gecko/layout/style/nsCSSDataBlock.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is nsCSSDataBlock.cpp.
 *
 * The Initial Developer of the Original Code is L. David Baron.
 * Portions created by the Initial Developer are Copyright (C) 2003
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   L. David Baron <dbaron@dbaron.org> (original author)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

/*
 * compact representation of the property-value pairs within a CSS
 * declaration, and the code for expanding and compacting it
 */

#include "nsCSSDataBlock.h"
#include "mozilla/css/Declaration.h"
#include "nsCSSProps.h"
#include "nsRuleData.h"
#include "nsRuleNode.h"
#include "nsStyleSet.h"
#include "nsStyleContext.h"

namespace css = mozilla::css;

/*
 * nsCSSCompressedDataBlock holds property-value pairs corresponding
 * to CSS declaration blocks.  The value is stored in one of the three
 * CSS data types: nsCSSValue, nsCSSValueList, and nsCSSValuePairList,
 * which each correspond to a value of the nsCSSType enumeration.
 *
 * The storage strategy uses the CDB*Storage structs below to help
 * ensure that all the types remain properly aligned.  nsCSSValue's
 * alignment requirements cannot be weaker than any others, since it
 * contains a pointer and an enumeration.
 *
 * nsCSSValue objects are stored directly in the block; list types
 * have only a pointer to the first element in the list stored in the
 * block.
 */

struct CDBValueStorage {
    nsCSSProperty property;
    nsCSSValue value;
};

struct CDBPointerStorage {
    nsCSSProperty property;
    void *value;
};

enum {
    CDBValueStorage_advance = sizeof(CDBValueStorage),
    // round up using the closest estimate we can get of the alignment
    // requirements of nsCSSValue:
    CDBPointerStorage_advance = PR_ROUNDUP(sizeof(CDBPointerStorage),
                                sizeof(CDBValueStorage) - sizeof(nsCSSValue))
};

/*
 * Define a bunch of utility functions for getting the property or any
 * of the value types when the cursor is at the beginning of the storage
 * for the property-value pair.  The versions taking a non-const cursor
 * argument return a reference so that the caller can assign into the
 * result.
 */

inline nsCSSProperty& PropertyAtCursor(char *aCursor) {
    return *reinterpret_cast<nsCSSProperty*>(aCursor);
}

inline nsCSSProperty PropertyAtCursor(const char *aCursor) {
    return *reinterpret_cast<const nsCSSProperty*>(aCursor);
}

inline nsCSSValue* ValueAtCursor(char *aCursor) {
    return & reinterpret_cast<CDBValueStorage*>(aCursor)->value;
}

inline const nsCSSValue* ValueAtCursor(const char *aCursor) {
    return & reinterpret_cast<const CDBValueStorage*>(aCursor)->value;
}

inline void*& PointerAtCursor(char *aCursor) {
    return reinterpret_cast<CDBPointerStorage*>(aCursor)->value;
}

inline void* PointerAtCursor(const char *aCursor) {
    return reinterpret_cast<const CDBPointerStorage*>(aCursor)->value;
}

inline nsCSSValueList*& ValueListAtCursor(char *aCursor) {
    return * reinterpret_cast<nsCSSValueList**>
                             (& reinterpret_cast<CDBPointerStorage*>(aCursor)->value);
}

inline nsCSSValueList* ValueListAtCursor(const char *aCursor) {
    return static_cast<nsCSSValueList*>
                      (reinterpret_cast<const CDBPointerStorage*>(aCursor)->value);
}

inline nsCSSValuePairList*& ValuePairListAtCursor(char *aCursor) {
    return * reinterpret_cast<nsCSSValuePairList**>
                             (& reinterpret_cast<CDBPointerStorage*>(aCursor)->value);
}

inline nsCSSValuePairList* ValuePairListAtCursor(const char *aCursor) {
    return static_cast<nsCSSValuePairList*>
                      (reinterpret_cast<const CDBPointerStorage*>(aCursor)->value);
}

static PRBool
ShouldIgnoreColors(nsRuleData *aRuleData)
{
    return aRuleData->mLevel != nsStyleSet::eAgentSheet &&
           aRuleData->mLevel != nsStyleSet::eUserSheet &&
           !aRuleData->mPresContext->UseDocumentColors();
}

