| 1 | /*
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| 2 | * Souffle - A Datalog Compiler
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| 3 | * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved
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| 4 | * Licensed under the Universal Permissive License v 1.0 as shown at:
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| 5 | * - https://opensource.org/licenses/UPL
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| 6 | * - <souffle root>/licenses/SOUFFLE-UPL.txt
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| 7 | */
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| 8 |
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| 9 | /************************************************************************
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| 10 | *
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| 11 | * @file Table.h
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| 12 | *
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| 13 | * An implementation of a generic Table storing a position-fixed collection
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| 14 | * of objects in main memory.
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| 15 | *
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| 16 | ***********************************************************************/
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| 17 |
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| 18 | #pragma once
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| 19 |
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| 20 | #include <iosfwd>
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| 21 | #include <iterator>
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| 22 |
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| 23 | namespace souffle {
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| 24 |
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| 25 | template <typename T, unsigned blockSize = 4096>
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| 26 | class Table {
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| 27 | struct Block {
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| 28 | Block* next;
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| 29 | std::size_t used = 0;
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| 30 | T data[blockSize];
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| 31 |
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| 32 | Block() : next(nullptr) {}
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| 33 |
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| 34 | bool isFull() const {
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| 35 | return used == blockSize;
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| 36 | }
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| 37 |
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| 38 | const T& append(const T& element) {
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| 39 | const T& res = data[used];
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| 40 | data[used] = element;
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| 41 | used++;
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| 42 | return res;
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| 43 | }
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| 44 | };
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| 45 |
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| 46 | Block* head;
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| 47 | Block* tail;
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| 48 |
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| 49 | std::size_t count = 0;
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| 50 |
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| 51 | public:
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| 52 | class iterator {
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| 53 | Block* block;
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| 54 | unsigned pos;
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| 55 |
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| 56 | public:
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| 57 | using iterator_category = std::forward_iterator_tag;
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| 58 | using value_type = T;
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| 59 | using difference_type = void;
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| 60 | using pointer = T*;
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| 61 | using reference = T&;
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| 62 |
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| 63 | iterator(Block* block = nullptr, unsigned pos = 0) : block(block), pos(pos) {}
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| 64 |
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| 65 | iterator(const iterator&) = default;
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| 66 | iterator(iterator&&) = default;
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| 67 | iterator& operator=(const iterator&) = default;
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| 68 |
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| 69 | // the equality operator as required by the iterator concept
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| 70 | bool operator==(const iterator& other) const {
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| 71 | return (block == nullptr && other.block == nullptr) || (block == other.block && pos == other.pos);
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| 72 | }
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| 73 |
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| 74 | // the not-equality operator as required by the iterator concept
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| 75 | bool operator!=(const iterator& other) const {
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| 76 | return !(*this == other);
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| 77 | }
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| 78 |
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| 79 | // the deref operator as required by the iterator concept
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| 80 | const T& operator*() const {
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| 81 | return block->data[pos];
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| 82 | }
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| 83 |
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| 84 | // the increment operator as required by the iterator concept
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| 85 | iterator& operator++() {
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| 86 | // move on in block
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| 87 | if (++pos < block->used) {
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| 88 | return *this;
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| 89 | }
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| 90 | // or to next block
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| 91 | block = block->next;
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| 92 | pos = 0;
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| 93 | return *this;
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| 94 | }
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| 95 | };
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| 96 |
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| 97 | Table() : head(nullptr), tail(nullptr) {}
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| 98 |
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| 99 | ~Table() {
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| 100 | clear();
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| 101 | }
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| 102 |
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| 103 | bool empty() const {
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| 104 | return (!head);
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| 105 | }
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| 106 |
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| 107 | std::size_t size() const {
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| 108 | return count;
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| 109 | }
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| 110 |
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| 111 | const T& insert(const T& element) {
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| 112 | // check whether the head is initialized
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| 113 | if (!head) {
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| 114 | head = new Block();
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| 115 | tail = head;
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| 116 | }
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| 117 |
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| 118 | // check whether tail is full
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| 119 | if (tail->isFull()) {
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| 120 | tail->next = new Block();
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| 121 | tail = tail->next;
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| 122 | }
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| 123 |
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| 124 | // increment counter
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| 125 | count++;
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| 126 |
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| 127 | // add another element
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| 128 | return tail->append(element);
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| 129 | }
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| 130 |
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| 131 | iterator begin() const {
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| 132 | return iterator(head);
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| 133 | }
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| 134 |
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| 135 | iterator end() const {
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| 136 | return iterator();
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| 137 | }
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| 138 |
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| 139 | void clear() {
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| 140 | while (head != nullptr) {
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| 141 | auto cur = head;
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| 142 | head = head->next;
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| 143 | delete cur;
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| 144 | }
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| 145 | count = 0;
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| 146 | head = nullptr;
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| 147 | tail = nullptr;
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| 148 | }
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| 149 | };
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| 150 |
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| 151 | } // end namespace souffle
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