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lvm2/base/data-struct/radix-tree.c
Joe Thornber 06c789eda1 radix-tree: fix some bugs in remove_prefix and iterate 
These weren't working if the prefix key was part of a prefix_chain.
2018-05-30 14:21:27 +01:00

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// Copyright (C) 2018 Red Hat, Inc. All rights reserved.
//
// This file is part of LVM2.
//
// This copyrighted material is made available to anyone wishing to use,
// modify, copy, or redistribute it subject to the terms and conditions
// of the GNU Lesser General Public License v.2.1.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program; if not, write to the Free Software Foundation,
// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#include "radix-tree.h"
#include "base/memory/container_of.h"
#include "base/memory/zalloc.h"
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
//----------------------------------------------------------------
enum node_type {
UNSET = 0,
VALUE,
VALUE_CHAIN,
PREFIX_CHAIN,
NODE4,
NODE16,
NODE48,
NODE256
};
struct value {
enum node_type type;
union radix_value value;
};
// This is used for entries that have a key which is a prefix of another key.
struct value_chain {
union radix_value value;
struct value child;
};
struct prefix_chain {
struct value child;
unsigned len;
uint8_t prefix[0];
};
struct node4 {
uint32_t nr_entries;
uint8_t keys[4];
struct value values[4];
};
struct node16 {
uint32_t nr_entries;
uint8_t keys[16];
struct value values[16];
};
struct node48 {
uint32_t nr_entries;
uint8_t keys[256];
struct value values[48];
};
struct node256 {
uint32_t nr_entries;
struct value values[256];
};
struct radix_tree {
unsigned nr_entries;
struct value root;
radix_value_dtr dtr;
void *dtr_context;
};
//----------------------------------------------------------------
struct radix_tree *radix_tree_create(radix_value_dtr dtr, void *dtr_context)
{
struct radix_tree *rt = malloc(sizeof(*rt));
if (rt) {
rt->nr_entries = 0;
rt->root.type = UNSET;
rt->dtr = dtr;
rt->dtr_context = dtr_context;
}
return rt;
}
static inline void _dtr(struct radix_tree *rt, union radix_value v)
{
if (rt->dtr)
rt->dtr(rt->dtr_context, v);
}
// Returns the number of values removed
static unsigned _free_node(struct radix_tree *rt, struct value v)
{
unsigned i, nr = 0;
struct value_chain *vc;
struct prefix_chain *pc;
struct node4 *n4;
struct node16 *n16;
struct node48 *n48;
struct node256 *n256;
switch (v.type) {
case UNSET:
break;
case VALUE:
_dtr(rt, v.value);
nr = 1;
break;
case VALUE_CHAIN:
vc = v.value.ptr;
_dtr(rt, vc->value);
nr = 1 + _free_node(rt, vc->child);
free(vc);
break;
case PREFIX_CHAIN:
pc = v.value.ptr;
nr = _free_node(rt, pc->child);
free(pc);
break;
case NODE4:
n4 = (struct node4 *) v.value.ptr;
for (i = 0; i < n4->nr_entries; i++)
nr += _free_node(rt, n4->values[i]);
free(n4);
break;
case NODE16:
n16 = (struct node16 *) v.value.ptr;
for (i = 0; i < n16->nr_entries; i++)
nr += _free_node(rt, n16->values[i]);
free(n16);
break;
case NODE48:
n48 = (struct node48 *) v.value.ptr;
for (i = 0; i < n48->nr_entries; i++)
nr += _free_node(rt, n48->values[i]);
free(n48);
break;
case NODE256:
n256 = (struct node256 *) v.value.ptr;
for (i = 0; i < 256; i++)
nr += _free_node(rt, n256->values[i]);
free(n256);
break;
}
return nr;
}
void radix_tree_destroy(struct radix_tree *rt)
{
_free_node(rt, rt->root);
free(rt);
}
unsigned radix_tree_size(struct radix_tree *rt)
{
return rt->nr_entries;
}
static bool _insert(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv);
static bool _insert_unset(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
unsigned len = ke - kb;
if (!len) {
// value
v->type = VALUE;
v->value = rv;
rt->nr_entries++;
} else {
// prefix -> value
struct prefix_chain *pc = zalloc(sizeof(*pc) + len);
if (!pc)
return false;
pc->child.type = VALUE;
pc->child.value = rv;
pc->len = len;
memcpy(pc->prefix, kb, len);
v->type = PREFIX_CHAIN;
v->value.ptr = pc;
rt->nr_entries++;
}
return true;
}
static bool _insert_value(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
unsigned len = ke - kb;
if (!len)
// overwrite
v->value = rv;
else {
// value_chain -> value
struct value_chain *vc = zalloc(sizeof(*vc));
if (!vc)
return false;
vc->value = v->value;
if (!_insert(rt, &vc->child, kb, ke, rv)) {
free(vc);
return false;
}
v->type = VALUE_CHAIN;
v->value.ptr = vc;
}
return true;
}
static bool _insert_value_chain(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct value_chain *vc = v->value.ptr;
return _insert(rt, &vc->child, kb, ke, rv);
}
static unsigned min(unsigned lhs, unsigned rhs)
{
if (lhs <= rhs)
return lhs;
else
return rhs;
}
static bool _insert_prefix_chain(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct prefix_chain *pc = v->value.ptr;
if (*kb == pc->prefix[0]) {
// There's a common prefix let's split the chain into two and
// recurse.
