Draft of iterator and enumerator (CityOfZion/neo-storm#26)

* Draft of iterator and enumerator

* Added iterator API to the syscall mapping

* Added draft of the enumerator.go file

* Added enumerator interop API.

* Updated the changelog

Imported from CityOfZion/neo-storm (156093318b8612e810965bb1ea26e1babfb46cdd).

examples/iterator/iterator.go

@@ -0,0 +1,18 @@
+package iterator_contract
+
+import (
+	"github.com/CityOfZion/neo-storm/interop/iterator"
+	"github.com/CityOfZion/neo-storm/interop/runtime"
+	"github.com/CityOfZion/neo-storm/interop/storage"
+)
+
+func Main() bool {
+	iter := storage.Find(storage.GetContext(), []byte("foo"))
+	values := iterator.Values(iter)
+	keys := iterator.Keys(iter)
+
+	runtime.Notify("found storage values", values)
+	runtime.Notify("found storage keys", keys)
+
+	return true
+}

interop/enumerator/enumerator.go

@@ -0,0 +1,29 @@
+package enumerator
+
+// Package enumerator provides function signatures that can be used inside
+// smart contracts that are written in the neo-storm framework.
+
+// TODO: Check enumerator use cases and add them to the examples folder.
+
+// Enumerator stubs a NEO enumerator type.
+type Enumerator struct{}
+
+// Create creates a new enumerator from the given items.
+func Create(items []interface{}) Enumerator {
+	return Enumerator{}
+}
+
+// Next returns the next item in the iteration.
+func Next(e Enumerator) interface{} {
+	return nil
+}
+
+// Value returns the enumerator value.
+func Value(e Enumerator) interface{} {
+	return nil
+}
+
+// Concat concats the 2 given enumerators.
+func Concat(a, b Enumerator) Enumerator {
+	return Enumerator{}
+}

interop/iterator/iterator.go

@@ -0,0 +1,28 @@
+package iterator
+
+// Package iterator provides function signatures that can be used inside
+// smart contracts that are written in the neo-storm framework.
+
+// Iterator stubs a NEO iterator object type.
+type Iterator struct{}
+
+// Create creates an iterator from the given items.
+func Create(items []interface{}) Iterator {
+	return Iterator{}
+}
+
+// TODO: Better description for this.
+// Key returns the iterator key.
+func Key(it Iterator) interface{} {
+	return nil
+}
+
+// Keys returns the iterator keys.
+func Keys(it Iterator) []interface{} {
+	return nil
+}
+
+// Values returns the iterator values.
+func Values(it Iterator) []interface{} {
+	return nil
+}

interop/storage/storage.go

@@ -1,5 +1,7 @@
 package storage
 
+import "github.com/CityOfZion/neo-storm/interop/iterator"
+
 // Package storage provides function signatures that can be used inside
 // smart contracts that are written in the neo-storm framework.
 
@@ -18,5 +20,5 @@ func Get(ctx Context, key interface{}) interface{} { return 0 }
 // Delete key value pair from storage
 func Delete(ctx Context, key interface{}) {}
 
-// Find values stored on keys partially matching given key
+// Find returns an iterator.Iterator over the keys that matched the given key.
-func Find(ctx Context, key interface{}) interface{} { return 0 }
+func Find(ctx Context, key interface{}) iterator.Iterator { return iterator.Iterator{} }

pkg/vm/compiler/syscall.go

@@ -81,4 +81,10 @@ var syscalls = map[string]map[string]string{
 		"GetEntryScriptHash":     "System.ExecutionEngine.GetEntryScriptHash",
 		"GetExecutingScriptHash": "System.ExecutionEngine.GetExecutingScriptHash",
 	},
+	"iterator": {
+		"Create": "Neo.Iterator.Create",
+		"Key":    "Neo.Iterator.Key",
+		"Keys":   "Neo.Iterator.Keys",
+		"Values": "Neo.Iterator.Values",
+	},
 }