thin-provisioning-tools/persistent-data/data-structures/btree.tcc

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// Copyright (C) 2011 Red Hat, Inc. All rights reserved.
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//
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// This file is part of the thin-provisioning-tools source.
//
// thin-provisioning-tools is free software: you can redistribute it
// and/or modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation, either version 3 of
// the License, or (at your option) any later version.
//
// thin-provisioning-tools is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with thin-provisioning-tools. If not, see
// <http://www.gnu.org/licenses/>.
#include "btree.h"
#include "persistent-data/errors.h"
#include "persistent-data/checksum.h"
#include "persistent-data/transaction_manager.h"
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#include <iostream>
//----------------------------------------------------------------
namespace {
using namespace base;
using namespace persistent_data;
using namespace btree_detail;
using namespace std;
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struct btree_node_validator : public bcache::validator {
virtual void check(void const *raw, block_address location) const {
disk_node const *data = reinterpret_cast<disk_node const *>(raw);
node_header const *n = &data->header;
crc32c sum(BTREE_CSUM_XOR);
sum.append(&n->flags, MD_BLOCK_SIZE - sizeof(uint32_t));
if (sum.get_sum() != to_cpu<uint32_t>(n->csum)) {
std::ostringstream out;
out << "bad checksum in btree node (block " << location << ")";
throw checksum_error(out.str());
}
if (to_cpu<uint64_t>(n->blocknr) != location) {
std::ostringstream out;
out << "bad block nr in btree node (block = " << location << ")";
throw checksum_error(out.str());
}
}
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virtual void prepare(void *raw, block_address location) const {
disk_node *data = reinterpret_cast<disk_node *>(raw);
node_header *n = &data->header;
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n->blocknr = to_disk<base::le64, uint64_t>(location);
crc32c sum(BTREE_CSUM_XOR);
sum.append(&n->flags, MD_BLOCK_SIZE - sizeof(uint32_t));
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n->csum = to_disk<base::le32>(sum.get_sum());
}
};
}
//----------------------------------------------------------------
namespace persistent_data {
inline void
ro_spine::step(block_address b)
{
spine_.push_back(tm_.read_lock(b, validator_));
if (spine_.size() > 2)
spine_.pop_front();
}
inline bool
shadow_spine::step(block_address b)
{
pair<write_ref, bool> p = tm_.shadow(b, validator_);
try {
step(p.first);
} catch (...) {
tm_.get_sm()->dec(p.first.get_location());
throw;
}
return p.second;
}
//----------------------------------------------------------------
template <typename ValueTraits>
node_ref<ValueTraits>::node_ref(block_address location, disk_node *raw)
: location_(location),
raw_(raw),
checked_(false)
{
}
template <typename ValueTraits>
uint32_t
node_ref<ValueTraits>::get_checksum() const
{
return to_cpu<uint32_t>(raw_->header.csum);
}
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template <typename ValueTraits>
block_address
node_ref<ValueTraits>::get_block_nr() const
{
return to_cpu<uint64_t>(raw_->header.blocknr);
}
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template <typename ValueTraits>
btree_detail::node_type
node_ref<ValueTraits>::get_type() const
{
uint32_t flags = to_cpu<uint32_t>(raw_->header.flags);
if (flags & INTERNAL_NODE) {
if (flags & LEAF_NODE)
throw runtime_error("btree node is both internal and leaf");
return INTERNAL;
} else if (flags & LEAF_NODE)
return LEAF;
else
throw runtime_error("unknown node type");
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::set_type(node_type t)
{
uint32_t flags = to_cpu<uint32_t>(raw_->header.flags);
switch (t) {
case INTERNAL:
flags = INTERNAL_NODE;
break;
case LEAF:
flags = LEAF_NODE;
break;
}
raw_->header.flags = to_disk<le32>(flags);
}
template <typename ValueTraits>
unsigned
node_ref<ValueTraits>::get_nr_entries() const
{
return to_cpu<uint32_t>(raw_->header.nr_entries);
