add page size to segment header

Author: MarinPostma

libsql-wal/src/error.rs

@@ -15,6 +15,8 @@ pub enum Error {
     InvalidHeaderMagic,
     #[error("invalid segment header version")]
     InvalidHeaderVersion,
+    #[error("Invalid page size, only 4095 is supported")]
+    InvalidPageSize,
 }
 
 impl Into<libsql_sys::ffi::Error> for Error {

libsql-wal/src/lib.rs

@@ -12,6 +12,8 @@ pub mod transaction;
 pub mod wal;
 
 const LIBSQL_MAGIC: u64 = u64::from_be_bytes(*b"LIBSQL\0\0");
+const LIBSQL_PAGE_SIZE: u16 = 4096;
+const LIBSQL_WAL_VERSION: u16 = 1;
 
 #[cfg(any(debug_assertions, test))]
 pub mod test {

libsql-wal/src/segment/compacted.rs

@@ -6,6 +6,7 @@ use zerocopy::{AsBytes, FromBytes, FromZeroes};
 
 use crate::io::buf::{ZeroCopyBoxIoBuf, ZeroCopyBuf};
 use crate::io::FileExt;
+use crate::{LIBSQL_MAGIC, LIBSQL_PAGE_SIZE, LIBSQL_WAL_VERSION};
 
 use super::{Frame, Result};
 
@@ -19,6 +20,25 @@ pub struct CompactedSegmentDataHeader {
     pub(crate) start_frame_no: lu64,
     pub(crate) end_frame_no: lu64,
     pub(crate) size_after: lu32,
+    /// for now, always 4096
+    pub(crate) page_size: lu16,
+}
+impl CompactedSegmentDataHeader {
+    fn check(&self) -> Result<()> {
+        if self.magic.get() != LIBSQL_MAGIC {
+            return Err(super::Error::InvalidHeaderMagic);
+        }
+
+        if self.page_size.get() != LIBSQL_PAGE_SIZE {
+            return Err(super::Error::InvalidPageSize);
+        }
+
+        if self.version.get() != LIBSQL_WAL_VERSION {
+            return Err(super::Error::InvalidPageSize);
+        }
+
+        Ok(())
+    }
 }
 
 #[derive(Debug, AsBytes, FromZeroes, FromBytes)]
@@ -37,7 +57,8 @@ impl<F: FileExt> CompactedSegment<F> {
         let buf = ZeroCopyBuf::new_uninit();
         let (buf, ret) = file.read_exact_at_async(buf, 0).await;
         ret?;
-        let header = buf.into_inner();
+        let header: CompactedSegmentDataHeader = buf.into_inner();
+        header.check()?;
         Ok(Self { file, header })
     }
 

libsql-wal/src/segment/current.rs

@@ -23,7 +23,7 @@ use crate::io::Inspect;
 use crate::segment::{checked_frame_offset, SegmentFlags};
 use crate::segment::{frame_offset, page_offset, sealed::SealedSegment};
 use crate::transaction::{Transaction, TxGuard};
-use crate::LIBSQL_MAGIC;
+use crate::{LIBSQL_MAGIC, LIBSQL_PAGE_SIZE, LIBSQL_WAL_VERSION};
 
 use super::list::SegmentList;
 use super::{CheckedFrame, Frame, FrameHeader, SegmentHeader};
@@ -67,8 +67,9 @@ impl<F> CurrentSegment<F> {
             header_cheksum: 0.into(),
             flags: 0.into(),
             magic: LIBSQL_MAGIC.into(),
-            version: 1.into(),
+            version: LIBSQL_WAL_VERSION.into(),
             salt: salt.into(),
+            page_size: LIBSQL_PAGE_SIZE.into(),
         };
 
         header.recompute_checksum();

libsql-wal/src/segment/mod.rs

@@ -22,6 +22,7 @@ use crate::error::{Error, Result};
 use crate::io::buf::IoBufMut;
 use crate::io::FileExt;
 use crate::LIBSQL_MAGIC;
+use crate::LIBSQL_PAGE_SIZE;
 
 pub(crate) mod compacted;
 pub mod current;
@@ -58,6 +59,9 @@ pub struct SegmentHeader {
     pub flags: U32,
     /// salt for the segment checksum
     pub salt: U32,
+    /// right now we only support 4096, but if se decided to support other sizes,
+    /// we could do it without changing the header
+    pub page_size: U16,
 
     /// checksum of the header fields, excluding the checksum itself. This field must be the last
     pub header_cheksum: U32,
@@ -71,6 +75,10 @@ impl SegmentHeader {
     }
 
     fn check(&self) -> Result<()> {
+        if self.page_size.get() != LIBSQL_PAGE_SIZE {
+            return Err(Error::InvalidPageSize);
+        }
+
         if self.magic.get() != LIBSQL_MAGIC {
             return Err(Error::InvalidHeaderChecksum);
         }
@@ -261,7 +269,7 @@ impl CheckedFrame {
 #[derive(Debug, zerocopy::AsBytes, zerocopy::FromBytes, zerocopy::FromZeroes)]
 pub struct Frame {
     header: FrameHeader,
-    data: [u8; 4096],
+    data: [u8; LIBSQL_PAGE_SIZE as usize],
 }
 
 impl Frame {

libsql-wal/src/segment/sealed.rs

@@ -17,7 +17,7 @@ use crate::io::buf::{IoBufMut, ZeroCopyBuf};
 use crate::io::file::{BufCopy, FileExt};
 use crate::io::Inspect;
 use crate::segment::{checked_frame_offset, CheckedFrame};
-use crate::LIBSQL_MAGIC;
+use crate::{LIBSQL_MAGIC, LIBSQL_WAL_VERSION};
 
 use super::compacted::{CompactedSegmentDataFooter, CompactedSegmentDataHeader};
 use super::{frame_offset, page_offset, Frame, Segment, SegmentFlags, SegmentHeader};
@@ -91,8 +91,9 @@ where
             start_frame_no: self.header().start_frame_no,
             end_frame_no: self.header().last_commited_frame_no,
             size_after: self.header.size_after,
-            version: 1.into(),
+            version: LIBSQL_WAL_VERSION.into(),
             magic: LIBSQL_MAGIC.into(),
+            page_size: self.header().page_size,
         };
 
         hasher.update(header.as_bytes());