Initial QSfera import

Server/vendor/github.com/open-policy-agent/opa/internal/planner/varstack.go

@@ -0,0 +1,71 @@
+// Copyright 2019 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package planner
+
+import (
+	"github.com/open-policy-agent/opa/v1/ast"
+	"github.com/open-policy-agent/opa/v1/ir"
+)
+
+type varstack []map[ast.Var]ir.Local
+
+func newVarstack(frames ...map[ast.Var]ir.Local) *varstack {
+	vs := &varstack{}
+	for _, f := range frames {
+		vs.Push(f)
+	}
+	return vs
+}
+
+func (vs varstack) GetOrElse(k ast.Var, orElse func() ir.Local) ir.Local {
+	l, ok := vs.Get(k)
+	if !ok {
+		l = orElse()
+		vs.Put(k, l)
+	}
+	return l
+}
+
+func (vs varstack) GetOrEmpty(k ast.Var) ir.Local {
+	l, _ := vs.Get(k)
+	return l
+}
+
+func (vs varstack) Get(k ast.Var) (ir.Local, bool) {
+	for i := len(vs) - 1; i >= 0; i-- {
+		if l, ok := vs[i][k]; ok {
+			return l, true
+		}
+	}
+	return 0, false
+}
+
+func (vs varstack) GetOpOrEmpty(k ast.Var) ir.Operand {
+	l := vs.GetOrEmpty(k)
+	return ir.Operand{Value: l}
+}
+
+func (vs varstack) GetOp(k ast.Var) (ir.Operand, bool) {
+	l, ok := vs.Get(k)
+	if !ok {
+		return ir.Operand{}, false
+	}
+	return ir.Operand{Value: l}, true
+}
+
+func (vs varstack) Put(k ast.Var, v ir.Local) {
+	vs[len(vs)-1][k] = v
+}
+
+func (vs *varstack) Push(frame map[ast.Var]ir.Local) {
+	*vs = append(*vs, frame)
+}
+
+func (vs *varstack) Pop() map[ast.Var]ir.Local {
+	sl := *vs
+	last := sl[len(sl)-1]
+	*vs = sl[:len(sl)-1]
+	return last
+}