1 files changed, 170 insertions, 0 deletions
diff --git a/include/framework/structure/BufferView.h b/include/framework/structure/BufferView.h
new file mode 100644
index 0000000..9e0872b
--- /dev/null
+++ b/include/framework/structure/BufferView.h
@@ -0,0 +1,170 @@
+/*
+ * include/framework/structure/BufferView.h
+ *
+ * Copyright (C) 2023 Douglas B. Rumbaugh <drumbaugh@psu.edu> 
+ *
+ * Distributed under the Modified BSD License.
+ *
+ * TODO: This file is very poorly commented.
+ */
+#pragma once
+
+#include <cstdlib>
+#include <cassert>
+#include <functional>
+#include <utility>
+
+#include "psu-util/alignment.h"
+#include "psu-ds/BloomFilter.h"
+#include "framework/interface/Record.h"
+
+namespace de {
+
+typedef std::_Bind<void (*(void*, long unsigned int))(void*, long unsigned int)> ReleaseFunction;
+
+template <RecordInterface R>
+class BufferView {
+public:
+    BufferView() = default;
+
+    /* 
+     * the BufferView's lifetime is tightly linked to buffer versioning, and so
+     * copying and assignment are disabled.
+     */
+    BufferView(const BufferView&) = delete;
+    BufferView &operator=(BufferView &) = delete;
+
+    BufferView(BufferView &&other) 
+        : m_data(std::exchange(other.m_data, nullptr))
+        , m_release(std::move(other.m_release))
+        , m_head(std::exchange(other.m_head, 0))
+        , m_tail(std::exchange(other.m_tail, 0))
+        , m_start(std::exchange(other.m_start, 0))
+        , m_stop(std::exchange(other.m_stop, 0))
+        , m_cap(std::exchange(other.m_cap, 0))
+        , m_approx_ts_cnt(std::exchange(other.m_approx_ts_cnt, 0))
+        , m_tombstone_filter(std::exchange(other.m_tombstone_filter, nullptr))
+        , m_active(std::exchange(other.m_active, false)) {}
+
+    BufferView &operator=(BufferView &&other) = delete;
+
+
+    BufferView(Wrapped<R> *buffer, size_t cap, size_t head, size_t tail, size_t tombstone_cnt, psudb::BloomFilter<R> *filter,
+               ReleaseFunction release) 
+        : m_data(buffer)
+        , m_release(release)
+        , m_head(head)
+        , m_tail(tail)
+        , m_start(m_head % cap)
+        , m_stop(m_tail % cap)
+        , m_cap(cap)
+        , m_approx_ts_cnt(tombstone_cnt)
+        , m_tombstone_filter(filter)
+        , m_active(true) {}
+
+    ~BufferView() {
+        if (m_active) {
+            m_release();
+        }
+    }
+
+    bool check_tombstone(const R& rec) {
+        if (m_tombstone_filter && !m_tombstone_filter->lookup(rec)) return false;
+
+        for (size_t i=0; i<get_record_count(); i++) {
+            if (m_data[to_idx(i)].rec == rec && m_data[to_idx(i)].is_tombstone()) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    bool delete_record(const R& rec) {
+        if (m_start < m_stop) {
+            for (size_t i=m_start; i<m_stop; i++) {
+                if (m_data[i].rec == rec) {
+                    m_data[i].set_delete();
+                    return true;
+                }
+            }
+        } else {
+            for (size_t i=m_start; i<m_cap; i++) {
+                if (m_data[i].rec == rec) {
+                    m_data[i].set_delete();
+                    return true;
+                }
+            }
+
+            for (size_t i=0; i<m_stop; i++) {
+                if (m_data[i].rec == rec) {
+                    m_data[i].set_delete();
+                    return true;
+                }
+
+            }
+
+        }
+
+        return false;
+    }
+
+    size_t get_record_count() {
+        return m_tail - m_head;
+    }
+    
+    /*
+     * NOTE: This function returns an upper bound on the number
+     *       of tombstones within the view. There may be less than
+     *       this, due to synchronization issues during view creation.
+     */
+    size_t get_tombstone_count() {
+        return m_approx_ts_cnt;
+    }
+
+    Wrapped<R> *get(size_t i) {
+        assert(i < get_record_count());
+        return m_data + to_idx(i);
+    }
+
+    void copy_to_buffer(psudb::byte *buffer) {
+        /* check if the region to be copied circles back to start. If so, do it in two steps */
+        if (m_start > m_stop) { 
+            size_t split_idx = m_cap - m_start;
+
+            memcpy(buffer, (std::byte*) (m_data + m_start), split_idx* sizeof(Wrapped<R>));
+            memcpy(buffer + (split_idx * sizeof(Wrapped<R>)), (std::byte*) m_data, m_stop * sizeof(Wrapped<R>));
+        } else {
+            memcpy(buffer, (std::byte*) (m_data + m_start), get_record_count() * sizeof(Wrapped<R>));
+        }
+    }
+
+    size_t get_tail() {
+        return m_tail;
+    }
+
+    size_t get_head() {
+        return m_head;
+    }
+
+private:
+    Wrapped<R>* m_data;
+    ReleaseFunction m_release;
+    size_t m_head;
+    size_t m_tail;
+    size_t m_start;
+    size_t m_stop;
+    size_t m_cap;
+    size_t m_approx_ts_cnt;
+    psudb::BloomFilter<R> *m_tombstone_filter;
+    bool m_active;
+
+    size_t to_idx(size_t i) {
+        size_t idx = (m_start + i >= m_cap) ? i = (m_cap - m_start) 
+                                            : m_start + i;
+        assert(idx < m_cap);
+        return idx;
+    }
+};
+
+}