layout/style/nsCSSPropertySet.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 /* bit vectors for sets of CSS properties */
   6
   7 #ifndef nsCSSPropertySet_h__
   8 #define nsCSSPropertySet_h__
   9
  10 #include "mozilla/ArrayUtils.h"
  11
  12 #include "nsCSSProperty.h"
  13 #include <limits.h> // for CHAR_BIT
  14
  15 /**
  16  * nsCSSPropertySet maintains a set of non-shorthand CSS properties.  In
  17  * other words, for each longhand CSS property we support, it has a bit
  18  * for whether that property is in the set.
  19  */
  20 class nsCSSPropertySet {
  21 public:
  22     nsCSSPropertySet() { Empty(); }
  23     // auto-generated copy-constructor OK
  24
  25     void AssertInSetRange(nsCSSProperty aProperty) const {
  26         NS_ASSERTION(0 <= aProperty &&
  27                      aProperty < eCSSProperty_COUNT_no_shorthands,
  28                      "out of bounds");
  29     }
  30
  31     // Conversion of aProperty to |size_t| after AssertInSetRange
  32     // lets the compiler generate significantly tighter code.
  33
  34     void AddProperty(nsCSSProperty aProperty) {
  35         AssertInSetRange(aProperty);
  36         size_t p = aProperty;
  37         mProperties[p / kBitsInChunk] |=
  38           property_set_type(1) << (p % kBitsInChunk);
  39     }
  40
  41     void RemoveProperty(nsCSSProperty aProperty) {
  42         AssertInSetRange(aProperty);
  43         size_t p = aProperty;
  44         mProperties[p / kBitsInChunk] &=
  45             ~(property_set_type(1) << (p % kBitsInChunk));
  46     }
  47
  48     bool HasProperty(nsCSSProperty aProperty) const {
  49         AssertInSetRange(aProperty);
  50         size_t p = aProperty;
  51         return (mProperties[p / kBitsInChunk] &
  52                 (property_set_type(1) << (p % kBitsInChunk))) != 0;
  53     }
  54
  55     void Empty() {
  56         memset(mProperties, 0, sizeof(mProperties));
  57     }
  58
  59     void AssertIsEmpty(const char* aText) const {
  60         for (size_t i = 0; i < mozilla::ArrayLength(mProperties); ++i) {
  61             NS_ASSERTION(mProperties[i] == 0, aText);
  62         }
  63     }
  64
  65 private:
  66     typedef unsigned long property_set_type;
  67 public:
  68     // number of bits in |property_set_type|.
  69     static const size_t kBitsInChunk = sizeof(property_set_type)*CHAR_BIT;
  70     // number of |property_set_type|s in the set
  71     static const size_t kChunkCount =
  72         (eCSSProperty_COUNT_no_shorthands + kBitsInChunk - 1) / kBitsInChunk;
  73
  74     /*
  75      * For fast enumeration of all the bits that are set, callers can
  76      * check each chunk against zero (since in normal cases few bits are
  77      * likely to be set).
  78      */
  79     bool HasPropertyInChunk(size_t aChunk) const {
  80         return mProperties[aChunk] != 0;
  81     }
  82     bool HasPropertyAt(size_t aChunk, size_t aBit) const {
  83         return (mProperties[aChunk] & (property_set_type(1) << aBit)) != 0;
  84     }
  85     static nsCSSProperty CSSPropertyAt(size_t aChunk, size_t aBit) {
  86         return nsCSSProperty(aChunk * kBitsInChunk + aBit);
  87     }
  88
  89 private:
  90     property_set_type mProperties[kChunkCount];
  91 };
  92
  93 #endif /* !defined(nsCSSPropertySet_h__) */