idb/innodb/

page.rs

//! InnoDB page header and trailer parsing.
//!
//! Every InnoDB page begins with a 38-byte FIL header ([`FilHeader`]) containing
//! the checksum, page number, prev/next pointers, LSN, page type, flush LSN, and
//! space ID. The last 8 bytes form the FIL trailer ([`FilTrailer`]) with the
//! old-style checksum and low 32 bits of the LSN.
//!
//! Page 0 of every tablespace also contains the FSP header ([`FspHeader`]) at
//! byte offset 38, which stores the space ID, tablespace size, and feature flags
//! (page size, compression, encryption).

use byteorder::{BigEndian, ByteOrder};
use serde::Serialize;

use crate::innodb::constants::*;
use crate::innodb::page_types::PageType;

/// Parsed FIL header (38 bytes, present at the start of every InnoDB page).
#[derive(Debug, Clone, Serialize)]
pub struct FilHeader {
    /// Checksum (or space id in older formats). Bytes 0-3.
    pub checksum: u32,
    /// Page number within the tablespace. Bytes 4-7.
    pub page_number: u32,
    /// Previous page in the doubly-linked list. Bytes 8-11.
    /// FIL_NULL (0xFFFFFFFF) if not used.
    pub prev_page: u32,
    /// Next page in the doubly-linked list. Bytes 12-15.
    /// FIL_NULL (0xFFFFFFFF) if not used.
    pub next_page: u32,
    /// LSN of newest modification to this page. Bytes 16-23.
    pub lsn: u64,
    /// Page type. Bytes 24-25.
    pub page_type: PageType,
    /// Flush LSN (only meaningful for page 0 of system tablespace). Bytes 26-33.
    pub flush_lsn: u64,
    /// Space ID this page belongs to. Bytes 34-37.
    pub space_id: u32,
}

impl FilHeader {
    /// Parse a FIL header from a byte slice.
    ///
    /// The slice must be at least SIZE_FIL_HEAD (38) bytes.
    ///
    /// # Examples
    ///
    /// ```
    /// use idb::innodb::page::FilHeader;
    /// use idb::innodb::page_types::PageType;
    /// use byteorder::{BigEndian, WriteBytesExt};
    /// use std::io::{Cursor, Write};
    ///
    /// // Build a 38-byte FIL header with known values
    /// let mut buf = vec![0u8; 38];
    /// let mut c = Cursor::new(&mut buf);
    /// c.write_u32::<BigEndian>(0xDEADBEEF).unwrap(); // checksum
    /// c.write_u32::<BigEndian>(3).unwrap();           // page number
    /// c.write_u32::<BigEndian>(2).unwrap();           // prev page
    /// c.write_u32::<BigEndian>(4).unwrap();           // next page
    /// c.write_u64::<BigEndian>(5000).unwrap();        // LSN
    /// c.write_u16::<BigEndian>(17855).unwrap();       // page type (INDEX)
    /// c.write_u64::<BigEndian>(4000).unwrap();        // flush LSN
    /// c.write_u32::<BigEndian>(1).unwrap();           // space ID
    ///
    /// let header = FilHeader::parse(&buf).unwrap();
    /// assert_eq!(header.checksum, 0xDEADBEEF);
    /// assert_eq!(header.page_number, 3);
    /// assert_eq!(header.prev_page, 2);
    /// assert_eq!(header.next_page, 4);
    /// assert_eq!(header.lsn, 5000);
    /// assert_eq!(header.page_type, PageType::Index);
    /// assert_eq!(header.flush_lsn, 4000);
    /// assert_eq!(header.space_id, 1);
    /// ```
    pub fn parse(data: &[u8]) -> Option<Self> {
        if data.len() < SIZE_FIL_HEAD {
            return None;
        }

