1 files changed, 372 insertions, 0 deletions
diff --git a/layout/style/nsCSSDataBlock.h b/layout/style/nsCSSDataBlock.h
new file mode 100644
index 000000000..76deaa911
--- /dev/null
+++ b/layout/style/nsCSSDataBlock.h
@@ -0,0 +1,372 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/*
+ * 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 "mozilla/MemoryReporting.h"
+#include "nsCSSProps.h"
+#include "nsCSSPropertyIDSet.h"
+#include "nsCSSValue.h"
+#include "nsStyleStruct.h"
+#include "imgRequestProxy.h"
+
+struct nsRuleData;
+class nsCSSExpandedDataBlock;
+class nsIDocument;
+
+namespace mozilla {
+namespace css {
+class Declaration;
+} // namespace css
+} // namespace mozilla
+
+/**
+ * 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.
+  explicit nsCSSCompressedDataBlock(uint32_t aNumProps)
+    : mStyleBits(0), mNumProps(aNumProps)
+  {}
+
+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(nsCSSPropertyID 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(nsCSSPropertyID 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();
+
+  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+
+  bool HasDefaultBorderImageSlice() const;
+  bool HasDefaultBorderImageWidth() const;
+  bool HasDefaultBorderImageOutset() const;
+  bool HasDefaultBorderImageRepeat() const;
+
+  bool HasInheritedStyleData() const
+  {
+    return mStyleBits & NS_STYLE_INHERITED_STRUCT_MASK;
+  }
+
+private:
+  void* operator new(size_t aBaseSize, uint32_t aNumProps) {
+    MOZ_ASSERT(aBaseSize == sizeof(nsCSSCompressedDataBlock),
+               "unexpected size for nsCSSCompressedDataBlock");
+    return ::operator new(aBaseSize + DataSize(aNumProps));
+  }
+
+public:
+  // Ideally, |nsCSSPropertyID| would be |enum nsCSSPropertyID : int16_t|.  But
+  // not all of the compilers we use are modern enough to support small
+  // enums.  So we manually squeeze nsCSSPropertyID into 16 bits ourselves.
+  // The static assertion below ensures it fits.
+  typedef int16_t CompressedCSSProperty;
+  static const size_t MaxCompressedCSSProperty = INT16_MAX;
+
+private:
+  static size_t DataSize(uint32_t aNumProps) {
+    return size_t(aNumProps) *
+           (sizeof(nsCSSValue) + sizeof(CompressedCSSProperty));
+  }
+
+  int32_t mStyleBits; // the structs for which we have data, according to
+                      // |nsCachedStyleData::GetBitForSID|.
+  uint32_t mNumProps;
+  // nsCSSValue elements are stored after these fields, and
+  // nsCSSPropertyID elements are stored -- each one compressed as a
+  // CompressedCSSProperty -- after the nsCSSValue elements.  Space for them
+  // is allocated in |operator new| above.  The static assertions following
+  // this class make sure that the value and property elements are aligned
+  // appropriately.
+
+  nsCSSValue* Values() const {
+    return (nsCSSValue*)(this + 1);
+  }
+
+  CompressedCSSProperty* CompressedProperties() const {
+    return (CompressedCSSProperty*)(Values() + mNumProps);
+  }
+
+  nsCSSValue* ValueAtIndex(uint32_t i) const {
+    MOZ_ASSERT(i < mNumProps, "value index out of range");
+    return Values() + i;
+  }
+
+  nsCSSPropertyID PropertyAtIndex(uint32_t i) const {
+    MOZ_ASSERT(i < mNumProps, "property index out of range");
+    nsCSSPropertyID prop = (nsCSSPropertyID)CompressedProperties()[i];
+    MOZ_ASSERT(!nsCSSProps::IsShorthand(prop), "out of range");
+    return prop;
+  }
+
+  void CopyValueToIndex(uint32_t i, nsCSSValue* aValue) {
+    new (ValueAtIndex(i)) nsCSSValue(*aValue);
+  }
+
+  void RawCopyValueToIndex(uint32_t i, nsCSSValue* aValue) {
+    memcpy(ValueAtIndex(i), aValue, sizeof(nsCSSValue));
+  }
+
+  void SetPropertyAtIndex(uint32_t i, nsCSSPropertyID aProperty) {
+    MOZ_ASSERT(i < mNumProps, "set property index out of range");
+    CompressedProperties()[i] = (CompressedCSSProperty)aProperty;
+  }
+
+  void SetNumPropsToZero() {
+    mNumProps = 0;
+  }
+};
+
+// Make sure the values and properties are aligned appropriately.  (These
+// assertions are stronger than necessary to keep them simple.)
+static_assert(sizeof(nsCSSCompressedDataBlock) == 8,
+              "nsCSSCompressedDataBlock's size has changed");
+static_assert(NS_ALIGNMENT_OF(nsCSSValue) == 4 || NS_ALIGNMENT_OF(nsCSSValue) == 8,
+              "nsCSSValue doesn't align with nsCSSCompressedDataBlock");
+static_assert(NS_ALIGNMENT_OF(nsCSSCompressedDataBlock::CompressedCSSProperty) == 2,
+              "CompressedCSSProperty doesn't align with nsCSSValue");
+
+// Make sure that sizeof(CompressedCSSProperty) is big enough.
