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LibJS: Store DFS instead of opaque StringImpl inside StringOrSymbol

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Additionally, use the second bit (instead of the first) to differentiate
between strings and symbols there. This will allow transparent
conversion of DFS to StringBase in the future.
This commit is contained in:
Dan Klishch 2024-01-22 16:10:45 -05:00 • committed by Andrew Kaster
parent a53911717f
commit 761d16141d
1 changed files with 38 additions and 36 deletions
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74
Userland/Libraries/LibJS/Runtime/StringOrSymbol.h
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@ -15,7 +15,10 @@ namespace JS {
class StringOrSymbol { class StringOrSymbol {
public: public:
StringOrSymbol() = default; StringOrSymbol()
: m_bits(0)
{
}
StringOrSymbol(char const* chars) StringOrSymbol(char const* chars)
: StringOrSymbol(DeprecatedFlyString(chars)) : StringOrSymbol(DeprecatedFlyString(chars))
@ -28,50 +31,53 @@ public:
} }
StringOrSymbol(DeprecatedFlyString const& string) StringOrSymbol(DeprecatedFlyString const& string)
: m_ptr(string.impl()) : m_string(string)
{ {
VERIFY(!string.is_null()); VERIFY(!string.is_null());
as_string_impl().ref();
} }
~StringOrSymbol() ~StringOrSymbol()
{ {
if (is_string()) if (is_string())
as_string_impl().unref(); m_string.~DeprecatedFlyString();
} }
StringOrSymbol(Symbol const* symbol) StringOrSymbol(Symbol const* symbol)
: m_ptr(symbol) : m_symbol_with_tag(symbol)
{ {
set_symbol_flag(); set_symbol_flag();
} }
StringOrSymbol(StringOrSymbol const& other) StringOrSymbol(StringOrSymbol const& other)
{ {
m_ptr = other.m_ptr; if (other.is_string())
if (is_string()) new (&m_string) DeprecatedFlyString(other.m_string);
as_string_impl().ref(); else
m_bits = other.m_bits;
} }
StringOrSymbol(StringOrSymbol&& other) StringOrSymbol(StringOrSymbol&& other)
{ {
m_ptr = exchange(other.m_ptr, nullptr); if (other.is_string())
new (&m_string) DeprecatedFlyString(move(other.m_string));
else
m_bits = exchange(other.m_bits, 0);
} }
ALWAYS_INLINE bool is_valid() const { return m_ptr != nullptr; } ALWAYS_INLINE bool is_valid() const { return m_bits != 0; }
ALWAYS_INLINE bool is_symbol() const { return is_valid() && (bits() & 1ul); } ALWAYS_INLINE bool is_symbol() const { return is_valid() && (m_bits & 2); }
ALWAYS_INLINE bool is_string() const { return is_valid() && !(bits() & 1ul); } ALWAYS_INLINE bool is_string() const { return is_valid() && !(m_bits & 2); }
ALWAYS_INLINE DeprecatedFlyString as_string() const ALWAYS_INLINE DeprecatedFlyString as_string() const
{ {
VERIFY(is_string()); VERIFY(is_string());
return DeprecatedFlyString::from_fly_impl(as_string_impl()); return m_string;
} }
ALWAYS_INLINE Symbol const* as_symbol() const ALWAYS_INLINE Symbol const* as_symbol() const
{ {
VERIFY(is_symbol()); VERIFY(is_symbol());
return reinterpret_cast<Symbol const*>(bits() & ~1ul); return reinterpret_cast<Symbol const*>(m_bits & ~2ULL);
} }
ByteString to_display_string() const ByteString to_display_string() const
@ -101,7 +107,7 @@ public:
ALWAYS_INLINE bool operator==(StringOrSymbol const& other) const ALWAYS_INLINE bool operator==(StringOrSymbol const& other) const
{ {
if (is_string()) if (is_string())
return other.is_string() && &as_string_impl() == &other.as_string_impl(); return other.is_string() && m_string == other.m_string;
if (is_symbol()) if (is_symbol())
return other.is_symbol() && as_symbol() == other.as_symbol(); return other.is_symbol() && as_symbol() == other.as_symbol();
return true; return true;
@ -109,47 +115,43 @@ public:
StringOrSymbol& operator=(StringOrSymbol const& other) StringOrSymbol& operator=(StringOrSymbol const& other)
{ {
if (this == &other) if (this != &other) {
return *this; this->~StringOrSymbol();
m_ptr = other.m_ptr; new (this) StringOrSymbol(other);
if (is_string()) }
as_string_impl().ref();
return *this; return *this;
} }
StringOrSymbol& operator=(StringOrSymbol&& other) StringOrSymbol& operator=(StringOrSymbol&& other)
{ {
if (this != &other) if (this != &other) {
m_ptr = exchange(other.m_ptr, nullptr); this->~StringOrSymbol();
new (this) StringOrSymbol(move(other));
}
return *this; return *this;
} }
unsigned hash() const unsigned hash() const
{ {
if (is_string()) if (is_string())
return as_string_impl().hash(); return m_string.hash();
return ptr_hash(as_symbol()); return ptr_hash(as_symbol());
} }
private: private:
ALWAYS_INLINE u64 bits() const
{
return reinterpret_cast<uintptr_t>(m_ptr);
}
ALWAYS_INLINE void set_symbol_flag() ALWAYS_INLINE void set_symbol_flag()
{ {
m_ptr = reinterpret_cast<void const*>(bits() | 1ul); m_bits |= 2;
} }
ALWAYS_INLINE StringImpl const& as_string_impl() const union {
{ DeprecatedFlyString m_string;
VERIFY(is_string()); Symbol const* m_symbol_with_tag;
return *reinterpret_cast<StringImpl const*>(m_ptr); uintptr_t m_bits;
}
void const* m_ptr { nullptr };
}; };
};
static_assert(sizeof(StringOrSymbol) == sizeof(uintptr_t));
} }