/**
 * Tries to call |nsCSSValue::StartImageLoad()| on an image source.
 * Image sources are specified by |url()| or |-moz-image-rect()| function.
 */
static void
TryToStartImageLoadOnValue(const nsCSSValue& aValue, nsIDocument* aDocument)
{
  if (aValue.GetUnit() == eCSSUnit_URL) {
    aValue.StartImageLoad(aDocument);
  }
  else if (aValue.EqualsFunction(eCSSKeyword__moz_image_rect)) {
    nsCSSValue::Array* arguments = aValue.GetArrayValue();
    NS_ABORT_IF_FALSE(arguments->Count() == 6, "unexpected num of arguments");

    const nsCSSValue& image = arguments->Item(1);
    if (image.GetUnit() == eCSSUnit_URL)
      image.StartImageLoad(aDocument);
  }
}

static void
TryToStartImageLoad(const nsCSSValue& aValue, nsIDocument* aDocument,
                    nsCSSProperty aProperty)
{
  if (nsCSSProps::PropHasFlags(aProperty, CSS_PROPERTY_IMAGE_IS_IN_ARRAY_0)) {
    if (aValue.GetUnit() == eCSSUnit_Array) {
      TryToStartImageLoadOnValue(aValue.GetArrayValue()->Item(0), aDocument);
    }
  } else {
    TryToStartImageLoadOnValue(aValue, aDocument);
  }
}

static inline PRBool
ShouldStartImageLoads(nsRuleData *aRuleData, nsCSSProperty aProperty)
{
  // Don't initiate image loads for if-visited styles.  This is
  // important because:
  //  (1) it's a waste of CPU and bandwidth
  //  (2) in some cases we'd start the image load on a style change
  //      where we wouldn't have started the load initially, which makes
  //      which links are visited detectable to Web pages (see bug
  //      557287)
  return !aRuleData->mStyleContext->IsStyleIfVisited() &&
         nsCSSProps::PropHasFlags(aProperty, CSS_PROPERTY_START_IMAGE_LOADS);
}

void
nsCSSCompressedDataBlock::MapRuleInfoInto(nsRuleData *aRuleData) const
{
    // If we have no data for these structs, then return immediately.
    // This optimization should make us return most of the time, so we
    // have to worry much less (although still some) about the speed of
    // the rest of the function.
    if (!(aRuleData->mSIDs & mStyleBits))
        return;

    nsIDocument* doc = aRuleData->mPresContext->Document();

    const char* cursor = Block();
    const char* cursor_end = BlockEnd();
    while (cursor < cursor_end) {
        nsCSSProperty iProp = PropertyAtCursor(cursor);
        NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                     "out of range");
        if (nsCachedStyleData::GetBitForSID(nsCSSProps::kSIDTable[iProp]) &
            aRuleData->mSIDs) {
            void *prop = aRuleData->StorageFor(iProp);
            switch (nsCSSProps::kTypeTable[iProp]) {
                case eCSSType_Value: {
                    nsCSSValue* target = static_cast<nsCSSValue*>(prop);
                    if (target->GetUnit() == eCSSUnit_Null) {
                        const nsCSSValue *val = ValueAtCursor(cursor);
                        NS_ASSERTION(val->GetUnit() != eCSSUnit_Null, "oops");
                        if (ShouldStartImageLoads(aRuleData, iProp)) {
                            TryToStartImageLoad(*val, doc, iProp);
                        }
                        *target = *val;
                        if (iProp == eCSSProperty_font_family) {
                            // XXX Are there other things like this?
                            aRuleData->mFontData->mFamilyFromHTML = PR_FALSE;
                        }
                        if (nsCSSProps::PropHasFlags(iProp,
                                CSS_PROPERTY_IGNORED_WHEN_COLORS_DISABLED) &&
                            ShouldIgnoreColors(aRuleData))
                        {
                            if (iProp == eCSSProperty_background_color) {
                                // Force non-'transparent' background
                                // colors to the user's default.
                                if (target->IsNonTransparentColor()) {
                                    target->SetColorValue(aRuleData->
                                        mPresContext->
                                        DefaultBackgroundColor());
                                }
                            } else {
                                // Ignore 'color', 'border-*-color', etc.
                                *target = nsCSSValue();
                            }
                        }
                    }
                    cursor += CDBValueStorage_advance;
                } break;

