diff options
Diffstat (limited to 'js/src/vm/StringType.h')
| -rw-r--r-- | js/src/vm/StringType.h | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/js/src/vm/StringType.h b/js/src/vm/StringType.h index ea2174be42..f2850c33a4 100644 --- a/js/src/vm/StringType.h +++ b/js/src/vm/StringType.h @@ -297,7 +297,10 @@ class JSString : public js::gc::CellWithLengthAndFlags { * If LATIN1_CHARS_BIT is set, the string's characters are stored as Latin1 * instead of TwoByte. This flag can also be set for ropes, if both the * left and right nodes are Latin1. Flattening will result in a Latin1 - * string in this case. + * string in this case. When we flatten a TwoByte rope, we turn child ropes + * (including Latin1 ropes) into TwoByte dependent strings. If one of these + * strings is also part of another Latin1 rope tree, we can have a Latin1 rope + * with a TwoByte descendent. * * The other flags store the string's type. Instead of using a dense index * to represent the most-derived type, string types are encoded to allow @@ -385,6 +388,15 @@ class JSString : public js::gc::CellWithLengthAndFlags { static_assert((TYPE_FLAGS_MASK & js::gc::HeaderWord::RESERVED_MASK) == 0, "GC reserved bits must not be used for Strings"); + // Linear strings: + // - Content and representation are Latin-1 characters. + // - Unmodifiable after construction. + // + // Ropes: + // - Content are Latin-1 characters. + // - Flag may be cleared when the rope is changed into a dependent string. + // + // Also see LATIN1_CHARS_BIT description under "Flag Encoding". static const uint32_t LATIN1_CHARS_BIT = js::Bit(9); // Whether this atom's characters store an uint32 index value less than or |