storage/Variant.h
author Nathan Froyd <froydnj@mozilla.com>
Wed, 03 Apr 2019 00:06:04 +0000
changeset 467750 1b9e5f4b0589a636233affb84666a469a4cc4ef5
parent 458136 466f9c24e749d7b3701b60c5ed424e586634a718
child 472094 e1993a1f09ac53cd1a04fdf6a87f8cad8e44f73e
permissions -rw-r--r--
Bug 1537643 - update cc crate; r=glandium This update from the official sources brings in the changes that we were using glandium's fork for, as well as changes enabling us to tweak more settings on Windows. Differential Revision: https://phabricator.services.mozilla.com/D25888

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
 * 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 mozilla_storage_Variant_h__
#define mozilla_storage_Variant_h__

#include <utility>

#include "nsIVariant.h"
#include "nsMemory.h"
#include "nsString.h"
#include "nsTArray.h"

#define VARIANT_BASE_IID                             \
  { /* 78888042-0fa3-4f7a-8b19-7996f99bf1aa */       \
    0x78888042, 0x0fa3, 0x4f7a, {                    \
      0x8b, 0x19, 0x79, 0x96, 0xf9, 0x9b, 0xf1, 0xaa \
    }                                                \
  }

/**
 * This class is used by the storage module whenever an nsIVariant needs to be
 * returned.  We provide traits for the basic sqlite types to make use easier.
 * The following types map to the indicated sqlite type:
 * int64_t   -> INTEGER (use IntegerVariant)
 * double    -> FLOAT (use FloatVariant)
 * nsString  -> TEXT (use TextVariant)
 * nsCString -> TEXT (use UTF8TextVariant)
 * uint8_t[] -> BLOB (use BlobVariant)
 * nullptr   -> NULL (use NullVariant)
 *
 * The kvstore component also reuses this class as a common implementation
 * of a simple threadsafe variant for the storage of primitive values only.
 * The BooleanVariant type has been introduced for kvstore use cases and should
 * be enhanced to provide full boolean variant support for mozStorage.
 *
 * Bug 1494102 tracks that work.
 */

namespace mozilla {
namespace storage {

////////////////////////////////////////////////////////////////////////////////
//// Base Class

class Variant_base : public nsIVariant {
 public:
  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIVARIANT
  NS_DECLARE_STATIC_IID_ACCESSOR(VARIANT_BASE_IID)

 protected:
  virtual ~Variant_base() {}
};

NS_DEFINE_STATIC_IID_ACCESSOR(Variant_base, VARIANT_BASE_IID)

////////////////////////////////////////////////////////////////////////////////
//// Traits

/**
 * Generics
 */

template <typename DataType>
struct variant_traits {
  static inline uint16_t type() { return nsIDataType::VTYPE_EMPTY; }
};

template <typename DataType, bool Adopting = false>
struct variant_storage_traits {
  typedef DataType ConstructorType;
  typedef DataType StorageType;
  static inline void storage_conversion(const ConstructorType aData,
                                        StorageType *_storage) {
    *_storage = aData;
  }

  static inline void destroy(const StorageType &_storage) {}
};

#define NO_CONVERSION return NS_ERROR_CANNOT_CONVERT_DATA;

template <typename DataType, bool Adopting = false>
struct variant_boolean_traits {
  typedef typename variant_storage_traits<DataType, Adopting>::StorageType
      StorageType;
  static inline nsresult asBool(const StorageType &, bool *) { NO_CONVERSION }
};

template <typename DataType, bool Adopting = false>
struct variant_integer_traits {
  typedef typename variant_storage_traits<DataType, Adopting>::StorageType
      StorageType;
  static inline nsresult asInt32(const StorageType &, int32_t *) {
    NO_CONVERSION
  }
  static inline nsresult asInt64(const StorageType &, int64_t *) {
    NO_CONVERSION
  }
};

template <typename DataType, bool Adopting = false>
struct variant_float_traits {
  typedef typename variant_storage_traits<DataType, Adopting>::StorageType
      StorageType;
  static inline nsresult asDouble(const StorageType &, double *) {
    NO_CONVERSION
  }
};

template <typename DataType, bool Adopting = false>
struct variant_text_traits {
  typedef typename variant_storage_traits<DataType, Adopting>::StorageType
      StorageType;
  static inline nsresult asUTF8String(const StorageType &, nsACString &) {
    NO_CONVERSION
  }
  static inline nsresult asString(const StorageType &, nsAString &) {
    NO_CONVERSION
  }
};

template <typename DataType, bool Adopting = false>
struct variant_blob_traits {
  typedef typename variant_storage_traits<DataType, Adopting>::StorageType
      StorageType;
  static inline nsresult asArray(const StorageType &, uint16_t *, uint32_t *,
                                 void **) {
    NO_CONVERSION
  }
};

#undef NO_CONVERSION

/**
 * BOOLEAN type
 */

template <>
struct variant_traits<bool> {
  static inline uint16_t type() { return nsIDataType::VTYPE_BOOL; }
};
template <>
struct variant_boolean_traits<bool> {
  static inline nsresult asBool(bool aValue, bool *_result) {
    *_result = aValue;
    return NS_OK;
  }

  // NB: It might be worth also providing conversions to int types.

