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355 lines
7.3 KiB
355 lines
7.3 KiB
package db
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import (
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"bytes"
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"fmt"
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"sync"
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)
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// IteratePrefix is a convenience function for iterating over a key domain
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// restricted by prefix.
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func IteratePrefix(db DB, prefix []byte) Iterator {
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var start, end []byte
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if len(prefix) == 0 {
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start = nil
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end = nil
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} else {
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start = cp(prefix)
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end = cpIncr(prefix)
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}
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return db.Iterator(start, end)
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}
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/*
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TODO: Make test, maybe rename.
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// Like IteratePrefix but the iterator strips the prefix from the keys.
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func IteratePrefixStripped(db DB, prefix []byte) Iterator {
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start, end := ...
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return newPrefixIterator(prefix, start, end, IteratePrefix(db, prefix))
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}
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*/
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//----------------------------------------
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// prefixDB
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type prefixDB struct {
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mtx sync.Mutex
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prefix []byte
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db DB
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}
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// NewPrefixDB lets you namespace multiple DBs within a single DB.
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func NewPrefixDB(db DB, prefix []byte) *prefixDB {
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return &prefixDB{
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prefix: prefix,
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db: db,
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}
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}
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// Implements atomicSetDeleter.
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func (pdb *prefixDB) Mutex() *sync.Mutex {
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return &(pdb.mtx)
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}
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// Implements DB.
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func (pdb *prefixDB) Get(key []byte) []byte {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pkey := pdb.prefixed(key)
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value := pdb.db.Get(pkey)
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return value
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}
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// Implements DB.
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func (pdb *prefixDB) Has(key []byte) bool {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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return pdb.db.Has(pdb.prefixed(key))
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}
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// Implements DB.
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func (pdb *prefixDB) Set(key []byte, value []byte) {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pkey := pdb.prefixed(key)
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pdb.db.Set(pkey, value)
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}
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// Implements DB.
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func (pdb *prefixDB) SetSync(key []byte, value []byte) {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pdb.db.SetSync(pdb.prefixed(key), value)
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}
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// Implements DB.
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func (pdb *prefixDB) Delete(key []byte) {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pdb.db.Delete(pdb.prefixed(key))
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}
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// Implements DB.
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func (pdb *prefixDB) DeleteSync(key []byte) {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pdb.db.DeleteSync(pdb.prefixed(key))
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}
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// Implements DB.
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func (pdb *prefixDB) Iterator(start, end []byte) Iterator {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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var pstart, pend []byte
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pstart = append(cp(pdb.prefix), start...)
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if end == nil {
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pend = cpIncr(pdb.prefix)
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} else {
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pend = append(cp(pdb.prefix), end...)
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}
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return newPrefixIterator(
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pdb.prefix,
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start,
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end,
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pdb.db.Iterator(
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pstart,
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pend,
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),
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)
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}
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// Implements DB.
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func (pdb *prefixDB) ReverseIterator(start, end []byte) Iterator {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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var pstart, pend []byte
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if start == nil {
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// This may cause the underlying iterator to start with
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// an item which doesn't start with prefix. We will skip
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// that item later in this function. See 'skipOne'.
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pstart = cpIncr(pdb.prefix)
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} else {
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pstart = append(cp(pdb.prefix), start...)
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}
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if end == nil {
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// This may cause the underlying iterator to end with an
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// item which doesn't start with prefix. The
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// prefixIterator will terminate iteration
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// automatically upon detecting this.
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pend = cpDecr(pdb.prefix)
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} else {
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pend = append(cp(pdb.prefix), end...)
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}
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ritr := pdb.db.ReverseIterator(pstart, pend)
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if start == nil {
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skipOne(ritr, cpIncr(pdb.prefix))
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}
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return newPrefixIterator(
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pdb.prefix,
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start,
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end,
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ritr,
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)
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}
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// Implements DB.
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// Panics if the underlying DB is not an
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// atomicSetDeleter.
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func (pdb *prefixDB) NewBatch() Batch {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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return newPrefixBatch(pdb.prefix, pdb.db.NewBatch())
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}
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/* NOTE: Uncomment to use memBatch instead of prefixBatch
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// Implements atomicSetDeleter.
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func (pdb *prefixDB) SetNoLock(key []byte, value []byte) {
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pdb.db.(atomicSetDeleter).SetNoLock(pdb.prefixed(key), value)
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}
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// Implements atomicSetDeleter.
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func (pdb *prefixDB) SetNoLockSync(key []byte, value []byte) {
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pdb.db.(atomicSetDeleter).SetNoLockSync(pdb.prefixed(key), value)
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}
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// Implements atomicSetDeleter.
