gecko-dev/layout/style/nsCSSDataBlock.h

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/* -*- 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.h.
*
* 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
*/
#ifndef nsCSSDataBlock_h__
#define nsCSSDataBlock_h__
#include "nsCSSProps.h"
#include "nsCSSPropertySet.h"
struct nsRuleData;
class nsCSSExpandedDataBlock;
namespace mozilla {
namespace css {
class Declaration;
}
}
/*
* nsCSSCompressedDataBlock holds property-value pairs corresponding
* to CSS declaration blocks. Each pair is stored in a CDBValueStorage
* object; these objects form an array at the end of the data block.
*/
struct CDBValueStorage {
nsCSSProperty property;
nsCSSValue value;
};
/**
* An |nsCSSCompressedDataBlock| holds a usually-immutable chunk of
* property-value data for a CSS declaration block (which we misname a
* |css::Declaration|). Mutation is accomplished through
* |nsCSSExpandedDataBlock| or in some cases via direct slot access.
*/
class nsCSSCompressedDataBlock {
private:
friend class nsCSSExpandedDataBlock;
// Only this class (via |CreateEmptyBlock|) or nsCSSExpandedDataBlock
// (in |Compress|) can create compressed data blocks.
nsCSSCompressedDataBlock() : mStyleBits(0) {}
public:
~nsCSSCompressedDataBlock();
/**
* Do what |nsIStyleRule::MapRuleInfoInto| needs to do for a style
* rule using this block for storage.
*/
void MapRuleInfoInto(nsRuleData *aRuleData) const;
/**
* Return the location at which the *value* for the property is
* stored, or null if the block does not contain a value for the
* property.
*
* Inefficient (by design).
*
* Must not be called for shorthands.
*/
const nsCSSValue* ValueFor(nsCSSProperty aProperty) const;
/**
* Attempt to replace the value for |aProperty| stored in this block
* with the matching value stored in |aFromBlock|.
* This method will fail (returning false) if |aProperty| is not
* already in this block. It will set |aChanged| to true if it
* actually made a change to the block, but regardless, if it
* returns true, the value in |aFromBlock| was erased.
*/
bool TryReplaceValue(nsCSSProperty aProperty,
nsCSSExpandedDataBlock& aFromBlock,
bool* aChanged);
/**
* Clone this block, or return null on out-of-memory.
*/
nsCSSCompressedDataBlock* Clone() const;
/**
* Create a new nsCSSCompressedDataBlock holding no declarations.
*/
static nsCSSCompressedDataBlock* CreateEmptyBlock();
private:
void* operator new(size_t aBaseSize, size_t aDataSize) {
NS_ABORT_IF_FALSE(aBaseSize == sizeof(nsCSSCompressedDataBlock),
"unexpected size for nsCSSCompressedDataBlock");
return ::operator new(aBaseSize + aDataSize);
}
/**
* Delete all the data stored in this block, and the block itself.
*/
void Destroy();
PRInt32 mStyleBits; // the structs for which we have data, according to
// |nsCachedStyleData::GetBitForSID|.
PRUint32 mDataSize;
// CDBValueStorage elements are stored after these fields. Space for them
// is allocated in |operator new| above. The static assertions following
// this class make sure that the CDBValueStorage elements are aligned
// appropriately.
char* Block() { return (char*)this + sizeof(*this); }
char* BlockEnd() { return Block() + mDataSize; }
const char* Block() const { return (char*)this + sizeof(*this); }
const char* BlockEnd() const { return Block() + mDataSize; }
void SetBlockEnd(char *blockEnd) {
/*
* Note: if we ever change nsCSSDeclaration to store the declarations
* in order and also store repeated declarations of the same property,
* then we need to worry about checking for integer overflow here.
*/
NS_ABORT_IF_FALSE(size_t(blockEnd - Block()) <= size_t(PR_UINT32_MAX),
"overflow of mDataSize");
mDataSize = PRUint32(blockEnd - Block());
}
ptrdiff_t DataSize() const { return mDataSize; }
};
/* Make sure the CDBValueStorage elements are aligned appropriately. */
PR_STATIC_ASSERT(sizeof(nsCSSCompressedDataBlock) == 8);
PR_STATIC_ASSERT(NS_ALIGNMENT_OF(CDBValueStorage) <= 8);
class nsCSSExpandedDataBlock {
friend class nsCSSCompressedDataBlock;
public:
nsCSSExpandedDataBlock();
~nsCSSExpandedDataBlock();
private:
/* Property storage may not be accessed directly; use AddLonghandProperty
* and friends.