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::set_nr_entries(unsigned n)
{
raw_->header.nr_entries = to_disk<le32>(n);
}
template <typename ValueTraits>
unsigned
node_ref<ValueTraits>::get_max_entries() const
{
return to_cpu<uint32_t>(raw_->header.max_entries);
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::set_max_entries(unsigned n)
{
raw_->header.max_entries = to_disk<le32>(n);
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::set_max_entries()
{
set_max_entries(calc_max_entries());
}
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template <typename ValueTraits>
size_t
node_ref<ValueTraits>::get_value_size() const
{
return to_cpu<uint32_t>(raw_->header.value_size);
}
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template <typename ValueTraits>
void
node_ref<ValueTraits>::set_value_size(size_t s)
{
raw_->header.value_size = to_disk<le32>(static_cast<uint32_t>(s));
}
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template <typename ValueTraits>
uint64_t
node_ref<ValueTraits>::key_at(unsigned i) const
{
if (i >= get_nr_entries())
throw runtime_error("key index out of bounds");
return to_cpu<uint64_t>(raw_->keys[i]);
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::set_key(unsigned i, uint64_t k)
{
raw_->keys[i] = to_disk<le64>(k);
}
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template <typename ValueTraits>
typename ValueTraits::value_type
node_ref<ValueTraits>::value_at(unsigned i) const
{
if (i >= get_nr_entries())
throw runtime_error("value index out of bounds");
// We have to copy because of alignment issues.
typename ValueTraits::disk_type d;
::memcpy(&d, value_ptr(i), sizeof(d));
typename ValueTraits::value_type v;
ValueTraits::unpack(d, v);
return v;
}
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template <typename ValueTraits>
void
node_ref<ValueTraits>::set_value(unsigned i,
typename ValueTraits::value_type const &v)
{
typename ValueTraits::disk_type d;
ValueTraits::pack(v, d);
::memcpy(value_ptr(i), &d, sizeof(d));
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::insert_at(unsigned i,
uint64_t key,
typename ValueTraits::value_type const &v)
{
unsigned n = get_nr_entries();
if ((n + 1) > get_max_entries())
throw runtime_error("too many entries");
set_nr_entries(n + 1);
::memmove(key_ptr(i + 1), key_ptr(i), sizeof(uint64_t) * (n - i));
::memmove(value_ptr(i + 1), value_ptr(i), sizeof(typename ValueTraits::disk_type) * (n - i));
overwrite_at(i, key, v);
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::overwrite_at(unsigned i,
uint64_t key,
typename ValueTraits::value_type const &v)
{
set_key(i, key);
set_value(i, v);
}
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template <typename ValueTraits>
void
node_ref<ValueTraits>::copy_entries(node_ref const &rhs,
unsigned begin,
unsigned end)
{
unsigned count = end - begin;
unsigned n = get_nr_entries();
if ((n + count) > get_max_entries())
throw runtime_error("too many entries");
::memcpy(key_ptr(n), rhs.key_ptr(begin), sizeof(uint64_t) * count);
::memcpy(value_ptr(n), rhs.value_ptr(begin), sizeof(typename ValueTraits::disk_type) * count);
set_nr_entries(n + count);
}
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template <typename ValueTraits>
int
node_ref<ValueTraits>::bsearch(uint64_t key, int want_hi) const
{
int lo = -1, hi = get_nr_entries();
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while(hi - lo > 1) {
int mid = lo + ((hi - lo) / 2);
uint64_t mid_key = key_at(mid);
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if (mid_key == key)
return mid;
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if (mid_key < key)
lo = mid;
else
hi = mid;
}
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return want_hi ? hi : lo;
}
template <typename ValueTraits>
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boost::optional<unsigned>
node_ref<ValueTraits>::exact_search(uint64_t key) const
{
int i = bsearch(key, 0);
if (i < 0 || static_cast<unsigned>(i) >= get_nr_entries())
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return boost::optional<unsigned>();
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if (key != key_at(i))
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return boost::optional<unsigned>();
