test_05.bt

BigEndian();
BitfieldDisablePadding();

#define PAGE_SIZE (16 * 1024)

typedef ubyte u1;
typedef uint16 u2;
typedef uint32 u4;
typedef uint64 u8;
typedef byte i1;
typedef int16 i2;
typedef int32 i4;

enum <u2> PAGE_TYPE {
	 FIL_PAGE_INDEX	=	17855,	/*!< B-tree node */
	 FIL_PAGE_RTREE	=	17854,	/*!< B-tree node */
	 FIL_PAGE_UNDO_LOG	=2,	/*!< Undo log page */
	 FIL_PAGE_INODE		=3	,/*!< Index node */
	 FIL_PAGE_IBUF_FREE_LIST	=4,	/*!< Insert buffer free list */ /* File page types introduced in MySQL/InnoDB 5.1.7 */
	 FIL_PAGE_TYPE_ALLOCATED	=0	,/*!< Freshly allocated page */
	 FIL_PAGE_IBUF_BITMAP	=5 ,	/*!< Insert buffer bitmap */
	 FIL_PAGE_TYPE_SYS	=6	,/*!< System page */
	 FIL_PAGE_TYPE_TRX_SYS	=7,	/*!< Transaction system data */
	 FIL_PAGE_TYPE_FSP_HDR	=8	,/*!< File space header */
	 FIL_PAGE_TYPE_XDES	=9	,/*!< Extent descriptor page */
	 FIL_PAGE_TYPE_BLOB	=10	,/*!< Uncompressed BLOB page */
	 FIL_PAGE_TYPE_ZBLOB	=11	,/*!< First compressed BLOB page */
	 FIL_PAGE_TYPE_ZBLOB2	=12	,/*!< Subsequent compressed BLOB page */
	 FIL_PAGE_TYPE_UNKNOWN	=13	,/*!< In old tablespaces, garbage in FIL_PAGE_TYPE is replaced with this value when flushing pages. */
	 FIL_PAGE_COMPRESSED	=14	,/*!< Compressed page */
	 FIL_PAGE_ENCRYPTED	=15	,/*!< Encrypted page */
	 FIL_PAGE_COMPRESSED_AND_ENCRYPTED =16  , /*!< Compressed and Encrypted page */
	 FIL_PAGE_ENCRYPTED_RTREE =17,	/*!< Encrypted R-tree page */
};

// 38 字节的 File Header，存储了页的一些通用信息
typedef struct FilHeader {
    u4 FIL_PAGE_SPACE_OR_CHKSUM<format=hex,comment="页的校验和（checksum值）">;
    u4 FIL_PAGE_OFFSET<fgcolor=0xFF0000,comment="页号">;
    u4 FIL_PAGE_PREV<comment="上一个页的页号">;
    u4 FIL_PAGE_NEXT<comment="下一个页的页号">;
    u8 FIL_PAGE_LSN<comment="页面被最后修改时对应的日志序列位置（英文名是：Log Sequence Number）">;
    PAGE_TYPE FIL_PAGE_TYPE<comment="页面类型">;
    u8 FIL_PAGE_FILE_FLUSH_LSN<comment="仅在系统表空间的一个页中定义，代表文件至少被刷新到了对应的LSN值">;
    u4 FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID<comment="页属于哪个表空间">;
};

enum <u1> PAGE_FORMAT_ENUM {
		 REDUNDANT	= 0,
		 COMPACT    = 1,
};
// 56 字节的 Page Header
typedef struct PageHeader {
	u2 PAGE_N_DIR_SLOTS<comment="在页目录中的槽数量">;
	u2 PAGE_HEAP_TOP<comment="还未使用的空间最小地址，也就是说从该地址之后就是Free Space">;
	PAGE_FORMAT_ENUM PAGE_FORMAT : 1 <comment="页面类型">;
	u2 NUM_OF_HEAP_RECORDS : 15 <comment="本页中的记录的数量（包括最小和最大记录以及标记为删除的记录）">;
	u2 PAGE_FREE<comment="next_record也会组成一个单链表，这个单链表中的记录可以被重新利用）">;
	u2 PAGE_GARBAGE<comment="已删除记录占用的字节数">;
	u2 PAGE_LAST_INSERT<comment="最后插入记录的位置">;
	u2 PAGE_DIRECTION<comment="记录插入的方向">;
	u2 PAGE_N_DIRECTION<comment="一个方向连续插入的记录数量">;
	u2 PAGE_N_RECS<comment="该页中记录的数量（不包括最小和最大记录以及被标记为删除的记录）">;
	u8 PAGE_MAX_TRX_ID<comment="修改当前页的最大事务ID，该值仅在二级索引中定义">;
	u2 PAGE_LEVEL<comment="当前页在B+树中所处的层级">;
	u8 PAGE_INDEX_ID<comment="索引ID，表示当前页属于哪个索引">;
	u1 PAGE_BTR_SEG_LEAF[10]<comment="B+树叶子段的头部信息，仅在B+树的Root页定义">;
	u1 PAGE_BTR_SEG_TOP[10]<comment="B+树非叶子段的头部信息，仅在B+树的Root页定义">;
};

// 记录类型枚举类
enum <u1> RECORD_TYPE {
		 CONVENTIONAL	= 0,
		 NODE_POINTER   = 1,
		 INFIMUM        = 2,
		 SUPREMUM       = 3
};

// 5 字节记录头
typedef struct   {
	u1                       : 2;
	u1 delete_mask           : 1;
	u1 min_rec_mask          : 1;
	u1 n_owned               : 4;
    u2 heap_no               : 13;
    RECORD_TYPE record_type  : 3;
    short next_record        : 16; 
} RecordHeader<fgcolor=0xFF00FF>;

// 最大最小虚拟记录
typedef struct  {
    RecordHeader record_header; // 5 字节的记录头
    char text[8];               // 8 字节的单词
} InfimumSupremumRecord;

// 定义一个 Page 结构体
typedef struct Page(int index) {
	FilHeader file_header;  // 38 字节的 file header
	if (file_header.FIL_PAGE_TYPE == FIL_PAGE_INDEX) {
		PageHeader page_header;                // 56 字节的 page header
		InfimumSupremumRecord infimum_record;  // 13 字节的虚拟最小记录
		local int page_start_pos = index * PAGE_SIZE;
		local int infimum_record_pos = FTell() - page_start_pos - 8; // 获取 infimum 记录的起始地址
		InfimumSupremumRecord supremum_record; // 13 字节的虚拟最大记录
		local int supremum_record_pos = FTell() - page_start_pos - 8; // 获取 supremum 记录的起始地址
		// 第一条记录的相对位置
		local int next_rec_rel_pos = infimum_record_pos + infimum_record.record_header.next_record;

		// 遍历链表
		while(next_rec_rel_pos != supremum_record_pos) {
			FSeek(page_start_pos + next_rec_rel_pos - 5); // 往前走五个字节，读取记录头，便于获取下一条记录的相对位置
			RecordHeader record_header;
			next_rec_rel_pos += record_header.next_record;
		}
	}
	// 跳到 Page 页的尾部
	FSeek((index + 1) * PAGE_SIZE);
};


local int file_size = FileSize();
local int i;
for (i = 0; i < file_size / PAGE_SIZE; ++i) {
	Page page(i); // 读取 16KB 的内容映射到 Page 结构体中
}