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Diffstat (limited to 'lib/support/sort_r.h')
| -rw-r--r-- | lib/support/sort_r.h | 325 |
1 files changed, 325 insertions, 0 deletions
diff --git a/lib/support/sort_r.h b/lib/support/sort_r.h new file mode 100644 index 0000000..8473ca8 --- /dev/null +++ b/lib/support/sort_r.h @@ -0,0 +1,325 @@ +/* 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 HAVE_GNU_QSORT_R) +# define _SORT_R_GNU +#elif (defined HAVE_BSD_QSORT_R) +# define _SORT_R_BSD +#elif (defined __gnu_hurd__ || defined __GNU__ || \ + defined __MINGW32__ || defined __GLIBC__) +# define _SORT_R_GNU +#elif (defined __APPLE__ || defined __MACH__ || defined __DARWIN__ || \ + defined __FreeBSD__ || defined __DragonFly__) +# define _SORT_R_BSD +#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_GNU + + 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_GNU + + #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_GNU +#undef _SORT_R_BSD + +#endif /* SORT_R_H_ */ |