pointer onto an unprocessed item */
+ cmp = compar(pr, pivot, arg);
+ if(cmp == 0) {
+ pre -= w;
+ if(pr < pre) { sort_r_swap(pr, pre, w); }
+ }
+ else if(cmp < 0) {
+ if(pl < pr) { sort_r_swap(pl, pr, w); }
+ pl += w;
+ break;
+ }
+ }
+ }
+
+ pl = pr; /* pr may have gone below pl */
+
+ /*
+ Now we need to go from: EEELLLGGGGEEEE
+ to: LLLEEEEEEEGGGG
+
+ Pivot comparison key:
+ E = equal, L = less than, u = unknown, G = greater than, E = equal
+ */
+ sort_r_swap_blocks(b, ple-b, pl-ple);
+ sort_r_swap_blocks(pr, pre-pr, end-pre);
+
+ /*for(size_t i=0; i<nel; i++) {printf("%4i", *(int*)(b + i*sizeof(int)));}
+ printf("\n");*/
+
+ sort_r_simple(b, (pl-ple)/w, w, compar, arg);
+ sort_r_simple(end-(pre-pr), (pre-pr)/w, w, compar, arg);
+ }
+}
+
+
+#if defined NESTED_QSORT
+
+ static _SORT_R_INLINE void sort_r(void *base, size_t nel, size_t width,
+ int (*compar)(const void *_a,
+ const void *_b,
+ void *aarg),
+ void *arg)
+ {
+ int nested_cmp(const void *a, const void *b)
+ {
+ return compar(a, b, arg);
+ }
+
+ qsort(base, nel, width, nested_cmp);
+ }
+
+#else /* !NESTED_QSORT */
+
+ /* Declare structs and functions */
+
+ #if defined _SORT_R_BSD
+
+ /* Ensure qsort_r is defined */
+ extern void qsort_r(void *base, size_t nel, size_t width, void *thunk,
+ int (*compar)(void *_thunk,
+ const void *_a, const void *_b));
+
+ #endif
+
+ #if defined _SORT_R_BSD || defined _SORT_R_WINDOWS
+
+ /* BSD (qsort_r), Windows (qsort_s) require argument swap */
+
+ struct sort_r_data
+ {
+ void *arg;
+ int (*compar)(const void *_a, const void *_b, void *_arg);
+ };
+
+ static _SORT_R_INLINE int sort_r_arg_swap(void *s,
+ const void *a, const void *b)
+ {
+ struct sort_r_data *ss = (struct sort_r_data*)s;
+ return (ss->compar)(a, b, ss->arg);
+ }
+
+ #endif
+
+ #if defined _SORT_R_LINUX
+
+ typedef int(* __compar_d_fn_t)(const void *, const void *, void *);
+ extern void qsort_r(void *base, size_t nel, size_t width,
+ __compar_d_fn_t __compar, void *arg)
+ __attribute__((nonnull (1, 4)));
+
+ #endif
+
+ /* implementation */
+
+ static _SORT_R_INLINE void sort_r(void *base, size_t nel, size_t width,
+ int (*compar)(const void *_a,
+ const void *_b, void *_arg),
+ void *arg)
+ {
+ #if defined _SORT_R_LINUX
+
+ #if defined __GLIBC__ && ((__GLIBC__ < 2) || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 8))
+
+ /* no qsort_r in glibc before 2.8, need to use nested qsort */
+ sort_r_simple(base, nel, width, compar, arg);
+
+ #else
+
+ qsort_r(base, nel, width, compar, arg);
+
+ #endif
+
+ #elif defined _SORT_R_BSD
+
+ struct sort_r_data tmp;
+ tmp.arg = arg;
+ tmp.compar = compar;
+ qsort_r(base, nel, width, &tmp, sort_r_arg_swap);
+
+ #elif defined _SORT_R_WINDOWS
+
+ struct sort_r_data tmp;
+ tmp.arg = arg;
+ tmp.compar = compar;
+ qsort_s(base, nel, width, sort_r_arg_swap, &tmp);
+
+ #else
+
+ /* Fall back to our own quicksort implementation */
+ sort_r_simple(base, nel, width, compar, arg);
+
+ #endif
+ }
+
+#endif /* !NESTED_QSORT */
+
+#undef _SORT_R_INLINE
+#undef _SORT_R_WINDOWS
+#undef _SORT_R_LINUX
+#undef _SORT_R_BSD
+
+#endif /* SORT_R_H_ */
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