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return boost::optional<unsigned>(i);
}
template <typename ValueTraits>
int
node_ref<ValueTraits>::lower_bound(uint64_t key) const
{
return bsearch(key, 0);
}
template <typename ValueTraits>
unsigned
node_ref<ValueTraits>::calc_max_entries(void)
{
uint32_t total;
// key + value
size_t elt_size = sizeof(uint64_t) + sizeof(typename ValueTraits::disk_type);
total = (MD_BLOCK_SIZE - sizeof(struct node_header)) / elt_size;
return (total / 3) * 3; // rounds down
}
template <typename ValueTraits>
void *
node_ref<ValueTraits>::key_ptr(unsigned i) const
{
check_fits_within_block();
return raw_->keys + i;
}
template <typename ValueTraits>
void *
node_ref<ValueTraits>::value_ptr(unsigned i) const
{
check_fits_within_block();
void *value_base = &raw_->keys[to_cpu<uint32_t>(raw_->header.max_entries)];
return static_cast<unsigned char *>(value_base) +
sizeof(typename ValueTraits::disk_type) * i;
}
template <typename ValueTraits>
template <typename RefCounter>
void
node_ref<ValueTraits>::inc_children(RefCounter &rc)
{
unsigned nr_entries = get_nr_entries();
for (unsigned i = 0; i < nr_entries; i++) {
typename ValueTraits::value_type v;
typename ValueTraits::disk_type d;
::memcpy(&d, value_ptr(i), sizeof(d));
ValueTraits::unpack(d, v);
rc.inc(v);
}
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}
template <typename ValueTraits>
bool
node_ref<ValueTraits>::value_sizes_match() const {
return sizeof(typename ValueTraits::disk_type) == get_value_size();
}
template <typename ValueTraits>
std::string
node_ref<ValueTraits>::value_mismatch_string() const {
std::ostringstream out;
out << "value size mismatch: expected " << sizeof(typename ValueTraits::disk_type)
<< ", but got " << get_value_size()
<< ". This is not the btree you are looking for." << std::endl;
return out.str();
}
template <typename ValueTraits>
void
node_ref<ValueTraits>::check_fits_within_block() const {
if (checked_)
return;
if (!value_sizes_match())
throw std::runtime_error(value_mismatch_string());
unsigned max = calc_max_entries();
if (max < get_nr_entries()) {
std::ostringstream out;
out << "Bad nr of elements: max per block = "
<< max << ", actual = " << get_nr_entries() << std::endl;
throw std::runtime_error(out.str());
}
checked_ = true;
}
//--------------------------------
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template <unsigned Levels, typename ValueTraits>
btree<Levels, ValueTraits>::
btree(transaction_manager &tm,
typename ValueTraits::ref_counter rc)
: tm_(tm),
destroy_(false),
internal_rc_(tm.get_sm()),
rc_(rc),
validator_(new btree_node_validator)
{
using namespace btree_detail;
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write_ref root = tm_.new_block(validator_);
if (Levels > 1) {
internal_node n = to_node<block_traits>(root);
n.set_type(btree_detail::LEAF);
n.set_nr_entries(0);
n.set_max_entries();
n.set_value_size(sizeof(typename block_traits::disk_type));
} else {
leaf_node n = to_node<ValueTraits>(root);
n.set_type(btree_detail::LEAF);
n.set_nr_entries(0);
n.set_max_entries();
n.set_value_size(sizeof(typename ValueTraits::disk_type));
}
root_ = root.get_location();
}
template <unsigned Levels, typename ValueTraits>
btree<Levels, ValueTraits>::
btree(transaction_manager &tm,
block_address root,
typename ValueTraits::ref_counter rc)
: tm_(tm),
destroy_(false),
root_(root),
internal_rc_(tm.get_sm()),
rc_(rc),
validator_(new btree_node_validator)
{
}
template <unsigned Levels, typename ValueTraits>
btree<Levels, ValueTraits>::~btree()
{
}
namespace {
template <typename ValueTraits>
struct lower_bound_search {
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static boost::optional<unsigned> search(btree_detail::node_ref<ValueTraits> n, uint64_t key) {
int i = n.lower_bound(key);
return (i < 0) ? boost::optional<unsigned>() : boost::optional<unsigned>(i);
}
};
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template <typename ValueTraits>
struct exact_search {
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static boost::optional<unsigned> search(btree_detail::node_ref<ValueTraits> n, uint64_t key) {
return n.exact_search(key);
}
};
}
