fil0types.h

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/** @file include/fil0types.h
 The low-level file system page header & trailer offsets
 
 Created 10/25/1995 Heikki Tuuri
 *******************************************************/
 
#ifndef fil0types_h
#define fil0types_h
 
#include "univ.i"
 
/** The byte offsets on a file page for various variables. */
 
/** MySQL-4.0.14 space id the page belongs to (== 0) but in later
versions the 'new' checksum of the page */
constexpr uint32_t FIL_PAGE_SPACE_OR_CHKSUM = 0;
 
/** page offset inside space */
constexpr uint32_t FIL_PAGE_OFFSET = 4;
 
/** if there is a 'natural' predecessor of the page, its offset.
Otherwise FIL_NULL. This field is not set on BLOB pages, which are stored as a
singly-linked list. See also FIL_PAGE_NEXT. */
constexpr uint32_t FIL_PAGE_PREV = 8;
 
/** On page 0 of the tablespace, this is the server version ID */
constexpr uint32_t FIL_PAGE_SRV_VERSION = 8;
 
/** if there is a 'natural' successor of the page, its offset. Otherwise
FIL_NULL. B-tree index pages(FIL_PAGE_TYPE contains FIL_PAGE_INDEX) on the
same PAGE_LEVEL are maintained as a doubly linked list via FIL_PAGE_PREV and
FIL_PAGE_NEXT in the collation order of the smallest user record on each
page. */
constexpr uint32_t FIL_PAGE_NEXT = 12;
 
/** On page 0 of the tablespace, this is the server version ID */
constexpr uint32_t FIL_PAGE_SPACE_VERSION = 12;
 
/** lsn of the end of the newest modification log record to the page */
constexpr uint32_t FIL_PAGE_LSN = 16;
 
/** file page type: FIL_PAGE_INDEX,..., 2 bytes. The contents of this field
can only be trusted in the following case: if the page is an uncompressed
B-tree index page, then it is guaranteed that the value is FIL_PAGE_INDEX.
The opposite does not hold.
 
In tablespaces created by MySQL/InnoDB 5.1.7 or later, the contents of this
field is valid for all uncompressed pages. */
constexpr uint32_t FIL_PAGE_TYPE = 24;
 
/** this is only defined for the first page of the system tablespace: the file
has been flushed to disk at least up to this LSN. For FIL_PAGE_COMPRESSED
pages, we store the compressed page control information in these 8 bytes. */
constexpr uint32_t FIL_PAGE_FILE_FLUSH_LSN = 26;
 
/** If page type is FIL_PAGE_COMPRESSED then the 8 bytes starting at
FIL_PAGE_FILE_FLUSH_LSN are broken down as follows: */
 
/** Control information version format (u8) */
constexpr uint32_t FIL_PAGE_VERSION = FIL_PAGE_FILE_FLUSH_LSN;
 
/** Compression algorithm (u8) */
constexpr uint32_t FIL_PAGE_ALGORITHM_V1 = FIL_PAGE_VERSION + 1;
 
/** Original page type (u16) */
constexpr uint32_t FIL_PAGE_ORIGINAL_TYPE_V1 = FIL_PAGE_ALGORITHM_V1 + 1;
 
/** Original data size in bytes (u16)*/
constexpr uint32_t FIL_PAGE_ORIGINAL_SIZE_V1 = FIL_PAGE_ORIGINAL_TYPE_V1 + 2;
 
/** Size after compression (u16) */
constexpr uint32_t FIL_PAGE_COMPRESS_SIZE_V1 = FIL_PAGE_ORIGINAL_SIZE_V1 + 2;
 
/** This overloads FIL_PAGE_FILE_FLUSH_LSN for RTREE Split Sequence Number */
constexpr uint32_t FIL_RTREE_SPLIT_SEQ_NUM = FIL_PAGE_FILE_FLUSH_LSN;
 
/** starting from 4.1.x this contains the space id of the page */
constexpr uint32_t FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID = 34;
 
/** alias for space id */
constexpr uint32_t FIL_PAGE_SPACE_ID = FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID;
 
/** start of the data on the page */
constexpr uint32_t FIL_PAGE_DATA = 38;
 
/** File page trailer */
/** the low 4 bytes of this are used to store the page checksum, the
last 4 bytes should be identical to the last 4 bytes of FIL_PAGE_LSN */
constexpr uint32_t FIL_PAGE_END_LSN_OLD_CHKSUM = 8;
 
/** size of the page trailer */
constexpr uint32_t FIL_PAGE_DATA_END = 8;
 
/** First in address is the page offset. */
constexpr size_t FIL_ADDR_PAGE = 0;
 
/** Then comes 2-byte byte offset within page.*/
constexpr size_t FIL_ADDR_BYTE = 4;
 
/** Address size is 6 bytes. */
constexpr size_t FIL_ADDR_SIZE = 6;
 
/** Path separator e.g., 'dir;...;dirN' */
constexpr char FIL_PATH_SEPARATOR = ';';
 
/** A wrapper class to help print and inspect the file page header. */
struct Fil_page_header {
  /** The constructor that takes a pointer to page header as argument.
  @param[in]  frame  the pointer to the page header. */
  explicit Fil_page_header(const byte *frame) : m_frame(frame) {}
 
  /** Get the space id from the page header.
  @return the space identifier. */
  [[nodiscard]] space_id_t get_space_id() const noexcept;
 
  /** Get the page number from the page header.
  @return the page number. */
  [[nodiscard]] page_no_t get_page_no() const noexcept;
 
  /** Get the page type from the page header.
  @return the page type. */
  [[nodiscard]] uint16_t get_page_type() const noexcept;
 
  /** Print the page header to the given output stream.
  @param[in]  out  the output stream.
  @return the output stream. */
  std::ostream &print(std::ostream &out) const noexcept;
 
 private:
  /** Pointer to the page header. */
  const byte *m_frame{};
};
 
/** Overload the global output operator to handle an object of type
Fil_page_header.
@param[in]  out      the output stream.
@param[in]  header   an object of type Fil_page_header.
@return the output stream. */
inline std::ostream &operator<<(std::ostream &out,
                                const Fil_page_header &header) noexcept {
  return (header.print(out));
}
 
#endif /* fil0types_h */