libsql: add unsafe Database::connect_raw

This adds a `connect_raw` function that can be called in an unsafe
manner. This will bypass `libsql`'s safety checks that enforce that
sqlite3's serialized thread safety mode is enabled. This is a use at
your own risk type of function.

Author: LucioFranco

libsql/src/database.rs

@@ -666,6 +666,91 @@ impl Database {
             _ => unreachable!("no database type set"),
         }
     }
+
+    /// Connect to a database without safety checks. Using `connect` will enforce that sqlite is
+    /// compiled and configured correctly. This can conflict if you have other sqlite3 processes
+    /// due to sqlite3's global config. This function allows a user to bypass those checks in
+    /// exchanged for the user enforcing that sqlite3 is compiled AND enabled for serailized thread
+    /// saftey mode.
+    ///
+    /// SAFTEY: Users must ensure that sqlite3 has SERIALIZED thread safe mode enabled or else this
+    /// will produce UBs.
+    #[allow(unreachable_patterns)]
+    pub unsafe fn connect_raw(&self) -> Result<Connection> {
+        match &self.db_type {
+            #[cfg(feature = "core")]
+            DbType::Memory { db: _ } => {
+                unimplemented!("memory dbs are not supported in connect_raw")
+            }
+
+            #[cfg(feature = "core")]
+            DbType::File {
+                path,
+                flags,
+                encryption_config,
+            } => {
+                use crate::local::impls::LibsqlConnection;
+
+                let db = crate::local::Database::open_raw(path, *flags)?;
+                let conn = db.connect()?;
+
+                if !cfg!(feature = "encryption") && encryption_config.is_some() {
+                    return Err(crate::Error::Misuse(
+                        "Encryption is not enabled: enable the `encryption` feature in order to enable encryption-at-rest".to_string(),
+                    ));
+                }
+
+                #[cfg(feature = "encryption")]
+                if let Some(cfg) = encryption_config {
+                    if unsafe {
+                        libsql_sys::connection::set_encryption_cipher(conn.raw, cfg.cipher_id())
+                    } == -1
+                    {
+                        return Err(crate::Error::Misuse(
+                            "failed to set encryption cipher".to_string(),
+                        ));
+                    }
+                    if unsafe {
+                        libsql_sys::connection::set_encryption_key(conn.raw, &cfg.encryption_key)
+                    } != crate::ffi::SQLITE_OK
+                    {
+                        return Err(crate::Error::Misuse(
+                            "failed to set encryption key".to_string(),
+                        ));
+                    }
+                }
+
+                let conn = std::sync::Arc::new(LibsqlConnection { conn });
+
+                Ok(Connection { conn })
+            }
+
+            #[cfg(feature = "replication")]
+            DbType::Sync {
+                db: _,
+                encryption_config: _,
+            } => {
+                unimplemented!("embedded replica is not supported in connect_raw")
+            }
+
+            #[cfg(feature = "sync")]
+            DbType::Offline { db: _ } => {
+                unimplemented!("offline sync not supported in connect_raw")
+            }
+
+            #[cfg(feature = "remote")]
+            DbType::Remote {
+                url: _,
+                auth_token: _,
+                connector: _,
+                version: _,
+            } => {
+                unimplemented!("remote connections are not supported in connect_raw")
+            }
+
+            _ => unreachable!("no database type set"),
+        }
+    }
 }
 
 #[cfg(any(

libsql/src/local/database.rs

@@ -53,6 +53,30 @@ impl Database {
         }
     }
 
+    /// Safety: this is like `open` but does not enfoce that sqlite_config has THREADSAFE set to
+    /// `SQLITE_CONFIG_SERIALIZED`, calling
+    pub unsafe fn open_raw<S: Into<String>>(db_path: S, flags: OpenFlags) -> Result<Database> {
+        let db_path = db_path.into();
+
+        if db_path.starts_with("libsql:")
+            || db_path.starts_with("http:")
+            || db_path.starts_with("https:")
+        {
+            Err(ConnectionFailed(format!(
+                "Unable to open local database {db_path} with Database::open()"
+            )))
+        } else {
+            Ok(Database {
+                db_path,
+                flags,
+                #[cfg(feature = "replication")]
+                replication_ctx: None,
+                #[cfg(feature = "sync")]
+                sync_ctx: None,
+            })
+        }
+    }
+
     #[cfg(feature = "replication")]
     pub async fn open_http_sync(
         connector: crate::util::ConnectorService,
@@ -420,7 +444,11 @@ impl Database {
     }
 
     #[cfg(feature = "sync")]
-    async fn try_push(&self, sync_ctx: &mut SyncContext, conn: &Connection) -> Result<crate::database::Replicated> {
+    async fn try_push(
+        &self,
+        sync_ctx: &mut SyncContext,
+        conn: &Connection,
+    ) -> Result<crate::database::Replicated> {
         let page_size = {
             let rows = conn
                 .query("PRAGMA page_size", crate::params::Params::None)?
@@ -471,7 +499,11 @@ impl Database {
     }
 
     #[cfg(feature = "sync")]
-    async fn try_pull(&self, sync_ctx: &mut SyncContext, conn: &Connection) -> Result<crate::database::Replicated> {
+    async fn try_pull(
+        &self,
+        sync_ctx: &mut SyncContext,
+        conn: &Connection,
+    ) -> Result<crate::database::Replicated> {
         let generation = sync_ctx.generation();
         let mut frame_no = sync_ctx.durable_frame_num() + 1;
         conn.wal_insert_begin()?;