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template <unsigned Levels, typename ValueTraits>
typename btree<Levels, ValueTraits>::maybe_value
btree<Levels, ValueTraits>::lookup(key const &key) const
{
using namespace btree_detail;
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ro_spine spine(tm_, validator_);
block_address root = root_;
for (unsigned level = 0; level < Levels - 1; ++level) {
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boost::optional<block_address> mroot =
lookup_raw<block_traits, lower_bound_search<block_traits> >(spine, root, key[level]);
if (!mroot)
return maybe_value();
root = *mroot;
}
return lookup_raw<ValueTraits, exact_search<ValueTraits> >(spine, root, key[Levels - 1]);
}
template <unsigned Levels, typename ValueTraits>
typename btree<Levels, ValueTraits>::maybe_pair
btree<Levels, ValueTraits>::lookup_le(key const &key) const
{
using namespace btree_detail;
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return maybe_pair();
}
template <unsigned Levels, typename ValueTraits>
typename btree<Levels, ValueTraits>::maybe_pair
btree<Levels, ValueTraits>::lookup_ge(key const &key) const
{
using namespace btree_detail;
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return maybe_pair();
}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::
insert(key const &key,
typename ValueTraits::value_type const &value)
{
using namespace btree_detail;
block_address block = root_;
int index = 0; // FIXME: ???
shadow_spine spine(tm_, validator_);
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for (unsigned level = 0; level < Levels - 1; ++level) {
bool need_insert = insert_location<block_traits>(spine, block, key[level], &index, internal_rc_);
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internal_node n = spine.template get_node<block_traits>();
if (need_insert) {
btree<Levels - 1, ValueTraits> new_tree(tm_, rc_);
n.insert_at(index, key[level], new_tree.get_root());
}
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block = n.value_at(index);
}
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bool need_insert = insert_location<ValueTraits>(spine, block, key[Levels - 1], &index, rc_);
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leaf_node n = spine.template get_node<ValueTraits>();
if (need_insert)
n.insert_at(index, key[Levels - 1], value);
else
// FIXME: check if we're overwriting with the same value.
n.set_value(index, value);
root_ = spine.get_root();
}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::remove(key const &key)
{
using namespace btree_detail;
}
template <unsigned Levels, typename ValueTraits>
block_address
btree<Levels, ValueTraits>::get_root() const
{
return root_;
}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::set_root(block_address root)
{
using namespace btree_detail;
root_ = root;
}
template <unsigned Levels, typename ValueTraits>
typename btree<Levels, ValueTraits>::ptr
btree<Levels, ValueTraits>::clone() const
{
tm_.get_sm()->inc(root_);
return ptr(new btree<Levels, ValueTraits>(tm_, root_, rc_));
}
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#if 0
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::destroy()
{
using namespace btree_detail;
}
#endif
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template <unsigned Levels, typename _>
template <typename ValueTraits, typename Search>
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boost::optional<typename ValueTraits::value_type>
btree<Levels, _>::
lookup_raw(ro_spine &spine, block_address block, uint64_t key) const
{
using namespace boost;
typedef typename ValueTraits::value_type leaf_type;
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for (;;) {
spine.step(block);
node_ref<ValueTraits> leaf = spine.template get_node<ValueTraits>();
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boost::optional<unsigned> mi;
if (leaf.get_type() == btree_detail::LEAF) {
mi = Search::search(leaf, key);
if (!mi)
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return boost::optional<leaf_type>();
return boost::optional<leaf_type>(leaf.value_at(*mi));
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}
{
int lb = leaf.lower_bound(key);
if (lb < 0)
