feat: add storage APi's and example

Imported from CityOfZion/neo-storm (86ac5c215a2c6ec710f2fd913e0ace63d6ea993e).

examples/storage/storage.go

@@ -0,0 +1,46 @@
+package storage_contract
+
+import (
+	"github.com/CityOfZion/neo-go-sc/interop/storage"
+)
+
+func Main(operation string, args []interface{}) interface{} {
+	var ctx = storage.GetContext()
+
+	// Puts value at key
+	if operation == "put" {
+		if checkArgs(args, 2) {
+			key := args[0].([]byte)
+			value := args[1].([]byte)
+			storage.Put(ctx, key, value)
+			return key
+		}
+	}
+
+	// Returns the value at passed key
+	if operation == "get" {
+		if checkArgs(args, 1) {
+			key := args[0].([]byte)
+			return storage.Get(ctx, key)
+		}
+	}
+
+	// Deletes the value at passed key
+	if operation == "delete" {
+		key := args[0].([]byte)
+		storage.Delete(ctx, key)
+		return true
+	}
+
+	// TODO: storage.Find()
+
+	return false
+}
+
+func checkArgs(args []interface{}, length int) bool {
+	if len(args) == length {
+		return true
+	}
+
+	return false
+}

interop/storage/storage.go

@@ -0,0 +1,19 @@
+package storage
+
+// Context represents the storage context
+type Context interface{}
+
+// GetContext returns the storage context
+func GetContext() interface{} { return nil }
+
+// Put value at given key
+func Put(ctx interface{}, key interface{}, value interface{}) {}
+
+// Get value matching given key
+func Get(ctx interface{}, key interface{}) interface{} { return 0 }
+
+// Delete key value pair from storage
+func Delete(ctx interface{}, key interface{}) {}
+
+// Find values stored on keys partially matching given key
+func Find(ctx interface{}, key interface{}) interface{} { return 0 }