57 lines
1.3 KiB
Go
57 lines
1.3 KiB
Go
package cachekv
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import (
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"bytes"
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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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)
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// Iterates over iterKVCache items.
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// if key is nil, means it was deleted.
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// Implements Iterator.
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type memIterator struct {
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types.Iterator
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lastKey []byte
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deleted map[string]struct{}
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}
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func newMemIterator(start, end []byte, items *dbm.MemDB, deleted map[string]struct{}, ascending bool) *memIterator {
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var iter types.Iterator
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var err error
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if ascending {
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iter, err = items.Iterator(start, end)
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} else {
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iter, err = items.ReverseIterator(start, end)
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}
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if err != nil {
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panic(err)
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}
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return &memIterator{
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Iterator: iter,
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lastKey: nil,
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deleted: deleted,
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}
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}
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func (mi *memIterator) Value() []byte {
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key := mi.Iterator.Key()
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// We need to handle the case where deleted is modified and includes our current key
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// We handle this by maintaining a lastKey object in the iterator.
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// If the current key is the same as the last key (and last key is not nil / the start)
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// then we are calling value on the same thing as last time.
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// Therefore we don't check the mi.deleted to see if this key is included in there.
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reCallingOnOldLastKey := (mi.lastKey != nil) && bytes.Equal(key, mi.lastKey)
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if _, ok := mi.deleted[string(key)]; ok && !reCallingOnOldLastKey {
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return nil
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}
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mi.lastKey = key
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return mi.Iterator.Value()
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}
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