+static_assert(eCSSProperty_COUNT_no_shorthands <=
+              nsCSSCompressedDataBlock::MaxCompressedCSSProperty,
+              "nsCSSPropertyID doesn't fit in StoredSizeOfCSSProperty");
+
+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.
+   *
+   * aOrder is an array of nsCSSPropertyID values specifying the order
+   * to store values in the two data blocks.
+   */
+  void Compress(nsCSSCompressedDataBlock **aNormalBlock,
+                nsCSSCompressedDataBlock **aImportantBlock,
+                const nsTArray<uint32_t>& aOrder);
+
+  /**
+   * Copy a value into this expanded block.  This does NOT destroy
+   * the source value object.  |aProperty| cannot be a shorthand.
+   */
+  void AddLonghandProperty(nsCSSPropertyID 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(nsCSSPropertyID aPropID);
+
+  /**
+   * Same as ClearProperty, but faster and cannot be used with shorthands.
+   */
+  void ClearLonghandProperty(nsCSSPropertyID 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.  |aEnabledState| is used to
+   * determine which longhand components of |aPropID| (if it is a
+   * shorthand) to transfer.
+   *
+   * 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.
+   * Calls |SetDocumentAndPageUseCounter| on |aSheetDocument| if it is
+   * non-null and |aPropID| has a use counter.
+   */
+  bool TransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
+                         nsCSSPropertyID aPropID,
+                         mozilla::CSSEnabledState aEnabledState,
+                         bool aIsImportant,
+                         bool aOverrideImportant,
+                         bool aMustCallValueAppended,
+                         mozilla::css::Declaration* aDeclaration,
+                         nsIDocument* aSheetDocument);
+
+  /**
+   * Copies the values for aPropID into the specified aRuleData object.
+   *
+   * This is used for copying parsed-at-computed-value-time properties
+   * that had variable references.  aPropID must be a longhand property.
+   */
+  void MapRuleInfoInto(nsCSSPropertyID aPropID, nsRuleData* aRuleData) const;
+
+  void AssertInitialState() {
+#ifdef DEBUG
+    DoAssertInitialState();
+#endif
+  }
+
+private:
+  /**
+   * Compute the number of properties that will be present in the
+   * result of |Compress|.
+   */
+  void ComputeNumProps(uint32_t* aNumPropsNormal,
+                       uint32_t* aNumPropsImportant);
+
+  void DoExpand(nsCSSCompressedDataBlock *aBlock, bool aImportant);
+
+  /**
+   * Worker for TransferFromBlock; cannot be used with shorthands.
+   */
+  bool DoTransferFromBlock(nsCSSExpandedDataBlock& aFromBlock,
+                             nsCSSPropertyID aPropID,
+                             bool aIsImportant,
+                             bool aOverrideImportant,
+                             bool aMustCallValueAppended,
+                             mozilla::css::Declaration* aDeclaration,
+                             nsIDocument* aSheetDocument);
+
+#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.
+   */
+  nsCSSPropertyIDSet mPropertiesSet;
+  /*
+   * mPropertiesImportant indicates which properties are '!important'.
+   */
+  nsCSSPropertyIDSet mPropertiesImportant;
+
+  /*
+   * Return the storage location within |this| of the value of the
+   * property |aProperty|.
+   */
+  nsCSSValue* PropertyAt(nsCSSPropertyID aProperty) {
+    MOZ_ASSERT(0 <= aProperty &&
+               aProperty < eCSSProperty_COUNT_no_shorthands,
+               "property out of range");
+    return &mValues[aProperty];
+  }
+  const nsCSSValue* PropertyAt(nsCSSPropertyID aProperty) const {
+    MOZ_ASSERT(0 <= aProperty &&
+               aProperty < eCSSProperty_COUNT_no_shorthands,
+               "property out of range");
+    return &mValues[aProperty];
+  }
+
+  void SetPropertyBit(nsCSSPropertyID aProperty) {
+    mPropertiesSet.AddProperty(aProperty);
+  }
+
+  void ClearPropertyBit(nsCSSPropertyID aProperty) {
+    mPropertiesSet.RemoveProperty(aProperty);
+  }
+
+  bool HasPropertyBit(nsCSSPropertyID aProperty) {
+    return mPropertiesSet.HasProperty(aProperty);
+  }
+
+  void SetImportantBit(nsCSSPropertyID aProperty) {
+    mPropertiesImportant.AddProperty(aProperty);
+  }
+
+  void ClearImportantBit(nsCSSPropertyID aProperty) {
+    mPropertiesImportant.RemoveProperty(aProperty);
+  }
+
+  bool HasImportantBit(nsCSSPropertyID aProperty) {
+    return mPropertiesImportant.HasProperty(aProperty);
+  }
+
+  void ClearSets() {
+    mPropertiesSet.Empty();
+    mPropertiesImportant.Empty();
+  }
+};
+
+#endif /* !defined(nsCSSDataBlock_h__) */