struct prefix_chain *pc2;
unsigned i, len = min(pc->len, ke - kb);
for (i = 0; i < len; i++)
if (kb[i] != pc->prefix[i])
break;
pc2 = zalloc(sizeof(*pc2) + pc->len - i);
pc2->len = pc->len - i;
memmove(pc2->prefix, pc->prefix + i, pc2->len);
pc2->child = pc->child;
// FIXME: this trashes pc so we can't back out
pc->child.type = PREFIX_CHAIN;
pc->child.value.ptr = pc2;
pc->len = i;
if (!_insert(rt, &pc->child, kb + i, ke, rv)) {
free(pc2);
return false;
}
} else {
// Stick an n4 in front.
struct node4 *n4 = zalloc(sizeof(*n4));
if (!n4)
return false;
n4->keys[0] = *kb;
if (!_insert(rt, n4->values, kb + 1, ke, rv)) {
free(n4);
return false;
}
if (pc->len) {
n4->keys[1] = pc->prefix[0];
if (pc->len == 1) {
n4->values[1] = pc->child;
free(pc);
} else {
memmove(pc->prefix, pc->prefix + 1, pc->len - 1);
pc->len--;
n4->values[1] = *v;
}
n4->nr_entries = 2;
} else
n4->nr_entries = 1;
v->type = NODE4;
v->value.ptr = n4;
}
return true;
}
static bool _insert_node4(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct node4 *n4 = v->value.ptr;
if (n4->nr_entries == 4) {
struct node16 *n16 = zalloc(sizeof(*n16));
if (!n16)
return false;
n16->nr_entries = 5;
memcpy(n16->keys, n4->keys, sizeof(n4->keys));
memcpy(n16->values, n4->values, sizeof(n4->values));
n16->keys[4] = *kb;
if (!_insert(rt, n16->values + 4, kb + 1, ke, rv)) {
free(n16);
return false;
}
free(n4);
v->type = NODE16;
v->value.ptr = n16;
} else {
n4 = v->value.ptr;
if (!_insert(rt, n4->values + n4->nr_entries, kb + 1, ke, rv))
return false;
n4->keys[n4->nr_entries] = *kb;
n4->nr_entries++;
}
return true;
}
static bool _insert_node16(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct node16 *n16 = v->value.ptr;
if (n16->nr_entries == 16) {
unsigned i;
struct node48 *n48 = zalloc(sizeof(*n48));
if (!n48)
return false;
n48->nr_entries = 17;
memset(n48->keys, 48, sizeof(n48->keys));
for (i = 0; i < 16; i++) {
n48->keys[n16->keys[i]] = i;
n48->values[i] = n16->values[i];
}
n48->keys[*kb] = 16;
if (!_insert(rt, n48->values + 16, kb + 1, ke, rv)) {
free(n48);
return false;
}
free(n16);
v->type = NODE48;
v->value.ptr = n48;
} else {
if (!_insert(rt, n16->values + n16->nr_entries, kb + 1, ke, rv))
return false;
n16->keys[n16->nr_entries] = *kb;
n16->nr_entries++;
}
return true;
}
static bool _insert_node48(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct node48 *n48 = v->value.ptr;
if (n48->nr_entries == 48) {
unsigned i;
struct node256 *n256 = zalloc(sizeof(*n256));
if (!n256)
return false;
for (i = 0; i < 256; i++) {
if (n48->keys[i] >= 48)
continue;
n256->values[i] = n48->values[n48->keys[i]];
}
if (!_insert(rt, n256->values + *kb, kb + 1, ke, rv)) {
free(n256);
return false;
}
free(n48);
v->type = NODE256;
v->value.ptr = n256;
} else {
if (!_insert(rt, n48->values + n48->nr_entries, kb + 1, ke, rv))
return false;
n48->keys[*kb] = n48->nr_entries;
n48->nr_entries++;
}
return true;
}
