From 9e4258bc460082385428b9aa3ac87b96ea4aced9 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Tue, 25 Mar 2025 12:45:27 +0000
Subject: [PATCH] Better fix #249.

---
 config.go   |  6 +++---
 conn.go     |  4 ++--
 vfs/cksm.go | 24 +++++++++++++++---------
 vtab.go     |  6 ++++--
 4 files changed, 24 insertions(+), 16 deletions(-)

diff --git a/config.go b/config.go
index d52cc05..decea18 100644
--- a/config.go
+++ b/config.go
@@ -279,6 +279,8 @@ func (c *Conn) WALCheckpoint(schema string, mode CheckpointMode) (nLog, nCkpt in
 	nLogPtr := c.arena.new(ptrlen)
 	nCkptPtr := c.arena.new(ptrlen)
 	schemaPtr := c.arena.string(schema)
+
+	c.checkInterrupt()
 	rc := res_t(c.call("sqlite3_wal_checkpoint_v2",
 		stk_t(c.handle), stk_t(schemaPtr), stk_t(mode),
 		stk_t(nLogPtr), stk_t(nCkptPtr)))
@@ -350,8 +352,6 @@ func (c *Conn) HardHeapLimit(n int64) int64 {
 }
 
 // EnableChecksums enables checksums on a database.
-// If the database is in WAL mode,
-// you should shutdown and reopen all database connections before continuing.
 //
 // https://sqlite.org/cksumvfs.html
 func (c *Conn) EnableChecksums(schema string) error {
@@ -390,6 +390,6 @@ func (c *Conn) EnableChecksums(schema string) error {
 	}
 
 	// Checkpoint the WAL.
-	_, _, err = c.WALCheckpoint(schema, CHECKPOINT_RESTART)
+	_, _, err = c.WALCheckpoint(schema, CHECKPOINT_FULL)
 	return err
 }
diff --git a/conn.go b/conn.go
index 2ea16a2..06b6637 100644
--- a/conn.go
+++ b/conn.go
@@ -185,10 +185,10 @@ func (c *Conn) Close() error {
 // https://sqlite.org/c3ref/exec.html
 func (c *Conn) Exec(sql string) error {
 	defer c.arena.mark()()
-	sqlPtr := c.arena.string(sql)
+	textPtr := c.arena.string(sql)
 
 	c.checkInterrupt()
-	rc := res_t(c.call("sqlite3_exec", stk_t(c.handle), stk_t(sqlPtr), 0, 0, 0))
+	rc := res_t(c.call("sqlite3_exec", stk_t(c.handle), stk_t(textPtr), 0, 0, 0))
 	return c.error(rc, sql)
 }
 
diff --git a/vfs/cksm.go b/vfs/cksm.go
index 1610549..0ff7b6f 100644
--- a/vfs/cksm.go
+++ b/vfs/cksm.go
@@ -49,9 +49,7 @@ func (c cksmFile) ReadAt(p []byte, off int64) (n int, err error) {
 	n, err = c.File.ReadAt(p, off)
 	p = p[:n]
 
-	// SQLite is reading the header of a database file.
-	if c.isDB && off == 0 && len(p) >= 100 &&
-		bytes.HasPrefix(p, []byte("SQLite format 3\000")) {
+	if isHeader(c.isDB, p, off) {
 		c.init((*[100]byte)(p))
 	}
 
@@ -67,9 +65,7 @@ func (c cksmFile) ReadAt(p []byte, off int64) (n int, err error) {
 }
 
 func (c cksmFile) WriteAt(p []byte, off int64) (n int, err error) {
-	// SQLite is writing the first page of a database file.
-	if (!c.isDB || off == 0) && sql3util.ValidPageSize(len(p)) &&
-		bytes.HasPrefix(p, []byte("SQLite format 3\000")) {
+	if isHeader(c.isDB, p, off) {
 		c.init((*[100]byte)(p))
 	}
 
@@ -116,9 +112,11 @@ func (c cksmFile) fileControl(ctx context.Context, mod api.Module, op _FcntlOpco
 		c.inCkpt = true
 	case _FCNTL_CKPT_DONE:
 		c.inCkpt = false
-	}
-	if rc := vfsFileControlImpl(ctx, mod, c, op, pArg); rc != _NOTFOUND {
-		return rc
+	case _FCNTL_PRAGMA:
+		rc := vfsFileControlImpl(ctx, mod, c, op, pArg)
+		if rc != _NOTFOUND {
+			return rc
+		}
 	}
 	return vfsFileControlImpl(ctx, mod, c.File, op, pArg)
 }
@@ -135,6 +133,14 @@ func (f *cksmFlags) init(header *[100]byte) {
 	}
 }
 
+func isHeader(isDB bool, p []byte, off int64) bool {
+	check := sql3util.ValidPageSize(len(p))
+	if isDB {
+		check = off == 0 && len(p) >= 100
+	}
+	return check && bytes.HasPrefix(p, []byte("SQLite format 3\000"))
+}
+
 func cksmCompute(a []byte) (cksm [8]byte) {
 	var s1, s2 uint32
 	for len(a) >= 8 {
diff --git a/vtab.go b/vtab.go
index f4282d9..1db142c 100644
--- a/vtab.go
+++ b/vtab.go
@@ -80,8 +80,10 @@ func implements[T any](typ reflect.Type) bool {
 // https://sqlite.org/c3ref/declare_vtab.html
 func (c *Conn) DeclareVTab(sql string) error {
 	defer c.arena.mark()()
-	sqlPtr := c.arena.string(sql)
-	rc := res_t(c.call("sqlite3_declare_vtab", stk_t(c.handle), stk_t(sqlPtr)))
+	textPtr := c.arena.string(sql)
+
+	c.checkInterrupt()
+	rc := res_t(c.call("sqlite3_declare_vtab", stk_t(c.handle), stk_t(textPtr)))
 	return c.error(rc)
 }