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/*
* Copyright (C) 2012-2024 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include "ExceptionHelpers.h"
#include "JSCJSValue.h"
#include "JSGlobalObject.h"
namespace JSC {
class JSStringJoiner {
WTF_FORBID_HEAP_ALLOCATION;
public:
struct Entry {
NO_UNIQUE_ADDRESS StringViewWithUnderlyingString m_view;
NO_UNIQUE_ADDRESS uint16_t m_additional { 0 };
};
using Entries = Vector<Entry, 16>;
JSStringJoiner(StringView separator);
~JSStringJoiner();
void reserveCapacity(JSGlobalObject*, size_t);
void append(JSGlobalObject*, JSValue);
void appendNumber(VM&, int32_t);
void appendNumber(VM&, double);
bool appendWithoutSideEffects(JSGlobalObject*, JSValue);
void appendEmptyString();
JSValue join(JSGlobalObject*);
private:
void append(JSString*, StringViewWithUnderlyingString&&);
void append8Bit(const String&);
unsigned joinedLength(JSGlobalObject*) const;
JSValue joinSlow(JSGlobalObject*);
StringView m_separator;
Entries m_strings;
CheckedUint32 m_accumulatedStringsLength;
CheckedUint32 m_stringsCount;
bool m_hasOverflowed { false };
bool m_isAll8Bit { true };
JSString* m_lastString { nullptr };
};
inline JSStringJoiner::JSStringJoiner(StringView separator)
: m_separator(separator)
, m_isAll8Bit(m_separator.is8Bit())
{
}
inline void JSStringJoiner::reserveCapacity(JSGlobalObject* globalObject, size_t count)
{
VM& vm = globalObject->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
if (UNLIKELY(!m_strings.tryReserveCapacity(count)))
throwOutOfMemoryError(globalObject, scope);
}
inline JSValue JSStringJoiner::join(JSGlobalObject* globalObject)
{
if (m_stringsCount == 1) {
// If m_stringsCount is 1, then there's no chance of an overflow because m_strings
// is a Vector<Entry, 16>, and has at least space for 16 entries.
ASSERT(!m_hasOverflowed);
if (m_lastString)
return m_lastString;
return jsString(globalObject->vm(), m_strings[0].m_view.toString());
}
return joinSlow(globalObject);
}
ALWAYS_INLINE void JSStringJoiner::append(JSString* jsString, StringViewWithUnderlyingString&& string)
{
++m_stringsCount;
if (m_lastString == jsString) {
auto& entry = m_strings.last();
if (LIKELY(entry.m_additional < UINT16_MAX)) {
++entry.m_additional;
m_accumulatedStringsLength += entry.m_view.view.length();
return;
}
}
m_accumulatedStringsLength += string.view.length();
m_isAll8Bit = m_isAll8Bit && string.view.is8Bit();
m_hasOverflowed |= !m_strings.tryAppend({ WTFMove(string), 0 });
m_lastString = jsString;
}
ALWAYS_INLINE void JSStringJoiner::append8Bit(const String& string)
{
ASSERT(string.is8Bit());
++m_stringsCount;
m_accumulatedStringsLength += string.length();
m_hasOverflowed |= !m_strings.tryAppend({ { string, string }, 0 });
m_lastString = nullptr;
}
ALWAYS_INLINE void JSStringJoiner::appendEmptyString()
{
++m_stringsCount;
m_hasOverflowed |= !m_strings.tryAppend({ { { }, { } }, 0 });
m_lastString = nullptr;
}
ALWAYS_INLINE bool JSStringJoiner::appendWithoutSideEffects(JSGlobalObject* globalObject, JSValue value)
{
// The following code differs from using the result of JSValue::toString in the following ways:
// 1) It's inlined more than JSValue::toString is.
// 2) It includes conversion to WTF::String in a way that avoids allocating copies of substrings.
// 3) It doesn't create a JSString for numbers, true, or false.
// 4) It turns undefined and null into the empty string instead of "undefined" and "null".
// 5) It uses optimized code paths for all the cases known to be 8-bit and for the empty string.
// If we might make an effectful calls, return false. Otherwise return true.
VM& vm = globalObject->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
if (value.isCell()) {
// FIXME: Support JSBigInt in side-effect-free append.
// https://bugs.webkit.org/show_bug.cgi?id=211173
if (JSString* jsString = jsDynamicCast<JSString*>(value)) {
auto view = jsString->view(globalObject);
RETURN_IF_EXCEPTION(scope, false);
// Since getting the view didn't OOM, we know that the underlying String exists and isn't
// a rope. Thus, `tryGetValue` on the owner JSString will succeed. Since jsString could be
// a substring we make sure to get the owner's String not jsString's.
append(jsString, StringViewWithUnderlyingString(view, jsCast<const JSString*>(view.owner)->tryGetValue()));
return true;
}
return false;
}
if (value.isInt32()) {
appendNumber(globalObject->vm(), value.asInt32());
return true;
}
if (value.isDouble()) {
appendNumber(globalObject->vm(), value.asDouble());
return true;
}
if (value.isTrue()) {
append8Bit(globalObject->vm().propertyNames->trueKeyword.string());
return true;
}
if (value.isFalse()) {
append8Bit(globalObject->vm().propertyNames->falseKeyword.string());
return true;
}
#if USE(BIGINT32)
if (value.isBigInt32()) {
appendNumber(globalObject->vm(), value.bigInt32AsInt32());
return true;
}
#endif
ASSERT(value.isUndefinedOrNull());
appendEmptyString();
return true;
}
ALWAYS_INLINE void JSStringJoiner::append(JSGlobalObject* globalObject, JSValue value)
{
VM& vm = globalObject->vm();
auto scope = DECLARE_THROW_SCOPE(vm);
bool success = appendWithoutSideEffects(globalObject, value);
RETURN_IF_EXCEPTION(scope, void());
if (!success) {
ASSERT(value.isCell());
ASSERT(!value.isString());
JSString* jsString = value.asCell()->toStringInline(globalObject);
RETURN_IF_EXCEPTION(scope, void());
auto view = jsString->view(globalObject);
RETURN_IF_EXCEPTION(scope, void());
RELEASE_AND_RETURN(scope, append(jsString, StringViewWithUnderlyingString(view, jsCast<const JSString*>(view.owner)->tryGetValue())));
}
}
ALWAYS_INLINE void JSStringJoiner::appendNumber(VM& vm, int32_t value)
{
append8Bit(vm.numericStrings.add(value));
}
ALWAYS_INLINE void JSStringJoiner::appendNumber(VM& vm, double value)
{
if (canBeStrictInt32(value))
appendNumber(vm, static_cast<int32_t>(value));
else
append8Bit(vm.numericStrings.add(value));
}
} // namespace JSC
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