static bool _insert_node256(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct node256 *n256 = v->value.ptr;
bool was_unset = n256->values[*kb].type == UNSET;
if (!_insert(rt, n256->values + *kb, kb + 1, ke, rv))
return false;
if (was_unset)
n256->nr_entries++;
return true;
}
// FIXME: the tree should not be touched if insert fails (eg, OOM)
static bool _insert(struct radix_tree *rt, struct value *v, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
if (kb == ke) {
if (v->type == UNSET) {
v->type = VALUE;
v->value = rv;
rt->nr_entries++;
} else if (v->type == VALUE) {
v->value = rv;
} else {
struct value_chain *vc = zalloc(sizeof(*vc));
if (!vc)
return false;
vc->value = rv;
vc->child = *v;
v->type = VALUE_CHAIN;
v->value.ptr = vc;
rt->nr_entries++;
}
return true;
}
switch (v->type) {
case UNSET:
return _insert_unset(rt, v, kb, ke, rv);
case VALUE:
return _insert_value(rt, v, kb, ke, rv);
case VALUE_CHAIN:
return _insert_value_chain(rt, v, kb, ke, rv);
case PREFIX_CHAIN:
return _insert_prefix_chain(rt, v, kb, ke, rv);
case NODE4:
return _insert_node4(rt, v, kb, ke, rv);
case NODE16:
return _insert_node16(rt, v, kb, ke, rv);
case NODE48:
return _insert_node48(rt, v, kb, ke, rv);
case NODE256:
return _insert_node256(rt, v, kb, ke, rv);
}
// can't get here
return false;
}
struct lookup_result {
struct value *v;
uint8_t *kb;
};
static struct lookup_result _lookup_prefix(struct value *v, uint8_t *kb, uint8_t *ke)
{
unsigned i;
struct value_chain *vc;
struct prefix_chain *pc;
struct node4 *n4;
struct node16 *n16;
struct node48 *n48;
struct node256 *n256;
if (kb == ke)
return (struct lookup_result) {.v = v, .kb = kb};
switch (v->type) {
case UNSET:
case VALUE:
break;
case VALUE_CHAIN:
vc = v->value.ptr;
return _lookup_prefix(&vc->child, kb, ke);
case PREFIX_CHAIN:
pc = v->value.ptr;
if (ke - kb < pc->len)
return (struct lookup_result) {.v = v, .kb = kb};
for (i = 0; i < pc->len; i++)
if (kb[i] != pc->prefix[i])
return (struct lookup_result) {.v = v, .kb = kb};
return _lookup_prefix(&pc->child, kb + pc->len, ke);
case NODE4:
n4 = v->value.ptr;
for (i = 0; i < n4->nr_entries; i++)
if (n4->keys[i] == *kb)
return _lookup_prefix(n4->values + i, kb + 1, ke);
break;
case NODE16:
// FIXME: use binary search or simd?
n16 = v->value.ptr;
for (i = 0; i < n16->nr_entries; i++)
if (n16->keys[i] == *kb)
return _lookup_prefix(n16->values + i, kb + 1, ke);
break;
case NODE48:
n48 = v->value.ptr;
i = n48->keys[*kb];
if (i < 48)
return _lookup_prefix(n48->values + i, kb + 1, ke);
break;
case NODE256:
n256 = v->value.ptr;
return _lookup_prefix(n256->values + *kb, kb + 1, ke);
}
return (struct lookup_result) {.v = v, .kb = kb};
}
bool radix_tree_insert(struct radix_tree *rt, uint8_t *kb, uint8_t *ke, union radix_value rv)
{
struct lookup_result lr = _lookup_prefix(&rt->root, kb, ke);
return _insert(rt, lr.v, lr.kb, ke, rv);
}
// Note the degrade functions also free the original node.
