And as always I forgot to svn add the new file...

git-svn-id: http://www.varnish-cache.org/svn/trunk@3455 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/hash_critbit.c

+/*-
+ * Copyright (c) 2008 Linpro AS
+ * All rights reserved.
+ *
+ * Author: Poul-Henning Kamp <phk@phk.freebsd.dk>
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
+ *
+ * $Id$
+ *
+ * A Crit Bit tree based hash
+ */
+
+#include "config.h"
+
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "shmlog.h"
+#include "cache.h"
+#include "hash_slinger.h"
+
+static struct lock hcb_mtx;
+
+/**********************************************************************
+ * Table for finding out how many bits two bytes have in common,
+ * counting from the MSB towards the LSB.
+ * ie: 
+ *	hcb_bittbl[0x01 ^ 0x22] == 2
+ *	hcb_bittbl[0x10 ^ 0x0b] == 3
+ * 
+ */
+
+static unsigned char hcb_bittbl[256];
+
+static unsigned char
+hcb_bits(unsigned char x, unsigned char y)
+{
+	return hcb_bittbl[x ^ y];
+}
+
+static void
+hcb_build_bittbl(void)
+{
+	unsigned x, y;
+
+	y = 0;
+	for (x = 0; x < 8; x++)
+		for (; y < (1U << x); y++)
+			hcb_bittbl[y] = 8 - x;
+
+	/* Quick asserts for sanity check */
+	assert(hcb_bits(0x34, 0x34) == 8);
+	assert(hcb_bits(0xaa, 0x55) == 0);
+	assert(hcb_bits(0x01, 0x22) == 2);
+	assert(hcb_bits(0x10, 0x0b) == 3);
+}
+
+/**********************************************************************
+ * For space reasons we overload the two pointers with two different
+ * kinds of of pointers.  We cast them to uintptr_t's and abuse the
+ * low two bits to tell them apart, assuming that Varnish will never
+ * run on machines with less than 32bit alignment.
+ *
+ * Asserts will explode if these assumptions are not met.
+ */
+
+struct hcb_y {
+	unsigned short	critbit;
+	unsigned char	ptr;
+	unsigned char	bitmask;
+	uintptr_t	leaf[2];
+};
+
+#define HCB_BIT_NODE		(1<<0)
+#define HCB_BIT_Y		(1<<1)
+
+struct hcb_root {
+	uintptr_t	origo;
+	unsigned	cmps;
+};
+
+static struct hcb_root	hcb_root;
+
+/**********************************************************************
+ * Pointer accessor functions
+ */
+static int
+hcb_is_node(uintptr_t u)
+{
+
+	return (u & HCB_BIT_NODE);
+}
+
+static int
+hcb_is_y(uintptr_t u)
+{
+
+	return (u & HCB_BIT_Y);
+}
+
+static uintptr_t
+hcb_r_node(struct objhead *n)
+{
+
+	assert(!((uintptr_t)n & (HCB_BIT_NODE|HCB_BIT_Y)));
+	return (HCB_BIT_NODE | (uintptr_t)n);
+}
+
+static struct objhead *
+hcb_l_node(uintptr_t u)
+{
+
+	assert(u & HCB_BIT_NODE);
+	assert(!(u & HCB_BIT_Y));
+	return ((struct objhead *)(u & ~HCB_BIT_NODE));
+}
+
+static uintptr_t
+hcb_r_y(struct hcb_y *y)
+{
+
+	assert(!((uintptr_t)y & (HCB_BIT_NODE|HCB_BIT_Y)));
+	return (HCB_BIT_Y | (uintptr_t)y);
+}
+
+static struct hcb_y *
+hcb_l_y(uintptr_t u)
+{
+
+	assert(!(u & HCB_BIT_NODE));
+	assert(u & HCB_BIT_Y);
