sqlite: fs.FS support via vfs

internal/rpm/find.go

@@ -1,6 +1,7 @@
 package rpm
 
 import (
+	"bytes"
 	"context"
 	"errors"
 	"fmt"
@@ -160,89 +161,45 @@ func OpenDB(ctx context.Context, sys fs.FS, found FoundDB) (*Database, error) {
 	// TODO(hank) Cook up some test against passing the wrong [fs.FS]. Don't use
 	// the unique package.
 
-	f, err := sys.Open(found.filename())
-	if err != nil {
-		return nil, fmt.Errorf("internal/rpm: unable to open %s db: %w", found.kind.String(), err)
-	}
-	defer func() {
-		if err := f.Close(); err != nil {
-			slog.WarnContext(ctx, "unable to close db", "kind", found, "reason", err)
-		}
-	}()
-
 	cleanup := &databaseCleanup{}
 	db := Database{
 		pkgdb:   found.String(),
 		cleanup: cleanup,
 	}
 
-	spool, err := os.CreateTemp(os.TempDir(), fmt.Sprintf(`rpm.package.%v.`, found.kind))
-	if err != nil {
-		return nil, fmt.Errorf("internal/rpm: error spooling db: %w", err)
-	}
-	log := slog.With("file", spool.Name())
-	cleanup.spool = spool
-	log.DebugContext(ctx, "copying db out of fs.FS")
-
-	// Need to have the file linked into the filesystem for the sqlite package.
-	//
-	// See [this post] for an idea on working around it:
-	//
-	//	int sqlite_fdopen(
-	//		int fd,
-	//		sqlite3 **connection)
-	//	{
-	//		char uri[48];
-	//
-	//		snprintf(uri, sizeof uri, "file:///dev/fd/%d?immutable=1", fd);
-	//		return sqlite3_open_v2(
-	//			uri,
-	//			connection,
-	//			SQLITE_OPEN_READONLY | SQLITE_OPEN_URI,
-	//			NULL);
-	//	}
-	//
-	// [this post]: https://sqlite.org/forum/info/57aaaf20cf703d301fed5aeaef59e70723f1d9454fb3a4e6383b2bfac6897e5a
-	if _, err := io.Copy(spool, f); err != nil {
-		if err := spool.Close(); err != nil {
-			log.WarnContext(ctx, "unable to close spool", "reason", err)
-		}
-		return nil, fmt.Errorf("internal/rpm: error spooling db: %w", err)
-	}
-	if err := spool.Sync(); err != nil {
-		log.WarnContext(ctx, "unable to sync spool; results may be Weird", "reason", err)
-	}
-
 	switch found.kind {
 	case kindSQLite:
-		sdb, err := sqlite.Open(spool.Name())
+		sdb, err := sqlite.OpenFS(sys, found.filename())
 		if err != nil {
-			if err := spool.Close(); err != nil {
-				log.WarnContext(ctx, "unable to close spool", "reason", err)
-			}
-			if err := os.Remove(spool.Name()); err != nil {
-				log.WarnContext(ctx, "unable to remove spool", "reason", err)
-			}
 			return nil, fmt.Errorf("internal/rpm: unable to open sqlite db: %w", err)
 		}
 		db.headers = sdb
 		cleanup.close = sdb.Close
-	case kindBDB:
-		var bpdb bdb.PackageDB
-		if err := bpdb.Parse(spool); err != nil {
-			return nil, fmt.Errorf("internal/rpm: error parsing bdb db: %w", err)
+	case kindBDB, kindNDB:
+		r, err := db.openOrBuffer(ctx, sys, found)
+		if err != nil {
+			return nil, fmt.Errorf("internal/rpm: unable to open %s db: %w", found.kind.String(), err)
 		}
-		db.headers = &bpdb
-	case kindNDB:
-		var npdb ndb.PackageDB
-		if err := npdb.Parse(spool); err != nil {
-			return nil, fmt.Errorf("internal/rpm: error parsing ndb db: %w", err)
+		switch found.kind {
+		case kindBDB:
+			var bpdb bdb.PackageDB
+			if err := bpdb.Parse(r); err != nil {
+				return nil, fmt.Errorf("internal/rpm: error parsing bdb db: %w", err)
+			}
+			db.headers = &bpdb
+		case kindNDB:
+			var npdb ndb.PackageDB
+			if err := npdb.Parse(r); err != nil {
+				return nil, fmt.Errorf("internal/rpm: error parsing ndb db: %w", err)
+			}
+			db.headers = &npdb
+		default:
+			panic("unreachable")
 		}
-		db.headers = &npdb
 	default:
 		panic("unreachable")
 	}
-	log.DebugContext(ctx, "opened database", "db", found)
+	slog.DebugContext(ctx, "opened database", "db", found)
 
