syncthing/lib/db/leveldb_dbinstance.go

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// Copyright (C) 2014 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 (
"bytes"
"encoding/binary"
"os"
"sort"
"strings"
"sync/atomic"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sync"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/errors"
"github.com/syndtr/goleveldb/leveldb/iterator"
"github.com/syndtr/goleveldb/leveldb/opt"
"github.com/syndtr/goleveldb/leveldb/storage"
"github.com/syndtr/goleveldb/leveldb/util"
)
type deletionHandler func(t readWriteTransaction, folder, device, name []byte, dbi iterator.Iterator)
type Instance struct {
committed int64 // this must be the first attribute in the struct to ensure 64 bit alignment on 32 bit plaforms
*leveldb.DB
location string
folderIdx *smallIndex
deviceIdx *smallIndex
}
const (
keyPrefixLen = 1
keyFolderLen = 4 // indexed
keyDeviceLen = 4 // indexed
keyHashLen = 32
)
func Open(file string) (*Instance, error) {
opts := &opt.Options{
OpenFilesCacheCapacity: 100,
WriteBuffer: 4 << 20,
}
db, err := leveldb.OpenFile(file, opts)
if leveldbIsCorrupted(err) {
db, err = leveldb.RecoverFile(file, opts)
}
if leveldbIsCorrupted(err) {
// The database is corrupted, and we've tried to recover it but it
// didn't work. At this point there isn't much to do beyond dropping
// the database and reindexing...
l.Infoln("Database corruption detected, unable to recover. Reinitializing...")
if err := os.RemoveAll(file); err != nil {
return nil, err
}
db, err = leveldb.OpenFile(file, opts)
}
if err != nil {
return nil, err
}
return newDBInstance(db, file), nil
}
func OpenMemory() *Instance {
db, _ := leveldb.Open(storage.NewMemStorage(), nil)
return newDBInstance(db, "<memory>")
}
func newDBInstance(db *leveldb.DB, location string) *Instance {
i := &Instance{
DB: db,
location: location,
}
i.folderIdx = newSmallIndex(i, []byte{KeyTypeFolderIdx})
i.deviceIdx = newSmallIndex(i, []byte{KeyTypeDeviceIdx})
return i
}
// UpdateSchema does transitions to the current db version if necessary
func (db *Instance) UpdateSchema() {
miscDB := NewNamespacedKV(db, string(KeyTypeMiscData))
prevVersion, _ := miscDB.Int64("dbVersion")
if prevVersion == 0 {
db.updateSchema0to1()
}
if prevVersion != dbVersion {
miscDB.PutInt64("dbVersion", dbVersion)
}
}
// Committed returns the number of items committed to the database since startup
func (db *Instance) Committed() int64 {
return atomic.LoadInt64(&db.committed)
}
// Location returns the filesystem path where the database is stored
func (db *Instance) Location() string {
return db.location
}
func (db *Instance) updateFiles(folder, device []byte, fs []protocol.FileInfo, meta *metadataTracker) {
t := db.newReadWriteTransaction()
defer t.close()
var fk []byte
for _, f := range fs {
name := []byte(f.Name)
fk = db.deviceKeyInto(fk[:cap(fk)], folder, device, name)
// Get and unmarshal the file entry. If it doesn't exist or can't be
// unmarshalled we'll add it as a new entry.
bs, err := t.Get(fk, nil)
var ef FileInfoTruncated
if err == nil {
err = ef.Unmarshal(bs)
}
// The Invalid flag might change without the version being bumped.
if err == nil && ef.Version.Equal(f.Version) && ef.Invalid == f.Invalid {
continue
}
devID := protocol.DeviceIDFromBytes(device)
if err == nil {
meta.removeFile(devID, ef)
}
meta.addFile(devID, f)
t.insertFile(folder, device, f)
t.updateGlobal(folder, device, f, meta)
// Write out and reuse the batch every few records, to avoid the batch
// growing too large and thus allocating unnecessarily much memory.
