Inline Iterator interface

go.mod

@@ -20,7 +20,7 @@ require (
 	github.com/golang/snappy v0.0.1 // indirect
 	github.com/google/btree v1.0.0 // indirect
 	github.com/jmhodges/levigo v1.0.0 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pkg/errors v0.8.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/syndtr/goleveldb v1.0.1-0.20200815110645-5c35d600f0ca // indirect
 	go.etcd.io/bbolt v1.3.6 // indirect

go.sum

@@ -81,9 +81,8 @@ github.com/onsi/gomega v1.7.1/go.mod h1:XdKZgCCFLUoM/7CFJVPcG8C1xQ1AJ0vpAezJrB7J
 github.com/onsi/gomega v1.10.1 h1:o0+MgICZLuZ7xjH7Vx6zS/zcu93/BEp1VwkIW1mEXCE=
 github.com/onsi/gomega v1.10.1/go.mod h1:iN09h71vgCQne3DLsj+A5owkum+a2tYe+TOCB1ybHNo=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
+github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
-github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=

internal/api/iterator.go

@@ -4,11 +4,11 @@ import (
 	"fmt"
 	"sync"
 
-	dbm "github.com/tendermint/tm-db"
+	"github.com/CosmWasm/wasmvm/types"
 )
 
 // frame stores all Iterators for one contract call
-type frame []dbm.Iterator
+type frame []types.Iterator
 
 // iteratorFrames contains one frame for each contract call, indexed by contract call ID.
 var (
@@ -56,7 +56,7 @@ func endCall(callID uint64) {
 // storeIterator will add this to the end of the frame for the given ID and return a reference to it.
 // We start counting with 1, so the 0 value is flagged as an error. This means we must
 // remember to do idx-1 when retrieving
-func storeIterator(callID uint64, it dbm.Iterator, frameLenLimit int) (uint64, error) {
+func storeIterator(callID uint64, it types.Iterator, frameLenLimit int) (uint64, error) {
 	iteratorFramesMutex.Lock()
 	defer iteratorFramesMutex.Unlock()
 
@@ -75,7 +75,7 @@ func storeIterator(callID uint64, it dbm.Iterator, frameLenLimit int) (uint64, e
 // retrieveIterator will recover an iterator based on index. This ensures it will not be garbage collected.
 // We start counting with 1, in storeIterator so the 0 value is flagged as an error. This means we must
 // remember to do idx-1 when retrieving
-func retrieveIterator(callID uint64, index uint64) dbm.Iterator {
+func retrieveIterator(callID uint64, index uint64) types.Iterator {
 	iteratorFramesMutex.Lock()
 	defer iteratorFramesMutex.Unlock()
 	myFrame := iteratorFrames[callID]

internal/api/mocks.go

@@ -305,7 +305,7 @@ func (l Lookup) Delete(key []byte) {
 }
 
 // Iterator wraps the underlying DB's Iterator method panicing on error.
-func (l Lookup) Iterator(start, end []byte) dbm.Iterator {
+func (l Lookup) Iterator(start, end []byte) types.Iterator {
 	l.meter.ConsumeGas(RangePrice, "range")
 	iter, err := l.db.Iterator(start, end)
 	if err != nil {
@@ -316,7 +316,7 @@ func (l Lookup) Iterator(start, end []byte) dbm.Iterator {
 }
 
 // ReverseIterator wraps the underlying DB's ReverseIterator method panicing on error.
-func (l Lookup) ReverseIterator(start, end []byte) dbm.Iterator {
+func (l Lookup) ReverseIterator(start, end []byte) types.Iterator {
 	l.meter.ConsumeGas(RangePrice, "range")
 	iter, err := l.db.ReverseIterator(start, end)
 	if err != nil {

types/store.go

@@ -1,9 +1,5 @@
 package types
 
-import (
-	dbm "github.com/tendermint/tm-db"
-)
-
 // KVStore copies a subset of types from cosmos-sdk
 // We may wish to make this more generic sometime in the future, but not now
 // https://github.com/cosmos/cosmos-sdk/blob/bef3689245bab591d7d169abd6bea52db97a70c7/store/types/store.go#L170
@@ -16,10 +12,61 @@ type KVStore interface {
 	// Start must be less than end, or the Iterator is invalid.
 	// Iterator must be closed by caller.
 	// To iterate over entire domain, use store.Iterator(nil, nil)
-	Iterator(start, end []byte) dbm.Iterator
+	Iterator(start, end []byte) Iterator
 
-	// Iterator over a domain of keys in descending order. End is exclusive.
+	// ReverseIterator iterator over a domain of keys in descending order. End is exclusive.
 	// Start must be less than end, or the Iterator is invalid.
 	// Iterator must be closed by caller.
-	ReverseIterator(start, end []byte) dbm.Iterator
+	ReverseIterator(start, end []byte) Iterator
+}
+
+// Iterator represents an iterator over a domain of keys. Callers must call Close when done.
+// No writes can happen to a domain while there exists an iterator over it, some backends may take
+// out database locks to ensure this will not happen.
+//
+// Callers must make sure the iterator is valid before calling any methods on it, otherwise
+// these methods will panic. This is in part caused by most backend databases using this convention.
+//
+// As with DB, keys and values should be considered read-only, and must be copied before they are
+// modified.
+//
+// Typical usage:
+//
+// var itr Iterator = ...
+// defer itr.Close()
+//
+//	for ; itr.Valid(); itr.Next() {
+//	  k, v := itr.Key(); itr.Value()
+//	  ...
+//	}
+//
+//	if err := itr.Error(); err != nil {
+//	  ...
+//	}
+type Iterator interface {
+	// Domain returns the start (inclusive) and end (exclusive) limits of the iterator.
+	// CONTRACT: start, end readonly []byte
+	Domain() (start []byte, end []byte)
+
+	// Valid returns whether the current iterator is valid. Once invalid, the Iterator remains
+	// invalid forever.
+	Valid() bool
+
+	// Next moves the iterator to the next key in the database, as defined by order of iteration.
+	// If Valid returns false, this method will panic.
+	Next()
+
+	// Key returns the key at the current position. Panics if the iterator is invalid.
+	// CONTRACT: key readonly []byte
+	Key() (key []byte)
+
+	// Value returns the value at the current position. Panics if the iterator is invalid.
+	// CONTRACT: value readonly []byte
+	Value() (value []byte)
+
+	// Error returns the last error encountered by the iterator, if any.
+	Error() error
+
+	// Close closes the iterator, relasing any allocated resources.
+	Close() error
 }