Add new mergesort function

Taken from FreeBSD.

4 files changed, 357 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 4aa64ef..3c5cdce 100644
--- a/Makefile
+++ b/Makefile
@@ -28,6 +28,7 @@ LIB_SRCS := \
 	flopen.c \
 	getpeereid.c \
 	heapsort.c \
+	merge.c \
 	humanize_number.c \
 	dehumanize_number.c \
 	inet_net_pton.c \
diff --git a/Versions b/Versions
index 7c9437e..cac2efe 100644
--- a/Versions
+++ b/Versions
@@ -68,5 +68,7 @@ LIBBSD_0.2 {
 LIBBSD_0.3 {
     reallocf;
     getpeereid;
+
+    mergesort;
 } LIBBSD_0.2;
 
diff --git a/include/bsd/stdlib.h b/include/bsd/stdlib.h
index 9e1d640..bfe3027 100644
--- a/include/bsd/stdlib.h
+++ b/include/bsd/stdlib.h
@@ -1,7 +1,7 @@
 /*
  * Copyright © 2005 Aurelien Jarno
  * Copyright © 2006 Robert Millan
- * Copyright © 2008, 2009, 2010 Guillem Jover
+ * Copyright © 2008-2011 Guillem Jover
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -52,6 +52,8 @@ const char *getprogname(void);
 void setprogname(const char *);
 
 int heapsort (void *, size_t, size_t, int (*)(const void *, const void *));
+int mergesort(void *base, size_t nmemb, size_t size,
+              int (*cmp)(const void *, const void *));
 
 void *reallocf(void *ptr, size_t size);
 
