Add a Require family of functions to pkg/util/contract

pkg/util/contract/require.go

@@ -0,0 +1,30 @@
+// Copyright 2016 Marapongo, Inc. All rights reserved.
+
+package contract
+
+import (
+	"fmt"
+)
+
+const requireMsg = "A precondition has failed for %v"
+
+// Require checks a precondition condition pertaining to a function parameter, and Fails if it is false.
+func Require(cond bool, param string) {
+	if !cond {
+		failfast(fmt.Sprintf(requireMsg, param))
+	}
+}
+
+// RequireM checks a precondition condition pertaining to a function parameter, and FailMs if it is false.
+func RequireM(cond bool, param string, msg string) {
+	if !cond {
+		failfast(fmt.Sprintf("%v: %v", fmt.Sprintf(requireMsg, param), msg))
+	}
+}
+
+// RequireMF checks a precondition condition pertaining to a function parameter, and FailMFs if it is false.
+func RequireMF(cond bool, param string, msg string, args ...interface{}) {
+	if !cond {
+		failfast(fmt.Sprintf("%v: %v", fmt.Sprintf(requireMsg, param), fmt.Sprintf(msg, args...)))
+	}
+}