Rename libohash to libopenbsd.

libopenbsd is an internal library which
to bring in compatibility stuff from OpenBSD.
This will allow us to bring in more
OpenBSD utilities into the FreeBSD base system.

We similarly use libnetbsd for bringing in stuff from NetBSD.

Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D4078

6 files changed, 797 insertions, 0 deletions

diff --git a/lib/libopenbsd/Makefile b/lib/libopenbsd/Makefile
new file mode 100644
index 0000000..33b9ff0
--- /dev/null
+++ b/lib/libopenbsd/Makefile
@@ -0,0 +1,9 @@
+# $FreeBSD$
+
+LIB=	openbsd
+SRCS=	ohash.c
+INTERNALLIB=
+
+WARNS=	3
+
+.include <bsd.lib.mk>
diff --git a/lib/libopenbsd/Makefile.depend b/lib/libopenbsd/Makefile.depend
new file mode 100644
index 0000000..18be76b
--- /dev/null
+++ b/lib/libopenbsd/Makefile.depend
@@ -0,0 +1,13 @@
+# $FreeBSD$
+# Autogenerated - do NOT edit!
+
+DIRDEPS = \
+	include \
+	include/xlocale \
+
+
+.include <dirdeps.mk>
+
+.if ${DEP_RELDIR} == ${_DEP_RELDIR}
+# local dependencies - needed for -jN in clean tree
+.endif
diff --git a/lib/libopenbsd/ohash.c b/lib/libopenbsd/ohash.c
new file mode 100644
index 0000000..3a0f5dd
--- /dev/null
+++ b/lib/libopenbsd/ohash.c
@@ -0,0 +1,330 @@
+/* $OpenBSD: src/lib/libutil/ohash.c,v 1.1 2014/06/02 18:52:03 deraadt Exp $ */
+
+/* Copyright (c) 1999, 2004 Marc Espie <espie@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <limits.h>
+#include "ohash.h"
+
+struct _ohash_record {
+	uint32_t	hv;
+	const char	*p;
+};
+
+#define DELETED		((const char *)h)
+#define NONE		(h->size)
+
+/* Don't bother changing the hash table if the change is small enough.  */
+#define MINSIZE		(1UL << 4)
+#define MINDELETED	4
+
+static void ohash_resize(struct ohash *);
+
+
+/* This handles the common case of variable length keys, where the
+ * key is stored at the end of the record.
+ */
+void *
+ohash_create_entry(struct ohash_info *i, const char *start, const char **end)
+{
+	char *p;
+
+	if (!*end)
+		*end = start + strlen(start);
+	p = (i->alloc)(i->key_offset + (*end - start) + 1, i->data);
+	if (p) {
+		memcpy(p+i->key_offset, start, *end-start);
+		p[i->key_offset + (*end - start)] = '\0';
+	}
+	return (void *)p;
+}
+
+/* hash_delete only frees the hash structure. Use hash_first/hash_next
+ * to free entries as well.  */
+void
+ohash_delete(struct ohash *h)
+{
+	(h->info.free)(h->t, h->info.data);
+#ifndef NDEBUG
+	h->t = NULL;
+#endif
+}
+
+static void
+ohash_resize(struct ohash *h)
+{
+	struct _ohash_record *n;
+	size_t ns;
+	unsigned int	j;
+	unsigned int	i, incr;
+
+	if (4 * h->deleted < h->total) {
+		if (h->size >= (UINT_MAX >> 1U))
+			ns = UINT_MAX;
+		else
+			ns = h->size << 1U;
+	} else if (3 * h->deleted > 2 * h->total)
+		ns = h->size >> 1U;
+	else
+		ns = h->size;
+	if (ns < MINSIZE)
+		ns = MINSIZE;
+#ifdef STATS_HASH
+	STAT_HASH_EXPAND++;
+	STAT_HASH_SIZE += ns - h->size;
+#endif
+
+	n = (h->info.calloc)(ns, sizeof(struct _ohash_record), h->info.data);
+	if (!n)
+		return;
+
