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Minor optimizations to SerializedScriptValue
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https://bugs.webkit.org/show_bug.cgi?id=259794

Reviewed by Ryosuke Niwa and Darin Adler.

Minor optimizations to SerializedScriptValue:
1. Encode boolean values as uint8_t instead of int32_t to save space.
2. Move String in when constructing a CachedString
3. Avoid double HashMap lookup and code duplication in fillTransferMap()

* Source/WebCore/bindings/js/SerializedScriptValue.cpp:
(WebCore::CloneSerializer::fillTransferMap):
(WebCore::CloneSerializer::dumpIfTerminal):
(WebCore::CloneSerializer::write):
(WebCore::CloneDeserializer::CachedString::CachedString):
(WebCore::CloneDeserializer::read):
(WebCore::CloneDeserializer::readStringData):

Canonical link: https://commits.webkit.org/266612@main
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@cdumez
cdumez committed Aug 5, 2023
1 parent 33bc17e commit 473600f
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Showing 2 changed files with 40 additions and 52 deletions.
2 changes: 1 addition & 1 deletion LayoutTests/fast/storage/serialized-script-value.html
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@
<body>
<script>

const currentVersion = 0x0d;
const currentVersion = 14;

// Here's a little Q&D helper for future adventurers needing to rebaseline this.

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90 changes: 39 additions & 51 deletions Source/WebCore/bindings/js/SerializedScriptValue.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -528,8 +528,9 @@ const uint8_t cryptoKeyOKPOpNameTagMaximumValue = 1;
* Version 11. added support for Blob's memory cost.
* Version 12. added support for agent cluster ID.
* Version 13. added support for ErrorInstance objects.
* Version 14. encode booleans as uint8_t instead of int32_t.
*/
static constexpr unsigned CurrentVersion = 13;
static constexpr unsigned CurrentVersion = 14;
static constexpr unsigned TerminatorTag = 0xFFFFFFFF;
static constexpr unsigned StringPoolTag = 0xFFFFFFFE;
static constexpr unsigned NonIndexPropertiesTag = 0xFFFFFFFD;
Expand Down Expand Up @@ -913,30 +914,13 @@ class CloneSerializer : CloneBase {
#endif
}

template <class T>
void fillTransferMap(const Vector<RefPtr<T>>& input, ObjectPool& result)
template<typename T>
void fillTransferMap(const Vector<T>& input, ObjectPool& result)
{
if (input.isEmpty())
return;
JSDOMGlobalObject* globalObject = jsCast<JSDOMGlobalObject*>(m_lexicalGlobalObject);
for (size_t i = 0; i < input.size(); i++) {
JSC::JSValue value = toJS(m_lexicalGlobalObject, globalObject, input[i].get());
JSC::JSObject* obj = value.getObject();
if (obj && !result.contains(obj))
result.add(obj, i);
}
}
template <class T>
void fillTransferMap(const Vector<Ref<T>>& input, ObjectPool& result)
{
if (input.isEmpty())
return;
JSDOMGlobalObject* globalObject = jsCast<JSDOMGlobalObject*>(m_lexicalGlobalObject);
for (size_t i = 0; i < input.size(); i++) {
JSC::JSValue value = toJS(m_lexicalGlobalObject, globalObject, input[i].get());
JSC::JSObject* obj = value.getObject();
if (obj && !result.contains(obj))
result.add(obj, i);
auto* globalObject = jsCast<JSDOMGlobalObject*>(m_lexicalGlobalObject);
for (size_t i = 0; i < input.size(); ++i) {
if (auto* object = toJS(globalObject, globalObject, input[i].get()).getObject())
result.add(object, i);
}
}

Expand Down Expand Up @@ -1125,7 +1109,7 @@ class CloneSerializer : CloneBase {
#if USE(BIGINT32)
void dumpBigInt32Data(int32_t integer)
{
write(static_cast<uint8_t>(integer < 0));
write(integer < 0);
if (!integer) {
write(static_cast<uint32_t>(0)); // Length-in-uint64_t
return;
Expand All @@ -1140,7 +1124,7 @@ class CloneSerializer : CloneBase {

void dumpHeapBigIntData(JSBigInt* bigInt)
{
write(static_cast<uint8_t>(bigInt->sign()));
write(bigInt->sign());
if constexpr (sizeof(JSBigInt::Digit) == sizeof(uint64_t)) {
write(static_cast<uint32_t>(bigInt->length()));
for (unsigned index = 0; index < bigInt->length(); ++index)
Expand Down Expand Up @@ -1279,7 +1263,7 @@ class CloneSerializer : CloneBase {

