layout/style/nsCSSDataBlock.h

   1 /* ***** BEGIN LICENSE BLOCK *****
   2  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3  *
   4  * The contents of this file are subject to the Mozilla Public License Version
   5  * 1.1 (the "License"); you may not use this file except in compliance with
   6  * the License. You may obtain a copy of the License at
   7  * http://www.mozilla.org/MPL/
   8  *
   9  * Software distributed under the License is distributed on an "AS IS" basis,
  10  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11  * for the specific language governing rights and limitations under the
  12  * License.
  13  *
  14  * The Original Code is nsCSSDataBlock.h.
  15  *
  16  * The Initial Developer of the Original Code is L. David Baron.
  17  * Portions created by the Initial Developer are Copyright (C) 2003
  18  * the Initial Developer. All Rights Reserved.
  19  *
  20  * Contributor(s):
  21  *   L. David Baron <dbaron@dbaron.org> (original author)
  22  *
  23  * Alternatively, the contents of this file may be used under the terms of
  24  * either the GNU General Public License Version 2 or later (the "GPL"), or
  25  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  26  * in which case the provisions of the GPL or the LGPL are applicable instead
  27  * of those above. If you wish to allow use of your version of this file only
  28  * under the terms of either the GPL or the LGPL, and not to allow others to
  29  * use your version of this file under the terms of the MPL, indicate your
  30  * decision by deleting the provisions above and replace them with the notice
  31  * and other provisions required by the GPL or the LGPL. If you do not delete
  32  * the provisions above, a recipient may use your version of this file under
  33  * the terms of any one of the MPL, the GPL or the LGPL.
  34  *
  35  * ***** END LICENSE BLOCK ***** */
  36
  37 /*
  38  * compact representation of the property-value pairs within a CSS
  39  * declaration, and the code for expanding and compacting it
  40  */
  41
  42 #ifndef nsCSSDataBlock_h__
  43 #define nsCSSDataBlock_h__
  44
  45 #include "nsCSSStruct.h"
  46
  47 struct nsRuleData;
  48
  49 class nsCSSExpandedDataBlock;
  50
  51 /**
  52  * An |nsCSSCompressedDataBlock| holds an immutable chunk of
  53  * property-value data for a CSS declaration block (which we misname a
  54  * |nsCSSDeclaration|).  Mutation is accomplished through
  55  * |nsCSSExpandedDataBlock|.
  56  */
  57 class nsCSSCompressedDataBlock {
  58 public:
  59     friend class nsCSSExpandedDataBlock;
  60
  61     /**
  62      * Do what |nsIStyleRule::MapRuleInfoInto| needs to do for a style
  63      * rule using this block for storage.
  64      */
  65     nsresult MapRuleInfoInto(nsRuleData *aRuleData) const;
  66
  67     /**
  68      * Return the location at which the *value* for the property is
  69      * stored, or null if the block does not contain a value for the
  70      * property.  This is either an |nsCSSValue*|, |nsCSSRect*|, or an
  71      * |nsCSSValueList**|, etc.
  72      *
  73      * Inefficient (by design).
  74      */
  75     const void* StorageFor(nsCSSProperty aProperty) const;
  76
  77     /**
  78      * Clone this block, or return null on out-of-memory.
  79      */
  80     nsCSSCompressedDataBlock* Clone() const;
  81
  82     /**
  83      * Delete all the data stored in this block, and the block itself.
  84      */
  85     void Destroy();
  86
  87     /**
  88      * Create a new nsCSSCompressedDataBlock holding no declarations.
  89      */
  90     static nsCSSCompressedDataBlock* CreateEmptyBlock();
  91
  92 private:
  93     PRInt32 mStyleBits; // the structs for which we have data, according to
  94                         // |nsCachedStyleData::GetBitForSID|.
  95
  96     enum { block_chars = 4 }; // put 4 chars in the definition of the class
  97                               // to ensure size not inflated by alignment
  98
  99     void* operator new(size_t aBaseSize, size_t aDataSize) {
 100         // subtract off the extra size to store |mBlock_|
 101         return ::operator new(aBaseSize + aDataSize -
 102                               sizeof(char) * block_chars);
 103     }
 104
 105     nsCSSCompressedDataBlock() : mStyleBits(0) {}
 106
 107     // Only this class (through |Destroy|) or nsCSSExpandedDataBlock (in
 108     // |Expand|) can delete compressed data blocks.
