cs660-pa/include/db/BTreeRootPtrPage.h at main · teobag/cs660-pa · GitHub

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#ifndef DB_BTREE_ROOTPTRPAGE_H
#define DB_BTREE_ROOTPTRPAGE_H

#include <db/Page.h>
#include <db/BTreePageId.h>

namespace db {
    /**
     * BTreeRootPtrPage stores the pointer to the root node used in the B+ tree and
     * implements Page Interface that is used by BufferPool
     *
     * @see BufferPool
     */
    class BTreeRootPtrPage : public Page {
        // size of this page
        const static int PAGE_SIZE = 9;

        const BTreePageId *pid;

        int root;
        int header;
        BTreePageType rootCategory;
    public:
        /**
         * Constructor.
         * Construct the BTreeRootPtrPage from a set of bytes of data read from
         * disk.
         * The format of an BTreeRootPtrPage is an integer for the page number
         * of the root node, followed by a byte to encode the category of the root page
         * (either leaf or internal), followed by an integer for the page number
         * of the first header page
         */
        BTreeRootPtrPage(const BTreePageId *id, void *data);

        /**
         * @return the PageId associated with this page.
         */
        const PageId &getId() const override;
        /**
         * There is only one instance of a BTreeRootPtrPage per table. This static
         * method is separate from getId() in order to maintain the Page interface
         * @param tableid - the tableid of this table
         * @return the root pointer page id for the given table
         */
        static BTreePageId *getId(int tableid);

        /**
         * Generates a byte array representing the contents of this root pointer page.
         * Used to serialize this root pointer page to disk.
         * The invariant here is that it should be possible to pass the byte array
         * generated by getPageData to the BTreeRootPtrPage constructor and have it
         * produce an identical BTreeRootPtrPage object.
         *
         * @return A byte array corresponding to the bytes of this root pointer page.
         */
        void *getPageData() const override;

        /**
         * Static method to generate a byte array corresponding to an empty
         * BTreeRootPtrPage.
         * Used to add new, empty pages to the file. Passing the results of
         * this method to the BTreeRootPtrPage constructor will create a BTreeRootPtrPage with
         * no valid entries in it.
         *
         * @return The returned ByteArray.
         */
        static void *createEmptyPageData();

        /**
         * Get the id of the root page in this B+ tree
         * @return the id of the root page
         */
        BTreePageId *getRootId();

        /**
         * Set the id of the root page in this B+ tree
         * @param id - the id of the root page
         */
        void setRootId(const BTreePageId *id);

        /**
         * Get the id of the first header page, or null if none exists
         * @return the id of the first header page
         */
        BTreePageId *getHeaderId() const;

        /**
         * Set the page id of the first header page
         * @param id - the id of the first header page
         */
        void setHeaderId(const BTreePageId *id);

        /**
         * Get the page size of root pointer pages
         * @return the page size
         */
        static int getPageSize();
    };
}
#endif