  // NB: It'd be nice to implement asBool conversions for 0 and 1, too.
  // That would let us clean up some conversions in Places, such as:
  // https://searchfox.org/mozilla-central/rev/0640ea80fbc8d48f8b197cd363e2535c95a15eb3/toolkit/components/places/SQLFunctions.cpp#564-565
  // https://searchfox.org/mozilla-central/rev/0640ea80fbc8d48f8b197cd363e2535c95a15eb3/toolkit/components/places/SQLFunctions.cpp#1057
  // https://searchfox.org/mozilla-central/rev/0640ea80fbc8d48f8b197cd363e2535c95a15eb3/toolkit/components/places/nsNavHistory.cpp#3189
};

/**
 * INTEGER types
 */

template <>
struct variant_traits<int64_t> {
  static inline uint16_t type() { return nsIDataType::VTYPE_INT64; }
};
template <>
struct variant_integer_traits<int64_t> {
  static inline nsresult asInt32(int64_t aValue, int32_t *_result) {
    if (aValue > INT32_MAX || aValue < INT32_MIN)
      return NS_ERROR_CANNOT_CONVERT_DATA;

    *_result = static_cast<int32_t>(aValue);
    return NS_OK;
  }
  static inline nsresult asInt64(int64_t aValue, int64_t *_result) {
    *_result = aValue;
    return NS_OK;
  }
};
// xpcvariant just calls get double for integers...
template <>
struct variant_float_traits<int64_t> {
  static inline nsresult asDouble(int64_t aValue, double *_result) {
    *_result = double(aValue);
    return NS_OK;
  }
};

/**
 * FLOAT types
 */

template <>
struct variant_traits<double> {
  static inline uint16_t type() { return nsIDataType::VTYPE_DOUBLE; }
};
template <>
struct variant_float_traits<double> {
  static inline nsresult asDouble(double aValue, double *_result) {
    *_result = aValue;
    return NS_OK;
  }
};

/**
 * TEXT types
 */

template <>
struct variant_traits<nsString> {
  static inline uint16_t type() { return nsIDataType::VTYPE_ASTRING; }
};
template <>
struct variant_storage_traits<nsString> {
  typedef const nsAString &ConstructorType;
  typedef nsString StorageType;
  static inline void storage_conversion(ConstructorType aText,
                                        StorageType *_outData) {
    *_outData = aText;
  }
  static inline void destroy(const StorageType &_outData) {}
};
template <>
struct variant_text_traits<nsString> {
  static inline nsresult asUTF8String(const nsString &aValue,
                                      nsACString &_result) {
    CopyUTF16toUTF8(aValue, _result);
    return NS_OK;
  }
  static inline nsresult asString(const nsString &aValue, nsAString &_result) {
    _result = aValue;
    return NS_OK;
  }
};

template <>
struct variant_traits<nsCString> {
  static inline uint16_t type() { return nsIDataType::VTYPE_UTF8STRING; }
};
template <>
struct variant_storage_traits<nsCString> {
  typedef const nsACString &ConstructorType;
  typedef nsCString StorageType;
  static inline void storage_conversion(ConstructorType aText,
                                        StorageType *_outData) {
    *_outData = aText;
  }
  static inline void destroy(const StorageType &aData) {}
};
template <>
struct variant_text_traits<nsCString> {
  static inline nsresult asUTF8String(const nsCString &aValue,
                                      nsACString &_result) {
    _result = aValue;
    return NS_OK;
  }
  static inline nsresult asString(const nsCString &aValue, nsAString &_result) {
    CopyUTF8toUTF16(aValue, _result);
    return NS_OK;
  }
};

/**
 * BLOB types
 */

template <>
struct variant_traits<uint8_t[]> {
  static inline uint16_t type() { return nsIDataType::VTYPE_ARRAY; }
};
template <>
struct variant_storage_traits<uint8_t[], false> {
  typedef std::pair<const void *, int> ConstructorType;
  typedef FallibleTArray<uint8_t> StorageType;
  static inline void storage_conversion(ConstructorType aBlob,
                                        StorageType *_outData) {
    _outData->Clear();
    (void)_outData->AppendElements(static_cast<const uint8_t *>(aBlob.first),
                                   aBlob.second, fallible);
  }
  static inline void destroy(const StorageType &_outData) {}
};
template <>
struct variant_storage_traits<uint8_t[], true> {
  typedef std::pair<uint8_t *, int> ConstructorType;
  typedef std::pair<uint8_t *, int> StorageType;
  static inline void storage_conversion(ConstructorType aBlob,
                                        StorageType *_outData) {
    *_outData = aBlob;
  }
  static inline void destroy(StorageType &aData) {
    if (aData.first) {
      free(aData.first);
      aData.first = nullptr;
    }
  }
};
template <>
struct variant_blob_traits<uint8_t[], false> {
  static inline nsresult asArray(FallibleTArray<uint8_t> &aData,
                                 uint16_t *_type, uint32_t *_size,
                                 void **_result) {
    // For empty blobs, we return nullptr.
    if (aData.Length() == 0) {
      *_result = nullptr;
      *_type = nsIDataType::VTYPE_UINT8;
      *_size = 0;
      return NS_OK;
    }

