lib: Revert needing invalid files (fixes #7608, ref #7476) (#7609)

lib/db/util.go

@@ -0,0 +1,70 @@
+// Copyright (C) 2021 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+package db
+
+import "github.com/syncthing/syncthing/lib/protocol"
+
+// How many files to send in each Index/IndexUpdate message.
+const (
+	MaxBatchSizeBytes = 250 * 1024 // Aim for making index messages no larger than 250 KiB (uncompressed)
+	MaxBatchSizeFiles = 1000       // Either way, don't include more files than this
+)
+
+// FileInfoBatch is a utility to do file operations on the database in suitably
+// sized batches.
+type FileInfoBatch struct {
+	infos   []protocol.FileInfo
+	size    int
+	flushFn func([]protocol.FileInfo) error
+}
+
+func NewFileInfoBatch(fn func([]protocol.FileInfo) error) *FileInfoBatch {
+	return &FileInfoBatch{
+		infos:   make([]protocol.FileInfo, 0, MaxBatchSizeFiles),
+		flushFn: fn,
+	}
+}
+
+func (b *FileInfoBatch) SetFlushFunc(fn func([]protocol.FileInfo) error) {
+	b.flushFn = fn
+}
+
+func (b *FileInfoBatch) Append(f protocol.FileInfo) {
+	b.infos = append(b.infos, f)
+	b.size += f.ProtoSize()
+}
+
+func (b *FileInfoBatch) Full() bool {
+	return len(b.infos) >= MaxBatchSizeFiles || b.size >= MaxBatchSizeBytes
+}
+
+func (b *FileInfoBatch) FlushIfFull() error {
+	if b.Full() {
+		return b.Flush()
+	}
+	return nil
+}
+
+func (b *FileInfoBatch) Flush() error {
+	if len(b.infos) == 0 {
+		return nil
+	}
+	if err := b.flushFn(b.infos); err != nil {
+		return err
+	}
+	b.Reset()
+	return nil
+}
+
+func (b *FileInfoBatch) Reset() {
+	b.infos = b.infos[:0]
+	b.size = 0
+}
+
+func (b *FileInfoBatch) Size() int {
+	return b.size
+}