        Some(FilHeader {
            checksum: BigEndian::read_u32(&data[FIL_PAGE_SPACE_OR_CHKSUM..]),
            page_number: BigEndian::read_u32(&data[FIL_PAGE_OFFSET..]),
            prev_page: BigEndian::read_u32(&data[FIL_PAGE_PREV..]),
            next_page: BigEndian::read_u32(&data[FIL_PAGE_NEXT..]),
            lsn: BigEndian::read_u64(&data[FIL_PAGE_LSN..]),
            page_type: PageType::from_u16(BigEndian::read_u16(&data[FIL_PAGE_TYPE..])),
            flush_lsn: BigEndian::read_u64(&data[FIL_PAGE_FILE_FLUSH_LSN..]),
            space_id: BigEndian::read_u32(&data[FIL_PAGE_SPACE_ID..]),
        })
    }

    /// Returns true if prev_page is FIL_NULL (not used).
    pub fn has_prev(&self) -> bool {
        self.prev_page != FIL_NULL && self.prev_page != 0
    }

    /// Returns true if next_page is FIL_NULL (not used).
    pub fn has_next(&self) -> bool {
        self.next_page != FIL_NULL && self.next_page != 0
    }
}

/// Parsed FIL trailer (8 bytes, present at the end of every InnoDB page).
#[derive(Debug, Clone, Serialize)]
pub struct FilTrailer {
    /// Old-style checksum (or low 32 bits of LSN, depending on version). Bytes 0-3 of trailer.
    pub checksum: u32,
    /// Low 32 bits of the LSN. Bytes 4-7 of trailer.
    pub lsn_low32: u32,
}

impl FilTrailer {
    /// Parse a FIL trailer from a byte slice.
    ///
    /// The slice should be the last 8 bytes of the page, or at least 8 bytes
    /// starting from the trailer position.
    ///
    /// # Examples
    ///
    /// ```
    /// use idb::innodb::page::FilTrailer;
    /// use byteorder::{BigEndian, WriteBytesExt};
    /// use std::io::Cursor;
    ///
    /// // Build an 8-byte FIL trailer
    /// let mut buf = vec![0u8; 8];
    /// let mut c = Cursor::new(&mut buf);
    /// c.write_u32::<BigEndian>(0xAABBCCDD).unwrap(); // old-style checksum
    /// c.write_u32::<BigEndian>(0x11223344).unwrap(); // LSN low 32 bits
    ///
    /// let trailer = FilTrailer::parse(&buf).unwrap();
    /// assert_eq!(trailer.checksum, 0xAABBCCDD);
    /// assert_eq!(trailer.lsn_low32, 0x11223344);
    /// ```
    pub fn parse(data: &[u8]) -> Option<Self> {
        if data.len() < SIZE_FIL_TRAILER {
            return None;
        }

        Some(FilTrailer {
            checksum: BigEndian::read_u32(&data[0..]),
            lsn_low32: BigEndian::read_u32(&data[4..]),
        })
    }
}

/// Parsed FSP header (from page 0 of a tablespace, starts at FIL_PAGE_DATA).
#[derive(Debug, Clone, Serialize)]
pub struct FspHeader {
    /// Space ID.
    pub space_id: u32,
    /// Size of the tablespace in pages.
    pub size: u32,
    /// Minimum page number not yet initialized.
    pub free_limit: u32,
    /// Space flags (contains page size, compression, encryption info).
    pub flags: u32,
    /// Number of used pages in the FSP_FREE_FRAG list.
    pub frag_n_used: u32,
}