                case eCSSType_ValueList: {
                    void** target = static_cast<void**>(prop);
                    if (!*target) {
                        if (ShouldStartImageLoads(aRuleData, iProp)) {
                            for (nsCSSValueList* l = ValueListAtCursor(cursor);
                                 l; l = l->mNext) {
                                TryToStartImageLoad(l->mValue, doc, iProp);
                            }
                        }

                        void* val = PointerAtCursor(cursor);
                        NS_ASSERTION(val, "oops");
                        *target = val;

                        if (nsCSSProps::PropHasFlags(iProp,
                                CSS_PROPERTY_IGNORED_WHEN_COLORS_DISABLED) &&
                            ShouldIgnoreColors(aRuleData))
                        {
                            *target = nsnull;
                        }
                    }
                    cursor += CDBPointerStorage_advance;
                } break;
            }
        } else {
            switch (nsCSSProps::kTypeTable[iProp]) {
                case eCSSType_Value: {
                    cursor += CDBValueStorage_advance;
                } break;

                case eCSSType_ValueList: {
                    cursor += CDBPointerStorage_advance;
                } break;
            }
        }
    }
    NS_ASSERTION(cursor == cursor_end, "inconsistent data");
}

const void*
nsCSSCompressedDataBlock::StorageFor(nsCSSProperty aProperty) const
{
    NS_PRECONDITION(!nsCSSProps::IsShorthand(aProperty),
                    "Don't call for shorthands");

    // If we have no data for this struct, then return immediately.
    // This optimization should make us return most of the time, so we
    // have to worry much less (although still some) about the speed of
    // the rest of the function.
    if (!(nsCachedStyleData::GetBitForSID(nsCSSProps::kSIDTable[aProperty]) &
          mStyleBits))
        return nsnull;

    const char* cursor = Block();
    const char* cursor_end = BlockEnd();
    while (cursor < cursor_end) {
        nsCSSProperty iProp = PropertyAtCursor(cursor);
        NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                     "out of range");
        if (iProp == aProperty) {
            switch (nsCSSProps::kTypeTable[iProp]) {
                case eCSSType_Value: {
                    return ValueAtCursor(cursor);
                }
                case eCSSType_ValueList: {
                    return &PointerAtCursor(const_cast<char*>(cursor));
                }
            }
        }
        switch (nsCSSProps::kTypeTable[iProp]) {
            case eCSSType_Value: {
                cursor += CDBValueStorage_advance;
            } break;

            case eCSSType_ValueList: {
                cursor += CDBPointerStorage_advance;
            } break;
        }
    }
    NS_ASSERTION(cursor == cursor_end, "inconsistent data");

    return nsnull;
}

nsCSSCompressedDataBlock*
nsCSSCompressedDataBlock::Clone() const
{
    const char *cursor = Block(), *cursor_end = BlockEnd();
    char *result_cursor;

    nsAutoPtr<nsCSSCompressedDataBlock> result
        (new(cursor_end - cursor) nsCSSCompressedDataBlock());
    if (!result)
        return nsnull;
    result_cursor = result->Block();

    while (cursor < cursor_end) {
        nsCSSProperty iProp = PropertyAtCursor(cursor);
        NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                     "out of range");
        PropertyAtCursor(result_cursor) = iProp;

        switch (nsCSSProps::kTypeTable[iProp]) {
            case eCSSType_Value: {
                const nsCSSValue* val = ValueAtCursor(cursor);
                NS_ASSERTION(val->GetUnit() != eCSSUnit_Null, "oops");
                nsCSSValue *result_val = ValueAtCursor(result_cursor);
                new (result_val) nsCSSValue(*val);
                cursor += CDBValueStorage_advance;
                result_cursor +=  CDBValueStorage_advance;
            } break;