 	if v, ok := db.headers.(validator); ok {
 		if err := v.Validate(ctx); err != nil {
@@ -253,6 +210,28 @@ func OpenDB(ctx context.Context, sys fs.FS, found FoundDB) (*Database, error) {
 	return &db, nil
 }
 
+func (db *Database) openOrBuffer(_ context.Context, sys fs.FS, found FoundDB) (io.ReaderAt, error) {
+	f, err := sys.Open(found.filename())
+	if err != nil {
+		return nil, err
+	}
+	r, ok := f.(io.ReaderAt)
+	if ok {
+		db.cleanup = f
+		return r, nil
+	}
+	defer f.Close()
+
+	var buf bytes.Buffer
+	if fi, err := f.Stat(); err == nil {
+		buf.Grow(int(fi.Size()))
+	}
+	if _, err := io.Copy(&buf, f); err != nil {
+		return nil, err
+	}
+	return bytes.NewReader(buf.Bytes()), nil
+}
+
 type databaseCleanup struct {
 	spool *os.File
 	close func() error

internal/rpm/sqlite/sqlite.go

@@ -9,16 +9,19 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"iter"
 	"net/url"
 	"runtime"
 
 	_ "modernc.org/sqlite" // register the sqlite driver
+	"modernc.org/sqlite/vfs"
 )
 
 // RPMDB is a handle to a SQLite RPM database.
 type RPMDB struct {
-	db *sql.DB
+	db  *sql.DB
+	vfs *vfs.FS
 }
 
 // Open opens the named SQLite database and interprets it as an RPM
@@ -56,13 +59,68 @@ func Open(f string) (*RPMDB, error) {
 	return &rdb, nil
 }
 
+// OpenFS opens the named SQLite database in the context of "sys" and interprets
+// it as an RPM database.
+//
+// The returned RPMDB struct must have its Close method called, or the process
+// may panic.
+func OpenFS(sys fs.FS, f string) (*RPMDB, error) {
+	name, vfs, err := vfs.New(sys)
+	if err != nil {
+		return nil, fmt.Errorf("sqlite: vfs creation failed: %w", err)
+	}
+	ok := false
+	defer func() {
+		if !ok {
+			vfs.Close()
+		}
+	}()
+	u := url.URL{
+		Scheme: `file`,
+		Opaque: f,
+		RawQuery: url.Values{
+			"vfs":       {name},
+			"immutable": {"1"},
+			"_pragma": {
+				"foreign_keys(1)",
+				"query_only(1)",
+			},
+		}.Encode(),
+	}
+	db, err := sql.Open(`sqlite`, u.String())
+	if err != nil {
+		return nil, fmt.Errorf("sqlite: unable to open db: %w", err)
+	}
+	if err := db.Ping(); err != nil {
+		return nil, fmt.Errorf("sqlite: unable to ping db: %w", err)
+	}
+	rdb := RPMDB{
+		db:  db,
+		vfs: vfs,
+	}
+	ok = true
+	_, file, line, _ := runtime.Caller(1)
+	runtime.SetFinalizer(&rdb, func(rdb *RPMDB) {
+		panic(fmt.Sprintf("%s:%d: RPM db not closed", file, line))
+	})
+	return &rdb, nil
+}
+
 // Close releases held resources.
 //
 // This must be called when the RPMDB is no longer needed, or the
 // process may panic.
 func (db *RPMDB) Close() error {
 	runtime.SetFinalizer(db, nil)
-	return db.db.Close()
+	return errors.Join(
+		db.db.Close(),
+		func() error {
+			if db.vfs != nil {
+				return db.vfs.Close()
+			}
+			return nil
+		}(),
+	)
 }
 
 // Headers returns an iterator over all RPM headers in the database.