354 lines
8.9 KiB
C++
354 lines
8.9 KiB
C++
#ifndef BTREE_H
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#define BTREE_H
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#include "endian_utils.h"
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#include "transaction_manager.h"
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#include <boost/noncopyable.hpp>
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#include <boost/optional.hpp>
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#include <list>
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//----------------------------------------------------------------
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namespace persistent_data {
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template <typename ValueType>
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class NoOpRefCounter {
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public:
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void inc(ValueType const &v) {}
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void dec(ValueType const &v) {}
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};
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struct uint64_traits {
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typedef base::__le64 disk_type;
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typedef uint64_t value_type;
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typedef NoOpRefCounter<uint64_t> ref_counter;
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static void unpack(disk_type const &disk, value_type &value) {
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value = base::to_cpu<uint64_t>(disk);
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}
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static void pack(value_type const &value, disk_type &disk) {
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disk = base::to_disk<base::__le64>(value);
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}
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};
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namespace btree_detail {
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using namespace base;
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using namespace std;
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using namespace boost;
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uint32_t const BTREE_CSUM_XOR = 121107;
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//------------------------------------------------
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// On disk data layout for btree nodes
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enum node_flags {
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INTERNAL_NODE = 1,
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LEAF_NODE = 1 << 1
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};
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struct node_header {
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__le32 csum;
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__le32 flags;
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__le64 blocknr; /* which block this node is supposed to live in */
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__le32 nr_entries;
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__le32 max_entries;
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__le32 value_size;
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__le32 padding;
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} __attribute__((packed));
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struct disk_node {
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struct node_header header;
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__le64 keys[0];
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} __attribute__((packed));
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enum node_type {
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INTERNAL,
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LEAF
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};
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//------------------------------------------------
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// Class that acts as an interface over the raw little endian btree
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// node data.
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template <typename ValueTraits>
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class node_ref {
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public:
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explicit node_ref(block_address b, disk_node *raw);
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uint32_t get_checksum() const;
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block_address get_location() const {
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return location_;
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}
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block_address get_block_nr() const;
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node_type get_type() const;
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void set_type(node_type t);
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unsigned get_nr_entries() const;
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void set_nr_entries(unsigned n);
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unsigned get_max_entries() const;
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void set_max_entries(unsigned n);
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// FIXME: remove this, and get the constructor to do it.
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void set_max_entries(); // calculates the max for you.
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size_t get_value_size() const;
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void set_value_size(size_t);
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uint64_t key_at(unsigned i) const;
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void set_key(unsigned i, uint64_t k);
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typename ValueTraits::value_type value_at(unsigned i) const;
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void set_value(unsigned i,
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typename ValueTraits::value_type const &v);
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// Increments the nr_entries field
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void insert_at(unsigned i,
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uint64_t key,
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typename ValueTraits::value_type const &v);
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// Does not increment nr_entries
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void overwrite_at(unsigned i,
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uint64_t key,
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typename ValueTraits::value_type const &v);
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// Copies entries from another node, appends them
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// to the back of this node. Adjusts nr_entries.
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void copy_entries(node_ref const &rhs,
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unsigned begin,
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unsigned end);
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// Various searches
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int bsearch(uint64_t key, int want_hi) const;
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optional<unsigned> exact_search(uint64_t key) const;
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int lower_bound(uint64_t key) const;
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template <typename RefCounter>
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void inc_children(RefCounter &rc);
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disk_node *raw() {
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return raw_;
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}
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disk_node const *raw() const {
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return raw_;
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}
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private:
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static unsigned calc_max_entries(void);
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void *key_ptr(unsigned i) const;
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void *value_ptr(unsigned i) const;
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block_address location_;
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disk_node *raw_;
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};
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//------------------------------------------------
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//
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template <typename ValueTraits>
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node_ref<ValueTraits>
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to_node(typename block_manager<>::read_ref &b)
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{
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// FIXME: this should return a const read_ref somehow.