            case eCSSType_ValueList: {
                void *copy = ValueListAtCursor(cursor)->Clone();
                if (!copy) {
                    // so the destructor knows where to stop clearing
                    result->mBlockEnd = result_cursor;
                    return nsnull;
                }
                PointerAtCursor(result_cursor) = copy;
                cursor += CDBPointerStorage_advance;
                result_cursor += CDBPointerStorage_advance;
            } break;
        }
    }
    NS_ASSERTION(cursor == cursor_end, "inconsistent data");

    result->mBlockEnd = result_cursor;
    result->mStyleBits = mStyleBits;
    NS_ASSERTION(result->DataSize() == DataSize(), "wrong size");

    return result.forget();
}

nsCSSCompressedDataBlock::~nsCSSCompressedDataBlock()
{
    const char* cursor = Block();
    const char* cursor_end = BlockEnd();
    while (cursor < cursor_end) {
        nsCSSProperty iProp = PropertyAtCursor(cursor);
        NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                     "out of range");

        switch (nsCSSProps::kTypeTable[iProp]) {
            case eCSSType_Value: {
                const nsCSSValue* val = ValueAtCursor(cursor);
                NS_ASSERTION(val->GetUnit() != eCSSUnit_Null, "oops");
                val->~nsCSSValue();
                cursor += CDBValueStorage_advance;
            } break;

            case eCSSType_ValueList: {
                nsCSSValueList* val = ValueListAtCursor(cursor);
                NS_ASSERTION(val, "oops");
                delete val;
                cursor += CDBPointerStorage_advance;
            } break;
        }
    }
    NS_ASSERTION(cursor == cursor_end, "inconsistent data");
}

/* static */ nsCSSCompressedDataBlock*
nsCSSCompressedDataBlock::CreateEmptyBlock()
{
    nsCSSCompressedDataBlock *result = new(0) nsCSSCompressedDataBlock();
    result->mBlockEnd = result->Block();
    return result;
}

/* static */ void
nsCSSCompressedDataBlock::MoveValue(void *aSource, void *aDest,
                                    nsCSSProperty aPropID,
                                    PRBool* aChanged)
{
  switch (nsCSSProps::kTypeTable[aPropID]) {
    case eCSSType_Value: {
      nsCSSValue *source = static_cast<nsCSSValue*>(aSource);
      nsCSSValue *dest = static_cast<nsCSSValue*>(aDest);
      if (*source != *dest)
        *aChanged = PR_TRUE;
      dest->~nsCSSValue();
      memcpy(dest, source, sizeof(nsCSSValue));
      new (source) nsCSSValue();
    } break;

    case eCSSType_ValueList: {
      nsCSSValueList **source = static_cast<nsCSSValueList**>(aSource);
      nsCSSValueList **dest = static_cast<nsCSSValueList**>(aDest);
      if (**source != **dest)
        *aChanged = PR_TRUE;
      delete *dest;
      *dest = *source;
      *source = nsnull;
    } break;
  }
}

/*****************************************************************************/

nsCSSExpandedDataBlock::nsCSSExpandedDataBlock()
{
    AssertInitialState();
}

nsCSSExpandedDataBlock::~nsCSSExpandedDataBlock()
{
    AssertInitialState();
}

const size_t
nsCSSExpandedDataBlock::kOffsetTable[] = {
    #define CSS_PROP(name_, id_, method_, flags_, datastruct_, member_, type_, \
                     kwtable_, stylestruct_, stylestructoffset_, animtype_)    \
        offsetof(nsCSSExpandedDataBlock, m##datastruct_.member_),
    #include "nsCSSPropList.h"
    #undef CSS_PROP
};

void
nsCSSExpandedDataBlock::DoExpand(nsCSSCompressedDataBlock *aBlock,
                                 PRBool aImportant)
{
    /*
     * Save needless copying and allocation by copying the memory
     * corresponding to the stored data in the compressed block.
     */
    const char* cursor = aBlock->Block();
    const char* cursor_end = aBlock->BlockEnd();
    while (cursor < cursor_end) {
        nsCSSProperty iProp = PropertyAtCursor(cursor);
        NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                     "out of range");
        NS_ASSERTION(!HasPropertyBit(iProp),
                     "compressed block has property multiple times");
        SetPropertyBit(iProp);
        if (aImportant)
            SetImportantBit(iProp);
        void *prop = PropertyAt(iProp);

