storage/src/Variant.h

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  21  * the Initial Developer. All Rights Reserved.
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  23  * Contributor(s):
  24  *   Shawn Wilsher <me@shawnwilsher.com> (Original Author)
  25  *   Drew Willcoxon <adw@mozilla.com>
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  39  * ***** END LICENSE BLOCK ***** */
  40
  41 #ifndef mozilla_storage_Variant_h__
  42 #define mozilla_storage_Variant_h__
  43
  44 #include <utility>
  45
  46 #include "nsIVariant.h"
  47 #include "nsString.h"
  48 #include "nsTArray.h"
  49
  50 /**
  51  * This class is used by the storage module whenever an nsIVariant needs to be
  52  * returned.  We provide traits for the basic sqlite types to make use easier.
  53  * The following types map to the indicated sqlite type:
  54  * PRInt64   -> INTEGER (use IntegerVariant)
  55  * double    -> FLOAT (use FloatVariant)
  56  * nsString  -> TEXT (use TextVariant)
  57  * nsCString -> TEXT (use UTF8TextVariant)
  58  * PRUint8[] -> BLOB (use BlobVariant)
  59  * nsnull    -> NULL (use NullVariant)
  60  */
  61
  62 namespace mozilla {
  63 namespace storage {
  64
  65 ////////////////////////////////////////////////////////////////////////////////
  66 //// Base Class
  67
  68 class Variant_base : public nsIVariant
  69 {
  70 public:
  71   NS_DECL_ISUPPORTS
  72   NS_DECL_NSIVARIANT
  73
  74 protected:
  75   virtual ~Variant_base() { }
  76 };
  77
  78 ////////////////////////////////////////////////////////////////////////////////
  79 //// Traits
  80
  81 /**
  82  * Generics
  83  */
  84
  85 template <typename DataType>
  86 struct variant_traits
  87 {
  88   static inline PRUint16 type() { return nsIDataType::VTYPE_EMPTY; }
  89 };
  90
  91 template <typename DataType>
  92 struct variant_storage_traits
  93 {
  94   typedef DataType ConstructorType;
  95   typedef DataType StorageType;
  96   static inline StorageType storage_conversion(ConstructorType aData) { return aData; }
  97 };
  98
  99 #define NO_CONVERSION return NS_ERROR_CANNOT_CONVERT_DATA;
 100
 101 template <typename DataType>
 102 struct variant_integer_traits
 103 {
 104   typedef typename variant_storage_traits<DataType>::StorageType StorageType;
 105   static inline nsresult asInt32(StorageType, PRInt32 *) { NO_CONVERSION }
 106   static inline nsresult asInt64(StorageType, PRInt64 *) { NO_CONVERSION }
 107 };
 108
 109 template <typename DataType>
 110 struct variant_float_traits
 111 {
 112   typedef typename variant_storage_traits<DataType>::StorageType StorageType;
 113   static inline nsresult asDouble(StorageType, double *) { NO_CONVERSION }
 114 };
 115
 116 template <typename DataType>
 117 struct variant_text_traits
 118 {
 119   typedef typename variant_storage_traits<DataType>::StorageType StorageType;
 120   static inline nsresult asUTF8String(StorageType, nsACString &) { NO_CONVERSION }
 121   static inline nsresult asString(StorageType, nsAString &) { NO_CONVERSION }
 122 };
 123
 124 template <typename DataType>
 125 struct variant_blob_traits
 126 {
 127   typedef typename variant_storage_traits<DataType>::StorageType StorageType;
 128   static inline nsresult asArray(StorageType, PRUint16 *, PRUint32 *, void **)
 129   { NO_CONVERSION }
 130 };
 131
 132 #undef NO_CONVERSION
 133
 134 /**
 135  * INTEGER types
 136  */
 137
 138 template < >
 139 struct variant_traits<PRInt64>
 140 {
 141   static inline PRUint16 type() { return nsIDataType::VTYPE_INT64; }
 142 };
 143 template < >
 144 struct variant_integer_traits<PRInt64>
 145 {
 146   static inline nsresult asInt32(PRInt64 aValue,
 147                                  PRInt32 *_result)
 148   {
 149     if (aValue > PR_INT32_MAX || aValue < PR_INT32_MIN)
 150       return NS_ERROR_CANNOT_CONVERT_DATA;
 151
 152     *_result = static_cast<PRInt32>(aValue);
 153     return NS_OK;
 154   }
 155   static inline nsresult asInt64(PRInt64 aValue,
 156                                  PRInt64 *_result)
 157   {
 158     *_result = aValue;
 159     return NS_OK;
 160   }
 161 };
 162 // xpcvariant just calls get double for integers...
