bpf_dsl: support Switch/Case expressions

sandbox/linux/bpf_dsl/bpf_dsl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
 
 #include <errno.h>
 
 #include <limits>
 
@@ skipping 72 matching lines @@
  private:
   virtual ~IfThenResultExprImpl() {}
 
   BoolExpr cond_;
   ResultExpr then_result_;
   ResultExpr else_result_;
 
   DISALLOW_COPY_AND_ASSIGN(IfThenResultExprImpl);
 };
 
+class ConstBoolExprImpl : public internal::BoolExprImpl {
+ public:
+  ConstBoolExprImpl(bool value) : value_(value) {}
+
+  virtual ErrorCode Compile(SandboxBPF* sb,
+                            ErrorCode true_ec,
+                            ErrorCode false_ec) const OVERRIDE {
+    return value_ ? true_ec : false_ec;
+  }
+
+ private:
+  virtual ~ConstBoolExprImpl() {}
+
+  bool value_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConstBoolExprImpl);
+};
+
 class PrimitiveBoolExprImpl : public internal::BoolExprImpl {
  public:
   PrimitiveBoolExprImpl(int argno,
                         ErrorCode::ArgType is_32bit,
                         uint64_t mask,
                         uint64_t value)
       : argno_(argno), is_32bit_(is_32bit), mask_(mask), value_(value) {}
 
   virtual ErrorCode Compile(SandboxBPF* sb,
                             ErrorCode true_ec,
@@ skipping 104 matching lines @@
 }
 
 ResultExpr Error(int err) {
   return ResultExpr(new const ErrorResultExprImpl(err));
 }
 
 ResultExpr Trap(Trap::TrapFnc trap_func, void* aux) {
   return ResultExpr(new const TrapResultExprImpl(trap_func, aux));
 }
 
+BoolExpr BoolConst(bool value) {
+  return BoolExpr(new const ConstBoolExprImpl(value));
+}
+
 BoolExpr operator!(const BoolExpr& cond) {
   return BoolExpr(new const NegateBoolExprImpl(cond));
 }
 
 BoolExpr operator&&(const BoolExpr& lhs, const BoolExpr& rhs) {
   return BoolExpr(new const AndBoolExprImpl(lhs, rhs));
 }
 
 BoolExpr operator||(const BoolExpr& lhs, const BoolExpr& rhs) {
   return BoolExpr(new const OrBoolExprImpl(lhs, rhs));
@@ skipping 61 matching lines @@
 ErrorCode SandboxBPFDSLPolicy::InvalidSyscall(SandboxBPF* sb) const {
   return InvalidSyscall()->Compile(sb);
 }
 
 ResultExpr SandboxBPFDSLPolicy::Trap(Trap::TrapFnc trap_func, void* aux) {
   return bpf_dsl::Trap(trap_func, aux);
 }
 
 }  // namespace bpf_dsl
 }  // namespace sandbox