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-rw-r--r--src/crimson/common/fixed_kv_node_layout.h700
1 files changed, 700 insertions, 0 deletions
diff --git a/src/crimson/common/fixed_kv_node_layout.h b/src/crimson/common/fixed_kv_node_layout.h
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+++ b/src/crimson/common/fixed_kv_node_layout.h
@@ -0,0 +1,700 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#pragma once
+
+#include <iostream>
+
+#include "include/byteorder.h"
+
+#include "crimson/common/layout.h"
+
+namespace crimson::common {
+
+template <typename T, bool is_const>
+struct maybe_const_t {
+};
+template<typename T>
+struct maybe_const_t<T, true> {
+ using type = const T*;
+};
+template<typename T>
+struct maybe_const_t<T, false> {
+ using type = T*;
+};
+
+
+/**
+ * FixedKVNodeLayout
+ *
+ * Reusable implementation of a fixed size block mapping
+ * K -> V with internal representations KINT and VINT.
+ *
+ * Uses absl::container_internal::Layout for the actual memory layout.
+ *
+ * The primary interface exposed is centered on the iterator
+ * and related methods.
+ *
+ * Also included are helpers for doing splits and merges as for a btree.
+ */
+template <
+ size_t CAPACITY,
+ typename Meta,
+ typename MetaInt,
+ typename K,
+ typename KINT,
+ typename V,
+ typename VINT,
+ bool VALIDATE_INVARIANTS=true>
+class FixedKVNodeLayout {
+ char *buf = nullptr;
+
+ using L = absl::container_internal::Layout<ceph_le32, MetaInt, KINT, VINT>;
+ static constexpr L layout{1, 1, CAPACITY, CAPACITY};
+
+public:
+ template <bool is_const>
+ struct iter_t {
+ friend class FixedKVNodeLayout;
+ using parent_t = typename maybe_const_t<FixedKVNodeLayout, is_const>::type;
+
+ parent_t node;
+ uint16_t offset;
+
+ iter_t(
+ parent_t parent,
+ uint16_t offset) : node(parent), offset(offset) {}
+
+ iter_t(const iter_t &) = default;
+ iter_t(iter_t &&) = default;
+ iter_t &operator=(const iter_t &) = default;
+ iter_t &operator=(iter_t &&) = default;
+
+ operator iter_t<!is_const>() const {
+ static_assert(!is_const);
+ return iter_t<!is_const>(node, offset);
+ }
+
+ // Work nicely with for loops without requiring a nested type.
+ iter_t &operator*() { return *this; }
+ iter_t *operator->() { return this; }
+
+ iter_t operator++(int) {
+ auto ret = *this;
+ ++offset;
+ return ret;
+ }
+
+ iter_t &operator++() {
+ ++offset;
+ return *this;
+ }
+
+ uint16_t operator-(const iter_t &rhs) const {
+ assert(rhs.node == node);
+ return offset - rhs.offset;
+ }
+
+ iter_t operator+(uint16_t off) const {
+ return iter_t(
+ node,
+ offset + off);
+ }
+ iter_t operator-(uint16_t off) const {
+ return iter_t(
+ node,
+ offset - off);
+ }
+
+ bool operator==(const iter_t &rhs) const {
+ assert(node == rhs.node);
+ return rhs.offset == offset;
+ }
+
+ bool operator!=(const iter_t &rhs) const {
+ return !(*this == rhs);
+ }
+
+ K get_key() const {
+ return K(node->get_key_ptr()[offset]);
+ }
+
+ K get_next_key_or_max() const {
+ auto next = *this + 1;
+ if (next == node->end())
+ return std::numeric_limits<K>::max();
+ else
+ return next->get_key();