 163 template < >
 164 struct variant_float_traits<PRInt64>
 165 {
 166   static inline nsresult asDouble(PRInt64 aValue,
 167                                   double *_result)
 168   {
 169     *_result = double(aValue);
 170     return NS_OK;
 171   }
 172 };
 173
 174 /**
 175  * FLOAT types
 176  */
 177
 178 template < >
 179 struct variant_traits<double>
 180 {
 181   static inline PRUint16 type() { return nsIDataType::VTYPE_DOUBLE; }
 182 };
 183 template < >
 184 struct variant_float_traits<double>
 185 {
 186   static inline nsresult asDouble(double aValue,
 187                                   double *_result)
 188   {
 189     *_result = aValue;
 190     return NS_OK;
 191   }
 192 };
 193
 194 /**
 195  * TEXT types
 196  */
 197
 198 template < >
 199 struct variant_traits<nsString>
 200 {
 201   static inline PRUint16 type() { return nsIDataType::VTYPE_ASTRING; }
 202 };
 203 template < >
 204 struct variant_storage_traits<nsString>
 205 {
 206   typedef const nsAString & ConstructorType;
 207   typedef nsString StorageType;
 208   static inline StorageType storage_conversion(ConstructorType aText)
 209   {
 210     return StorageType(aText);
 211   }
 212 };
 213 template < >
 214 struct variant_text_traits<nsString>
 215 {
 216   static inline nsresult asUTF8String(const nsString &aValue,
 217                                       nsACString &_result)
 218   {
 219     CopyUTF16toUTF8(aValue, _result);
 220     return NS_OK;
 221   }
 222   static inline nsresult asString(const nsString &aValue,
 223                                   nsAString &_result)
 224   {
 225     _result = aValue;
 226     return NS_OK;
 227   }
 228 };
 229
 230 template < >
 231 struct variant_traits<nsCString>
 232 {
 233   static inline PRUint16 type() { return nsIDataType::VTYPE_UTF8STRING; }
 234 };
 235 template < >
 236 struct variant_storage_traits<nsCString>
 237 {
 238   typedef const nsACString & ConstructorType;
 239   typedef nsCString StorageType;
 240   static inline StorageType storage_conversion(ConstructorType aText)
 241   {
 242     return StorageType(aText);
 243   }
 244 };
 245 template < >
 246 struct variant_text_traits<nsCString>
 247 {
 248   static inline nsresult asUTF8String(const nsCString &aValue,
 249                                       nsACString &_result)
 250   {
 251     _result = aValue;
 252     return NS_OK;
 253   }
 254   static inline nsresult asString(const nsCString &aValue,
 255                                   nsAString &_result)
 256   {
 257     CopyUTF8toUTF16(aValue, _result);
 258     return NS_OK;
 259   }
 260 };
 261
 262 /**
 263  * BLOB types
 264  */
 265
 266 template < >
 267 struct variant_traits<PRUint8[]>
 268 {
 269   static inline PRUint16 type() { return nsIDataType::VTYPE_ARRAY; }
 270 };
 271 template < >
 272 struct variant_storage_traits<PRUint8[]>
 273 {
 274   typedef std::pair<const void *, int> ConstructorType;
 275   typedef FallibleTArray<PRUint8> StorageType;
 276   static inline StorageType storage_conversion(ConstructorType aBlob)
 277   {
 278     StorageType data(aBlob.second);
 279     (void)data.AppendElements(static_cast<const PRUint8 *>(aBlob.first),
 280                               aBlob.second);
 281     return data;
 282   }
 283 };
 284 template < >
 285 struct variant_blob_traits<PRUint8[]>
 286 {
 287   static inline nsresult asArray(FallibleTArray<PRUint8> &aData,
 288                                  PRUint16 *_type,
 289                                  PRUint32 *_size,
 290                                  void **_result)
 291   {
 292     // For empty blobs, we return nsnull.