+	for (j = 0; j < h->size; j++) {
+		if (h->t[j].p != NULL && h->t[j].p != DELETED) {
+			i = h->t[j].hv % ns;
+			incr = ((h->t[j].hv % (ns - 2)) & ~1) + 1;
+			while (n[i].p != NULL) {
+				i += incr;
+				if (i >= ns)
+					i -= ns;
+			}
+			n[i].hv = h->t[j].hv;
+			n[i].p = h->t[j].p;
+		}
+	}
+	(h->info.free)(h->t, h->info.data);
+	h->t = n;
+	h->size = ns;
+	h->total -= h->deleted;
+	h->deleted = 0;
+}
+
+void *
+ohash_remove(struct ohash *h, unsigned int i)
+{
+	void		*result = (void *)h->t[i].p;
+
+	if (result == NULL || result == DELETED)
+		return NULL;
+
+#ifdef STATS_HASH
+	STAT_HASH_ENTRIES--;
+#endif
+	h->t[i].p = DELETED;
+	h->deleted++;
+	if (h->deleted >= MINDELETED && 4 * h->deleted > h->total)
+		ohash_resize(h);
+	return result;
+}
+
+void *
+ohash_find(struct ohash *h, unsigned int i)
+{
+	if (h->t[i].p == DELETED)
+		return NULL;
+	else
+		return (void *)h->t[i].p;
+}
+
+void *
+ohash_insert(struct ohash *h, unsigned int i, void *p)
+{
+#ifdef STATS_HASH
+	STAT_HASH_ENTRIES++;
+#endif
+	if (h->t[i].p == DELETED) {
+		h->deleted--;
+		h->t[i].p = p;
+	} else {
+		h->t[i].p = p;
+		/* Arbitrary resize boundary.  Tweak if not efficient enough.  */
+		if (++h->total * 4 > h->size * 3)
+			ohash_resize(h);
+	}
+	return p;
+}
+
+unsigned int
+ohash_entries(struct ohash *h)
+{
+	return h->total - h->deleted;
+}
+
+void *
+ohash_first(struct ohash *h, unsigned int *pos)
+{
+	*pos = 0;
+	return ohash_next(h, pos);
+}
+
+void *
+ohash_next(struct ohash *h, unsigned int *pos)
+{
+	for (; *pos < h->size; (*pos)++)
+		if (h->t[*pos].p != DELETED && h->t[*pos].p != NULL)
+			return (void *)h->t[(*pos)++].p;
+	return NULL;
+}
+
+void
+ohash_init(struct ohash *h, unsigned int size, struct ohash_info *info)
+{
+	h->size = 1UL << size;
+	if (h->size < MINSIZE)
+		h->size = MINSIZE;
+#ifdef STATS_HASH
+	STAT_HASH_CREATION++;
+	STAT_HASH_SIZE += h->size;
+#endif
+	/* Copy info so that caller may free it.  */
+	h->info.key_offset = info->key_offset;
+	h->info.calloc = info->calloc;
+	h->info.free = info->free;
+	h->info.alloc = info->alloc;
+	h->info.data = info->data;
+	h->t = (h->info.calloc)(h->size, sizeof(struct _ohash_record),
+		    h->info.data);
+	h->total = h->deleted = 0;
+}
+
+uint32_t
+ohash_interval(const char *s, const char **e)
+{
+	uint32_t k;
+
+	if (!*e)
+		*e = s + strlen(s);
+	if (s == *e)
+		k = 0;
+	else
+		k = *s++;
+	while (s != *e)
+		k =  ((k << 2) | (k >> 30)) ^ *s++;
+	return k;
+}
+
+unsigned int
+ohash_lookup_interval(struct ohash *h, const char *start, const char *end,
+    uint32_t hv)
+{
+	unsigned int	i, incr;
+	unsigned int	empty;
+
+#ifdef STATS_HASH
+	STAT_HASH_LOOKUP++;
+#endif
+	empty = NONE;
+	i = hv % h->size;
+	incr = ((hv % (h->size-2)) & ~1) + 1;
+	while (h->t[i].p != NULL) {
+#ifdef STATS_HASH
+		STAT_HASH_LENGTH++;
+#endif
+		if (h->t[i].p == DELETED) {
+			if (empty == NONE)
+				empty = i;
+		} else if (h->t[i].hv == hv &&
+		    strncmp(h->t[i].p+h->info.key_offset, start,