*/
nsCSSValue mValues[eCSSProperty_COUNT_no_shorthands];
public:
/**
* Transfer all of the state from a pair of compressed data blocks
* to this expanded block. This expanded block must be clear
* beforehand.
*
* This method DELETES both of the compressed data blocks it is
* passed. (This is necessary because ownership of sub-objects
* is transferred to the expanded block.)
*/
void Expand(nsCSSCompressedDataBlock *aNormalBlock,
nsCSSCompressedDataBlock *aImportantBlock);
/**
* Allocate new compressed blocks and transfer all of the state
* from this expanded block to the new blocks, clearing this
* expanded block. A normal block will always be allocated, but
* an important block will only be allocated if there are
* !important properties in the expanded block; otherwise
* |*aImportantBlock| will be set to null.
*/
void Compress(nsCSSCompressedDataBlock **aNormalBlock,
nsCSSCompressedDataBlock **aImportantBlock);
/**
* Copy a value into this expanded block. This does NOT destroy
* the source value object. |aProperty| cannot be a shorthand.
*/
void AddLonghandProperty(nsCSSProperty aProperty, const nsCSSValue& aValue);
/**
* Clear the state of this expanded block.
*/
void Clear();
/**
* Clear the data for the given property (including the set and
* important bits). Can be used with shorthand properties.
*/
void ClearProperty(nsCSSProperty aPropID);
/**
* Same as ClearProperty, but faster and cannot be used with shorthands.
*/
void ClearLonghandProperty(nsCSSProperty aPropID);
/**
* Transfer the state for |aPropID| (which may be a shorthand)
* from |aFromBlock| to this block. The property being transferred
* is !important if |aIsImportant| is true, and should replace an
* existing !important property regardless of its own importance
* if |aOverrideImportant| is true.
*
* Returns true if something changed, false otherwise. Calls
* |ValueAppended| on |aDeclaration| if the property was not
* previously set, or in any case if |aMustCallValueAppended| is true.
*/
bool TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
nsCSSProperty aPropID,
bool aIsImportant,
bool aOverrideImportant,
bool aMustCallValueAppended,
mozilla::css::Declaration* aDeclaration);
void AssertInitialState() {
#ifdef DEBUG
DoAssertInitialState();
#endif
}
private:
/**
* Compute the size that will be occupied by the result of
* |Compress|.
*/
struct ComputeSizeResult {
PRUint32 normal, important;
};
ComputeSizeResult ComputeSize();
void DoExpand(nsCSSCompressedDataBlock *aBlock, bool aImportant);
/**
* Worker for TransferFromBlock; cannot be used with shorthands.
*/
bool DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
nsCSSProperty aPropID,
bool aIsImportant,
bool aOverrideImportant,
bool aMustCallValueAppended,
mozilla::css::Declaration* aDeclaration);
#ifdef DEBUG
void DoAssertInitialState();
#endif
/*
* mPropertiesSet stores a bit for every property that is present,
* to optimize compression of blocks with small numbers of
* properties (the norm) and to allow quickly checking whether a
* property is set in this block.
*/
nsCSSPropertySet mPropertiesSet;
/*
* mPropertiesImportant indicates which properties are '!important'.
*/
nsCSSPropertySet mPropertiesImportant;
/*
* Return the storage location within |this| of the value of the
* property |aProperty|.
*/
nsCSSValue* PropertyAt(nsCSSProperty aProperty) {
NS_ABORT_IF_FALSE(0 <= aProperty &&
aProperty < eCSSProperty_COUNT_no_shorthands,
"property out of range");
return &mValues[aProperty];
}
void SetPropertyBit(nsCSSProperty aProperty) {
mPropertiesSet.AddProperty(aProperty);
}
void ClearPropertyBit(nsCSSProperty aProperty) {
mPropertiesSet.RemoveProperty(aProperty);
}
bool HasPropertyBit(nsCSSProperty aProperty) {
return mPropertiesSet.HasProperty(aProperty);
}
void SetImportantBit(nsCSSProperty aProperty) {
mPropertiesImportant.AddProperty(aProperty);
}
void ClearImportantBit(nsCSSProperty aProperty) {
mPropertiesImportant.RemoveProperty(aProperty);
}
bool HasImportantBit(nsCSSProperty aProperty) {
return mPropertiesImportant.HasProperty(aProperty);
}
void ClearSets() {
mPropertiesSet.Empty();
mPropertiesImportant.Empty();
}
};
#endif /* !defined(nsCSSDataBlock_h__) */