        switch (nsCSSProps::kTypeTable[iProp]) {
            case eCSSType_Value: {
                const nsCSSValue* val = ValueAtCursor(cursor);
                nsCSSValue* dest = static_cast<nsCSSValue*>(prop);
                NS_ASSERTION(val->GetUnit() != eCSSUnit_Null, "oops");
                NS_ASSERTION(dest->GetUnit() == eCSSUnit_Null,
                             "expanding into non-empty block");
#ifdef NS_BUILD_REFCNT_LOGGING
                dest->~nsCSSValue();
#endif
                memcpy(dest, val, sizeof(nsCSSValue));
                cursor += CDBValueStorage_advance;
            } break;

            case eCSSType_ValueList: {
                void* val = PointerAtCursor(cursor);
                void** dest = static_cast<void**>(prop);
                NS_ASSERTION(val, "oops");
                NS_ASSERTION(!*dest, "expanding into non-empty block");
                *dest = val;
                cursor += CDBPointerStorage_advance;
            } break;
        }
    }
    NS_ASSERTION(cursor == cursor_end, "inconsistent data");

    // Don't destroy remnants of what we just copied
    aBlock->mBlockEnd = aBlock->Block();
    delete aBlock;
}

void
nsCSSExpandedDataBlock::Expand(nsCSSCompressedDataBlock *aNormalBlock,
                               nsCSSCompressedDataBlock *aImportantBlock)
{
    NS_PRECONDITION(aNormalBlock, "unexpected null block");
    AssertInitialState();

    DoExpand(aNormalBlock, PR_FALSE);
    if (aImportantBlock) {
        DoExpand(aImportantBlock, PR_TRUE);
    }
}

nsCSSExpandedDataBlock::ComputeSizeResult
nsCSSExpandedDataBlock::ComputeSize()
{
    ComputeSizeResult result = {0, 0};
    for (size_t iHigh = 0; iHigh < nsCSSPropertySet::kChunkCount; ++iHigh) {
        if (!mPropertiesSet.HasPropertyInChunk(iHigh))
            continue;
        for (size_t iLow = 0; iLow < nsCSSPropertySet::kBitsInChunk; ++iLow) {
            if (!mPropertiesSet.HasPropertyAt(iHigh, iLow))
                continue;
            nsCSSProperty iProp = nsCSSPropertySet::CSSPropertyAt(iHigh, iLow);
            NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                         "out of range");
#ifdef DEBUG
            void *prop = PropertyAt(iProp);
#endif
            PRUint32 increment = 0;
            switch (nsCSSProps::kTypeTable[iProp]) {
                case eCSSType_Value: {
#ifdef DEBUG
                    nsCSSValue* val = static_cast<nsCSSValue*>(prop);
                    NS_ASSERTION(val->GetUnit() != eCSSUnit_Null,
                                 "null value while computing size");
#endif
                    increment = CDBValueStorage_advance;
                } break;

                case eCSSType_ValueList: {
#ifdef DEBUG
                    void* val = *static_cast<void**>(prop);
                    NS_ASSERTION(val, "Null pointer while computing size");
#endif
                    increment = CDBPointerStorage_advance;
                } break;
            }
            if (mPropertiesImportant.HasPropertyAt(iHigh, iLow))
                result.important += increment;
            else
                result.normal += increment;
        }
    }
    return result;
}

void
nsCSSExpandedDataBlock::Compress(nsCSSCompressedDataBlock **aNormalBlock,
                                 nsCSSCompressedDataBlock **aImportantBlock)
{
    nsAutoPtr<nsCSSCompressedDataBlock> result_normal, result_important;
    char *cursor_normal, *cursor_important;

    ComputeSizeResult size = ComputeSize();

    result_normal = new(size.normal) nsCSSCompressedDataBlock();
    if (!result_normal) {
        *aNormalBlock = nsnull;
        *aImportantBlock = nsnull;
        return;
    }
    cursor_normal = result_normal->Block();

    if (size.important != 0) {
        result_important = new(size.important) nsCSSCompressedDataBlock();
        if (!result_important) {
            *aNormalBlock = nsnull;
            *aImportantBlock = nsnull;
            return;
        }
        cursor_important = result_important->Block();
    } else {
        result_important = nsnull;
    }