t.checkFlush()
}
}
func (db *Instance) withHave(folder, device, prefix []byte, truncate bool, fn Iterator) {
t := db.newReadOnlyTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.deviceKey(folder, device, prefix)[:keyPrefixLen+keyFolderLen+keyDeviceLen+len(prefix)]), nil)
defer dbi.Release()
slashedPrefix := prefix
if !bytes.HasSuffix(prefix, []byte{'/'}) {
slashedPrefix = append(slashedPrefix, '/')
}
for dbi.Next() {
name := db.deviceKeyName(dbi.Key())
if len(prefix) > 0 && !bytes.Equal(name, prefix) && !bytes.HasPrefix(name, slashedPrefix) {
return
}
2016-02-02 11:48:09 +00:00
// The iterator function may keep a reference to the unmarshalled
// struct, which in turn references the buffer it was unmarshalled
// from. dbi.Value() just returns an internal slice that it reuses, so
// we need to copy it.
f, err := unmarshalTrunc(append([]byte{}, dbi.Value()...), truncate)
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
if cont := fn(f); !cont {
return
}
}
}
func (db *Instance) withAllFolderTruncated(folder []byte, fn func(device []byte, f FileInfoTruncated) bool) {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.deviceKey(folder, nil, nil)[:keyPrefixLen+keyFolderLen]), nil)
defer dbi.Release()
for dbi.Next() {
device := db.deviceKeyDevice(dbi.Key())
var f FileInfoTruncated
2016-02-02 11:48:09 +00:00
// The iterator function may keep a reference to the unmarshalled
// struct, which in turn references the buffer it was unmarshalled
// from. dbi.Value() just returns an internal slice that it reuses, so
// we need to copy it.
err := f.Unmarshal(append([]byte{}, dbi.Value()...))
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
switch f.Name {
case "", ".", "..", "/": // A few obviously invalid filenames
l.Infof("Dropping invalid filename %q from database", f.Name)
t.removeFromGlobal(folder, device, nil, nil)
t.Delete(dbi.Key())
t.checkFlush()
continue
}
if cont := fn(device, f); !cont {
return
}
}
}
func (db *Instance) getFile(folder, device, file []byte) (protocol.FileInfo, bool) {
return getFile(db, db.deviceKey(folder, device, file))
}
func (db *Instance) getGlobal(folder, file []byte, truncate bool) (FileIntf, bool) {
k := db.globalKey(folder, file)
t := db.newReadOnlyTransaction()
defer t.close()
bs, err := t.Get(k, nil)
if err != nil {
return nil, false
}
var vl VersionList
err = vl.Unmarshal(bs)
if err == leveldb.ErrNotFound {
return nil, false
}
if err != nil {
l.Debugln("unmarshal error:", k, err)
return nil, false
}
if len(vl.Versions) == 0 {
l.Debugln("no versions:", k)
return nil, false
}
k = db.deviceKey(folder, vl.Versions[0].Device, file)
bs, err = t.Get(k, nil)
if err != nil {
l.Debugln("surprise error:", k, err)
return nil, false
}
fi, err := unmarshalTrunc(bs, truncate)
if err != nil {
l.Debugln("unmarshal error:", k, err)
return nil, false
}
return fi, true
}
func (db *Instance) withGlobal(folder, prefix []byte, truncate bool, fn Iterator) {
t := db.newReadOnlyTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.globalKey(folder, prefix)), nil)
defer dbi.Release()
slashedPrefix := prefix
if !bytes.HasSuffix(prefix, []byte{'/'}) {
slashedPrefix = append(slashedPrefix, '/')
}
var fk []byte
for dbi.Next() {
var vl VersionList
err := vl.Unmarshal(dbi.Value())
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
if len(vl.Versions) == 0 {
l.Debugln("no versions:", dbi.Key())
continue
}
name := db.globalKeyName(dbi.Key())
if len(prefix) > 0 && !bytes.Equal(name, prefix) && !bytes.HasPrefix(name, slashedPrefix) {
return
}
fk = db.deviceKeyInto(fk[:cap(fk)], folder, vl.Versions[0].Device, name)
bs, err := t.Get(fk, nil)
if err != nil {
l.Debugln("surprise error:", err)
continue
}
f, err := unmarshalTrunc(bs, truncate)
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
if cont := fn(f); !cont {
return
}
}
}
func (db *Instance) availability(folder, file []byte) []protocol.DeviceID {
k := db.globalKey(folder, file)
bs, err := db.Get(k, nil)
if err == leveldb.ErrNotFound {
return nil
}
if err != nil {
l.Debugln("surprise error:", err)
return nil
}
var vl VersionList
err = vl.Unmarshal(bs)
if err != nil {
l.Debugln("unmarshal error:", err)
return nil
}
var devices []protocol.DeviceID
for _, v := range vl.Versions {
if !v.Version.Equal(vl.Versions[0].Version) {