+	return ((struct hcb_y *)(u & ~HCB_BIT_Y));
+}
+
+/**********************************************************************/
+
+static unsigned
+hcb_crit_bit(const struct objhead *oh1, const struct objhead *oh2, struct hcb_y *y)
+{
+	unsigned u, r;
+
+	for (u = 0; u < oh1->digest_len && oh1->digest[u] == oh2->digest[u]; u++)
+		;
+	r = hcb_bits(oh1->digest[u], oh2->digest[u]);
+	y->ptr = u;
+	y->bitmask = 0x80 >> r;
+	y->critbit = u * 8 + r;
+	return (y->critbit);
+}
+
+/**********************************************************************/
+
+static struct objhead *
+hcb_insert(struct hcb_root *root, struct objhead *oh, int has_lock)
+{
+	uintptr_t *p;
+	struct hcb_y *y, *y2;
+	struct objhead *oh2;
+	unsigned s, s2;
+
+
+	p = &root->origo;
+	if (*p == 0) {
+		if (!has_lock)
+			return (NULL);
+		*p = hcb_r_node(oh);
+		return (oh);
+	}
+
+	while(hcb_is_y(*p)) {
+		y = hcb_l_y(*p);
+		if (y->ptr > oh->digest_len)
+			s = 0;
+		else
+			s = (oh->digest[y->ptr] & y->bitmask) != 0;
+		assert(s < 2);
+		root->cmps++;
+		p = &y->leaf[s];
+	}
+
+	assert(hcb_is_node(*p));
+
+	/* We found a node, does it match ? */
+	oh2 = hcb_l_node(*p);
+	if (oh2->digest_len == oh->digest_len &&
+	    !memcmp(oh2->digest, oh->digest, oh->digest_len))
+		return (oh2);
+
+	if (!has_lock)
+		return (NULL);
+
+	/* Insert */
+
+	y2 = (void*)&oh->u;
+	memset(y2, 0, sizeof *y2);
+	(void)hcb_crit_bit(oh, hcb_l_node(*p), y2);
+	s2 = (oh->digest[y2->ptr] & y2->bitmask) != 0;
+	assert(s2 < 2);
+	y2->leaf[s2] = hcb_r_node(oh);
+	s2 = 1-s2;
+
+	p = &root->origo;
+	assert(*p != 0);
+
+	while(hcb_is_y(*p)) {
+		y = hcb_l_y(*p);
+		if (y->critbit > y2->critbit)
+			break;
+		if (y->ptr > oh->digest_len)
+			s = 0;
+		else
+			s = (oh->digest[y->ptr] & y->bitmask) != 0;
+		assert(s < 2);
+		root->cmps++;
+		p = &y->leaf[s];
+	}
+	y2->leaf[s2] = *p;
+	*p = hcb_r_y(y2);
+	return(oh);
+}
+
+/**********************************************************************/
+
+static void
+hcb_delete(struct hcb_root *r, struct objhead *oh)
+{
+	struct hcb_y *y;
+	uintptr_t *p;
+	unsigned s;
+
+	if (r->origo == hcb_r_node(oh)) {
+		r->origo = 0;
+		return;
+	}
+	p = &r->origo;
+	assert(hcb_is_y(*p));
+	
+	y = NULL;
+	while(hcb_is_y(*p)) {
+		y = hcb_l_y(*p);
+		if (y->ptr > oh->digest_len)
+			s = 0;
+		else
+			s = (oh->digest[y->ptr] & y->bitmask) != 0;
+		assert(s < 2);
+		if (y->leaf[s] == hcb_r_node(oh)) {
+			*p = y->leaf[1 - s];
+			y->leaf[0] = 0;
+			y->leaf[1] = 0;
+			return;
+		}
+		r->cmps++;
+		p = &y->leaf[s];
+	}
+abort();
+	*p = y->leaf[1 - s];
+}
+
+/**********************************************************************/
+
+static void
+dumptree(uintptr_t p, int indent, FILE *fd)
+{
+	int i;
+	const struct objhead *oh;
+	const struct hcb_y *y;
+
+	if (p == 0)
+		return;
+	if (hcb_is_node(p)) {