impl FspHeader {
    /// Parse the FSP header from page 0's data area.
    ///
    /// `data` should be the full page buffer. FSP header starts at FIL_PAGE_DATA (byte 38).
    ///
    /// # Examples
    ///
    /// ```
    /// use idb::innodb::page::FspHeader;
    /// use byteorder::{BigEndian, ByteOrder};
    ///
    /// // Build a buffer large enough for the FIL header (38 bytes) + FSP header (112 bytes)
    /// let mut buf = vec![0u8; 150];
    /// let fsp_offset = 38; // FSP header starts at FIL_PAGE_DATA
    ///
    /// // Write FSP header fields at their offsets within the FSP region
    /// BigEndian::write_u32(&mut buf[fsp_offset..], 42);       // space_id (offset 0)
    /// BigEndian::write_u32(&mut buf[fsp_offset + 8..], 1000); // size in pages (offset 8)
    /// BigEndian::write_u32(&mut buf[fsp_offset + 12..], 64);  // free_limit (offset 12)
    /// BigEndian::write_u32(&mut buf[fsp_offset + 16..], 0);   // flags (offset 16)
    /// BigEndian::write_u32(&mut buf[fsp_offset + 20..], 10);  // frag_n_used (offset 20)
    ///
    /// let fsp = FspHeader::parse(&buf).unwrap();
    /// assert_eq!(fsp.space_id, 42);
    /// assert_eq!(fsp.size, 1000);
    /// assert_eq!(fsp.free_limit, 64);
    /// assert_eq!(fsp.flags, 0);
    /// assert_eq!(fsp.frag_n_used, 10);
    /// ```
    pub fn parse(page_data: &[u8]) -> Option<Self> {
        let offset = FIL_PAGE_DATA;
        if page_data.len() < offset + FSP_HEADER_SIZE {
            return None;
        }
        let data = &page_data[offset..];

        Some(FspHeader {
            space_id: BigEndian::read_u32(&data[FSP_SPACE_ID..]),
            size: BigEndian::read_u32(&data[FSP_SIZE..]),
            free_limit: BigEndian::read_u32(&data[FSP_FREE_LIMIT..]),
            flags: BigEndian::read_u32(&data[FSP_SPACE_FLAGS..]),
            frag_n_used: BigEndian::read_u32(&data[FSP_FRAG_N_USED..]),
        })
    }

    /// Extract the page size from FSP flags.
    ///
    /// Returns the page size in bytes. For MariaDB full_crc32 tablespaces,
    /// the page size is in bits 0-3 instead of bits 6-9.
    pub fn page_size_from_flags(&self) -> u32 {
        use crate::innodb::vendor::detect_vendor_from_flags;

        let vendor_info = detect_vendor_from_flags(self.flags);
        self.page_size_from_flags_with_vendor(&vendor_info)
    }

    /// Extract the page size from FSP flags with explicit vendor info.
    pub fn page_size_from_flags_with_vendor(
        &self,
        vendor_info: &crate::innodb::vendor::VendorInfo,
    ) -> u32 {
        let ssize = if vendor_info.is_full_crc32() {
            // MariaDB full_crc32: page size in bits 0-3
            self.flags & MARIADB_FSP_FLAGS_FCRC32_PAGE_SSIZE_MASK
        } else {
            // MySQL / MariaDB original: page size in bits 6-9
            (self.flags & FSP_FLAGS_MASK_PAGE_SSIZE) >> FSP_FLAGS_POS_PAGE_SSIZE
        };

        if ssize == 0 {
            // Default/uncompressed: 16K
            SIZE_PAGE_DEFAULT
        } else {
            // ssize encodes page size as: 1 << (ssize + 9)
            // ssize=3 => 4K, ssize=4 => 8K, ssize=5 => 16K, ssize=6 => 32K, ssize=7 => 64K
            1u32 << (ssize + 9)
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn make_fil_header_bytes(
        checksum: u32,
        page_num: u32,
        prev: u32,
        next: u32,
        lsn: u64,
        page_type: u16,
        flush_lsn: u64,
        space_id: u32,
    ) -> Vec<u8> {
        let mut buf = vec![0u8; SIZE_FIL_HEAD];
        BigEndian::write_u32(&mut buf[FIL_PAGE_SPACE_OR_CHKSUM..], checksum);
        BigEndian::write_u32(&mut buf[FIL_PAGE_OFFSET..], page_num);
        BigEndian::write_u32(&mut buf[FIL_PAGE_PREV..], prev);
        BigEndian::write_u32(&mut buf[FIL_PAGE_NEXT..], next);
        BigEndian::write_u64(&mut buf[FIL_PAGE_LSN..], lsn);
        BigEndian::write_u16(&mut buf[FIL_PAGE_TYPE..], page_type);
        BigEndian::write_u64(&mut buf[FIL_PAGE_FILE_FLUSH_LSN..], flush_lsn);
        BigEndian::write_u32(&mut buf[FIL_PAGE_SPACE_ID..], space_id);
        buf
    }

