lnd.xprv/channeldb/kvdb/etcd/readwrite_tx.go

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// +build kvdb_etcd
package etcd
import (
"github.com/btcsuite/btcwallet/walletdb"
)
// readWriteTx holds a reference to the STM transaction.
type readWriteTx struct {
// stm is the reference to the parent STM.
stm STM
// rootBucketID holds the sha256 hash of the root bucket id, which is used
// for key space spearation.
rootBucketID [bucketIDLength]byte
// active is true if the transaction hasn't been committed yet.
active bool
// dirty is true if we intent to update a value in this transaction.
dirty bool
// lset holds key/value set that we want to lock on. If upon commit the
// transaction is dirty and the lset is not empty, we'll bump the mod
// version of these key/values.
lset map[string]string
}
// newReadWriteTx creates an rw transaction with the passed STM.
func newReadWriteTx(stm STM, prefix string) *readWriteTx {
return &readWriteTx{
stm: stm,
active: true,
rootBucketID: makeBucketID([]byte(prefix)),
lset: make(map[string]string),
}
}
// rooBucket is a helper function to return the always present
// pseudo root bucket.
func rootBucket(tx *readWriteTx) *readWriteBucket {
return newReadWriteBucket(tx, tx.rootBucketID[:], tx.rootBucketID[:])
}
// lock adds a key value to the lock set.
func (tx *readWriteTx) lock(key, val string) {
tx.stm.Lock(key)
if !tx.dirty {
tx.lset[key] = val
} else {
// Bump the mod version of the key,
// leaving the value intact.
tx.stm.Put(key, val)
}
}
// put updates the passed key/value.
func (tx *readWriteTx) put(key, val string) {
tx.stm.Put(key, val)
tx.setDirty()
}
// del marks the passed key deleted.
func (tx *readWriteTx) del(key string) {
tx.stm.Del(key)
tx.setDirty()
}
// setDirty marks the transaction dirty and bumps
// mod version for the existing lock set if it is
// not empty.
func (tx *readWriteTx) setDirty() {
// Bump the lock set.
if !tx.dirty && len(tx.lset) > 0 {
for key, val := range tx.lset {
// Bump the mod version of the key,
// leaving the value intact.
tx.stm.Put(key, val)
}
// Clear the lock set.
tx.lset = make(map[string]string)
}
// Set dirty.
tx.dirty = true
}
// ReadBucket opens the root bucket for read only access. If the bucket
// described by the key does not exist, nil is returned.
func (tx *readWriteTx) ReadBucket(key []byte) walletdb.ReadBucket {
return rootBucket(tx).NestedReadWriteBucket(key)
}
// Rollback closes the transaction, discarding changes (if any) if the
// database was modified by a write transaction.
func (tx *readWriteTx) Rollback() error {
// If the transaction has been closed roolback will fail.
if !tx.active {
return walletdb.ErrTxClosed
}
// Rollback the STM and set the tx to inactive.
tx.stm.Rollback()
tx.active = false
return nil
}
// ReadWriteBucket opens the root bucket for read/write access. If the
// bucket described by the key does not exist, nil is returned.
func (tx *readWriteTx) ReadWriteBucket(key []byte) walletdb.ReadWriteBucket {
return rootBucket(tx).NestedReadWriteBucket(key)
}
// CreateTopLevelBucket creates the top level bucket for a key if it
// does not exist. The newly-created bucket it returned.
func (tx *readWriteTx) CreateTopLevelBucket(key []byte) (walletdb.ReadWriteBucket, error) {
return rootBucket(tx).CreateBucketIfNotExists(key)
}
// DeleteTopLevelBucket deletes the top level bucket for a key. This
// errors if the bucket can not be found or the key keys a single value
// instead of a bucket.
func (tx *readWriteTx) DeleteTopLevelBucket(key []byte) error {
return rootBucket(tx).DeleteNestedBucket(key)
}
// Commit commits the transaction if not already committed. Will return
// error if the underlying STM fails.
func (tx *readWriteTx) Commit() error {
// Commit will fail if the transaction is already committed.
if !tx.active {
return walletdb.ErrTxClosed
}
// Try committing the transaction.
if err := tx.stm.Commit(); err != nil {
return err
}
// Mark the transaction as not active after commit.
tx.active = false
return nil
}
// OnCommit sets the commit callback (overriding if already set).
func (tx *readWriteTx) OnCommit(cb func()) {
tx.stm.OnCommit(cb)
}