break
}
if v.Invalid {
continue
}
n := protocol.DeviceIDFromBytes(v.Device)
devices = append(devices, n)
}
return devices
}
func (db *Instance) withNeed(folder, device []byte, truncate bool, fn Iterator) {
t := db.newReadOnlyTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.globalKey(folder, nil)[:keyPrefixLen+keyFolderLen]), nil)
defer dbi.Release()
var fk []byte
for dbi.Next() {
var vl VersionList
err := vl.Unmarshal(dbi.Value())
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
if len(vl.Versions) == 0 {
l.Debugln("no versions:", dbi.Key())
continue
}
have := false // If we have the file, any version
need := false // If we have a lower version of the file
var haveFileVersion FileVersion
for _, v := range vl.Versions {
if bytes.Equal(v.Device, device) {
have = true
haveFileVersion = v
// XXX: This marks Concurrent (i.e. conflicting) changes as
// needs. Maybe we should do that, but it needs special
// handling in the puller.
need = !v.Version.GreaterEqual(vl.Versions[0].Version)
break
}
}
if have && !need {
continue
}
name := db.globalKeyName(dbi.Key())
needVersion := vl.Versions[0].Version
needDevice := protocol.DeviceIDFromBytes(vl.Versions[0].Device)
for i := range vl.Versions {
if !vl.Versions[i].Version.Equal(needVersion) {
// We haven't found a valid copy of the file with the needed version.
break
}
if vl.Versions[i].Invalid {
// The file is marked invalid, don't use it.
continue
}
fk = db.deviceKeyInto(fk[:cap(fk)], folder, vl.Versions[i].Device, name)
bs, err := t.Get(fk, nil)
if err != nil {
l.Debugln("surprise error:", err)
continue
}
gf, err := unmarshalTrunc(bs, truncate)
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
if gf.IsDeleted() && !have {
// We don't need deleted files that we don't have
break
}
l.Debugf("need folder=%q device=%v name=%q need=%v have=%v invalid=%v haveV=%v globalV=%v globalDev=%v", folder, protocol.DeviceIDFromBytes(device), name, need, have, haveFileVersion.Invalid, haveFileVersion.Version, needVersion, needDevice)
if cont := fn(gf); !cont {
return
}
// This file is handled, no need to look further in the version list
break
}
}
}
func (db *Instance) ListFolders() []string {
t := db.newReadOnlyTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
defer dbi.Release()
folderExists := make(map[string]bool)
for dbi.Next() {
folder, ok := db.globalKeyFolder(dbi.Key())
if ok && !folderExists[string(folder)] {
folderExists[string(folder)] = true
}
}
folders := make([]string, 0, len(folderExists))
for k := range folderExists {
folders = append(folders, k)
}
sort.Strings(folders)
return folders
}
func (db *Instance) dropFolder(folder []byte) {
t := db.newReadOnlyTransaction()
defer t.close()
// Remove all items related to the given folder from the device->file bucket
dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeDevice}), nil)
for dbi.Next() {
itemFolder := db.deviceKeyFolder(dbi.Key())
if bytes.Equal(folder, itemFolder) {
db.Delete(dbi.Key(), nil)
}
}
dbi.Release()
// Remove all items related to the given folder from the global bucket
dbi = t.NewIterator(util.BytesPrefix([]byte{KeyTypeGlobal}), nil)
for dbi.Next() {
itemFolder, ok := db.globalKeyFolder(dbi.Key())
if ok && bytes.Equal(folder, itemFolder) {
db.Delete(dbi.Key(), nil)
}
}
dbi.Release()
}
func (db *Instance) dropDeviceFolder(device, folder []byte, meta *metadataTracker) {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.deviceKey(folder, device, nil)), nil)
defer dbi.Release()
for dbi.Next() {
key := dbi.Key()
name := db.deviceKeyName(key)
t.removeFromGlobal(folder, device, name, meta)
t.Delete(key)
t.checkFlush()
}
}
func (db *Instance) checkGlobals(folder []byte, meta *metadataTracker) {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(db.globalKey(folder, nil)[:keyPrefixLen+keyFolderLen]), nil)
defer dbi.Release()
var fk []byte
for dbi.Next() {
gk := dbi.Key()
var vl VersionList
err := vl.Unmarshal(dbi.Value())
if err != nil {
l.Debugln("unmarshal error:", err)
continue
}
// Check the global version list for consistency. An issue in previous
// versions of goleveldb could result in reordered writes so that
// there are global entries pointing to no longer existing files. Here
// we find those and clear them out.
