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@ -1,4 +1,4 @@ |
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/* $OpenBSD: qsort.c,v 1.16 2017/05/20 12:48:56 millert Exp $ */ |
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/* $OpenBSD: qsort.c,v 1.17 2017/05/24 21:18:25 millert Exp $ */ |
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/*- |
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* Copyright (c) 1992, 1993 |
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* The Regents of the University of California. All rights reserved. |
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@ -43,14 +43,26 @@ static __inline void swapfunc(char *, char *, size_t, int); |
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* 1. The partition value is swapped into a[0] instead of being |
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* stored out of line. |
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* |
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* 2. It uses David Musser's introsort algorithm to fall back to |
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* 2. The swap function can swap 32-bit aligned elements on 64-bit |
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* platforms instead of swapping them as byte-aligned. |
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* |
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* 3. It uses David Musser's introsort algorithm to fall back to |
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* heapsort(3) when the recursion depth reaches 2*lg(n + 1). |
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* This avoids quicksort's quadratic behavior for pathological |
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* input without appreciably changing the average run time. |
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* |
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* 3. Tail recursion is eliminated when sorting the larger of two |
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* 4. Tail recursion is eliminated when sorting the larger of two |
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* subpartitions to save stack space. |
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*/ |
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#define SWAPTYPE_BYTEV 1 |
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#define SWAPTYPE_INTV 2 |
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#define SWAPTYPE_LONGV 3 |
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#define SWAPTYPE_INT 4 |
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#define SWAPTYPE_LONG 5 |
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#define TYPE_ALIGNED(TYPE, a, es) \ |
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(((char *)a - (char *)0) % sizeof(TYPE) == 0 && es % sizeof(TYPE) == 0) |
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#define swapcode(TYPE, parmi, parmj, n) { \ |
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size_t i = (n) / sizeof (TYPE); \ |
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TYPE *pi = (TYPE *) (parmi); \ |
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@ -62,25 +74,42 @@ static __inline void swapfunc(char *, char *, size_t, int); |
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} while (--i > 0); \ |
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} |
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#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \ |
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es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1; |
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static __inline void |
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swapfunc(char *a, char *b, size_t n, int swaptype) |
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{ |
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if (swaptype <= 1) |
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swapcode(long, a, b, n) |
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else |
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swapcode(char, a, b, n) |
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switch (swaptype) { |
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case SWAPTYPE_INT: |
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case SWAPTYPE_INTV: |
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swapcode(int, a, b, n); |
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break; |
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case SWAPTYPE_LONG: |
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case SWAPTYPE_LONGV: |
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swapcode(long, a, b, n); |
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break; |
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default: |
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swapcode(char, a, b, n); |
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break; |
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} |
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} |
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#define swap(a, b) \ |
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if (swaptype == 0) { \ |
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#define swap(a, b) do { \ |
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switch (swaptype) { \ |
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case SWAPTYPE_INT: { \ |
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int t = *(int *)(a); \ |
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*(int *)(a) = *(int *)(b); \ |
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*(int *)(b) = t; \ |
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break; \ |
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} \ |
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case SWAPTYPE_LONG: { \ |
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long t = *(long *)(a); \ |
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*(long *)(a) = *(long *)(b); \ |
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*(long *)(b) = t; \ |
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} else \ |
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swapfunc(a, b, es, swaptype) |
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break; \ |
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} \ |
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default: \ |
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swapfunc(a, b, es, swaptype); \ |
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} \ |
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} while (0) |
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#define vecswap(a, b, n) if ((n) > 0) swapfunc(a, b, n, swaptype) |
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@ -93,11 +122,11 @@ med3(char *a, char *b, char *c, int (*cmp)(const void *, const void *)) |
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} |
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static void |
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introsort(char *a, size_t n, size_t es, size_t maxdepth, |
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introsort(char *a, size_t n, size_t es, size_t maxdepth, int swaptype, |
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int (*cmp)(const void *, const void *)) |
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{ |
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char *pa, *pb, *pc, *pd, *pl, *pm, *pn; |
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int cmp_result, swaptype; |
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int cmp_result; |
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size_t r, s; |
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loop: if (maxdepth == 0) { |
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@ -105,7 +134,6 @@ loop: if (maxdepth == 0) { |
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return; |
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} |
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maxdepth--; |
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SWAPINIT(a, es); |
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if (n < 7) { |
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for (pm = a + es; pm < a + n * es; pm += es) |
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for (pl = pm; pl > a && cmp(pl - es, pl) > 0; |
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@ -164,8 +192,10 @@ loop: if (maxdepth == 0) { |
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if (r < s) { |
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/* Recurse for 1st side, iterate for 2nd side. */ |
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if (s > es) { |
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if (r > es) |
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introsort(a, r / es, es, maxdepth, cmp); |
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if (r > es) { |
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introsort(a, r / es, es, maxdepth, |
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swaptype, cmp); |
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} |
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a = pn - s; |
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n = s / es; |
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goto loop; |
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@ -173,8 +203,10 @@ loop: if (maxdepth == 0) { |
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} else { |
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/* Recurse for 2nd side, iterate for 1st side. */ |
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if (r > es) { |
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if (s > es) |
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introsort(pn - s, s / es, es, maxdepth, cmp); |
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if (s > es) { |
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introsort(pn - s, s / es, es, maxdepth, |
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swaptype, cmp); |
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} |
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n = r / es; |
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goto loop; |
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} |
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@ -185,13 +217,22 @@ void |
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qsort(void *a, size_t n, size_t es, int (*cmp)(const void *, const void *)) |
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{ |
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size_t i, maxdepth = 0; |
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int swaptype; |
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/* Approximate 2*ceil(lg(n + 1)) */ |
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for (i = n; i > 0; i >>= 1) |
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maxdepth++; |
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maxdepth *= 2; |
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introsort(a, n, es, maxdepth, cmp); |
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if (TYPE_ALIGNED(long, a, es)) |
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swaptype = es == sizeof(long) ? SWAPTYPE_LONG : SWAPTYPE_LONGV; |
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else if (sizeof(int) != sizeof(long) && TYPE_ALIGNED(int, a, es)) |
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swaptype = es == sizeof(int) ? SWAPTYPE_INT : SWAPTYPE_INTV; |
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else |
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swaptype = SWAPTYPE_BYTEV; |
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introsort(a, n, es, maxdepth, swaptype, cmp); |
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} |
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DEF_STRONG(qsort); |