 109     ~nsCSSCompressedDataBlock() { }
 110
 111     char* mBlockEnd; // the byte after the last valid byte
 112     char mBlock_[block_chars]; // must be the last member!
 113
 114     char* Block() { return mBlock_; }
 115     char* BlockEnd() { return mBlockEnd; }
 116     const char* Block() const { return mBlock_; }
 117     const char* BlockEnd() const { return mBlockEnd; }
 118     ptrdiff_t DataSize() const { return BlockEnd() - Block(); }
 119 };
 120
 121 class nsCSSExpandedDataBlock {
 122 public:
 123     nsCSSExpandedDataBlock();
 124     ~nsCSSExpandedDataBlock();
 125     /*
 126      * When setting properties in an |nsCSSExpandedDataBlock|, callers
 127      * must make the appropriate |AddPropertyBit| call.
 128      */
 129
 130     nsCSSFont mFont;
 131     nsCSSDisplay mDisplay;
 132     nsCSSMargin mMargin;
 133     nsCSSList mList;
 134     nsCSSPosition mPosition;
 135     nsCSSTable mTable;
 136     nsCSSColor mColor;
 137     nsCSSContent mContent;
 138     nsCSSText mText;
 139     nsCSSUserInterface mUserInterface;
 140     nsCSSAural mAural;
 141     nsCSSPage mPage;
 142     nsCSSBreaks mBreaks;
 143     nsCSSXUL mXUL;
 144 #ifdef MOZ_SVG
 145     nsCSSSVG mSVG;
 146 #endif
 147     nsCSSColumn mColumn;
 148
 149     /**
 150      * Transfer all of the state from the compressed block to this
 151      * expanded block.  The state of this expanded block must be clear
 152      * beforehand.
 153      *
 154      * The compressed block passed in IS DESTROYED by this method and
 155      * set to null, and thus cannot be used again.  (This is necessary
 156      * because ownership of sub-objects is transferred to the expanded
 157      * block.)
 158      */
 159     void Expand(nsCSSCompressedDataBlock **aNormalBlock,
 160                 nsCSSCompressedDataBlock **aImportantBlock);
 161
 162     /**
 163      * Allocate a new compressed block and transfer all of the state
 164      * from this expanded block to the new compressed block, clearing
 165      * the state of this expanded block.
 166      */
 167     void Compress(nsCSSCompressedDataBlock **aNormalBlock,
 168                   nsCSSCompressedDataBlock **aImportantBlock);
 169
 170     /**
 171      * Clear (and thus destroy) the state of this expanded block.
 172      */
 173     void Clear();
 174
 175     /**
 176      * Clear the data for the given property (including the set and
 177      * important bits).
 178      */
 179     void ClearProperty(nsCSSProperty aPropID);
 180
 181     void AssertInitialState() {
 182 #ifdef DEBUG
 183         DoAssertInitialState();
 184 #endif
 185     }
 186
 187 private:
 188     /**
 189      * Compute the size that will be occupied by the result of
 190      * |Compress|.
 191      */
 192     struct ComputeSizeResult {
 193         PRUint32 normal, important;
 194     };
 195     ComputeSizeResult ComputeSize();
 196
 197     void DoExpand(nsCSSCompressedDataBlock *aBlock, PRBool aImportant);
 198
 199 #ifdef DEBUG
 200     void DoAssertInitialState();
 201 #endif
 202
 203     struct PropertyOffsetInfo {
 204         // XXX These could probably be pointer-to-member, if the casting can
 205         // be done correctly.
 206         size_t block_offset; // offset of value in nsCSSExpandedDataBlock
 207         size_t ruledata_struct_offset; // offset of nsRuleData* in nsRuleData
 208         size_t ruledata_member_offset; // offset of value in nsRuleData*
 209     };
 210
 211     static const PropertyOffsetInfo kOffsetTable[];
 212
 213     typedef PRUint8 property_set_type;
 214     enum { kPropertiesSetChunkSize = 8 }; // number of bits in
 215                                           // |property_set_type|.
 216     // number of |property_set_type|s in the set
 217     enum { kPropertiesSetChunkCount =
 218              (eCSSProperty_COUNT_no_shorthands + (kPropertiesSetChunkSize-1)) /
 219              kPropertiesSetChunkSize };
 220     /*
 221      * mPropertiesSet stores a bit for every property that is present,
 222      * to optimize compression of blocks with small numbers of
 223      * properties (the norm) and to allow quickly checking whether a
 224      * property is set in this block.