name := db.globalKeyName(gk)
var newVL VersionList
for i, version := range vl.Versions {
fk = db.deviceKeyInto(fk[:cap(fk)], folder, version.Device, name)
_, err := t.Get(fk, nil)
if err == leveldb.ErrNotFound {
continue
}
if err != nil {
l.Debugln("surprise error:", err)
return
}
newVL.Versions = append(newVL.Versions, version)
if i == 0 {
if fi, ok := t.getFile(folder, version.Device, name); ok {
meta.addFile(globalDeviceID, fi)
}
}
}
if len(newVL.Versions) != len(vl.Versions) {
t.Put(dbi.Key(), mustMarshal(&newVL))
t.checkFlush()
}
}
l.Debugf("db check completed for %q", folder)
}
func (db *Instance) updateSchema0to1() {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeDevice}), nil)
defer dbi.Release()
symlinkConv := 0
changedFolders := make(map[string]struct{})
ignAdded := 0
meta := newMetadataTracker() // dummy metadata tracker
for dbi.Next() {
folder := db.deviceKeyFolder(dbi.Key())
device := db.deviceKeyDevice(dbi.Key())
name := string(db.deviceKeyName(dbi.Key()))
// Remove files with absolute path (see #4799)
if strings.HasPrefix(name, "/") {
if _, ok := changedFolders[string(folder)]; !ok {
changedFolders[string(folder)] = struct{}{}
}
t.removeFromGlobal(folder, device, nil, nil)
t.Delete(dbi.Key())
t.checkFlush()
continue
}
// Change SYMLINK_FILE and SYMLINK_DIRECTORY types to the current SYMLINK
// type (previously SYMLINK_UNKNOWN). It does this for all devices, both
// local and remote, and does not reset delta indexes. It shouldn't really
// matter what the symlink type is, but this cleans it up for a possible
// future when SYMLINK_FILE and SYMLINK_DIRECTORY are no longer understood.
var f protocol.FileInfo
if err := f.Unmarshal(dbi.Value()); err != nil {
// probably can't happen
continue
}
if f.Type == protocol.FileInfoTypeDeprecatedSymlinkDirectory || f.Type == protocol.FileInfoTypeDeprecatedSymlinkFile {
f.Type = protocol.FileInfoTypeSymlink
bs, err := f.Marshal()
if err != nil {
panic("can't happen: " + err.Error())
}
t.Put(dbi.Key(), bs)
t.checkFlush()
symlinkConv++
}
// Add invalid files to global list
if f.Invalid {
if t.updateGlobal(folder, device, f, meta) {
if _, ok := changedFolders[string(folder)]; !ok {
changedFolders[string(folder)] = struct{}{}
}
ignAdded++
}
}
}
for folder := range changedFolders {
db.dropFolderMeta([]byte(folder))
}
l.Infof("Updated symlink type for %d index entries and added %d invalid files to global list", symlinkConv, ignAdded)
}
// deviceKey returns a byte slice encoding the following information:
// keyTypeDevice (1 byte)
// folder (4 bytes)
// device (4 bytes)
// name (variable size)
func (db *Instance) deviceKey(folder, device, file []byte) []byte {
return db.deviceKeyInto(nil, folder, device, file)
}
func (db *Instance) deviceKeyInto(k []byte, folder, device, file []byte) []byte {
reqLen := keyPrefixLen + keyFolderLen + keyDeviceLen + len(file)
if len(k) < reqLen {
k = make([]byte, reqLen)
}
k[0] = KeyTypeDevice
binary.BigEndian.PutUint32(k[keyPrefixLen:], db.folderIdx.ID(folder))
binary.BigEndian.PutUint32(k[keyPrefixLen+keyFolderLen:], db.deviceIdx.ID(device))
copy(k[keyPrefixLen+keyFolderLen+keyDeviceLen:], file)