    #[test]
    fn test_fil_header_parse() {
        let data = make_fil_header_bytes(
            0x12345678, // checksum
            42,         // page number
            41,         // prev page
            43,         // next page
            1000,       // lsn
            17855,      // INDEX page type
            2000,       // flush lsn
            5,          // space id
        );
        let hdr = FilHeader::parse(&data).unwrap();
        assert_eq!(hdr.checksum, 0x12345678);
        assert_eq!(hdr.page_number, 42);
        assert_eq!(hdr.prev_page, 41);
        assert_eq!(hdr.next_page, 43);
        assert_eq!(hdr.lsn, 1000);
        assert_eq!(hdr.page_type, PageType::Index);
        assert_eq!(hdr.flush_lsn, 2000);
        assert_eq!(hdr.space_id, 5);
        assert!(hdr.has_prev());
        assert!(hdr.has_next());
    }

    #[test]
    fn test_fil_header_null_pages() {
        let data = make_fil_header_bytes(0, 0, FIL_NULL, FIL_NULL, 0, 0, 0, 0);
        let hdr = FilHeader::parse(&data).unwrap();
        assert!(!hdr.has_prev());
        assert!(!hdr.has_next());
    }

    #[test]
    fn test_fil_header_too_short() {
        let data = vec![0u8; 10];
        assert!(FilHeader::parse(&data).is_none());
    }

    #[test]
    fn test_fil_trailer_parse() {
        let mut data = vec![0u8; 8];
        BigEndian::write_u32(&mut data[0..], 0xAABBCCDD);
        BigEndian::write_u32(&mut data[4..], 0x11223344);
        let trl = FilTrailer::parse(&data).unwrap();
        assert_eq!(trl.checksum, 0xAABBCCDD);
        assert_eq!(trl.lsn_low32, 0x11223344);
    }

    #[test]
    fn test_fsp_header_page_size() {
        let fsp = FspHeader {
            space_id: 0,
            size: 100,
            free_limit: 64,
            flags: 0, // ssize=0 => default 16K
            frag_n_used: 0,
        };
        assert_eq!(fsp.page_size_from_flags(), SIZE_PAGE_DEFAULT);

        // ssize=5 => 16384
        let fsp_16k = FspHeader {
            flags: 5 << FSP_FLAGS_POS_PAGE_SSIZE,
            ..fsp
        };
        assert_eq!(fsp_16k.page_size_from_flags(), 16384);

        // ssize=3 => 4096
        let fsp_4k = FspHeader {
            flags: 3 << FSP_FLAGS_POS_PAGE_SSIZE,
            ..fsp
        };
        assert_eq!(fsp_4k.page_size_from_flags(), 4096);
    }

    #[test]
    fn test_fsp_header_page_size_mariadb_full_crc32() {
        use crate::innodb::vendor::{MariaDbFormat, VendorInfo};

        let vendor = VendorInfo::mariadb(MariaDbFormat::FullCrc32);

        // MariaDB full_crc32: ssize in bits 0-3, marker at bit 4
        // ssize=5 (16K) + full_crc32 marker
        let fsp = FspHeader {
            space_id: 0,
            size: 100,
            free_limit: 64,
            flags: 0x10 | 5, // bit 4 marker + ssize=5 in bits 0-3
            frag_n_used: 0,
        };
        assert_eq!(fsp.page_size_from_flags_with_vendor(&vendor), 16384);

        // ssize=3 (4K)
        let fsp_4k = FspHeader {
            flags: 0x10 | 3,
            ..fsp
        };
        assert_eq!(fsp_4k.page_size_from_flags_with_vendor(&vendor), 4096);

        // ssize=0 (default 16K)
        let fsp_default = FspHeader { flags: 0x10, ..fsp };
        assert_eq!(
            fsp_default.page_size_from_flags_with_vendor(&vendor),
            SIZE_PAGE_DEFAULT
        );
    }
}