tor-browser

EnumSerializer.h (6155B)

---

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef __IPC_GLUE_ENUMSERIALIZER_H__
#define __IPC_GLUE_ENUMSERIALIZER_H__

#include "CrashAnnotations.h"
#include "chrome/common/ipc_message_utils.h"
#include "mozilla/Assertions.h"
#include "mozilla/IntegerTypeTraits.h"
#include "nsExceptionHandler.h"
#include "nsLiteralString.h"
#include "nsString.h"
#include "nsTLiteralString.h"

class PickleIterator;

namespace IPC {
class Message;
class MessageReader;
class MessageWriter;
}  // namespace IPC

#ifdef _MSC_VER
#  pragma warning(disable : 4800)
#endif

namespace IPC {

/**
* Generic enum serializer.
*
* Consider using the specializations below, such as ContiguousEnumSerializer.
*
* This is a generic serializer for any enum type used in IPDL.
* Programmers can define ParamTraits<E> for enum type E by deriving
* EnumSerializer<E, MyEnumValidator> where MyEnumValidator is a struct
* that has to define a static IsLegalValue function returning whether
* a given value is a legal value of the enum type at hand.
*
* \sa https://developer.mozilla.org/en/IPDL/Type_Serialization
*/
template <typename E, typename EnumValidator>
struct EnumSerializer {
 typedef E paramType;

 // XXX(Bug 1690343) Should this be changed to
 // std::make_unsigned_t<std::underlying_type_t<paramType>>, to make this more
 // consistent with the type used for validating values?
 typedef typename mozilla::UnsignedStdintTypeForSize<sizeof(paramType)>::Type
     uintParamType;

 static void Write(MessageWriter* aWriter, const paramType& aValue) {
   // XXX This assertion is somewhat meaningless at least for E that don't have
   // a fixed underlying type: if aValue weren't a legal value, we would
   // already have UB where this function is called.
   MOZ_RELEASE_ASSERT(EnumValidator::IsLegalValue(
       static_cast<std::underlying_type_t<paramType>>(aValue)));
   WriteParam(aWriter, uintParamType(aValue));
 }

 static bool Read(MessageReader* aReader, paramType* aResult) {
   uintParamType value;
   if (!ReadParam(aReader, &value)) {
     CrashReporter::RecordAnnotationCString(
         CrashReporter::Annotation::IPCReadErrorReason, "Bad iter");
     return false;
   }
   if (!EnumValidator::IsLegalValue(value)) {
     CrashReporter::RecordAnnotationCString(
         CrashReporter::Annotation::IPCReadErrorReason, "Illegal value");
     return false;
   }
   *aResult = paramType(value);
   return true;
 }
};

template <typename E, E MinLegal, E HighBound>
class ContiguousEnumValidator {
 // Silence overzealous -Wtype-limits bug in GCC fixed in GCC 4.8:
 // "comparison of unsigned expression >= 0 is always true"
 // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11856
 template <typename T>
 static bool IsLessThanOrEqual(T a, T b) {
   return a <= b;
 }

public:
 using IntegralType = std::underlying_type_t<E>;
 static constexpr auto kMinLegalIntegral = static_cast<IntegralType>(MinLegal);
 static constexpr auto kHighBoundIntegral =
     static_cast<IntegralType>(HighBound);

 static bool IsLegalValue(const IntegralType e) {
   return IsLessThanOrEqual(kMinLegalIntegral, e) && e < kHighBoundIntegral;
 }
};

template <typename E, E MinLegal, E MaxLegal>
class ContiguousEnumValidatorInclusive {
 // Silence overzealous -Wtype-limits bug in GCC fixed in GCC 4.8:
 // "comparison of unsigned expression >= 0 is always true"
 // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11856
 template <typename T>
 static bool IsLessThanOrEqual(T a, T b) {
   return a <= b;
 }

public:
 using IntegralType = std::underlying_type_t<E>;
 static constexpr auto kMinLegalIntegral = static_cast<IntegralType>(MinLegal);
 static constexpr auto kMaxLegalIntegral = static_cast<IntegralType>(MaxLegal);

 static bool IsLegalValue(const IntegralType e) {
   return IsLessThanOrEqual(kMinLegalIntegral, e) && e <= kMaxLegalIntegral;
 }
};

template <typename E, E AllBits>
struct BitFlagsEnumValidator {
 static bool IsLegalValue(const std::underlying_type_t<E> e) {
   return (e & static_cast<std::underlying_type_t<E>>(AllBits)) == e;
 }
};

/**
* Specialization of EnumSerializer for enums with contiguous enum values.
*
* Provide two values: MinLegal, HighBound. An enum value x will be
* considered legal if MinLegal <= x < HighBound.
*
* For example, following is definition of serializer for enum type FOO.
* \code
* enum FOO { FOO_FIRST, FOO_SECOND, FOO_LAST, NUM_FOO };
*
* template <>
* struct ParamTraits<FOO>:
*     public ContiguousEnumSerializer<FOO, FOO_FIRST, NUM_FOO> {};
* \endcode
* FOO_FIRST, FOO_SECOND, and FOO_LAST are valid value.
*/
template <typename E, E MinLegal, E HighBound>
struct ContiguousEnumSerializer
   : EnumSerializer<E, ContiguousEnumValidator<E, MinLegal, HighBound>> {};

/**
* This is similar to ContiguousEnumSerializer, but the last template
* parameter is expected to be the highest legal value, rather than a
* sentinel value. This is intended to support enumerations that don't
* have sentinel values.
*/
template <typename E, E MinLegal, E MaxLegal>
struct ContiguousEnumSerializerInclusive
   : EnumSerializer<E,
                    ContiguousEnumValidatorInclusive<E, MinLegal, MaxLegal>> {
};

/**
* Specialization of EnumSerializer for enums representing bit flags.
*
* Provide one value: AllBits. An enum value x will be
* considered legal if (x & AllBits) == x;
*
* Example:
* \code
* enum FOO {
*   FOO_FIRST =  1 << 0,
*   FOO_SECOND = 1 << 1,
*   FOO_LAST =   1 << 2,
*   ALL_BITS =   (1 << 3) - 1
* };
*
* template <>
* struct ParamTraits<FOO>:
*     public BitFlagsEnumSerializer<FOO, FOO::ALL_BITS> {};
* \endcode
*/
template <typename E, E AllBits>
struct BitFlagsEnumSerializer
   : EnumSerializer<E, BitFlagsEnumValidator<E, AllBits>> {};

} /* namespace IPC */

#endif /* __IPC_GLUE_ENUMSERIALIZER_H__ */