storage/Variant.h
author Chris H-C <chutten@mozilla.com>
Mon, 04 Jul 2016 11:16:05 -0400
changeset 312997 df28918fe2361f0b54ca9ce4773a29c4c0675d06
parent 246214 182efe94d6b3dfe073bb2f40c61da621cd68556b
child 315432 db4aece012b78248d23ae3f982c776db924c95f8
permissions -rw-r--r--
bug 1218576 - Support remote accumulation via JS histograms. r=gfritzsche The JS histograms, too, need to dispatch their accumulations from child to parent. JSHistograms_Add now only supports histograms that are in gHistogramsMap or that were created in the parent process. After bug 1288745, maybe we'll be able to change this to be less convoluted. MozReview-Commit-ID: 3qTH89YKbGP

/* -*- 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 "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)
 */

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_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

/**
 * 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 = nsMemory::Clone(aData.Elements(), aData.Length() * sizeof(uint8_t));
    NS_ENSURE_TRUE(*_result, NS_ERROR_OUT_OF_MEMORY);

    // 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:
  NS_IMETHOD GetDataType(uint16_t *_type)
  {
    NS_ENSURE_ARG_POINTER(_type);
    *_type = nsIDataType::VTYPE_EMPTY;
    return NS_OK;
  }

  NS_IMETHOD GetAsAUTF8String(nsACString &_str)
  {
    // Return a void string.
    _str.Truncate(0);
    _str.SetIsVoid(true);
    return NS_OK;
  }

  NS_IMETHOD GetAsAString(nsAString &_str)
  {
    // Return a void string.
    _str.Truncate(0);
    _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);
  }

  NS_IMETHOD GetDataType(uint16_t *_type)
  {
    *_type = variant_traits<DataType>::type();
    return NS_OK;
  }
  NS_IMETHOD GetAsInt32(int32_t *_integer)
  {
    return variant_integer_traits<DataType, Adopting>::asInt32(mData, _integer);
  }

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

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

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

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

  NS_IMETHOD GetAsArray(uint16_t *_type,
                        nsIID *,
                        uint32_t *_size,
                        void **_data)
  {
    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.

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__