return boost::optional<leaf_type>();
mi = lb;
}
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node_ref<block_traits> internal = spine.template get_node<block_traits>();
block = internal.value_at(*mi);
}
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}
template <unsigned Levels, typename _>
template <typename ValueTraits>
void
btree<Levels, _>::
split_node(btree_detail::shadow_spine &spine,
block_address parent_index,
uint64_t key,
bool top)
{
node_ref<ValueTraits> n = spine.template get_node<ValueTraits>();
if (n.get_nr_entries() == n.get_max_entries()) {
if (top)
split_beneath<ValueTraits>(spine, key);
else
split_sibling<ValueTraits>(spine, parent_index, key);
}
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}
template <unsigned Levels, typename _>
template <typename ValueTraits>
void
btree<Levels, _>::
split_beneath(btree_detail::shadow_spine &spine,
uint64_t key)
{
using namespace btree_detail;
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node_type type;
unsigned nr_left, nr_right;
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write_ref left = tm_.new_block(validator_);
node_ref<ValueTraits> l = to_node<ValueTraits>(left);
l.set_nr_entries(0);
l.set_max_entries();
l.set_value_size(sizeof(typename ValueTraits::disk_type));
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write_ref right = tm_.new_block(validator_);
node_ref<ValueTraits> r = to_node<ValueTraits>(right);
r.set_nr_entries(0);
r.set_max_entries();
r.set_value_size(sizeof(typename ValueTraits::disk_type));
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{
node_ref<ValueTraits> p = spine.template get_node<ValueTraits>();
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if (p.get_value_size() != sizeof(typename ValueTraits::disk_type))
throw std::runtime_error("bad value_size");
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nr_left = p.get_nr_entries() / 2;
nr_right = p.get_nr_entries() - nr_left;
type = p.get_type();
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l.set_type(type);
l.copy_entries(p, 0, nr_left);
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r.set_type(type);
r.copy_entries(p, nr_left, nr_left + nr_right);
}
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{
// The parent may have changed value type, so we re-get it.
internal_node p = spine.template get_node<block_traits>();
p.set_type(btree_detail::INTERNAL);
p.set_max_entries();
p.set_nr_entries(2);
p.set_value_size(sizeof(typename block_traits::disk_type));
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p.overwrite_at(0, l.key_at(0), left.get_location());
p.overwrite_at(1, r.key_at(0), right.get_location());
}
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if (key < r.key_at(0))
spine.step(left);
else
spine.step(right);
}
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template <unsigned Levels, typename _>
template <typename ValueTraits>
void
btree<Levels, _>::
split_sibling(btree_detail::shadow_spine &spine,
block_address parent_index,
uint64_t key)
{
using namespace btree_detail;
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node_ref<ValueTraits> l = spine.template get_node<ValueTraits>();
block_address left = spine.get_block();
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write_ref right = tm_.new_block(validator_);
node_ref<ValueTraits> r = to_node<ValueTraits>(right);
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unsigned nr_left = l.get_nr_entries() / 2;
unsigned nr_right = l.get_nr_entries() - nr_left;
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r.set_nr_entries(0);
r.set_max_entries();
r.set_type(l.get_type());
r.set_value_size(sizeof(typename ValueTraits::disk_type));
r.copy_entries(l, nr_left, nr_left + nr_right);
l.set_nr_entries(nr_left);
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internal_node p = spine.get_parent();
p.overwrite_at(parent_index, l.key_at(0), left);
p.insert_at(parent_index + 1, r.key_at(0), right.get_location());
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if (key >= r.key_at(0)) {
spine.pop();
spine.step(right);
}
}
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// Returns true if we need a new insertion, rather than overwrite.