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func (pdb *prefixDB) DeleteNoLock(key []byte) {
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pdb.db.(atomicSetDeleter).DeleteNoLock(pdb.prefixed(key))
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}
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// Implements atomicSetDeleter.
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func (pdb *prefixDB) DeleteNoLockSync(key []byte) {
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pdb.db.(atomicSetDeleter).DeleteNoLockSync(pdb.prefixed(key))
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}
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*/
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// Implements DB.
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func (pdb *prefixDB) Close() {
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pdb.mtx.Lock()
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defer pdb.mtx.Unlock()
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pdb.db.Close()
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}
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// Implements DB.
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func (pdb *prefixDB) Print() {
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fmt.Printf("prefix: %X\n", pdb.prefix)
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itr := pdb.Iterator(nil, nil)
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defer itr.Close()
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for ; itr.Valid(); itr.Next() {
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key := itr.Key()
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value := itr.Value()
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fmt.Printf("[%X]:\t[%X]\n", key, value)
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}
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}
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// Implements DB.
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func (pdb *prefixDB) Stats() map[string]string {
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stats := make(map[string]string)
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stats["prefixdb.prefix.string"] = string(pdb.prefix)
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stats["prefixdb.prefix.hex"] = fmt.Sprintf("%X", pdb.prefix)
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source := pdb.db.Stats()
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for key, value := range source {
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stats["prefixdb.source."+key] = value
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}
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return stats
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}
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func (pdb *prefixDB) prefixed(key []byte) []byte {
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return append(cp(pdb.prefix), key...)
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}
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//----------------------------------------
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// prefixBatch
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type prefixBatch struct {
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prefix []byte
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source Batch
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}
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func newPrefixBatch(prefix []byte, source Batch) prefixBatch {
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return prefixBatch{
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prefix: prefix,
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source: source,
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}
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}
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func (pb prefixBatch) Set(key, value []byte) {
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pkey := append(cp(pb.prefix), key...)
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pb.source.Set(pkey, value)
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}
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func (pb prefixBatch) Delete(key []byte) {
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pkey := append(cp(pb.prefix), key...)
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pb.source.Delete(pkey)
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}
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func (pb prefixBatch) Write() {
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pb.source.Write()
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}
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func (pb prefixBatch) WriteSync() {
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pb.source.WriteSync()
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}
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//----------------------------------------
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// prefixIterator
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// Strips prefix while iterating from Iterator.
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type prefixIterator struct {
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prefix []byte
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start []byte
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end []byte
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source Iterator
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valid bool
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}
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func newPrefixIterator(prefix, start, end []byte, source Iterator) prefixIterator {
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if !source.Valid() || !bytes.HasPrefix(source.Key(), prefix) {
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return prefixIterator{
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prefix: prefix,
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start: start,
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end: end,
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source: source,
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valid: false,
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}
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} else {
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return prefixIterator{
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prefix: prefix,
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start: start,
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end: end,
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source: source,
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valid: true,
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}
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}
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}
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func (itr prefixIterator) Domain() (start []byte, end []byte) {
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return itr.start, itr.end
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}
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func (itr prefixIterator) Valid() bool {
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return itr.valid && itr.source.Valid()
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}
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func (itr prefixIterator) Next() {
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if !itr.valid {
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panic("prefixIterator invalid, cannot call Next()")
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}
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itr.source.Next()
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if !itr.source.Valid() || !bytes.HasPrefix(itr.source.Key(), itr.prefix) {
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itr.source.Close()
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itr.valid = false
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return
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}
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}
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func (itr prefixIterator) Key() (key []byte) {
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if !itr.valid {
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panic("prefixIterator invalid, cannot call Key()")
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}
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return stripPrefix(itr.source.Key(), itr.prefix)
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}
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func (itr prefixIterator) Value() (value []byte) {
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if !itr.valid {
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panic("prefixIterator invalid, cannot call Value()")
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}
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return itr.source.Value()
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}
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func (itr prefixIterator) Close() {
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itr.source.Close()
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}
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//----------------------------------------
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func stripPrefix(key []byte, prefix []byte) (stripped []byte) {
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if len(key) < len(prefix) {
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panic("should not happen")
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}
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if !bytes.Equal(key[:len(prefix)], prefix) {
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panic("should not happne")
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}
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return key[len(prefix):]
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}
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// If the first iterator item is skipKey, then
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// skip it.
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func skipOne(itr Iterator, skipKey []byte) {
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if itr.Valid() {
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if bytes.Equal(itr.Key(), skipKey) {
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itr.Next()
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}
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}
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}
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