    /*
     * Save needless copying and allocation by copying the memory
     * corresponding to the stored data in the expanded block, and then
     * clearing the data in the expanded block.
     */
    for (size_t iHigh = 0; iHigh < nsCSSPropertySet::kChunkCount; ++iHigh) {
        if (!mPropertiesSet.HasPropertyInChunk(iHigh))
            continue;
        for (size_t iLow = 0; iLow < nsCSSPropertySet::kBitsInChunk; ++iLow) {
            if (!mPropertiesSet.HasPropertyAt(iHigh, iLow))
                continue;
            nsCSSProperty iProp = nsCSSPropertySet::CSSPropertyAt(iHigh, iLow);
            NS_ASSERTION(0 <= iProp && iProp < eCSSProperty_COUNT_no_shorthands,
                         "out of range");
            void *prop = PropertyAt(iProp);
            PRBool important =
                mPropertiesImportant.HasPropertyAt(iHigh, iLow);
            char *&cursor = important ? cursor_important : cursor_normal;
            nsCSSCompressedDataBlock *result =
                important ? result_important : result_normal;
            switch (nsCSSProps::kTypeTable[iProp]) {
                case eCSSType_Value: {
                    nsCSSValue* val = static_cast<nsCSSValue*>(prop);
                    NS_ASSERTION(val->GetUnit() != eCSSUnit_Null,
                                 "Null value while compressing");
                    CDBValueStorage *storage =
                        reinterpret_cast<CDBValueStorage*>(cursor);
                    storage->property = iProp;
                    memcpy(&storage->value, val, sizeof(nsCSSValue));
                    new (val) nsCSSValue();
                    cursor += CDBValueStorage_advance;
                } break;

                case eCSSType_ValueList: {
                    void*& val = *static_cast<void**>(prop);
                    NS_ASSERTION(val, "Null pointer while compressing");
                    CDBPointerStorage *storage =
                        reinterpret_cast<CDBPointerStorage*>(cursor);
                    storage->property = iProp;
                    storage->value = val;
                    val = nsnull;
                    cursor += CDBPointerStorage_advance;
                } break;
            }
            result->mStyleBits |=
                nsCachedStyleData::GetBitForSID(nsCSSProps::kSIDTable[iProp]);
        }
    }

    result_normal->mBlockEnd = cursor_normal;
    NS_ASSERTION(result_normal->DataSize() == ptrdiff_t(size.normal),
                 "size miscalculation");
    if (result_important) {
        result_important->mBlockEnd = cursor_important;
        NS_ASSERTION(result_important->DataSize() == ptrdiff_t(size.important),
                     "size miscalculation");
    }

    ClearSets();
    AssertInitialState();
    *aNormalBlock = result_normal.forget();
    *aImportantBlock = result_important.forget();
}

void
nsCSSExpandedDataBlock::Clear()
{
    for (size_t iHigh = 0; iHigh < nsCSSPropertySet::kChunkCount; ++iHigh) {
        if (!mPropertiesSet.HasPropertyInChunk(iHigh))
            continue;
        for (size_t iLow = 0; iLow < nsCSSPropertySet::kBitsInChunk; ++iLow) {
            if (!mPropertiesSet.HasPropertyAt(iHigh, iLow))
                continue;
            nsCSSProperty iProp = nsCSSPropertySet::CSSPropertyAt(iHigh, iLow);
            ClearLonghandProperty(iProp);
        }
    }

    AssertInitialState();
}

void
nsCSSExpandedDataBlock::ClearProperty(nsCSSProperty aPropID)
{
  if (nsCSSProps::IsShorthand(aPropID)) {
    CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(p, aPropID) {
      ClearLonghandProperty(*p);
    }
  } else {
    ClearLonghandProperty(aPropID);
  }
}

void
nsCSSExpandedDataBlock::ClearLonghandProperty(nsCSSProperty aPropID)
{
    NS_ABORT_IF_FALSE(0 <= aPropID &&
                      aPropID < eCSSProperty_COUNT_no_shorthands,
                      "out of range");

