lib/db: Refactor key handling (ref #5198) (#5199)

This breaks out the key generation stuff into a separate type. It's
cleaner on its own, and it prepares for future stuff.

1 files changed, 202 insertions, 0 deletions

diff --git a/lib/db/keyer.go b/lib/db/keyer.go
new file mode 100644
index 0000000000..ff3ce603f0
--- /dev/null
+++ b/lib/db/keyer.go
@@ -0,0 +1,202 @@
+// Copyright (C) 2018 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 (
+	"encoding/binary"
+)
+
+const (
+	keyPrefixLen   = 1
+	keyFolderLen   = 4 // indexed
+	keyDeviceLen   = 4 // indexed
+	keySequenceLen = 8
+	keyHashLen     = 32
+
+	maxInt64 int64 = 1<<63 - 1
+)
+
+const (
+	KeyTypeDevice          = 0
+	KeyTypeGlobal          = 1
+	KeyTypeBlock           = 2
+	KeyTypeDeviceStatistic = 3
+	KeyTypeFolderStatistic = 4
+	KeyTypeVirtualMtime    = 5
+	KeyTypeFolderIdx       = 6
+	KeyTypeDeviceIdx       = 7
+	KeyTypeIndexID         = 8
+	KeyTypeFolderMeta      = 9
+	KeyTypeMiscData        = 10
+	KeyTypeSequence        = 11
+	KeyTypeNeed            = 12
+)
+
+type keyer interface {
+	// device file key stuff
+	GenerateDeviceFileKey(key, folder, device, name []byte) deviceFileKey
+	NameFromDeviceFileKey(key []byte) []byte
+	DeviceFromDeviceFileKey(key []byte) ([]byte, bool)
+	FolderFromDeviceFileKey(key []byte) ([]byte, bool)
+
+	// global version key stuff
+	GenerateGlobalVersionKey(key, folder, name []byte) globalVersionKey
+	NameFromGlobalVersionKey(key []byte) []byte
+	FolderFromGlobalVersionKey(key []byte) ([]byte, bool)
+
+	// file need index
+	GenerateNeedFileKey(key, folder, name []byte) needFileKey
+
+	// file sequence index
+	GenerateSequenceKey(key, folder []byte, seq int64) sequenceKey
+	SequenceFromSequenceKey(key []byte) int64
+
+	// index IDs
+	GenerateIndexIDKey(key, device, folder []byte) indexIDKey
+	DeviceFromIndexIDKey(key []byte) ([]byte, bool)
+
+	// Mtimes
+	GenerateMtimesKey(key, folder []byte) mtimesKey
+
+	// Folder metadata
+	GenerateFolderMetaKey(key, folder []byte) folderMetaKey
+}
+
+// defaultKeyer implements our key scheme. It needs folder and device
+// indexes.
+type defaultKeyer struct {
+	folderIdx *smallIndex
+	deviceIdx *smallIndex
+}
+
+func newDefaultKeyer(folderIdx, deviceIdx *smallIndex) defaultKeyer {
+	return defaultKeyer{
+		folderIdx: folderIdx,
+		deviceIdx: deviceIdx,
+	}
+}
+
+type deviceFileKey []byte
+
+func (k deviceFileKey) WithoutName() []byte {
+	return k[:keyPrefixLen+keyFolderLen+keyDeviceLen]
+}
+
+func (k defaultKeyer) GenerateDeviceFileKey(key, folder, device, name []byte) deviceFileKey {
+	key = resize(key, keyPrefixLen+keyFolderLen+keyDeviceLen+len(name))
+	key[0] = KeyTypeDevice
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	binary.BigEndian.PutUint32(key[keyPrefixLen+keyFolderLen:], k.deviceIdx.ID(device))
+	copy(key[keyPrefixLen+keyFolderLen+keyDeviceLen:], name)
+	return key
+}
+
+func (k defaultKeyer) NameFromDeviceFileKey(key []byte) []byte {
+	return key[keyPrefixLen+keyFolderLen+keyDeviceLen:]
+}
+
+func (k defaultKeyer) DeviceFromDeviceFileKey(key []byte) ([]byte, bool) {
+	return k.deviceIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen+keyFolderLen:]))
