Began porting source files over from other repository

1 files changed, 135 insertions, 0 deletions

diff --git a/include/ds/PriorityQueue.h b/include/ds/PriorityQueue.h
new file mode 100644
index 0000000..49f3e41
--- /dev/null
+++ b/include/ds/PriorityQueue.h
@@ -0,0 +1,135 @@
+/*
+ * include/ds/PriorityQueue.h
+ *
+ * Copyright (C) 2023 Douglas Rumbaugh <drumbaugh@psu.edu> 
+ *                    Dong Xie <dongx@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+
+#include <vector>
+#include <cassert>
+
+#include "util/record.h"
+
+namespace lsm {
+
+struct queue_record {
+    const char *data;
+    size_t version;
+};
+
+
+class PriorityQueue {
+public:
+    PriorityQueue(size_t size) : data(size), tail(0) {}
+    ~PriorityQueue() = default;
+
+    size_t size() const {
+        return tail;
+    }
+
+    void pop() {
+        assert(this->tail != 0);
+
+        // If there is only one element, just decrement the
+        // tail.
+        if (this->size() == 1) {
+            this->tail--;
+            return;
+        }
+
+        swap(0, --this->tail);
+
+        ssize_t idx = 0;
+        ssize_t child_idx;
+
+        while ((child_idx = min_child(idx)) != -1 && heap_cmp(child_idx, idx)) {
+            swap(idx, child_idx);
+            idx = child_idx;
+        }
+    }
+
+    void push(const char* record, size_t version=0) {
+        assert(tail != this->data.size());
+
+        size_t new_idx = this->tail++;
+        this->data[new_idx] = {record, version};
+
+        while (new_idx != 0 && !heap_cmp(parent(new_idx), new_idx)) {
+            swap(parent(new_idx), new_idx);
+            new_idx = parent(new_idx);
+        }
+    }
+
+
+    queue_record peek(size_t depth=0) {
+        ssize_t idx = 0;
+        size_t cur_depth = 0;
+
+        while (cur_depth != depth) {
+            idx = min_child(idx);
+            assert(idx != -1);
+            cur_depth++;
+        }
+
+        return this->data[idx];
+    }
+
+private:
+    std::vector<queue_record> data;
+    size_t tail;
+
+    /*
+     * Swap the elements at position a and position
+     * b within the heap
+     */
+    inline void swap(size_t a, size_t b) {
+        if (a == b) return;
+
+        queue_record temp = this->data[a];
+        this->data[a] = this->data[b];
+        this->data[b] = temp;
+    }
+
+    inline size_t left_child(size_t idx) {
+        return 2 * idx + 1;
+    }
+
+    inline size_t right_child(size_t idx) {
+        return 2 * idx + 2;
+    }
+
+    inline size_t parent(size_t idx) {
+        return (idx - 1) / 2;
+    }
+
+    inline ssize_t min_child(size_t idx) {
+        ssize_t left = left_child(idx) < tail ? left_child(idx) : -1;
+        ssize_t right = right_child(idx) < tail ? right_child(idx) : -1;
+
+        if (left == -1 && right == -1) {
+            return -1;
+        } else if (left == -1) {
+            return right;
+        } else  if (right == -1) {
+            return left;
+        }
+
+        return (heap_cmp(left, right)) ? left : right;
+    }
+
+    inline bool heap_cmp(size_t a, size_t b) {
+        auto cmp = record_cmp(this->data[a].data, this->data[b].data);
+        if (cmp == 0) {
+            if (this->data[a].version != this->data[b].version)
+                return this->data[a].version < this->data[b].version;
+            else return is_tombstone(this->data[a].data) && is_tombstone(this->data[b].data);
+        }
+        return cmp == -1;
+    }
+
+};
+}