+ }
+
+ void set_val(V val) const {
+ static_assert(!is_const);
+ node->get_val_ptr()[offset] = VINT(val);
+ }
+
+ V get_val() const {
+ return V(node->get_val_ptr()[offset]);
+ };
+
+ bool contains(K addr) const {
+ return (get_key() <= addr) && (get_next_key_or_max() > addr);
+ }
+
+ uint16_t get_offset() const {
+ return offset;
+ }
+
+ private:
+ void set_key(K _lb) const {
+ static_assert(!is_const);
+ KINT lb;
+ lb = _lb;
+ node->get_key_ptr()[offset] = lb;
+ }
+
+ typename maybe_const_t<char, is_const>::type get_key_ptr() const {
+ return reinterpret_cast<
+ typename maybe_const_t<char, is_const>::type>(
+ node->get_key_ptr() + offset);
+ }
+
+ typename maybe_const_t<char, is_const>::type get_val_ptr() const {
+ return reinterpret_cast<
+ typename maybe_const_t<char, is_const>::type>(
+ node->get_val_ptr() + offset);
+ }
+ };
+ using const_iterator = iter_t<true>;
+ using iterator = iter_t<false>;
+
+ struct delta_t {
+ enum class op_t : uint8_t {
+ INSERT,
+ REMOVE,
+ UPDATE,
+ } op;
+ KINT key;
+ VINT val;
+
+ void replay(FixedKVNodeLayout &l) {
+ switch (op) {
+ case op_t::INSERT: {
+ l.insert(l.lower_bound(key), key, val);
+ break;
+ }
+ case op_t::REMOVE: {
+ auto iter = l.find(key);
+ assert(iter != l.end());
+ l.remove(iter);
+ break;
+ }
+ case op_t::UPDATE: {
+ auto iter = l.find(key);
+ assert(iter != l.end());
+ l.update(iter, val);
+ break;
+ }
+ default:
+ assert(0 == "Impossible");
+ }
+ }
+
+ bool operator==(const delta_t &rhs) const {
+ return op == rhs.op &&
+ key == rhs.key &&
+ val == rhs.val;
+ }
+ };
+
+public:
+ class delta_buffer_t {
+ std::vector<delta_t> buffer;
+ public:
+ bool empty() const {
+ return buffer.empty();
+ }
+ void insert(
+ const K &key,
+ const V &val) {
+ KINT k;
+ k = key;
+ buffer.push_back(
+ delta_t{
+ delta_t::op_t::INSERT,
+ k,
+ VINT(val)
+ });
+ }
+ void update(
+ const K &key,
+ const V &val) {
+ KINT k;
+ k = key;
+ buffer.push_back(
+ delta_t{
+ delta_t::op_t::UPDATE,
+ k,
+ VINT(val)
+ });
+ }
+ void remove(const K &key) {
+ KINT k;
+ k = key;
+ buffer.push_back(
+ delta_t{
+ delta_t::op_t::REMOVE,
+ k,
+ VINT()
+ });
+ }
+ void replay(FixedKVNodeLayout &node) {
+ for (auto &i: buffer) {
+ i.replay(node);
+ }
+ }
+ size_t get_bytes() const {
+ return buffer.size() * sizeof(delta_t);
+ }
+ void copy_out(char *out, size_t len) {
+ assert(len == get_bytes());
+ ::memcpy(out, reinterpret_cast<const void *>(buffer.data()), get_bytes());
+ buffer.clear();
+ }
+ void copy_in(const char *out, size_t len) {
+ assert(empty());
+ assert(len % sizeof(delta_t) == 0);
+ buffer = std::vector(
+ reinterpret_cast<const delta_t*>(out),
+ reinterpret_cast<const delta_t*>(out + len));
+ }
+ bool operator==(const delta_buffer_t &rhs) const {
+ return buffer == rhs.buffer;
+ }
+ };
+
+ void journal_insert(
+ const_iterator _iter,
+ const K &key,
+ const V &val,
+ delta_buffer_t *recorder) {
+ auto iter = iterator(this, _iter.offset);
+ if (recorder) {
+ recorder->insert(
+ key,
+ val);
+ }
+ insert(iter, key, val);
+ }
+
+ void journal_update(
+ const_iterator _iter,
+ const V &val,
+ delta_buffer_t *recorder) {
