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Diffstat (limited to 'src/contrib/ucw/array-sort.h')
| -rw-r--r-- | src/contrib/ucw/array-sort.h | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/src/contrib/ucw/array-sort.h b/src/contrib/ucw/array-sort.h new file mode 100644 index 0000000..1ff1377 --- /dev/null +++ b/src/contrib/ucw/array-sort.h @@ -0,0 +1,195 @@ +/* + * UCW Library -- Universal Simple Array Sorter + * + * (c) 2003--2008 Martin Mares <mj@ucw.cz> + * + * This software may be freely distributed and used according to the terms + * of the GNU Lesser General Public License. + */ + +#pragma once + +#include "contrib/macros.h" + +/* + * This is not a normal header file, it's a generator of sorting + * routines. Each time you include it with parameters set in the + * corresponding preprocessor macros, it generates an array sorter + * with the parameters given. + * + * You might wonder why the heck do we implement our own array sorter + * instead of using qsort(). The primary reason is that qsort handles + * only continuous arrays, but we need to sort array-like data structures + * where the only way to access elements is by using an indexing macro. + * Besides that, we are more than 2 times faster. + * + * So much for advocacy, there are the parameters (those marked with [*] + * are mandatory): + * + * ASORT_PREFIX(x) [*] add a name prefix (used on all global names + * defined by the sorter) + * ASORT_KEY_TYPE [*] data type of a single array entry key + * ASORT_ELT(i) returns the key of i-th element; if this macro is not + * defined, the function gets a pointer to an array to be sorted + * ASORT_LT(x,y) x < y for ASORT_KEY_TYPE (default: "x<y") + * ASORT_SWAP(i,j) swap i-th and j-th element (default: assume _ELT + * is an l-value and swap just the keys) + * ASORT_THRESHOLD threshold for switching between quicksort and insertsort + * ASORT_EXTRA_ARGS extra arguments for the sort function (they are always + * visible in all the macros supplied above), starts with comma + * + * After including this file, a function ASORT_PREFIX(sort)(unsigned array_size) + * or ASORT_PREFIX(sort)(ASORT_KEY_TYPE *array, unsigned array_size) [if ASORT_ELT + * is not defined] is declared and all parameter macros are automatically + * undef'd. + */ + +#ifndef ASORT_LT +#define ASORT_LT(x,y) ((x) < (y)) +#endif + +#ifndef ASORT_SWAP +#define ASORT_SWAP(i,j) do { ASORT_KEY_TYPE tmp = ASORT_ELT(i); ASORT_ELT(i)=ASORT_ELT(j); ASORT_ELT(j)=tmp; } while (0) +#endif + +#ifndef ASORT_THRESHOLD +#define ASORT_THRESHOLD 8 /* Guesswork and experimentation */ +#endif + +#ifndef ASORT_EXTRA_ARGS +#define ASORT_EXTRA_ARGS +#endif + +#ifndef ASORT_ELT +#define ASORT_ARRAY_ARG ASORT_KEY_TYPE *array, +#define ASORT_ELT(i) array[i] +#else +#define ASORT_ARRAY_ARG +#endif + +/** + * The generated sorting function. If `ASORT_ELT` macro is not provided, the + * @ASORT_ARRAY_ARG is equal to `ASORT_KEY_TYPE *array` and is the array to be + * sorted. If the macro is provided, this parameter is omitted. In that case, + * you can sort global variables or pass your structure by @ASORT_EXTRA_ARGS. + **/ +static void ASORT_PREFIX(sort)(ASORT_ARRAY_ARG unsigned array_size ASORT_EXTRA_ARGS) +{ + struct stk { int l, r; } stack[8*sizeof(unsigned)]; + int l, r, left, right, m; + unsigned sp = 0; + ASORT_KEY_TYPE pivot; + + if (array_size <= 1) + return; + + /* QuickSort with optimizations a'la Sedgewick, but stop at ASORT_THRESHOLD */ + + left = 0; + right = array_size - 1; + for(;;) + { + l = left; + r = right; + m = (l+r)/2; + if (ASORT_LT(ASORT_ELT(m), ASORT_ELT(l))) + ASORT_SWAP(l,m); + if (ASORT_LT(ASORT_ELT(r), ASORT_ELT(m))) + { + ASORT_SWAP(m,r); + if (ASORT_LT(ASORT_ELT(m), ASORT_ELT(l))) + ASORT_SWAP(l,m); + } + pivot = ASORT_ELT(m); + do + { + while (ASORT_LT(ASORT_ELT(l), pivot)) + l++; + while (ASORT_LT(pivot, ASORT_ELT(r))) + r--; + if (l < r) + { + ASORT_SWAP(l,r); + l++; + r--; + } + else if (l == r) + { + l++; + r--; + } + } + while (l <= r); + if ((r - left) >= ASORT_THRESHOLD && (right - l) >= ASORT_THRESHOLD) + { + /* Both partitions ok => push the larger one */ + if ((r - left) > (right - l)) + { + stack[sp].l = left; + stack[sp].r = r; + left = l; + } + else + { + stack[sp].l = l; + stack[sp].r = right; + right = r; + } + sp++; + } + else if ((r - left) >= ASORT_THRESHOLD) + { + /* Left partition OK, right undersize */ + right = r; + } + else if ((right - l) >= ASORT_THRESHOLD) + { + /* Right partition OK, left undersize */ + left = l; + } + else + { + /* Both partitions undersize => pop */ + if (!sp) + break; + sp--; + left = stack[sp].l; + right = stack[sp].r; + } + } + + /* + * We have a partially sorted array, finish by insertsort. Inspired + * by qsort() in GNU libc. + */ + + /* Find minimal element which will serve as a barrier */ + r = MIN(array_size, ASORT_THRESHOLD); + m = 0; + for (l=1; l<r; l++) + if (ASORT_LT(ASORT_ELT(l),ASORT_ELT(m))) + m = l; + ASORT_SWAP(0,m); + + /* Insertion sort */ + for (m=1; m<(int)array_size; m++) + { + l=m; + while (ASORT_LT(ASORT_ELT(m),ASORT_ELT(l-1))) + l--; + while (l < m) + { + ASORT_SWAP(l,m); + l++; + } + } +} + +#undef ASORT_PREFIX +#undef ASORT_KEY_TYPE +#undef ASORT_ELT +#undef ASORT_LT +#undef ASORT_SWAP +#undef ASORT_THRESHOLD +#undef ASORT_EXTRA_ARGS +#undef ASORT_ARRAY_ARG |