From fdf5ef27fec1368a33801a98bbc5ed3556476979 Mon Sep 17 00:00:00 2001
From: Douglas Rumbaugh <dbr4@psu.edu>
Date: Mon, 8 May 2023 12:59:46 -0400
Subject: Began porting source files over from other repository

---
 include/util/internal_record.h | 96 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 include/util/internal_record.h

(limited to 'include/util/internal_record.h')

diff --git a/include/util/internal_record.h b/include/util/internal_record.h
new file mode 100644
index 0000000..d898b8b
--- /dev/null
+++ b/include/util/internal_record.h
@@ -0,0 +1,96 @@
+/*
+ * include/util/internal_record.h
+ *
+ * Copyright (C) 2023 Douglas Rumbaugh <drumbaugh@psu.edu>
+ *
+ * All rights reserved. Published under the Modified BSD License.
+ *
+ */
+#pragma once
+#pragma once
+
+#include "util/record.h"
+#include "util/types.h"
+
+/*
+ * Utility functions for use in handling internal nodes within an ISAM
+ * tree.
+ */
+
+namespace de {
+
+struct ISAMTreeInternalNodeHeader {
+    PageNum next_sibling; // INVALID_PNUM this is the last node on a level
+    PageNum prev_sibling; // INVALID_PNUM if this is the first node on a level
+    size_t leaf_rec_cnt; // number of records in leaf nodes under this node
+    size_t internal_rec_cnt; // number of internal records in this node
+};
+
+/*
+ * The total (aligned) size of an ISAMTreeInternalNodeHeader object. 
+ */
+static constexpr PageOffset ISAMTreeInternalNodeHeaderSize = MAXALIGN(sizeof(ISAMTreeInternalNodeHeader));
+
+/*
+ * The number of bytes occupied by an ISAM tree internal record, including alignment bytes.
+ */
+static constexpr size_t internal_record_size = sizeof(key_t) + MAXALIGN(sizeof(PageNum));
+
+/*
+ * The maximum number of internal records that can be stored in an internal
+ * node, accounting for alignment and the node header.
+ */
+static constexpr size_t internal_records_per_page = (PAGE_SIZE - ISAMTreeInternalNodeHeaderSize) / internal_record_size;
+
+/*
+ * Format an internal record, starting in the first byte of buffer, with the
+ * specified key and target page number. If either buffer or key refer to
+ * memory regions of insufficient size, the results are undefined.
+ */
+static inline void build_internal_record(char *buffer, const char *key, PageNum target_page) {
+    memcpy(buffer, key, sizeof(key_t));
+    memcpy(buffer + sizeof(key_t), &target_page, sizeof(PageNum));
+}
+
+/*
+ * Return the idx'th internal record within an internal node.
+ * internal_page_buffer must refer to the first byte of a page containing a
+ * full internal node, including the header. The returned value is undefined if
+ * idx is greater than or equal to the number of internal records within the
+ * node.
+ */
+static inline char *get_internal_record(char *internal_page_buffer, size_t idx) {
+    return internal_page_buffer + ISAMTreeInternalNodeHeaderSize + internal_record_size * idx;
+}
+
+/*
+ * Return a pointer to the key contained within an internal record, pointed
+ * to by buffer. Buffer must point to the beginning of a valid internal record,
+ * or the result of this function is undefined.
+ */
+static inline const char *get_internal_key(const char *buffer) {
+    return buffer;
+}
+
+/*
+ * Return the Page Number (value) of an internal record, pointed to by buffer.
+ * Buffer must point to the beginning of a valid internal record, or the result
+ * of this function is undefined.
+ */
+static inline PageNum get_internal_value(const char *buffer) {
+    return *((PageNum *) (buffer + sizeof(key_t)));
+}
+
+/*
+ * Return a pointer to the header of an ISAM Tree internal node, referred to by
+ * buffer. If buffer contains multiple nodes, a specific node can be requested 
+ * using the idx parameter, otherwise the header of the first node will be returned.
+ * Buffer must point to the beginning of a valid ISAM Tree internal node, and idx
+ * must be less than the number of internal nodes within the buffer, or the 
+ * returned value is undefined.
+ */
+static inline ISAMTreeInternalNodeHeader *get_header(char *buffer, size_t idx=0) {
+    return (ISAMTreeInternalNodeHeader *) get_page(buffer, idx);
+}
+
+}
-- 
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