+ auto iter = iterator(this, _iter.offset);
+ if (recorder) {
+ recorder->update(iter->get_key(), val);
+ }
+ update(iter, val);
+ }
+
+ void journal_replace(
+ const_iterator _iter,
+ const K &key,
+ const V &val,
+ delta_buffer_t *recorder) {
+ auto iter = iterator(this, _iter.offset);
+ if (recorder) {
+ recorder->remove(iter->get_key());
+ recorder->insert(key, val);
+ }
+ replace(iter, key, val);
+ }
+
+
+ void journal_remove(
+ const_iterator _iter,
+ delta_buffer_t *recorder) {
+ auto iter = iterator(this, _iter.offset);
+ if (recorder) {
+ recorder->remove(iter->get_key());
+ }
+ remove(iter);
+ }
+
+
+ FixedKVNodeLayout(char *buf) :
+ buf(buf) {}
+
+ virtual ~FixedKVNodeLayout() = default;
+
+ const_iterator begin() const {
+ return const_iterator(
+ this,
+ 0);
+ }
+
+ const_iterator end() const {
+ return const_iterator(
+ this,
+ get_size());
+ }
+
+ iterator begin() {
+ return iterator(
+ this,
+ 0);
+ }
+
+ iterator end() {
+ return iterator(
+ this,
+ get_size());
+ }
+
+ const_iterator iter_idx(uint16_t off) const {
+ return const_iterator(
+ this,
+ off);
+ }
+
+ const_iterator find(K l) const {
+ auto ret = begin();
+ for (; ret != end(); ++ret) {
+ if (ret->get_key() == l)
+ break;
+ }
+ return ret;
+ }
+ iterator find(K l) {
+ const auto &tref = *this;
+ return iterator(this, tref.find(l).offset);
+ }
+
+ const_iterator lower_bound(K l) const {
+ auto ret = begin();
+ for (; ret != end(); ++ret) {
+ if (ret->get_key() >= l)
+ break;
+ }
+ return ret;
+ }
+ iterator lower_bound(K l) {
+ const auto &tref = *this;
+ return iterator(this, tref.lower_bound(l).offset);
+ }
+
+ const_iterator upper_bound(K l) const {
+ auto ret = begin();
+ for (; ret != end(); ++ret) {
+ if (ret->get_key() > l)
+ break;
+ }
+ return ret;
+ }
+ iterator upper_bound(K l) {
+ const auto &tref = *this;
+ return iterator(this, tref.upper_bound(l).offset);
+ }
+
+ const_iterator get_split_pivot() const {
+ return iter_idx(get_size() / 2);
+ }
+
+ uint16_t get_size() const {
+ return *layout.template Pointer<0>(buf);
+ }
+
+ /**
+ * set_size
+ *
+ * Set size representation to match size
+ */
+ void set_size(uint16_t size) {
+ *layout.template Pointer<0>(buf) = size;
+ }
+
+ /**
+ * get_meta/set_meta
+ *
+ * Enables stashing a templated type within the layout.
+ * Cannot be modified after initial write as it is not represented
+ * in delta_t
+ */
+ Meta get_meta() const {
+ MetaInt &metaint = *layout.template Pointer<1>(buf);
+ return Meta(metaint);
+ }
+ void set_meta(const Meta &meta) {
+ *layout.template Pointer<1>(buf) = MetaInt(meta);
+ }
+
+ constexpr static size_t get_capacity() {
+ return CAPACITY;
+ }
+
+ bool operator==(const FixedKVNodeLayout &rhs) const {
+ if (get_size() != rhs.get_size()) {
+ return false;
+ }
+
+ auto iter = begin();
+ auto iter2 = rhs.begin();
+ while (iter != end()) {
+ if (iter->get_key() != iter2->get_key() ||
+ iter->get_val() != iter2->get_val()) {
+ return false;
+ }
+ iter++;
+ iter2++;
+ }
+ return true;
+ }
+
+ /**
+ * split_into
+ *
+ * Takes *this and splits its contents into left and right.