+			end - start) == 0 &&
+		    (h->t[i].p+h->info.key_offset)[end-start] == '\0') {
+			if (empty != NONE) {
+				h->t[empty].hv = hv;
+				h->t[empty].p = h->t[i].p;
+				h->t[i].p = DELETED;
+				return empty;
+			} else {
+#ifdef STATS_HASH
+				STAT_HASH_POSITIVE++;
+#endif
+				return i;
+			}
+		}
+		i += incr;
+		if (i >= h->size)
+			i -= h->size;
+	}
+
+	/* Found an empty position.  */
+	if (empty != NONE)
+		i = empty;
+	h->t[i].hv = hv;
+	return i;
+}
+
+unsigned int
+ohash_lookup_memory(struct ohash *h, const char *k, size_t size, uint32_t hv)
+{
+	unsigned int	i, incr;
+	unsigned int	empty;
+
+#ifdef STATS_HASH
+	STAT_HASH_LOOKUP++;
+#endif
+	empty = NONE;
+	i = hv % h->size;
+	incr = ((hv % (h->size-2)) & ~1) + 1;
+	while (h->t[i].p != NULL) {
+#ifdef STATS_HASH
+		STAT_HASH_LENGTH++;
+#endif
+		if (h->t[i].p == DELETED) {
+			if (empty == NONE)
+				empty = i;
+		} else if (h->t[i].hv == hv &&
+		    memcmp(h->t[i].p+h->info.key_offset, k, size) == 0) {
+			if (empty != NONE) {
+				h->t[empty].hv = hv;
+				h->t[empty].p = h->t[i].p;
+				h->t[i].p = DELETED;
+				return empty;
+			} else {
+#ifdef STATS_HASH
+				STAT_HASH_POSITIVE++;
+#endif
+			}	return i;
+		}
+		i += incr;
+		if (i >= h->size)
+			i -= h->size;
+	}
+
+	/* Found an empty position.  */
+	if (empty != NONE)
+		i = empty;
+	h->t[i].hv = hv;
+	return i;
+}
+
+unsigned int
+ohash_qlookup(struct ohash *h, const char *s)
+{
+	const char *e = NULL;
+	return ohash_qlookupi(h, s, &e);
+}
+
+unsigned int
+ohash_qlookupi(struct ohash *h, const char *s, const char **e)
+{
+	uint32_t hv;
+
+	hv = ohash_interval(s, e);
+	return ohash_lookup_interval(h, s, *e, hv);
+}
diff --git a/lib/libopenbsd/ohash.h b/lib/libopenbsd/ohash.h
new file mode 100644
index 0000000..ff21c85
--- /dev/null
+++ b/lib/libopenbsd/ohash.h
@@ -0,0 +1,77 @@
+/* $OpenBSD: src/lib/libutil/ohash.h,v 1.2 2014/06/02 18:52:03 deraadt Exp $ */
+
+/* Copyright (c) 1999, 2004 Marc Espie <espie@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef OHASH_H
+#define OHASH_H
+
+#include <stddef.h>
+
+/* Open hashing support. 
+ * Open hashing was chosen because it is much lighter than other hash
+ * techniques, and more efficient in most cases.
+ */
+
+/* user-visible data structure */
+struct ohash_info {
+	ptrdiff_t key_offset;
+	void *data;	/* user data */
+	void *(*calloc)(size_t, size_t, void *);
+	void (*free)(void *, void *);
+	void *(*alloc)(size_t, void *);
+};
+
+struct _ohash_record;
+
+/* private structure. It's there just so you can do a sizeof */
+struct ohash {
+	struct _ohash_record 	*t;
+	struct ohash_info 	info;
+	unsigned int 		size;
+	unsigned int 		total;
+	unsigned int 		deleted;
+};
+
+/* For this to be tweakable, we use small primitives, and leave part of the
+ * logic to the client application.  e.g., hashing is left to the client
+ * application.  We also provide a simple table entry lookup that yields
+ * a hashing table index (opaque) to be used in find/insert/remove.