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return node_ref<ValueTraits>(
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b.get_location(),
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reinterpret_cast<disk_node *>(
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const_cast<unsigned char *>(b.data())));
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}
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template <typename ValueTraits>
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node_ref<ValueTraits>
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to_node(typename block_manager<>::write_ref &b)
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{
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return node_ref<ValueTraits>(
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b.get_location(),
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reinterpret_cast<disk_node *>(
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const_cast<unsigned char *>(b.data())));
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}
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class ro_spine : private noncopyable {
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public:
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ro_spine(transaction_manager::ptr tm)
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: tm_(tm) {
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}
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void step(block_address b);
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template <typename ValueTraits>
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node_ref<ValueTraits> get_node() {
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return to_node<ValueTraits>(spine_.back());
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}
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private:
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transaction_manager::ptr tm_;
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std::list<block_manager<>::read_ref> spine_;
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};
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class shadow_spine : private noncopyable {
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public:
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typedef transaction_manager::read_ref read_ref;
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typedef transaction_manager::write_ref write_ref;
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shadow_spine(transaction_manager::ptr tm)
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: tm_(tm) {
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}
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// true if the children of the shadow need incrementing
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bool step(block_address b);
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void step(transaction_manager::write_ref b) {
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spine_.push_back(b);
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if (spine_.size() == 1)
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root_ = spine_.front().get_location();
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else if (spine_.size() > 2)
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spine_.pop_front();
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}
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void pop() {
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spine_.pop_back();
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}
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template <typename ValueTraits>
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node_ref<ValueTraits> get_node() {
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return to_node<ValueTraits>(spine_.back());
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}
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block_address get_block() const {
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return spine_.back().get_location();
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}
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bool has_parent() const {
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return spine_.size() > 1;
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}
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node_ref<uint64_traits> get_parent() {
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if (spine_.size() < 2)
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throw std::runtime_error("no parent");
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return to_node<uint64_traits>(spine_.front());
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}
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block_address get_parent_location() const {
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return spine_.front().get_location();
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}
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block_address get_root() const {
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return root_;
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}
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private:
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transaction_manager::ptr tm_;
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std::list<block_manager<>::write_ref> spine_;
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block_address root_;
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};
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}
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template <unsigned Levels, typename ValueTraits>
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class btree {
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public:
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typedef boost::shared_ptr<btree<Levels, ValueTraits> > ptr;
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typedef uint64_t key[Levels];
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typedef typename ValueTraits::value_type value_type;
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typedef boost::optional<value_type> maybe_value;
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typedef boost::optional<std::pair<unsigned, value_type> > maybe_pair;
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typedef typename block_manager<>::read_ref read_ref;
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typedef typename block_manager<>::write_ref write_ref;
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typedef typename btree_detail::node_ref<ValueTraits> leaf_node;
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typedef typename btree_detail::node_ref<uint64_traits> internal_node;
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btree(typename persistent_data::transaction_manager::ptr tm,
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typename ValueTraits::ref_counter rc);
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btree(typename transaction_manager::ptr tm,
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block_address root,
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typename ValueTraits::ref_counter rc);
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~btree();
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maybe_value lookup(key const &key) const;
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maybe_pair lookup_le(key const &key) const;
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maybe_pair lookup_ge(key const &key) const;
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void insert(key const &key, typename ValueTraits::value_type const &value);
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void remove(key const &key);
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void set_root(block_address root);
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block_address get_root() const;
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ptr clone() const;
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// free the on disk btree when the destructor is called
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void destroy();
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// Derive a class from this base class if you need to
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// inspect the individual nodes that make up a btree.
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class visitor {
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public:
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virtual ~visitor() {}
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typedef boost::shared_ptr<visitor> ptr;
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// The bool return values indicate whether the walk
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// should be continued into sub trees of the node (true == continue).
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virtual bool visit_internal(unsigned level, bool sub_root, boost::optional<uint64_t> key,
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internal_node const &n) = 0;
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virtual bool visit_internal_leaf(unsigned level, bool sub_root, boost::optional<uint64_t> key,
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internal_node const &n) = 0;
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virtual bool visit_leaf(unsigned level, bool sub_root, boost::optional<uint64_t> key,
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leaf_node const &n) = 0;
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virtual void visit_complete() {}
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};
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// Walks the tree in depth first order
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void visit(typename visitor::ptr visitor) const;
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private:
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template <typename ValueTraits2, typename Search>
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optional<typename ValueTraits2::value_type>
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lookup_raw(btree_detail::ro_spine &spine, block_address block, uint64_t key) const;
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template <typename ValueTraits2>
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void split_node(btree_detail::shadow_spine &spine,
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block_address parent_index,
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uint64_t key,
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bool top);
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template <typename ValueTraits2>
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void split_beneath(btree_detail::shadow_spine &spine, uint64_t key);
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template <typename ValueTraits2>
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void split_sibling(btree_detail::shadow_spine &spine,
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block_address parent_index,
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uint64_t key);
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template <typename ValueTraits2>
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bool
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insert_location(btree_detail::shadow_spine &spine,
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block_address block,
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uint64_t key,
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int *index);
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void walk_tree(typename visitor::ptr visitor,
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unsigned level, bool root, boost::optional<uint64_t> key,
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block_address b) const;
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typename persistent_data::transaction_manager::ptr tm_;
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bool destroy_;
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block_address root_;
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NoOpRefCounter<uint64_t> internal_rc_;
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typename ValueTraits::ref_counter rc_;
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};
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};
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#include "btree.tcc"
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//----------------------------------------------------------------
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#endif
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