226 lines
5.2 KiB
Go
226 lines
5.2 KiB
Go
package cachekv
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import (
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"bytes"
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"container/list"
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"io"
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"sort"
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"sync"
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cmn "github.com/tendermint/tendermint/libs/common"
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dbm "github.com/tendermint/tm-db"
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"github.com/cosmos/cosmos-sdk/store/types"
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"github.com/cosmos/cosmos-sdk/store/tracekv"
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)
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// If value is nil but deleted is false, it means the parent doesn't have the
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// key. (No need to delete upon Write())
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type cValue struct {
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value []byte
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deleted bool
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dirty bool
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}
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// Store wraps an in-memory cache around an underlying types.KVStore.
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type Store struct {
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mtx sync.Mutex
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cache map[string]*cValue
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unsortedCache map[string]struct{}
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sortedCache *list.List // always ascending sorted
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parent types.KVStore
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}
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var _ types.CacheKVStore = (*Store)(nil)
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// nolint
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func NewStore(parent types.KVStore) *Store {
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return &Store{
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cache: make(map[string]*cValue),
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unsortedCache: make(map[string]struct{}),
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sortedCache: list.New(),
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parent: parent,
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}
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}
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// Implements Store.
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func (store *Store) GetStoreType() types.StoreType {
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return store.parent.GetStoreType()
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}
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// Implements types.KVStore.
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func (store *Store) Get(key []byte) (value []byte) {
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store.mtx.Lock()
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defer store.mtx.Unlock()
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types.AssertValidKey(key)
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cacheValue, ok := store.cache[string(key)]
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if !ok {
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value = store.parent.Get(key)
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store.setCacheValue(key, value, false, false)
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} else {
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value = cacheValue.value
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}
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return value
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}
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// Implements types.KVStore.
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func (store *Store) Set(key []byte, value []byte) {
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store.mtx.Lock()
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defer store.mtx.Unlock()
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types.AssertValidKey(key)
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types.AssertValidValue(value)
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store.setCacheValue(key, value, false, true)
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}
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// Implements types.KVStore.
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func (store *Store) Has(key []byte) bool {
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value := store.Get(key)
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return value != nil
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}
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// Implements types.KVStore.
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func (store *Store) Delete(key []byte) {
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store.mtx.Lock()
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defer store.mtx.Unlock()
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types.AssertValidKey(key)
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store.setCacheValue(key, nil, true, true)
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}
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// Implements Cachetypes.KVStore.
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func (store *Store) Write() {
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store.mtx.Lock()
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defer store.mtx.Unlock()
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// We need a copy of all of the keys.
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// Not the best, but probably not a bottleneck depending.
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keys := make([]string, 0, len(store.cache))
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for key, dbValue := range store.cache {
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if dbValue.dirty {
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keys = append(keys, key)
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}
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}
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sort.Strings(keys)
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// TODO: Consider allowing usage of Batch, which would allow the write to
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// at least happen atomically.
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for _, key := range keys {
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cacheValue := store.cache[key]
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if cacheValue.deleted {
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store.parent.Delete([]byte(key))
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} else if cacheValue.value == nil {
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// Skip, it already doesn't exist in parent.
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} else {
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store.parent.Set([]byte(key), cacheValue.value)
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}
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}
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// Clear the cache
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store.cache = make(map[string]*cValue)
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store.unsortedCache = make(map[string]struct{})
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store.sortedCache = list.New()
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}
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//----------------------------------------
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// To cache-wrap this Store further.
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// Implements CacheWrapper.
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func (store *Store) CacheWrap() types.CacheWrap {
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return NewStore(store)
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}
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// CacheWrapWithTrace implements the CacheWrapper interface.
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func (store *Store) CacheWrapWithTrace(w io.Writer, tc types.TraceContext) types.CacheWrap {
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return NewStore(tracekv.NewStore(store, w, tc))
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}
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//----------------------------------------
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// Iteration
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// Implements types.KVStore.
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func (store *Store) Iterator(start, end []byte) types.Iterator {
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return store.iterator(start, end, true)
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}
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// Implements types.KVStore.
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func (store *Store) ReverseIterator(start, end []byte) types.Iterator {
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return store.iterator(start, end, false)
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}
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func (store *Store) iterator(start, end []byte, ascending bool) types.Iterator {
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store.mtx.Lock()
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defer store.mtx.Unlock()
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var parent, cache types.Iterator
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if ascending {
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parent = store.parent.Iterator(start, end)
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} else {
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parent = store.parent.ReverseIterator(start, end)
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}
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store.dirtyItems(start, end)
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cache = newMemIterator(start, end, store.sortedCache, ascending)
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return newCacheMergeIterator(parent, cache, ascending)
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}
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// Constructs a slice of dirty items, to use w/ memIterator.
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func (store *Store) dirtyItems(start, end []byte) {
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unsorted := make([]*cmn.KVPair, 0)
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for key := range store.unsortedCache {
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cacheValue := store.cache[key]
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if dbm.IsKeyInDomain([]byte(key), start, end) {
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unsorted = append(unsorted, &cmn.KVPair{Key: []byte(key), Value: cacheValue.value})
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delete(store.unsortedCache, key)
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}
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}
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sort.Slice(unsorted, func(i, j int) bool {
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return bytes.Compare(unsorted[i].Key, unsorted[j].Key) < 0
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})
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for e := store.sortedCache.Front(); e != nil && len(unsorted) != 0; {
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uitem := unsorted[0]
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sitem := e.Value.(*cmn.KVPair)
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comp := bytes.Compare(uitem.Key, sitem.Key)
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switch comp {
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case -1:
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unsorted = unsorted[1:]
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store.sortedCache.InsertBefore(uitem, e)
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case 1:
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e = e.Next()
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case 0:
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unsorted = unsorted[1:]
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e.Value = uitem
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e = e.Next()
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}
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}
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for _, kvp := range unsorted {
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store.sortedCache.PushBack(kvp)
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}
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}
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//----------------------------------------
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// etc
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// Only entrypoint to mutate store.cache.
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func (store *Store) setCacheValue(key, value []byte, deleted bool, dirty bool) {
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store.cache[string(key)] = &cValue{
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value: value,
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deleted: deleted,
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dirty: dirty,
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}
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if dirty {
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store.unsortedCache[string(key)] = struct{}{}
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}
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}
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