Corruption detection

vfs/cksm is a pure-Go, page-level Fletcher-style checksum VFS — an 8-byte trailer per page, on-disk compatible with SQLite’s cksumvfs extension.

import (
  "gosqlite.org/vfs/cksm"
  sqlite "gosqlite.org"
)

name, fs, _ := cksm.New(cksm.Options{})
defer fs.Close()

db, _ := sql.Open("sqlite", "file:journal.db?vfs="+name)
sc, _ := db.Conn(ctx)
sc.Raw(func(d any) error { return d.(*sqlite.Conn).EnableChecksums("main") })

(*sqlite.Conn).EnableChecksums("main") sets reserved_bytes=8 on the schema and VACUUMs so every existing page is rewritten with the trailer.

• On reopen the VFS detects byte 20 == 8 in the SQLite header and auto-activates verification; a flipped bit surfaces as SQLITE_IOERR_DATA on read instead of silent corruption.
• On-disk compatible with stock SQLite + cksumvfs — a database written here is readable by that combination.

Both cksm.Options and crypto.Options accept WrapVFS to stack — register cksm first, then point crypto at it for checksum-on-the-inside / encrypt-on-the-outside.

Runnable: examples/features/vfs/cksm/ (corrupt-a-byte demo). Trailer format: vfs/cksm/doc.go; coverage: dev/coverage/vfs.md.