return k[:reqLen]
}
// deviceKeyName returns the device ID from the key
func (db *Instance) deviceKeyName(key []byte) []byte {
return key[keyPrefixLen+keyFolderLen+keyDeviceLen:]
}
// deviceKeyFolder returns the folder name from the key
func (db *Instance) deviceKeyFolder(key []byte) []byte {
folder, ok := db.folderIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
if !ok {
panic("bug: lookup of nonexistent folder ID")
}
return folder
}
// deviceKeyDevice returns the device ID from the key
func (db *Instance) deviceKeyDevice(key []byte) []byte {
device, ok := db.deviceIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen+keyFolderLen:]))
if !ok {
panic("bug: lookup of nonexistent device ID")
}
return device
}
// globalKey returns a byte slice encoding the following information:
// keyTypeGlobal (1 byte)
// folder (4 bytes)
// name (variable size)
func (db *Instance) globalKey(folder, file []byte) []byte {
k := make([]byte, keyPrefixLen+keyFolderLen+len(file))
k[0] = KeyTypeGlobal
binary.BigEndian.PutUint32(k[keyPrefixLen:], db.folderIdx.ID(folder))
copy(k[keyPrefixLen+keyFolderLen:], file)
return k
}
// globalKeyName returns the filename from the key
func (db *Instance) globalKeyName(key []byte) []byte {
return key[keyPrefixLen+keyFolderLen:]
}
// globalKeyFolder returns the folder name from the key
func (db *Instance) globalKeyFolder(key []byte) ([]byte, bool) {
return db.folderIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
}
func (db *Instance) getIndexID(device, folder []byte) protocol.IndexID {
key := db.indexIDKey(device, folder)
cur, err := db.Get(key, nil)
if err != nil {
return 0
}
var id protocol.IndexID
if err := id.Unmarshal(cur); err != nil {
return 0
}
return id
}
func (db *Instance) setIndexID(device, folder []byte, id protocol.IndexID) {
key := db.indexIDKey(device, folder)
bs, _ := id.Marshal() // marshalling can't fail
if err := db.Put(key, bs, nil); err != nil {
panic("storing index ID: " + err.Error())
}
}
func (db *Instance) indexIDKey(device, folder []byte) []byte {
k := make([]byte, keyPrefixLen+keyDeviceLen+keyFolderLen)
k[0] = KeyTypeIndexID
binary.BigEndian.PutUint32(k[keyPrefixLen:], db.deviceIdx.ID(device))
binary.BigEndian.PutUint32(k[keyPrefixLen+keyDeviceLen:], db.folderIdx.ID(folder))
return k
}
func (db *Instance) indexIDDevice(key []byte) []byte {
device, ok := db.deviceIdx.Val(binary.BigEndian.Uint32(key[keyPrefixLen:]))
if !ok {
// uuh ...
return nil
}
return device
}
func (db *Instance) mtimesKey(folder []byte) []byte {
prefix := make([]byte, 5) // key type + 4 bytes folder idx number
prefix[0] = KeyTypeVirtualMtime
binary.BigEndian.PutUint32(prefix[1:], db.folderIdx.ID(folder))
return prefix
}
func (db *Instance) folderMetaKey(folder []byte) []byte {
prefix := make([]byte, 5) // key type + 4 bytes folder idx number
prefix[0] = KeyTypeFolderMeta
binary.BigEndian.PutUint32(prefix[1:], db.folderIdx.ID(folder))
return prefix
}
// DropLocalDeltaIndexIDs removes all index IDs for the local device ID from
// the database. This will cause a full index transmission on the next
// connection.