+ * The keys are stored at a known position in the client data.
+ */
+__BEGIN_DECLS
+void ohash_init(struct ohash *, unsigned, struct ohash_info *);
+void ohash_delete(struct ohash *);
+
+unsigned int ohash_lookup_interval(struct ohash *, const char *,
+	    const char *, uint32_t);
+unsigned int ohash_lookup_memory(struct ohash *, const char *,
+	    size_t, uint32_t);
+void *ohash_find(struct ohash *, unsigned int);
+void *ohash_remove(struct ohash *, unsigned int);
+void *ohash_insert(struct ohash *, unsigned int, void *);
+void *ohash_first(struct ohash *, unsigned int *);
+void *ohash_next(struct ohash *, unsigned int *);
+unsigned int ohash_entries(struct ohash *);
+
+void *ohash_create_entry(struct ohash_info *, const char *, const char **);
+uint32_t ohash_interval(const char *, const char **);
+
+unsigned int ohash_qlookupi(struct ohash *, const char *, const char **);
+unsigned int ohash_qlookup(struct ohash *, const char *);
+__END_DECLS
+#endif
diff --git a/lib/libopenbsd/ohash_init.3 b/lib/libopenbsd/ohash_init.3
new file mode 100644
index 0000000..184c4e3
--- /dev/null
+++ b/lib/libopenbsd/ohash_init.3
@@ -0,0 +1,273 @@
+.\"	$OpenBSD: ohash_init.3,v 1.2 2014/05/13 14:01:41 jmc Exp $
+.\" Copyright (c) 1999 Marc Espie <espie@openbsd.org>
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd May 12, 2014
+.Dt OHASH_INIT 3
+.Os
+.Sh NAME
+.Nm ohash_init ,
+.Nm ohash_delete ,
+.Nm ohash_lookup_interval ,
+.Nm ohash_lookup_memory ,
+.Nm ohash_find ,
+.Nm ohash_remove ,
+.Nm ohash_insert ,
+.Nm ohash_first ,
+.Nm ohash_next ,
+.Nm ohash_entries
+.Nd light-weight open hashing
+.Sh SYNOPSIS
+.In stdint.h
+.In stddef.h
+.In ohash.h
+.Ft void
+.Fn ohash_init "struct ohash *h" "unsigned int size" "struct ohash_info *info"
+.Ft void
+.Fn ohash_delete "struct ohash *h"
+.Ft "unsigned int"
+.Fn ohash_lookup_interval "struct ohash *h" "const char *start" "const char *end" "uint32_t hv"
+.Ft "unsigned int"
+.Fn ohash_lookup_memory "struct ohash *h" "const char *k" "size_t s" "uint32_t hv"
+.Ft void *
+.Fn ohash_find "struct ohash *h" "unsigned int i"
+.Ft void *
+.Fn ohash_remove "struct ohash *h" "unsigned int i"
+.Ft void *
+.Fn ohash_insert "struct ohash *h" "unsigned int i" "void *p"
+.Ft void *
+.Fn ohash_first "struct ohash *h" "unsigned int *i"
+.Ft void *
+.Fn ohash_next "struct ohash *h" "unsigned int *i"
+.Ft "unsigned int"
+.Fn ohash_entries "struct ohash *h"
+.Sh DESCRIPTION
+These functions have been designed as a fast, extensible alternative to
+the usual hash table functions.
+They provide storage and retrieval of records indexed by keys,
+where a key is a contiguous sequence of bytes at a fixed position in
+each record.
+Keys can either be NUL-terminated strings or fixed-size memory areas.
+All functions take a pointer to an ohash structure as the
+.Fa h
+function argument.
+Storage for this structure should be provided by user code.
+.Pp
+.Fn ohash_init
+initializes the table to store roughly 2 to the power
+.Fa size
+elements.
+.Fa info
+is a pointer to a
+.Fa struct ohash_info .
