move db upgrade logic into db crate

This allows shrinking db's API surface.

db/upgrade/v2_to_v3.rs

@@ -0,0 +1,116 @@
+// This file is part of Moonfire NVR, a security camera digital video recorder.
+// Copyright (C) 2018 Scott Lamb <slamb@slamb.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// In addition, as a special exception, the copyright holders give
+// permission to link the code of portions of this program with the
+// OpenSSL library under certain conditions as described in each
+// individual source file, and distribute linked combinations including
+// the two.
+//
+// You must obey the GNU General Public License in all respects for all
+// of the code used other than OpenSSL. If you modify file(s) with this
+// exception, you may extend this exception to your version of the
+// file(s), but you are not obligated to do so. If you do not wish to do
+// so, delete this exception statement from your version. If you delete
+// this exception statement from all source files in the program, then
+// also delete it here.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+/// Upgrades a version 2 schema to a version 3 schema.
+
+use db::{self, FromSqlUuid};
+use dir;
+use failure::Error;
+use libc;
+use std::io::{self, Write};
+use std::mem;
+use rusqlite;
+use uuid::Uuid;
+
+pub struct U;
+
+pub fn new<'a>(_args: &'a super::Args) -> Result<Box<super::Upgrader + 'a>, Error> {
+    Ok(Box::new(U))
+}
+
+/// Gets a pathname for a sample file suitable for passing to open or unlink.
+fn get_uuid_pathname(uuid: Uuid) -> [libc::c_char; 37] {
+    let mut buf = [0u8; 37];
+    write!(&mut buf[..36], "{}", uuid.hyphenated()).expect("can't format uuid to pathname buf");
+
+    // libc::c_char seems to be i8 on some platforms (Linux/arm) and u8 on others (Linux/amd64).
+    unsafe { mem::transmute::<[u8; 37], [libc::c_char; 37]>(buf) }
+}
+
+fn get_id_pathname(id: db::CompositeId) -> [libc::c_char; 17] {
+    let mut buf = [0u8; 17];
+    write!(&mut buf[..16], "{:016x}", id.0).expect("can't format id to pathname buf");
+    unsafe { mem::transmute::<[u8; 17], [libc::c_char; 17]>(buf) }
+}
+
+impl super::Upgrader for U {
+    fn in_tx(&mut self, tx: &rusqlite::Transaction) -> Result<(), Error> {
+        let path: String = tx.query_row(r#"
+            select path from sample_file_dir
+        "#, &[], |row| { row.get_checked(0) })??;
+
+        // Build map of stream -> dirname.
+        let d = dir::Fd::open(None, &path, false)?;
+        //let stream_to_dir = build_stream_to_dir(&d, tx)?;
+
+        let mut stmt = tx.prepare(r#"
+            select
+              composite_id,
+              sample_file_uuid
+            from
+              recording_playback
+        "#)?;
+        let mut rows = stmt.query(&[])?;
+        while let Some(row) = rows.next() {
+            let row = row?;
+            let id = db::CompositeId(row.get_checked(0)?);
+            let sample_file_uuid: FromSqlUuid = row.get_checked(1)?;
+            let from_path = get_uuid_pathname(sample_file_uuid.0);
+            let to_path = get_id_pathname(id);
+            //let to_dir: &dir::Fd = stream_to_dir[stream_id as usize].as_ref().unwrap();
+            let r = unsafe { dir::renameat(&d, from_path.as_ptr(), &d, to_path.as_ptr()) };
+            if let Err(e) = r {
+                if e.kind() == io::ErrorKind::NotFound {
+                    continue;  // assume it was already moved.
+                }
+                Err(e)?;
+            }
+        }
+
+        // These create statements match the schema.sql when version 3 was the latest.
+        tx.execute_batch(r#"
+            alter table recording_playback rename to old_recording_playback;
+            create table recording_playback (
+              composite_id integer primary key references recording (composite_id),
+              sample_file_sha1 blob not null check (length(sample_file_sha1) = 20),
+              video_index blob not null check (length(video_index) > 0)
+            );
+            insert into recording_playback
+            select
+              composite_id,
+              sample_file_sha1,
+              video_index
+            from
+              old_recording_playback;
+            drop table old_recording_playback;
+        "#)?;
+        Ok(())
+    }
+}