func (db *Instance) DropLocalDeltaIndexIDs() {
db.dropDeltaIndexIDs(true)
}
// DropRemoteDeltaIndexIDs removes all index IDs for the other devices than
// the local one from the database. This will cause them to send us a full
// index on the next connection.
func (db *Instance) DropRemoteDeltaIndexIDs() {
db.dropDeltaIndexIDs(false)
}
func (db *Instance) dropDeltaIndexIDs(local bool) {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix([]byte{KeyTypeIndexID}), nil)
defer dbi.Release()
for dbi.Next() {
device := db.indexIDDevice(dbi.Key())
if bytes.Equal(device, protocol.LocalDeviceID[:]) == local {
t.Delete(dbi.Key())
}
}
}
func (db *Instance) dropMtimes(folder []byte) {
db.dropPrefix(db.mtimesKey(folder))
}
func (db *Instance) dropFolderMeta(folder []byte) {
db.dropPrefix(db.folderMetaKey(folder))
}
func (db *Instance) dropPrefix(prefix []byte) {
t := db.newReadWriteTransaction()
defer t.close()
dbi := t.NewIterator(util.BytesPrefix(prefix), nil)
defer dbi.Release()
for dbi.Next() {
t.Delete(dbi.Key())
}
}
func unmarshalTrunc(bs []byte, truncate bool) (FileIntf, error) {
if truncate {
var tf FileInfoTruncated
err := tf.Unmarshal(bs)
return tf, err
}
var tf protocol.FileInfo
err := tf.Unmarshal(bs)
return tf, err
}
// A "better" version of leveldb's errors.IsCorrupted.
func leveldbIsCorrupted(err error) bool {
switch {
case err == nil:
return false
case errors.IsCorrupted(err):
return true
case strings.Contains(err.Error(), "corrupted"):
return true
}
return false
}
// A smallIndex is an in memory bidirectional []byte to uint32 map. It gives
// fast lookups in both directions and persists to the database. Don't use for
// storing more items than fit comfortably in RAM.
type smallIndex struct {
db *Instance
prefix []byte
id2val map[uint32]string
val2id map[string]uint32
nextID uint32
mut sync.Mutex
}
func newSmallIndex(db *Instance, prefix []byte) *smallIndex {
idx := &smallIndex{
db: db,
prefix: prefix,
id2val: make(map[uint32]string),
val2id: make(map[string]uint32),
mut: sync.NewMutex(),
}
idx.load()
return idx
}
// load iterates over the prefix space in the database and populates the in
// memory maps.
func (i *smallIndex) load() {
tr := i.db.newReadOnlyTransaction()
it := tr.NewIterator(util.BytesPrefix(i.prefix), nil)
for it.Next() {
val := string(it.Value())
id := binary.BigEndian.Uint32(it.Key()[len(i.prefix):])
i.id2val[id] = val
i.val2id[val] = id
if id >= i.nextID {
i.nextID = id + 1
}
}
it.Release()
tr.close()
}
// ID returns the index number for the given byte slice, allocating a new one
// and persisting this to the database if necessary.
func (i *smallIndex) ID(val []byte) uint32 {
i.mut.Lock()
// intentionally avoiding defer here as we want this call to be as fast as
// possible in the general case (folder ID already exists). The map lookup
// with the conversion of []byte to string is compiler optimized to not
// copy the []byte, which is why we don't assign it to a temp variable
// here.
if id, ok := i.val2id[string(val)]; ok {
i.mut.Unlock()
return id
}
id := i.nextID
i.nextID++
valStr := string(val)
i.val2id[valStr] = id
i.id2val[id] = valStr
key := make([]byte, len(i.prefix)+8) // prefix plus uint32 id
copy(key, i.prefix)
binary.BigEndian.PutUint32(key[len(i.prefix):], id)
i.db.Put(key, val, nil)
i.mut.Unlock()
return id
}
// Val returns the value for the given index number, or (nil, false) if there
// is no such index number.
func (i *smallIndex) Val(id uint32) ([]byte, bool) {
i.mut.Lock()
val, ok := i.id2val[id]
i.mut.Unlock()
if !ok {
return nil, false
}
return []byte(val), true
}