static void _degrade_to_n4(struct node16 *n16, struct value *result)
{
struct node4 *n4 = zalloc(sizeof(*n4));
n4->nr_entries = n16->nr_entries;
memcpy(n4->keys, n16->keys, n16->nr_entries * sizeof(*n4->keys));
memcpy(n4->values, n16->values, n16->nr_entries * sizeof(*n4->values));
free(n16);
result->type = NODE4;
result->value.ptr = n4;
}
static void _degrade_to_n16(struct node48 *n48, struct value *result)
{
struct node4 *n16 = zalloc(sizeof(*n16));
n16->nr_entries = n48->nr_entries;
memcpy(n16->keys, n48->keys, n48->nr_entries * sizeof(*n16->keys));
memcpy(n16->values, n48->values, n48->nr_entries * sizeof(*n16->values));
free(n48);
result->type = NODE16;
result->value.ptr = n16;
}
static void _degrade_to_n48(struct node256 *n256, struct value *result)
{
unsigned i, count = 0;
struct node4 *n48 = zalloc(sizeof(*n48));
n48->nr_entries = n256->nr_entries;
for (i = 0; i < 256; i++) {
if (n256->values[i].type == UNSET)
continue;
n48->keys[count] = i;
n48->values[count] = n256->values[i];
count++;
}
free(n256);
result->type = NODE48;
result->value.ptr = n48;
}
static bool _remove(struct radix_tree *rt, struct value *root, uint8_t *kb, uint8_t *ke)
{
bool r;
unsigned i;
struct value_chain *vc;
struct prefix_chain *pc;
struct node4 *n4;
struct node16 *n16;
struct node48 *n48;
struct node256 *n256;
if (kb == ke) {
if (root->type == VALUE) {
root->type = UNSET;
_dtr(rt, root->value);
return true;
} else if (root->type == VALUE_CHAIN) {
vc = root->value.ptr;
_dtr(rt, vc->value);
memcpy(root, &vc->child, sizeof(*root));
free(vc);
return true;
} else
return false;
}
switch (root->type) {
case UNSET:
case VALUE:
// this is a value for a prefix of the key
return false;
case VALUE_CHAIN:
vc = root->value.ptr;
r = _remove(rt, &vc->child, kb, ke);
if (r && (vc->child.type == UNSET)) {
memcpy(root, &vc->child, sizeof(*root));
free(vc);
}
return r;
case PREFIX_CHAIN:
pc = root->value.ptr;
if (ke - kb < pc->len)
return false;
for (i = 0; i < pc->len; i++)
if (kb[i] != pc->prefix[i])
return false;
return _remove(rt, &pc->child, kb + pc->len, ke);
case NODE4:
n4 = root->value.ptr;
for (i = 0; i < n4->nr_entries; i++) {
if (n4->keys[i] == *kb) {
r = _remove(rt, n4->values + i, kb + 1, ke);
if (r && n4->values[i].type == UNSET) {
n4->nr_entries--;
if (i < n4->nr_entries)
// slide the entries down
memmove(n4->keys + i, n4->keys + i + 1,
sizeof(*n4->keys) * (n4->nr_entries - i));
if (!n4->nr_entries)
root->type = UNSET;
}
return r;
}
}
return false;
case NODE16:
n16 = root->value.ptr;
for (i = 0; i < n16->nr_entries; i++) {
if (n16->keys[i] == *kb) {
r = _remove(rt, n16->values + i, kb + 1, ke);
if (r && n16->values[i].type == UNSET) {
n16->nr_entries--;
if (i < n16->nr_entries)
// slide the entries down
memmove(n16->keys + i, n16->keys + i + 1,
sizeof(*n16->keys) * (n16->nr_entries - i));
if (n16->nr_entries <= 4)
_degrade_to_n4(n16, root);
}
return r;
}
}
return false;
case NODE48:
n48 = root->value.ptr;
i = n48->keys[*kb];
if (i < 48) {
r = _remove(rt, n48->values + i, kb + 1, ke);
if (r && n48->values[i].type == UNSET) {
n48->keys[*kb] = 48;
n48->nr_entries--;
if (n48->nr_entries <= 16)
_degrade_to_n16(n48, root);
}
return r;
}
return false;
case NODE256:
n256 = root->value.ptr;
r = _remove(rt, n256->values + (*kb), kb + 1, ke);
if (r && n256->values[*kb].type == UNSET) {
n256->nr_entries--;
if (n256->nr_entries <= 48)
_degrade_to_n48(n256, root);
}
return r;
}
return false;
}
bool radix_tree_remove(struct radix_tree *rt, uint8_t *key_begin, uint8_t *key_end)
{
if (_remove(rt, &rt->root, key_begin, key_end)) {
rt->nr_entries--;
return true;
}
return false;
}
static bool _prefix_chain_matches(struct lookup_result *lr, uint8_t *ke)
{
// It's possible the top node is a prefix chain, and
// the remaining key matches part of it.