diff --git a/src/merge.c b/src/merge.c
new file mode 100644
index 0000000..e1078e7
--- /dev/null
+++ b/src/merge.c
@@ -0,0 +1,351 @@
+/*-
+ * Copyright (c) 1992, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Peter McIlroy.
+ *
+ * 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.
+ * 4. 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)merge.c	8.2 (Berkeley) 2/14/94";
+#endif /* LIBC_SCCS and not lint */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/*
+ * Hybrid exponential search/linear search merge sort with hybrid
+ * natural/pairwise first pass.  Requires about .3% more comparisons
+ * for random data than LSMS with pairwise first pass alone.
+ * It works for objects as small as two bytes.
+ */
+
+#define NATURAL
+#define THRESHOLD 16	/* Best choice for natural merge cut-off. */
+
+/* #define NATURAL to get hybrid natural merge.
+ * (The default is pairwise merging.)
+ */
+
+#include <sys/types.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void setup(u_char *, u_char *, size_t, size_t,
+    int (*)(const void *, const void *));
+static void insertionsort(u_char *, size_t, size_t,
+    int (*)(const void *, const void *));
+
+#define ISIZE sizeof(int)
+#define PSIZE sizeof(u_char *)
+#define ICOPY_LIST(src, dst, last)				\
+	do							\
+	*(int*)dst = *(int*)src, src += ISIZE, dst += ISIZE;	\
+	while(src < last)
+#define ICOPY_ELT(src, dst, i)					\
+	do							\
+	*(int*) dst = *(int*) src, src += ISIZE, dst += ISIZE;	\
+	while (i -= ISIZE)
+
+#define CCOPY_LIST(src, dst, last)		\
+	do					\
+		*dst++ = *src++;		\
+	while (src < last)
+#define CCOPY_ELT(src, dst, i)			\
+	do					\
+		*dst++ = *src++;		\
+	while (i -= 1)
+
+/*
+ * Find the next possible pointer head.  (Trickery for forcing an array
+ * to do double duty as a linked list when objects do not align with word
+ * boundaries.
+ */
+/* Assumption: PSIZE is a power of 2. */
+#define EVAL(p) (u_char **)						\
+	((u_char *)0 +							\
+	    (((u_char *)p + PSIZE - 1 - (u_char *) 0) & ~(PSIZE - 1)))
+
+/*
+ * Arguments are as for qsort.
+ */
+int
+mergesort(base, nmemb, size, cmp)
+	void *base;
+	size_t nmemb;
+	size_t size;
+	int (*cmp)(const void *, const void *);
+{
+	size_t i;
+	int sense;
+	int big, iflag;
+	u_char *f1, *f2, *t, *b, *tp2, *q, *l1, *l2;
+	u_char *list2, *list1, *p2, *p, *last, **p1;
+
+	if (size < PSIZE / 2) {		/* Pointers must fit into 2 * size. */
+		errno = EINVAL;
+		return (-1);
+	}
+
+	if (nmemb == 0)
+		return (0);
+
+	/*
+	 * XXX
+	 * Stupid subtraction for the Cray.
+	 */
+	iflag = 0;
+	if (!(size % ISIZE) && !(((char *)base - (char *)0) % ISIZE))
+		iflag = 1;
+
+	if ((list2 = malloc(nmemb * size + PSIZE)) == NULL)
+		return (-1);
+
+	list1 = base;
+	setup(list1, list2, nmemb, size, cmp);
+	last = list2 + nmemb * size;
+	i = big = 0;
+	while (*EVAL(list2) != last) {
+	    l2 = list1;
+	    p1 = EVAL(list1);
+	    for (tp2 = p2 = list2; p2 != last; p1 = EVAL(l2)) {
+	    	p2 = *EVAL(p2);
+	    	f1 = l2;
+	    	f2 = l1 = list1 + (p2 - list2);
+	    	if (p2 != last)
+	    		p2 = *EVAL(p2);
+	    	l2 = list1 + (p2 - list2);
+	    	while (f1 < l1 && f2 < l2) {
+	    		if ((*cmp)(f1, f2) <= 0) {
+	    			q = f2;
+	    			b = f1, t = l1;
+	    			sense = -1;
+	    		} else {
+	    			q = f1;
+	    			b = f2, t = l2;
+	    			sense = 0;
+	    		}
+	    		if (!big) {	/* here i = 0 */
+				while ((b += size) < t && cmp(q, b) >sense)
+	    				if (++i == 6) {
+	    					big = 1;
+	    					goto EXPONENTIAL;
+	    				}
+	    		} else {
+EXPONENTIAL:	    		for (i = size; ; i <<= 1)
+	    				if ((p = (b + i)) >= t) {
+	    					if ((p = t - size) > b &&
+						    (*cmp)(q, p) <= sense)
+	    						t = p;
+	    					else
+	    						b = p;
+	    					break;
+	    				} else if ((*cmp)(q, p) <= sense) {
+	    					t = p;
+	    					if (i == size)
+	    						big = 0;
+	    					goto FASTCASE;
+	    				} else
+	    					b = p;
+				while (t > b+size) {
+	    				i = (((t - b) / size) >> 1) * size;
+	    				if ((*cmp)(q, p = b + i) <= sense)
+	    					t = p;
+	    				else