+.Bd -literal -offset indent
+struct ohash_info {
+	ptrdiff_t key_offset;
+	void *data;	/* user data */
+	void *(*calloc)(size_t, size_t, void *);
+	void (*free)(void *, void *);
+	void *(*alloc)(size_t, void *);
+};
+.Ed
+.Pp
+The
+.Va offset
+field holds the position of the key in each record;
+the
+.Va calloc
+and
+.Va free
+fields are pointers to
+.Xr calloc 3
+and
+.Xr free 3 Ns -like
+functions, used for managing the table internal storage;
+the
+.Va alloc
+field is only used by the utility function
+.Xr ohash_create_entry 3 .
+.Pp
+Each of these functions are called similarly to their standard counterpart,
+but with an extra
+.Ft void *
+parameter corresponding to the content of the field
+.Fa data ,
+which can be used to communicate specific information to the functions.
+.Pp
+.Fn ohash_init
+stores a copy of those fields internally, so
+.Fa info
+can be reclaimed after initialization.
+.Pp
+.Fn ohash_delete
+frees storage internal to
+.Fa h .
+Elements themselves should be freed by the user first, using for instance
+.Fn ohash_first
+and
+.Fn ohash_next .
+.Pp
+.Fn ohash_lookup_interval
+and
+.Fn ohash_lookup_memory
+are the basic look-up element functions.
+The hashing function result is provided by the user as
+.Fa hv .
+These return a
+.Qq slot
+in the ohash table
+.Fa h ,
+to be used with
+.Fn ohash_find ,
+.Fn ohash_insert ,
+or
+.Fn ohash_remove .
+This slot is only valid up to the next call to
+.Fn ohash_insert
+or
+.Fn ohash_remove .
+.Pp
+.Fn ohash_lookup_interval
+handles string-like keys.
+.Fn ohash_lookup_interval
+assumes the key is the interval between
+.Fa start
+and
+.Fa end ,
+exclusive,
+though the actual elements stored in the table should only contain
+NUL-terminated keys.
+.Pp
+.Fn ohash_lookup_memory
+assumes the key is the memory area starting at
+.Fa k
+of size
+.Fa s .
+All bytes are significant in key comparison.
+.Pp
+.Fn ohash_find
+retrieves an element from a slot
+.Fa i
+returned by the
+.Fn ohash_lookup*
+functions.
+It returns
+.Dv NULL
+if the slot is empty.
+.Pp
+.Fn ohash_insert
+inserts a new element
+.Fa p
+at slot
+.Fa i .
+Slot
+.Fa i
+must be empty and element
+.Fa p
+must have a key corresponding to the
+.Fn ohash_lookup*
+call.
+.Pp
+.Fn ohash_remove
+removes the element at slot
+.Fa i .
+It returns the removed element, for user code to dispose of, or
+.Dv NULL
+if the slot was empty.
+.Pp
+.Fn ohash_first
+and
+.Fn ohash_next
+can be used to access all elements in an ohash table, like this:
+.Bd -literal -offset indent
+for (n = ohash_first(h, &i); n != NULL; n = ohash_next(h, &i))
+	do_something_with(n);
+.Ed
+.Pp
+.Fa i
+points to an auxiliary unsigned integer used to record the current position
+in the ohash table.
+Those functions are safe to use even while entries are added to/removed
+from the table, but in such a case they don't guarantee that new entries
+will be returned.
+As a special case, they can safely be used to free elements in the table.
+.Pp
+.Fn ohash_entries
+returns the number of elements in the hash table.
+.Sh STORAGE HANDLING
+Only
+.Fn ohash_init ,
+.Fn ohash_insert ,
+.Fn ohash_remove
+and
+.Fn ohash_delete
+may call the user-supplied memory functions:
+.Bd -literal -offset indent
+p = (*info->calloc)(n, sizeof_record, info->data);
+/* copy data from old to p */
+(*info->free)(old, info->data);
+.Ed
+.Pp
+It is the responsibility of the user memory allocation code to verify
+that those calls did not fail.
+.Pp
+If memory allocation fails,
+.Fn ohash_init
+returns a useless hash table.
+.Fn ohash_insert
+and
+.Fn ohash_remove
+still perform the requested operation, but the returned table should be
+considered read-only.
