256 lines
5.7 KiB
C++
256 lines
5.7 KiB
C++
#include "btree.h"
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#include <boost/noncopyable.hpp>
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#include <boost/optional.hpp>
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using namespace boost;
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using namespace persistent_data;
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//----------------------------------------------------------------
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namespace {
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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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} __attribute__((packed));
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struct 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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//------------------------------------------------
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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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class node {
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public:
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enum type {
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INTERNAL,
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LEAF
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};
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type get_type() const;
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void set_type(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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uint64_t key_at(unsigned i) const;
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template <typename ValueTraits>
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typename ValueTraits::value_type value_at(unsigned i) const;
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private:
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struct node *raw_;
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};
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//------------------------------------------------
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// Various searches
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int bsearch(node const &n, uint64_t key, int want_hi)
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{
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int lo = -1, hi = n.get_nr_entries();
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while(hi - lo > 1) {
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int mid = lo + ((hi - lo) / 2);
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uint64_t mid_key = n.key_at(mid);
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if (mid_key == key)
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return mid;
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if (mid_key < key)
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lo = mid;
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else
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hi = mid;
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}
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return want_hi ? hi : lo;
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}
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optional<unsigned> exact_search(node const &n, uint64_t key) {
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int i = bsearch(n, key, 0);
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if (i < 0 || static_cast<unsigned>(i) >= n.get_nr_entries())
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return optional<unsigned>();
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return optional<unsigned>(i);
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}
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//------------------------------------------------
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//
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template <uint32_t BlockSize>
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node &to_node(typename block_manager<BlockSize>::write_ref b);
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unsigned
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calc_max_entries(uint32_t bs);
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// Spines
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template <uint32_t BlockSize>
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class ro_spine : private noncopyable {
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public:
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void step(block_address b);
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node get_node() const;
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private:
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};
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class internal_traits {
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public:
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typedef uint64_t value_type;
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};
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template <typename ValueTraits, uint32_t BlockSize, typename Search>
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optional<typename ValueTraits::value_type>
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lookup_raw(ro_spine<BlockSize> &spine, block_address block, uint64_t key) {
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using namespace boost;
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typedef typename ValueTraits::value_type leaf_type;
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typedef typename internal_traits::value_type internal_type;
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Search find;
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for (;;) {
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spine.step(block);
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node &n = spine.node();
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auto mi = find(n, key);
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if (!mi)
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return optional<leaf_type>();
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if (n.get_type() == node::LEAF)
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return optional<leaf_type>(n.value_at(*mi));
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block = n.value_at<internal_type>(*mi);
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}
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}
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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btree<Levels, ValueTraits, BlockSize>::btree(shared_ptr<transaction_manager<BlockSize> > tm)
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: tm_(tm),
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destroy_(false)
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{
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write_ref root = tm_.new_block();
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node &n = to_node(root);
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n.set_type(node::LEAF);
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n.set_nr_entries(0);
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n.set_max_entries(calc_max_entries(BlockSize));
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root_ = root.location();
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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btree<Levels, ValueTraits, BlockSize>::btree(shared_ptr<transaction_manager<BlockSize> > tm,
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block_address root)
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: tm_(tm),
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destroy_(false),
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root_(root)
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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btree<Levels, ValueTraits, BlockSize>::~btree()
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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typename btree<Levels, ValueTraits, BlockSize>::maybe_value
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btree<Levels, ValueTraits, BlockSize>::lookup(key const &key) const
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{
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ro_spine<BlockSize> spine;
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block_address root = root_;
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for (unsigned level = 0; level < Levels - 1; ++level) {
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auto mroot = lookup_raw<internal_traits, BlockSize, exact_search>(spine, root, key[level]);
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if (!mroot)
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return maybe_value();
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root = *mroot;
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}
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return lookup_raw<ValueTraits, BlockSize, exact_search>(spine, root, key[Levels - 1]);
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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typename btree<Levels, ValueTraits, BlockSize>::maybe_pair
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btree<Levels, ValueTraits, BlockSize>::lookup_le(key const &key) const
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{
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return maybe_pair();
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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typename btree<Levels, ValueTraits, BlockSize>::maybe_pair
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btree<Levels, ValueTraits, BlockSize>::lookup_ge(key const &key) const
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{
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return maybe_pair();
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}
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#if 0
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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void
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btree<Levels, ValueTraits, BlockSize>::insert(key const &key, typename ValueTraits::value_type const &value)
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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void
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btree<Levels, ValueTraits, BlockSize>::remove(key const &key)
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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block_address
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btree<Levels, ValueTraits, BlockSize>::get_root() const
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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void
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btree<Levels, ValueTraits, BlockSize>::set_root(block_address root)
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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block_address
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btree<Levels, ValueTraits, BlockSize>::get_root() const
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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ptr
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btree<Levels, ValueTraits, BlockSize>::clone() const
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{
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}
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template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
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void
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btree<Levels, ValueTraits, BlockSize>::destroy()
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{
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}
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#endif
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//----------------------------------------------------------------
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