template <unsigned Levels, typename _>
template <typename ValueTraits, typename RC>
bool
btree<Levels, _>::
insert_location(btree_detail::shadow_spine &spine,
block_address block,
uint64_t key,
int *index,
RC &leaf_rc)
{
using namespace btree_detail;
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bool top = true; // this isn't the same as spine.has_parent()
int i = *index;
bool inc = false;
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for (;;) {
inc = spine.step(block);
if (inc)
inc_children<ValueTraits>(spine, leaf_rc);
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// patch up the parent to point to the new shadow
if (spine.has_parent()) {
internal_node p = spine.get_parent();
p.set_value(i, spine.get_block());
}
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internal_node internal = spine.template get_node<block_traits>();
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// Split the node if we're full
if (internal.get_type() == INTERNAL)
split_node<block_traits>(spine, i, key, top);
else
split_node<ValueTraits>(spine, i, key, top);
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internal = spine.template get_node<block_traits>();
i = internal.lower_bound(key);
if (internal.get_type() == btree_detail::LEAF)
break;
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if (i < 0) {
internal.set_key(0, key);
i = 0;
}
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block = internal.value_at(i);
top = false;
}
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node_ref<ValueTraits> leaf = spine.template get_node<ValueTraits>();
// FIXME: gross
if (i < 0 || leaf.key_at(i) != key)
i++;
// do decrement the old value if it already exists
// FIXME: I'm not sure about this, I don't understand the |inc| reference
if (static_cast<unsigned>(i) < leaf.get_nr_entries() && leaf.key_at(i) == key && inc) {
// dec old entry
}
*index = i;
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return ((static_cast<unsigned>(i) >= leaf.get_nr_entries()) ||
(leaf.key_at(i) != key));
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}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::visit_depth_first(visitor &v) const
{
node_location loc;
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walk_tree(v, loc, root_);
v.visit_complete();
}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::walk_tree(visitor &v,
node_location const &loc,
block_address b) const
{
try {
walk_tree_internal(v, loc, b);
} catch (std::runtime_error const &e) {
switch (v.error_accessing_node(loc, b, e.what())) {
case visitor::EXCEPTION_HANDLED:
break;
case visitor::RETHROW_EXCEPTION:
throw;
}
}
}
template <unsigned Levels, typename ValueTraits>
void
btree<Levels, ValueTraits>::walk_tree_internal(visitor &v,
node_location const &loc,
block_address b) const
{
using namespace btree_detail;
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read_ref blk = tm_.read_lock(b, validator_);
internal_node o = to_node<block_traits>(blk);
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// FIXME: use a switch statement
if (o.get_type() == INTERNAL) {
if (v.visit_internal(loc, o)) {
for (unsigned i = 0; i < o.get_nr_entries(); i++)
tm_.prefetch(o.value_at(i));
for (unsigned i = 0; i < o.get_nr_entries(); i++) {
node_location loc2(loc);
loc2.inc_depth();
loc2.key = o.key_at(i);
walk_tree(v, loc2, o.value_at(i));
}
}
} else if (loc.path.size() < Levels - 1) {
if (v.visit_internal_leaf(loc, o))
for (unsigned i = 0; i < o.get_nr_entries(); i++) {
node_location loc2(loc);
loc2.push_key(o.key_at(i));
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loc2.key = boost::optional<uint64_t>();
walk_tree(v, loc2, o.value_at(i));
}
} else {
leaf_node ov = to_node<ValueTraits>(blk);
v.visit_leaf(loc, ov);
}
}
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template <unsigned Levels, typename _>
template <typename ValueTraits, typename RefCounter>
void
btree<Levels, _>::inc_children(btree_detail::shadow_spine &spine, RefCounter &leaf_rc)
{
node_ref<block_traits> nr = spine.template get_node<block_traits>();
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if (nr.get_type() == INTERNAL)
nr.inc_children(internal_rc_);
else {
node_ref<ValueTraits> leaf = spine.template get_node<ValueTraits>();
leaf.inc_children(leaf_rc);
}
}
}
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//----------------------------------------------------------------