/* * Copyright 2020 WebAssembly Community Group participants * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef wasm_support_space_h #define wasm_support_space_h #include "utilities.h" #include namespace wasm { struct DisjointSpans { // A span of form [a, b), i.e., that does not include the end point. struct Span { Address left, right; bool checkOverlap(const Span& other) const { return !(left >= other.right || right <= other.left); } }; struct SortByLeft { bool operator()(const Span& left, const Span& right) const { return left.left < right.left || (left.left == right.left && left.right < right.right); } }; // The spans seen so far. Guaranteed to be disjoint. std::set spans; // Adds an item and checks overlap while doing so, returning true if such // overlap exists. bool addAndCheckOverlap(Span span) { // Insert the new span. We can then find its predecessor and successor. // They are disjoint by assumption, so the question is then does the new // span overlap with them, or not. decltype(spans)::iterator iter; bool inserted; std::tie(iter, inserted) = spans.insert(span); if (!inserted) { // This exact span was already there, so there is definite overlap. return true; } // Check predecessor and successor, if they exist. if (iter != spans.begin() && std::prev(iter)->checkOverlap(span)) { return true; } if (std::next(iter) != spans.end() && std::next(iter)->checkOverlap(span)) { return true; } return false; } // Inefficient - mostly for testing. void add(Span span) { addAndCheckOverlap(span); } // Inefficient - mostly for testing. bool checkOverlap(Span span) { bool existsBefore = spans.find(span) != spans.end(); auto hasOverlap = addAndCheckOverlap(span); if (!existsBefore) { spans.erase(span); } return hasOverlap; } }; } // namespace wasm #endif // wasm_support_space_h