if (lr->v->type == PREFIX_CHAIN) {
unsigned i, rlen = ke - lr->kb;
struct prefix_chain *pc = lr->v->value.ptr;
if (rlen < pc->len) {
for (i = 0; i < rlen; i++)
if (pc->prefix[i] != lr->kb[i])
return false;
return true;
}
}
return false;
}
unsigned radix_tree_remove_prefix(struct radix_tree *rt, uint8_t *kb, uint8_t *ke)
{
unsigned count = 0;
struct lookup_result lr = _lookup_prefix(&rt->root, kb, ke);
if (lr.kb == ke || _prefix_chain_matches(&lr, ke)) {
count = _free_node(rt, *lr.v);
lr.v->type = UNSET;
}
rt->nr_entries -= count;
return count;
}
bool radix_tree_lookup(struct radix_tree *rt,
uint8_t *kb, uint8_t *ke, union radix_value *result)
{
struct value_chain *vc;
struct lookup_result lr = _lookup_prefix(&rt->root, kb, ke);
if (lr.kb == ke) {
switch (lr.v->type) {
case VALUE:
*result = lr.v->value;
return true;
case VALUE_CHAIN:
vc = lr.v->value.ptr;
*result = vc->value;
return true;
default:
return false;
}
}
return false;
}
// FIXME: build up the keys too
static bool _iterate(struct value *v, struct radix_tree_iterator *it)
{
unsigned i;
struct value_chain *vc;
struct prefix_chain *pc;
struct node4 *n4;
struct node16 *n16;
struct node48 *n48;
struct node256 *n256;
switch (v->type) {
case UNSET:
// can't happen
break;
case VALUE:
return it->visit(it, NULL, NULL, v->value);
case VALUE_CHAIN:
vc = v->value.ptr;
return it->visit(it, NULL, NULL, vc->value) && _iterate(&vc->child, it);
case PREFIX_CHAIN:
pc = v->value.ptr;
return _iterate(&pc->child, it);
case NODE4:
n4 = (struct node4 *) v->value.ptr;
for (i = 0; i < n4->nr_entries; i++)
if (!_iterate(n4->values + i, it))
return false;
return true;
case NODE16:
n16 = (struct node16 *) v->value.ptr;
for (i = 0; i < n16->nr_entries; i++)
if (!_iterate(n16->values + i, it))
return false;
return true;
case NODE48:
n48 = (struct node48 *) v->value.ptr;
for (i = 0; i < n48->nr_entries; i++)
if (!_iterate(n48->values + i, it))
return false;
return true;
case NODE256:
n256 = (struct node256 *) v->value.ptr;
for (i = 0; i < 256; i++)
if (n256->values[i].type != UNSET && !_iterate(n256->values + i, it))
return false;
return true;
}
// can't get here
return false;
}
void radix_tree_iterate(struct radix_tree *rt, uint8_t *kb, uint8_t *ke,
struct radix_tree_iterator *it)
{
struct lookup_result lr = _lookup_prefix(&rt->root, kb, ke);
if (lr.kb == ke || _prefix_chain_matches(&lr, ke))
_iterate(lr.v, it);
}
//----------------------------------------------------------------
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