+	    					b = p;
+	    			}
+	    			goto COPY;
+FASTCASE:	    		while (i > size)
+	    				if ((*cmp)(q,
+	    					p = b + (i >>= 1)) <= sense)
+	    					t = p;
+	    				else
+	    					b = p;
+COPY:	    			b = t;
+	    		}
+	    		i = size;
+	    		if (q == f1) {
+	    			if (iflag) {
+	    				ICOPY_LIST(f2, tp2, b);
+	    				ICOPY_ELT(f1, tp2, i);
+	    			} else {
+	    				CCOPY_LIST(f2, tp2, b);
+	    				CCOPY_ELT(f1, tp2, i);
+	    			}
+	    		} else {
+	    			if (iflag) {
+	    				ICOPY_LIST(f1, tp2, b);
+	    				ICOPY_ELT(f2, tp2, i);
+	    			} else {
+	    				CCOPY_LIST(f1, tp2, b);
+	    				CCOPY_ELT(f2, tp2, i);
+	    			}
+	    		}
+	    	}
+	    	if (f2 < l2) {
+	    		if (iflag)
+	    			ICOPY_LIST(f2, tp2, l2);
+	    		else
+	    			CCOPY_LIST(f2, tp2, l2);
+	    	} else if (f1 < l1) {
+	    		if (iflag)
+	    			ICOPY_LIST(f1, tp2, l1);
+	    		else
+	    			CCOPY_LIST(f1, tp2, l1);
+	    	}
+	    	*p1 = l2;
+	    }
+	    tp2 = list1;	/* swap list1, list2 */
+	    list1 = list2;
+	    list2 = tp2;
+	    last = list2 + nmemb*size;
+	}
+	if (base == list2) {
+		memmove(list2, list1, nmemb*size);
+		list2 = list1;
+	}
+	free(list2);
+	return (0);
+}
+
+#define	swap(a, b) {					\
+		s = b;					\
+		i = size;				\
+		do {					\
+			tmp = *a; *a++ = *s; *s++ = tmp; \
+		} while (--i);				\
+		a -= size;				\
+	}
+#define reverse(bot, top) {				\
+	s = top;					\
+	do {						\
+		i = size;				\
+		do {					\
+			tmp = *bot; *bot++ = *s; *s++ = tmp; \
+		} while (--i);				\
+		s -= size2;				\
+	} while(bot < s);				\
+}
+
+/*
+ * Optional hybrid natural/pairwise first pass.  Eats up list1 in runs of
+ * increasing order, list2 in a corresponding linked list.  Checks for runs
+ * when THRESHOLD/2 pairs compare with same sense.  (Only used when NATURAL
+ * is defined.  Otherwise simple pairwise merging is used.)
+ */
+void
+setup(list1, list2, n, size, cmp)
+	size_t n, size;
+	int (*cmp)(const void *, const void *);
+	u_char *list1, *list2;
+{
+	int i, length, size2, tmp, sense;
+	u_char *f1, *f2, *s, *l2, *last, *p2;
+
+	size2 = size*2;
+	if (n <= 5) {
+		insertionsort(list1, n, size, cmp);
+		*EVAL(list2) = (u_char*) list2 + n*size;
+		return;
+	}
+	/*
+	 * Avoid running pointers out of bounds; limit n to evens
+	 * for simplicity.
+	 */
+	i = 4 + (n & 1);
+	insertionsort(list1 + (n - i) * size, i, size, cmp);
+	last = list1 + size * (n - i);
+	*EVAL(list2 + (last - list1)) = list2 + n * size;
+
+#ifdef NATURAL
+	p2 = list2;
+	f1 = list1;
+	sense = (cmp(f1, f1 + size) > 0);
+	for (; f1 < last; sense = !sense) {
+		length = 2;
+					/* Find pairs with same sense. */
+		for (f2 = f1 + size2; f2 < last; f2 += size2) {
+			if ((cmp(f2, f2+ size) > 0) != sense)
+				break;
+			length += 2;
+		}
+		if (length < THRESHOLD) {		/* Pairwise merge */
+			do {
+				p2 = *EVAL(p2) = f1 + size2 - list1 + list2;
+				if (sense > 0)
+					swap (f1, f1 + size);
+			} while ((f1 += size2) < f2);
+		} else {				/* Natural merge */
+			l2 = f2;
+			for (f2 = f1 + size2; f2 < l2; f2 += size2) {
+				if ((cmp(f2-size, f2) > 0) != sense) {
+					p2 = *EVAL(p2) = f2 - list1 + list2;
+					if (sense > 0)
+						reverse(f1, f2-size);
+					f1 = f2;
+				}
+			}
+			if (sense > 0)
+				reverse (f1, f2-size);
+			f1 = f2;
+			if (f2 < last || cmp(f2 - size, f2) > 0)
+				p2 = *EVAL(p2) = f2 - list1 + list2;
+			else
+				p2 = *EVAL(p2) = list2 + n*size;
+		}
+	}
+#else		/* pairwise merge only. */
+	for (f1 = list1, p2 = list2; f1 < last; f1 += size2) {
+		p2 = *EVAL(p2) = p2 + size2;
+		if (cmp (f1, f1 + size) > 0)
+			swap(f1, f1 + size);
+	}
+#endif /* NATURAL */
+}
+
+/*
+ * This is to avoid out-of-bounds addresses in sorting the
+ * last 4 elements.
+ */
+static void
+insertionsort(a, n, size, cmp)
+	u_char *a;
+	size_t n, size;
+	int (*cmp)(const void *, const void *);
+{
+	u_char *ai, *s, *t, *u, tmp;
+	int i;
+
+	for (ai = a+size; --n >= 1; ai += size)
+		for (t = ai; t > a; t -= size) {
+			u = t - size;
+			if (cmp(u, t) <= 0)
+				break;
+			swap(u, t);
+		}
+}