 293     if (aData.Length() == 0) {
 294       *_result = nsnull;
 295       *_type = nsIDataType::VTYPE_UINT8;
 296       *_size = 0;
 297       return NS_OK;
 298     }
 299
 300     // Otherwise, we copy the array.
 301     *_result = nsMemory::Clone(aData.Elements(), aData.Length() * sizeof(PRUint8));
 302     NS_ENSURE_TRUE(*_result, NS_ERROR_OUT_OF_MEMORY);
 303
 304     // Set type and size
 305     *_type = nsIDataType::VTYPE_UINT8;
 306     *_size = aData.Length();
 307     return NS_OK;
 308   }
 309 };
 310
 311 /**
 312  * NULL type
 313  */
 314
 315 class NullVariant : public Variant_base
 316 {
 317 public:
 318   NS_IMETHOD GetDataType(PRUint16 *_type)
 319   {
 320     NS_ENSURE_ARG_POINTER(_type);
 321     *_type = nsIDataType::VTYPE_EMPTY;
 322     return NS_OK;
 323   }
 324
 325   NS_IMETHOD GetAsAUTF8String(nsACString &_str)
 326   {
 327     // Return a void string.
 328     _str.Truncate(0);
 329     _str.SetIsVoid(PR_TRUE);
 330     return NS_OK;
 331   }
 332
 333   NS_IMETHOD GetAsAString(nsAString &_str)
 334   {
 335     // Return a void string.
 336     _str.Truncate(0);
 337     _str.SetIsVoid(PR_TRUE);
 338     return NS_OK;
 339   }
 340 };
 341
 342 ////////////////////////////////////////////////////////////////////////////////
 343 //// Template Implementation
 344
 345 template <typename DataType>
 346 class Variant : public Variant_base
 347 {
 348 public:
 349   Variant(typename variant_storage_traits<DataType>::ConstructorType aData)
 350     : mData(variant_storage_traits<DataType>::storage_conversion(aData))
 351   {
 352   }
 353
 354   NS_IMETHOD GetDataType(PRUint16 *_type)
 355   {
 356     *_type = variant_traits<DataType>::type();
 357     return NS_OK;
 358   }
 359   NS_IMETHOD GetAsInt32(PRInt32 *_integer)
 360   {
 361     return variant_integer_traits<DataType>::asInt32(mData, _integer);
 362   }
 363
 364   NS_IMETHOD GetAsInt64(PRInt64 *_integer)
 365   {
 366     return variant_integer_traits<DataType>::asInt64(mData, _integer);
 367   }
 368
 369   NS_IMETHOD GetAsDouble(double *_double)
 370   {
 371     return variant_float_traits<DataType>::asDouble(mData, _double);
 372   }
 373
 374   NS_IMETHOD GetAsAUTF8String(nsACString &_str)
 375   {
 376     return variant_text_traits<DataType>::asUTF8String(mData, _str);
 377   }
 378
 379   NS_IMETHOD GetAsAString(nsAString &_str)
 380   {
 381     return variant_text_traits<DataType>::asString(mData, _str);
 382   }
 383
 384   NS_IMETHOD GetAsArray(PRUint16 *_type,
 385                         nsIID *,
 386                         PRUint32 *_size,
 387                         void **_data)
 388   {
 389     return variant_blob_traits<DataType>::asArray(mData, _type, _size, _data);
 390   }
 391
 392 private:
 393   typename variant_storage_traits<DataType>::StorageType mData;
 394 };
 395
 396 ////////////////////////////////////////////////////////////////////////////////
 397 //// Handy typedefs!  Use these for the right mapping.
 398
 399 typedef Variant<PRInt64> IntegerVariant;
 400 typedef Variant<double> FloatVariant;
 401 typedef Variant<nsString> TextVariant;
 402 typedef Variant<nsCString> UTF8TextVariant;
 403 typedef Variant<PRUint8[]> BlobVariant;
 404
 405 } // namespace storage
 406 } // namespace mozilla
 407
 408 #include "Variant_inl.h"
 409
 410 #endif // mozilla_storage_Variant_h__