+ */
+ K split_into(
+ FixedKVNodeLayout &left,
+ FixedKVNodeLayout &right) const {
+ auto piviter = get_split_pivot();
+
+ left.copy_from_foreign(left.begin(), begin(), piviter);
+ left.set_size(piviter - begin());
+
+ right.copy_from_foreign(right.begin(), piviter, end());
+ right.set_size(end() - piviter);
+
+ auto [lmeta, rmeta] = get_meta().split_into(piviter->get_key());
+ left.set_meta(lmeta);
+ right.set_meta(rmeta);
+
+ return piviter->get_key();
+ }
+
+ /**
+ * merge_from
+ *
+ * Takes two nodes and copies their contents into *this.
+ *
+ * precondition: left.size() + right.size() < CAPACITY
+ */
+ void merge_from(
+ const FixedKVNodeLayout &left,
+ const FixedKVNodeLayout &right)
+ {
+ copy_from_foreign(
+ end(),
+ left.begin(),
+ left.end());
+ set_size(left.get_size());
+ copy_from_foreign(
+ end(),
+ right.begin(),
+ right.end());
+ set_size(left.get_size() + right.get_size());
+ set_meta(Meta::merge_from(left.get_meta(), right.get_meta()));
+ }
+
+ /**
+ * balance_into_new_nodes
+ *
+ * Takes the contents of left and right and copies them into
+ * replacement_left and replacement_right such that in the
+ * event that the number of elements is odd the extra goes to
+ * the left side iff prefer_left.
+ */
+ static K balance_into_new_nodes(
+ const FixedKVNodeLayout &left,
+ const FixedKVNodeLayout &right,
+ bool prefer_left,
+ FixedKVNodeLayout &replacement_left,
+ FixedKVNodeLayout &replacement_right)
+ {
+ auto total = left.get_size() + right.get_size();
+ auto pivot_idx = (left.get_size() + right.get_size()) / 2;
+ if (total % 2 && prefer_left) {
+ pivot_idx++;
+ }
+ auto replacement_pivot = pivot_idx >= left.get_size() ?
+ right.iter_idx(pivot_idx - left.get_size())->get_key() :
+ left.iter_idx(pivot_idx)->get_key();
+
+ if (pivot_idx < left.get_size()) {
+ replacement_left.copy_from_foreign(
+ replacement_left.end(),
+ left.begin(),
+ left.iter_idx(pivot_idx));
+ replacement_left.set_size(pivot_idx);
+
+ replacement_right.copy_from_foreign(
+ replacement_right.end(),
+ left.iter_idx(pivot_idx),
+ left.end());
+
+ replacement_right.set_size(left.get_size() - pivot_idx);
+ replacement_right.copy_from_foreign(
+ replacement_right.end(),
+ right.begin(),
+ right.end());
+ replacement_right.set_size(total - pivot_idx);
+ } else {
+ replacement_left.copy_from_foreign(
+ replacement_left.end(),
+ left.begin(),
+ left.end());
+ replacement_left.set_size(left.get_size());
+
+ replacement_left.copy_from_foreign(
+ replacement_left.end(),
+ right.begin(),
+ right.iter_idx(pivot_idx - left.get_size()));
+ replacement_left.set_size(pivot_idx);
+
+ replacement_right.copy_from_foreign(
+ replacement_right.end(),
+ right.iter_idx(pivot_idx - left.get_size()),
+ right.end());
+ replacement_right.set_size(total - pivot_idx);
+ }
+
+ auto [lmeta, rmeta] = Meta::rebalance(
+ left.get_meta(), right.get_meta(), replacement_pivot);
+ replacement_left.set_meta(lmeta);
+ replacement_right.set_meta(rmeta);
+ return replacement_pivot;
+ }
+
+private:
+ void insert(
+ iterator iter,
+ const K &key,