auto& matrix = jsCast<JSDOMMatrixReadOnly*>(obj)->wrapped();
bool is2D = matrix.is2D();
write(static_cast<uint8_t>(is2D));
write(is2D);
if (is2D) {
write(matrix.m11());
write(matrix.m12());
Expand Down Expand Up @@ -1624,8 +1608,7 @@ class CloneSerializer : CloneBase {
write(index->value);
return true;
} else if (m_context == SerializationContext::CloneAcrossWorlds) {
// FIXME: Only in clone accross worlds mode.
write (InMemoryMessagePortTag);
write(InMemoryMessagePortTag);
write(static_cast<uint32_t>(m_inMemoryMessagePorts.size()));
m_inMemoryMessagePorts.append(&jsCast<JSMessagePort*>(obj)->wrapped());
return true;
Expand Down Expand Up @@ -1878,7 +1861,7 @@ class CloneSerializer : CloneBase {

void write(bool b)
{
writeLittleEndian(m_buffer, static_cast<int32_t>(b));
write(static_cast<uint8_t>(b));
}

void write(uint8_t c)
Expand Down Expand Up @@ -2662,8 +2645,8 @@ class CloneDeserializer : CloneBase {

private:
struct CachedString {
CachedString(const String& string)
: m_string(string)
CachedString(String&& string)
: m_string(WTFMove(string))
{
}

Expand All @@ -2682,11 +2665,8 @@ class CloneDeserializer : CloneBase {
};

struct CachedStringRef {
CachedStringRef()
: m_base(0)
, m_index(0)
{
}
CachedStringRef() = default;

CachedStringRef(Vector<CachedString>* base, size_t index)
: m_base(base)
, m_index(index)
Expand All @@ -2696,8 +2676,8 @@ class CloneDeserializer : CloneBase {
CachedString* operator->() { ASSERT(m_base); return &m_base->at(m_index); }

private:
Vector<CachedString>* m_base;
size_t m_index;
Vector<CachedString>* m_base { nullptr };
size_t m_index { 0 };
};

CloneDeserializer(JSGlobalObject* lexicalGlobalObject, JSGlobalObject* globalObject, const Vector<RefPtr<MessagePort>>& messagePorts, ArrayBufferContentsArray* arrayBufferContents, Vector<std::optional<ImageBitmapBacking>>&& backingStores, const Vector<uint8_t>& buffer
Expand Down Expand Up @@ -2856,12 +2836,20 @@ class CloneDeserializer : CloneBase {
}
#endif

bool read(bool& b)
enum class ForceReadingAs8Bit : bool { No, Yes };
bool read(bool& b, ForceReadingAs8Bit forceReadingAs8Bit = ForceReadingAs8Bit::No)
{
int32_t integer;
if (!readLittleEndian(integer) || integer > 1)
return false;
b = !!integer;
if (m_version >= 14 || forceReadingAs8Bit == ForceReadingAs8Bit::Yes) {
uint8_t integer;
if (!read(integer) || integer > 1)
return false;
b = !!integer;
} else {
int32_t integer;
if (!read(integer) || integer > 1)
return false;
b = !!integer;
}
return true;
}

Expand Down Expand Up @@ -3019,7 +3007,7 @@ class CloneDeserializer : CloneBase {
fail();
return false;
}
m_constantPool.append(str);
m_constantPool.append(WTFMove(str));
cachedString = CachedStringRef(&m_constantPool, m_constantPool.size() - 1);
return true;
}
Expand Down Expand Up @@ -3487,7 +3475,7 @@ class CloneDeserializer : CloneBase {
if (!read(algorithm))
return false;

int32_t isRestrictedToHash;
bool isRestrictedToHash;
CryptoAlgorithmIdentifier hash = CryptoAlgorithmIdentifier::SHA_1;
if (!read(isRestrictedToHash))
return false;
Expand Down Expand Up @@ -3624,7 +3612,7 @@ class CloneDeserializer : CloneBase {
if (!read(keyFormatVersion) || keyFormatVersion > currentKeyFormatVersion)
return false;

int32_t extractable;
bool extractable;
if (!read(extractable))
return false;

Expand Down Expand Up @@ -3738,8 +3726,8 @@ class CloneDeserializer : CloneBase {
template<class T>
JSValue readDOMMatrix()
{
uint8_t is2D;
if (!read(is2D))
bool is2D;
if (!read(is2D, ForceReadingAs8Bit::Yes))
return { };

if (is2D) {
Expand Down Expand Up @@ -4064,8 +4052,8 @@ class CloneDeserializer : CloneBase {

JSValue readBigInt()
{
uint8_t sign = 0;
if (!read(sign))
bool sign;
if (!read(sign, ForceReadingAs8Bit::Yes))
return JSValue();
uint32_t lengthInUint64 = 0;
if (!read(lengthInUint64))
Expand Down

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