    // Otherwise, we copy the array.
    *_result = moz_xmemdup(aData.Elements(), aData.Length() * sizeof(uint8_t));

    // Set type and size
    *_type = nsIDataType::VTYPE_UINT8;
    *_size = aData.Length();
    return NS_OK;
  }
};

template <>
struct variant_blob_traits<uint8_t[], true> {
  static inline nsresult asArray(std::pair<uint8_t *, int> &aData,
                                 uint16_t *_type, uint32_t *_size,
                                 void **_result) {
    // For empty blobs, we return nullptr.
    if (aData.second == 0) {
      *_result = nullptr;
      *_type = nsIDataType::VTYPE_UINT8;
      *_size = 0;
      return NS_OK;
    }

    // Otherwise, transfer the data out.
    *_result = aData.first;
    aData.first = nullptr;
    MOZ_ASSERT(*_result);  // We asked for it twice, better not use adopting!

    // Set type and size
    *_type = nsIDataType::VTYPE_UINT8;
    *_size = aData.second;
    return NS_OK;
  }
};

/**
 * nullptr type
 */

class NullVariant : public Variant_base {
 public:
  uint16_t GetDataType() override { return nsIDataType::VTYPE_EMPTY; }

  NS_IMETHOD GetAsAUTF8String(nsACString &_str) override {
    // Return a void string.
    _str.SetIsVoid(true);
    return NS_OK;
  }

  NS_IMETHOD GetAsAString(nsAString &_str) override {
    // Return a void string.
    _str.SetIsVoid(true);
    return NS_OK;
  }
};

////////////////////////////////////////////////////////////////////////////////
//// Template Implementation

template <typename DataType, bool Adopting = false>
class Variant final : public Variant_base {
  ~Variant() { variant_storage_traits<DataType, Adopting>::destroy(mData); }

 public:
  explicit Variant(
      const typename variant_storage_traits<DataType, Adopting>::ConstructorType
          aData) {
    variant_storage_traits<DataType, Adopting>::storage_conversion(aData,
                                                                   &mData);
  }

  uint16_t GetDataType() override { return variant_traits<DataType>::type(); }

  NS_IMETHOD GetAsBool(bool *_boolean) override {
    return variant_boolean_traits<DataType, Adopting>::asBool(mData, _boolean);
  }

  NS_IMETHOD GetAsInt32(int32_t *_integer) override {
    return variant_integer_traits<DataType, Adopting>::asInt32(mData, _integer);
  }

  NS_IMETHOD GetAsInt64(int64_t *_integer) override {
    return variant_integer_traits<DataType, Adopting>::asInt64(mData, _integer);
  }

  NS_IMETHOD GetAsDouble(double *_double) override {
    return variant_float_traits<DataType, Adopting>::asDouble(mData, _double);
  }

  NS_IMETHOD GetAsAUTF8String(nsACString &_str) override {
    return variant_text_traits<DataType, Adopting>::asUTF8String(mData, _str);
  }

  NS_IMETHOD GetAsAString(nsAString &_str) override {
    return variant_text_traits<DataType, Adopting>::asString(mData, _str);
  }

  NS_IMETHOD GetAsArray(uint16_t *_type, nsIID *, uint32_t *_size,
                        void **_data) override {
    return variant_blob_traits<DataType, Adopting>::asArray(mData, _type, _size,
                                                            _data);
  }

 private:
  typename variant_storage_traits<DataType, Adopting>::StorageType mData;
};

////////////////////////////////////////////////////////////////////////////////
//// Handy typedefs!  Use these for the right mapping.

// Currently, BooleanVariant is only useful for kvstore.
// Bug 1494102 tracks implementing full boolean variant support for mozStorage.
typedef Variant<bool> BooleanVariant;

typedef Variant<int64_t> IntegerVariant;
typedef Variant<double> FloatVariant;
typedef Variant<nsString> TextVariant;
typedef Variant<nsCString> UTF8TextVariant;
typedef Variant<uint8_t[], false> BlobVariant;
typedef Variant<uint8_t[], true> AdoptedBlobVariant;

}  // namespace storage
}  // namespace mozilla

#include "Variant_inl.h"

#endif  // mozilla_storage_Variant_h__