 225      */
 226     property_set_type mPropertiesSet[kPropertiesSetChunkCount];
 227     /*
 228      * mPropertiesImportant indicates which properties are '!important'.
 229      */
 230     property_set_type mPropertiesImportant[kPropertiesSetChunkCount];
 231
 232 public:
 233     /*
 234      * Return the storage location within |this| of the value of the
 235      * property (i.e., either an |nsCSSValue*|, |nsCSSRect*|, or
 236      * |nsCSSValueList**| (etc.).
 237      */
 238     void* PropertyAt(nsCSSProperty aProperty) {
 239         const PropertyOffsetInfo& offsets =
 240             nsCSSExpandedDataBlock::kOffsetTable[aProperty];
 241         return reinterpret_cast<void*>(reinterpret_cast<char*>(this) +
 242                                           offsets.block_offset);
 243     }
 244
 245     /*
 246      * Return the storage location within |aRuleData| of the value of
 247      * the property (i.e., either an |nsCSSValue*|, |nsCSSRect*|, or
 248      * |nsCSSValueList**| (etc.).
 249      */
 250     static void* RuleDataPropertyAt(nsRuleData *aRuleData,
 251                                     nsCSSProperty aProperty) {
 252         const PropertyOffsetInfo& offsets =
 253             nsCSSExpandedDataBlock::kOffsetTable[aProperty];
 254         NS_ASSERTION(offsets.ruledata_struct_offset != size_t(-1),
 255                      "property should not use CSS_PROP_BACKENDONLY");
 256         char* cssstruct = *reinterpret_cast<char**>
 257                                            (reinterpret_cast<char*>(aRuleData) +
 258                               offsets.ruledata_struct_offset);
 259         return reinterpret_cast<void*>
 260                                (cssstruct + offsets.ruledata_member_offset);
 261     }
 262
 263     void AssertInSetRange(nsCSSProperty aProperty) {
 264         NS_ASSERTION(0 <= aProperty &&
 265                      aProperty < eCSSProperty_COUNT_no_shorthands,
 266                      "out of bounds");
 267     }
 268
 269     void SetPropertyBit(nsCSSProperty aProperty) {
 270         AssertInSetRange(aProperty);
 271         mPropertiesSet[aProperty / kPropertiesSetChunkSize] |=
 272             property_set_type(1 << (aProperty % kPropertiesSetChunkSize));
 273     }
 274
 275     void ClearPropertyBit(nsCSSProperty aProperty) {
 276         AssertInSetRange(aProperty);
 277         mPropertiesSet[aProperty / kPropertiesSetChunkSize] &=
 278             ~property_set_type(1 << (aProperty % kPropertiesSetChunkSize));
 279     }
 280
 281     PRBool HasPropertyBit(nsCSSProperty aProperty) {
 282         AssertInSetRange(aProperty);
 283         return (mPropertiesSet[aProperty / kPropertiesSetChunkSize] &
 284                 (1 << (aProperty % kPropertiesSetChunkSize))) != 0;
 285     }
 286
 287     void SetImportantBit(nsCSSProperty aProperty) {
 288         AssertInSetRange(aProperty);
 289         mPropertiesImportant[aProperty / kPropertiesSetChunkSize] |=
 290             property_set_type(1 << (aProperty % kPropertiesSetChunkSize));
 291     }
 292
 293     void ClearImportantBit(nsCSSProperty aProperty) {
 294         AssertInSetRange(aProperty);
 295         mPropertiesImportant[aProperty / kPropertiesSetChunkSize] &=
 296             ~property_set_type(1 << (aProperty % kPropertiesSetChunkSize));
 297     }
 298
 299     PRBool HasImportantBit(nsCSSProperty aProperty) {
 300         AssertInSetRange(aProperty);
 301         return (mPropertiesImportant[aProperty / kPropertiesSetChunkSize] &
 302                 (1 << (aProperty % kPropertiesSetChunkSize))) != 0;
 303     }
 304
 305     void ClearSets() {
 306         memset(mPropertiesSet, 0, sizeof(mPropertiesSet));
 307         memset(mPropertiesImportant, 0, sizeof(mPropertiesImportant));
 308     }
 309 };
 310
 311 #endif /* !defined(nsCSSDataBlock_h__) */