+}
+
+func (k defaultKeyer) FolderFromDeviceFileKey(key []byte) ([]byte, bool) {
+	return k.folderIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
+}
+
+type globalVersionKey []byte
+
+func (k globalVersionKey) WithoutName() []byte {
+	return k[:keyPrefixLen+keyFolderLen]
+}
+
+func (k defaultKeyer) GenerateGlobalVersionKey(key, folder, name []byte) globalVersionKey {
+	key = resize(key, keyPrefixLen+keyFolderLen+len(name))
+	key[0] = KeyTypeGlobal
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	copy(key[keyPrefixLen+keyFolderLen:], name)
+	return key
+}
+
+func (k defaultKeyer) NameFromGlobalVersionKey(key []byte) []byte {
+	return key[keyPrefixLen+keyFolderLen:]
+}
+
+func (k defaultKeyer) FolderFromGlobalVersionKey(key []byte) ([]byte, bool) {
+	return k.folderIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
+}
+
+type needFileKey []byte
+
+func (k needFileKey) WithoutName() []byte {
+	return k[:keyPrefixLen+keyFolderLen]
+}
+
+func (k defaultKeyer) GenerateNeedFileKey(key, folder, name []byte) needFileKey {
+	key = resize(key, keyPrefixLen+keyFolderLen+len(name))
+	key[0] = KeyTypeNeed
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	copy(key[keyPrefixLen+keyFolderLen:], name)
+	return key
+}
+
+type sequenceKey []byte
+
+func (k sequenceKey) WithoutSequence() []byte {
+	return k[:keyPrefixLen+keyFolderLen]
+}
+
+func (k defaultKeyer) GenerateSequenceKey(key, folder []byte, seq int64) sequenceKey {
+	key = resize(key, keyPrefixLen+keyFolderLen+keySequenceLen)
+	key[0] = KeyTypeSequence
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	binary.BigEndian.PutUint64(key[keyPrefixLen+keyFolderLen:], uint64(seq))
+	return key
+}
+
+func (k defaultKeyer) SequenceFromSequenceKey(key []byte) int64 {
+	return int64(binary.BigEndian.Uint64(key[keyPrefixLen+keyFolderLen:]))
+}
+
+type indexIDKey []byte
+
+func (k defaultKeyer) GenerateIndexIDKey(key, device, folder []byte) indexIDKey {
+	key = resize(key, keyPrefixLen+keyDeviceLen+keyFolderLen)
+	key[0] = KeyTypeIndexID
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.deviceIdx.ID(device))
+	binary.BigEndian.PutUint32(key[keyPrefixLen+keyDeviceLen:], k.folderIdx.ID(folder))
+	return key
+}
+
+func (k defaultKeyer) DeviceFromIndexIDKey(key []byte) ([]byte, bool) {
+	return k.deviceIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
+}
+
+type mtimesKey []byte
+
+func (k defaultKeyer) GenerateMtimesKey(key, folder []byte) mtimesKey {
+	key = resize(key, keyPrefixLen+keyFolderLen)
+	key[0] = KeyTypeVirtualMtime
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	return key
+}
+
+type folderMetaKey []byte
+
+func (k defaultKeyer) GenerateFolderMetaKey(key, folder []byte) folderMetaKey {
+	key = resize(key, keyPrefixLen+keyFolderLen)
+	key[0] = KeyTypeFolderMeta
+	binary.BigEndian.PutUint32(key[keyPrefixLen:], k.folderIdx.ID(folder))
+	return key
+}
+
+// resize returns a byte slice of the specified size, reusing bs if possible
+func resize(bs []byte, size int) []byte {
+	if cap(bs) < size {
+		return make([]byte, size)
+	}
+	return bs[:size]
+}