+		oh = hcb_l_node(p);
+		fprintf(fd, "%*.*sN %u %u r%d <%02x%02x%02x...> <%s>\n",
+		    indent, indent, "", oh->digest_len, indent / 2,
+		    oh->refcnt,
+		    oh->digest[0], oh->digest[1], oh->digest[2],
+		    oh->hash);
+		return;
+	}
+	assert(hcb_is_y(p));
+	y = hcb_l_y(p);
+	fprintf(fd, "%*.*sY c %u p %u b %02x i %d\n",
+	    indent, indent, "",
+	    y->critbit, y->ptr, y->bitmask, indent / 2);
+	indent += 2;
+	for (i = 0; i < 2; i++)
+		dumptree(y->leaf[i], indent, fd);
+}
+
+static void
+dump(const struct hcb_root *root, FILE *fd)
+{
+	fprintf(fd, "-------------\n");
+	dumptree(root->origo, 0, fd);
+	fprintf(fd, "-------------\n");
+	fflush(fd);
+}
+
+
+/**********************************************************************/
+
+static void
+hcb_start(void)
+{
+	struct objhead *oh = NULL;
+
+	(void)oh;
+	assert(params->hash_sha256);
+	assert(sizeof(struct hcb_y) <= sizeof(oh->u));
+	memset(&hcb_root, 0, sizeof hcb_root);
+	hcb_build_bittbl();
+	Lck_New(&hcb_mtx);
+}
+
+static int
+hcb_deref(struct objhead *oh)
+{
+	int r;
+	struct hcb_y *y;
+
+	r = 1;
+	CHECK_OBJ_NOTNULL(oh, OBJHEAD_MAGIC);
+	Lck_Lock(&oh->mtx);
+	if (--oh->refcnt == 0) {
+		Lck_Lock(&hcb_mtx);
+		hcb_delete(&hcb_root, oh);
+		y = (void*)&oh->u;
+		if (y->leaf[0] == 0 && y->leaf[1] == 0)
+			r = 0;
+		else {
+			/* XXX: on waiting list */
+		}
+		Lck_Unlock(&hcb_mtx);
+	}
+	Lck_Unlock(&oh->mtx);
+	if (0) {
+		fprintf(stderr, "%s %d %d <%s>\n", __func__, __LINE__, r, oh->hash);
+		dump(&hcb_root, stderr);
+	}
+	return (r);
+}
+
+static struct objhead *
+hcb_lookup(const struct sess *sp, struct objhead *noh)
+{
+	struct objhead *oh;
+	
+	assert(params->hash_sha256);
+	oh =  hcb_insert(&hcb_root, noh, 0);
+	if (oh != NULL) {
+		/* Assert that we didn't muck with the tree without lock */
+		assert(oh != noh);
+		Lck_Lock(&oh->mtx);
+		oh->refcnt++;
+		Lck_Unlock(&oh->mtx);
+		VSL_stats->hcb_nolock++;
+		if (0) {
+			fprintf(stderr, "%s %d\n", __func__, __LINE__);
+			dump(&hcb_root, stderr);
+		}
+		return (oh);
+	}
+
+	/*
+	 * Try again, holding lock and fully ready objhead, so that if
+	 * somebody else beats us back, they do not get surprised.
+	 */
+	HSH_Copy(sp, noh);
+	Lck_Lock(&hcb_mtx);
+	oh =  hcb_insert(&hcb_root, noh, 1);
+	if (oh == noh) {
+		VSL_stats->hcb_insert++;
+		if (0) {
+			fprintf(stderr, "%s %d\n", __func__, __LINE__);
+			dump(&hcb_root, stderr);
+		}
+	} else {
+		free(noh->hash);
+		noh->hash = NULL;
+		noh->hashlen = 0;
+		VSL_stats->hcb_lock++;
+		if (0) {
+			fprintf(stderr, "%s %d\n", __func__, __LINE__);
+			dump(&hcb_root, stderr);
+		}
+	}
+	Lck_Unlock(&hcb_mtx);
+	return (oh);
+}
+
+
+struct hash_slinger hcb_slinger = {
+	.magic  =       SLINGER_MAGIC,
+	.name   =       "critbit",
+	.start  =       hcb_start,
+	.lookup =       hcb_lookup,
+	.deref  =       hcb_deref,
+};