    ClearPropertyBit(aPropID);
    ClearImportantBit(aPropID);

    void *prop = PropertyAt(aPropID);
    switch (nsCSSProps::kTypeTable[aPropID]) {
        case eCSSType_Value: {
            nsCSSValue* val = static_cast<nsCSSValue*>(prop);
            val->Reset();
        } break;

        case eCSSType_ValueList: {
            nsCSSValueList*& val = *static_cast<nsCSSValueList**>(prop);
            if (val) {
                delete val;
                val = nsnull;
            }
        } break;
    }
}

void
nsCSSExpandedDataBlock::TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
                                          nsCSSProperty aPropID,
                                          PRBool aIsImportant,
                                          PRBool aOverrideImportant,
                                          PRBool aMustCallValueAppended,
                                          css::Declaration* aDeclaration,
                                          PRBool* aChanged)
{
  if (nsCSSProps::IsShorthand(aPropID)) {
    CSSPROPS_FOR_SHORTHAND_SUBPROPERTIES(p, aPropID) {
      DoTransferFromBlock(aFromBlock, *p, aIsImportant, aOverrideImportant,
                          aMustCallValueAppended, aDeclaration, aChanged);
    }
  } else {
    DoTransferFromBlock(aFromBlock, aPropID, aIsImportant, aOverrideImportant,
                        aMustCallValueAppended, aDeclaration, aChanged);
  }
}

void
nsCSSExpandedDataBlock::DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
                                            nsCSSProperty aPropID,
                                            PRBool aIsImportant,
                                            PRBool aOverrideImportant,
                                            PRBool aMustCallValueAppended,
                                            css::Declaration* aDeclaration,
                                            PRBool* aChanged)
{
  NS_ASSERTION(aFromBlock.HasPropertyBit(aPropID), "oops");
  if (aIsImportant) {
    if (!HasImportantBit(aPropID))
      *aChanged = PR_TRUE;
    SetImportantBit(aPropID);
  } else {
    if (HasImportantBit(aPropID)) {
      // When parsing a declaration block, an !important declaration
      // is not overwritten by an ordinary declaration of the same
      // property later in the block.  However, CSSOM manipulations
      // come through here too, and in that case we do want to
      // overwrite the property.
      if (!aOverrideImportant) {
        aFromBlock.ClearLonghandProperty(aPropID);
        return;
      }
      *aChanged = PR_TRUE;
      ClearImportantBit(aPropID);
    }
  }

  if (aMustCallValueAppended || !HasPropertyBit(aPropID)) {
    aDeclaration->ValueAppended(aPropID);
  }

  SetPropertyBit(aPropID);
  aFromBlock.ClearPropertyBit(aPropID);

  /*
   * Save needless copying and allocation by calling the destructor in
   * the destination, copying memory directly, and then using placement
   * new.
   */
  void *v_source = aFromBlock.PropertyAt(aPropID);
  void *v_dest = PropertyAt(aPropID);
  nsCSSCompressedDataBlock::MoveValue(v_source, v_dest, aPropID, aChanged);
}

#ifdef DEBUG
void
nsCSSExpandedDataBlock::DoAssertInitialState()
{
    mPropertiesSet.AssertIsEmpty("not initial state");
    mPropertiesImportant.AssertIsEmpty("not initial state");

    for (PRUint32 i = 0; i < eCSSProperty_COUNT_no_shorthands; ++i) {
        void *prop = PropertyAt(nsCSSProperty(i));
        switch (nsCSSProps::kTypeTable[i]) {
            case eCSSType_Value: {
                nsCSSValue* val = static_cast<nsCSSValue*>(prop);
                NS_ASSERTION(val->GetUnit() == eCSSUnit_Null,
                             "not initial state");
            } break;

            case eCSSType_ValueList: {
                nsCSSValueList* val = *static_cast<nsCSSValueList**>(prop);
                NS_ASSERTION(val == nsnull, "not initial state");
            } break;
        }
    }
}
#endif