+ const V &val) {
+ if (VALIDATE_INVARIANTS) {
+ if (iter != begin()) {
+ assert((iter - 1)->get_key() < key);
+ }
+ if (iter != end()) {
+ assert(iter->get_key() > key);
+ }
+ assert(get_size() < CAPACITY);
+ }
+ copy_from_local(iter + 1, iter, end());
+ iter->set_key(key);
+ iter->set_val(val);
+ set_size(get_size() + 1);
+ }
+
+ void update(
+ iterator iter,
+ V val) {
+ assert(iter != end());
+ iter->set_val(val);
+ }
+
+ void replace(
+ iterator iter,
+ const K &key,
+ const V &val) {
+ assert(iter != end());
+ if (VALIDATE_INVARIANTS) {
+ if (iter != begin()) {
+ assert((iter - 1)->get_key() < key);
+ }
+ if ((iter + 1) != end()) {
+ assert((iter + 1)->get_key() > key);
+ }
+ }
+ iter->set_key(key);
+ iter->set_val(val);
+ }
+
+ void remove(iterator iter) {
+ assert(iter != end());
+ copy_from_local(iter, iter + 1, end());
+ set_size(get_size() - 1);
+ }
+
+ /**
+ * get_key_ptr
+ *
+ * Get pointer to start of key array
+ */
+ KINT *get_key_ptr() {
+ return layout.template Pointer<2>(buf);
+ }
+ const KINT *get_key_ptr() const {
+ return layout.template Pointer<2>(buf);
+ }
+
+ /**
+ * get_val_ptr
+ *
+ * Get pointer to start of val array
+ */
+ VINT *get_val_ptr() {
+ return layout.template Pointer<3>(buf);
+ }
+ const VINT *get_val_ptr() const {
+ return layout.template Pointer<3>(buf);
+ }
+
+ /**
+ * node_resolve/unresolve_vals
+ *
+ * If the representation for values depends in some way on the
+ * node in which they are located, users may implement
+ * resolve/unresolve to enable copy_from_foreign to handle that
+ * transition.
+ */
+ virtual void node_resolve_vals(iterator from, iterator to) const {}
+ virtual void node_unresolve_vals(iterator from, iterator to) const {}
+
+ /**
+ * copy_from_foreign
+ *
+ * Copies entries from [from_src, to_src) to tgt.
+ *
+ * tgt and from_src must be from different nodes.
+ * from_src and to_src must be from the same node.
+ */
+ static void copy_from_foreign(
+ iterator tgt,
+ const_iterator from_src,
+ const_iterator to_src) {
+ assert(tgt->node != from_src->node);
+ assert(to_src->node == from_src->node);
+ memcpy(
+ tgt->get_val_ptr(), from_src->get_val_ptr(),
+ to_src->get_val_ptr() - from_src->get_val_ptr());
+ memcpy(
+ tgt->get_key_ptr(), from_src->get_key_ptr(),
+ to_src->get_key_ptr() - from_src->get_key_ptr());
+ from_src->node->node_resolve_vals(tgt, tgt + (to_src - from_src));
+ tgt->node->node_unresolve_vals(tgt, tgt + (to_src - from_src));
+ }
+
+ /**
+ * copy_from_local
+ *
+ * Copies entries from [from_src, to_src) to tgt.
+ *
+ * tgt, from_src, and to_src must be from the same node.
+ */
+ static void copy_from_local(
+ iterator tgt,
+ iterator from_src,
+ iterator to_src) {
+ assert(tgt->node == from_src->node);
+ assert(to_src->node == from_src->node);
+ memmove(
+ tgt->get_val_ptr(), from_src->get_val_ptr(),
+ to_src->get_val_ptr() - from_src->get_val_ptr());
+ memmove(
+ tgt->get_key_ptr(), from_src->get_key_ptr(),
+ to_src->get_key_ptr() - from_src->get_key_ptr());
+ }
+};
+
+}
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