+It can still be accessed by
+.Fn ohash_lookup* ,
+.Fn ohash_find ,
+.Fn ohash_first
+and
+.Fn ohash_next
+to dump relevant information to disk before aborting.
+.Sh THREAD SAFETY
+The open hashing functions are not thread-safe by design.
+In particular, in a threaded environment, there is no guarantee that a
+.Qq slot
+will not move between a
+.Fn ohash_lookup*
+and a
+.Fn ohash_find ,
+.Fn ohash_insert
+or
+.Fn ohash_remove
+call.
+.Pp
+Multi-threaded applications should explicitly protect ohash table access.
+.Sh SEE ALSO
+.Xr hcreate 3 ,
+.Xr ohash_interval 3
+.Rs
+.%A Donald E. Knuth
+.%B The Art of Computer Programming
+.%V Vol. 3
+.%P pp 506-550
+.%D 1973
+.Re
+.Sh STANDARDS
+Those functions are completely non-standard and should be avoided in
+portable programs.
+.Sh HISTORY
+Those functions were designed and written for
+.Ox
+.Xr make 1
+by Marc Espie in 1999.
diff --git a/lib/libopenbsd/ohash_interval.3 b/lib/libopenbsd/ohash_interval.3
new file mode 100644
index 0000000..3809c34
--- /dev/null
+++ b/lib/libopenbsd/ohash_interval.3
@@ -0,0 +1,95 @@
+.\"	$OpenBSD: ohash_interval.3,v 1.1 2014/05/12 19:09:00 espie Exp $
+.\" Copyright (c) 2001 Marc Espie <espie@openbsd.org>
+.\"
+.\" Permission to use, copy, modify, and distribute this software for any
+.\" purpose with or without fee is hereby granted, provided that the above
+.\" copyright notice and this permission notice appear in all copies.
+.\"
+.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd June 5, 2013
+.Dt OHASH_INTERVAL 3
+.Os
+.Sh NAME
+.Nm ohash_interval ,
+.Nm ohash_create_entry ,
+.Nm ohash_qlookup ,
+.Nm ohash_qlookupi
+.Nd helper functions for open hashing
+.Sh SYNOPSIS
+.In stdint.h
+.In stddef.h
+.In ohash.h
+.Ft uint32_t
+.Fn ohash_interval "const char *start" "const char **pend"
+.Ft "void *"
+.Fn ohash_create_entry "struct ohash_info *info" "const char *start" "const char **pend"
+.Ft "unsigned int"
+.Fn ohash_qlookupi "struct ohash *h" "const char *start" "const char **pend"
+.Ft "unsigned int"
+.Fn ohash_qlookup "struct ohash *h" "const char *start"
+.Sh DESCRIPTION
+These functions are commonly used to simplify open hashing usage, and use
+similar conventions.
+They operate indifferently on NUL-terminated strings
+.Po
+by setting
+.Fa *pend
+=
+.Dv NULL
+.Pc
+or memory ranges
+.Po
+delimited by
+.Fa start
+and
+.Fa *pend
+.Pc .
+For NUL-terminated strings, as a side effect, those functions
+set
+.Fa *pend
+to the terminating NUL byte.
+.Pp
+.Fn ohash_interval
+is a simple hashing function that yields good results on common data sets.
+.Pp
+.Fn ohash_create_entry
+can be used to create a new record with a given key.
+In that case,
+the alloc field of
+.Fa info
+should point to a
+.Xr malloc 3 Ns -like
+function to allocate the storage:
+.Bd -literal -offset indent
+p = (*info->alloc)(sz, info->data);
+.Ed
+.Pp
+.Fn ohash_qlookupi
+is a wrapper function that simply calls
+.Fn ohash_interval
+and
+.Fn ohash_lookup_interval .
+.Pp
+.Fn ohash_qlookup
+is a variation on
+.Fn ohash_qlookupi
+designed for NUL-terminated strings.
+.Sh SEE ALSO
+.Xr ohash_init 3
+.Sh STANDARDS
+Those functions are completely non-standard and should be avoided in
+portable programs.
+.Sh HISTORY
+Those functions were designed and written for
+.Ox
+.Xr make 1
+by Marc Espie in 1999.