зеркало из https://github.com/mozilla/gecko-dev.git
Bug 1379983 - Part 1: Move InlineCharBuffer to top of file. r=jandem
--HG-- extra : rebase_source : 70c989d42130ed9a65cab4fe20b438d949d58128
This commit is contained in:
André Bargull
Родитель
f746a86c3e
Коммит
3be3eaa5d7
238
js/src/jsstr.cpp
238
js/src/jsstr.cpp
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@ -87,6 +87,125 @@ ArgToRootedString(JSContext* cx, const CallArgs& args, unsigned argno)
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return str->ensureLinear(cx);
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}
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template <typename CharT> struct MaximumInlineLength;
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template<> struct MaximumInlineLength<Latin1Char> {
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static constexpr size_t value = JSFatInlineString::MAX_LENGTH_LATIN1;
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};
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template<> struct MaximumInlineLength<char16_t> {
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static constexpr size_t value = JSFatInlineString::MAX_LENGTH_TWO_BYTE;
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};
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// Character buffer class used for ToLowerCase and ToUpperCase operations.
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//
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// Case conversion operations normally return a string with the same length as
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// the input string. To avoid over-allocation, we optimistically allocate an
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// array with same size as the input string and only when we detect special
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// casing characters, which can change the output string length, we reallocate
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// the output buffer to the final string length.
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//
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// As a further mean to improve runtime performance, the character buffer
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// contains an inline storage, so we don't need to heap-allocate an array when
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// a JSInlineString will be used for the output string.
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//
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// Why not use mozilla::Vector instead? mozilla::Vector doesn't provide enough
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// fine-grained control to avoid over-allocation when (re)allocating for exact
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// buffer sizes. This led to visible performance regressions in µ-benchmarks.
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template <typename CharT>
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class MOZ_NON_PARAM InlineCharBuffer
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{
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using CharPtr = UniquePtr<CharT[], JS::FreePolicy>;
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static constexpr size_t InlineCapacity = MaximumInlineLength<CharT>::value;
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CharT inlineStorage[InlineCapacity];
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CharPtr heapStorage;
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#ifdef DEBUG
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// In debug mode, we keep track of the requested string lengths to ensure
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// all character buffer methods are called in the correct order and with
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// the expected argument values.
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size_t lastRequestedLength = 0;
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void assertValidRequest(size_t expectedLastLength, size_t length) {
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MOZ_ASSERT(length > expectedLastLength, "cannot shrink requested length");
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MOZ_ASSERT(lastRequestedLength == expectedLastLength);
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lastRequestedLength = length;
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}
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#else
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void assertValidRequest(size_t expectedLastLength, size_t length) {}
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#endif
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public:
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CharT* get()
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{
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return heapStorage ? heapStorage.get() : inlineStorage;
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}
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bool maybeAlloc(JSContext* cx, size_t length)
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{
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assertValidRequest(0, length);
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if (length <= InlineCapacity)
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return true;
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MOZ_ASSERT(!heapStorage, "heap storage already allocated");
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heapStorage = cx->make_pod_array<CharT>(length + 1);
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return !!heapStorage;
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}
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bool maybeRealloc(JSContext* cx, size_t oldLength, size_t newLength)
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{
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assertValidRequest(oldLength, newLength);
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if (newLength <= InlineCapacity)
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return true;
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if (!heapStorage) {
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heapStorage = cx->make_pod_array<CharT>(newLength + 1);
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if (!heapStorage)
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return false;
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MOZ_ASSERT(oldLength <= InlineCapacity);
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PodCopy(heapStorage.get(), inlineStorage, oldLength);
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return true;
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}
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CharT* oldChars = heapStorage.release();
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CharT* newChars = cx->pod_realloc(oldChars, oldLength + 1, newLength + 1);
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if (!newChars) {
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js_free(oldChars);
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return false;
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}
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heapStorage.reset(newChars);
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return true;
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}
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JSString* toString(JSContext* cx, size_t length)
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{
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MOZ_ASSERT(length == lastRequestedLength);
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if (JSInlineString::lengthFits<CharT>(length)) {
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MOZ_ASSERT(!heapStorage,
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"expected only inline storage when length fits in inline string");
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mozilla::Range<const CharT> range(inlineStorage, length);
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return NewInlineString<CanGC>(cx, range);
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}
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MOZ_ASSERT(heapStorage, "heap storage was not allocated for non-inline string");
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heapStorage.get()[length] = '\0'; // Null-terminate
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JSString* res = NewStringDontDeflate<CanGC>(cx, heapStorage.get(), length);
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if (!res)
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return nullptr;
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mozilla::Unused << heapStorage.release();
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return res;
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}
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};
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/*
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* Forward declarations for URI encode/decode and helper routines
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*/
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@ -603,125 +722,6 @@ js::SubstringKernel(JSContext* cx, HandleString str, int32_t beginInt, int32_t l
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return NewDependentString(cx, str, begin, len);
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}
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template <typename CharT> struct MaximumInlineLength;
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template<> struct MaximumInlineLength<Latin1Char> {
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static constexpr size_t value = JSFatInlineString::MAX_LENGTH_LATIN1;
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};
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template<> struct MaximumInlineLength<char16_t> {
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static constexpr size_t value = JSFatInlineString::MAX_LENGTH_TWO_BYTE;
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};
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// Character buffer class used for ToLowerCase and ToUpperCase operations.
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//
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// Case conversion operations normally return a string with the same length as
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// the input string. To avoid over-allocation, we optimistically allocate an
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// array with same size as the input string and only when we detect special
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// casing characters, which can change the output string length, we reallocate
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// the output buffer to the final string length.
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//
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// As a further mean to improve runtime performance, the character buffer
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// contains an inline storage, so we don't need to heap-allocate an array when
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// a JSInlineString will be used for the output string.
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//
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// Why not use mozilla::Vector instead? mozilla::Vector doesn't provide enough
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// fine-grained control to avoid over-allocation when (re)allocating for exact
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// buffer sizes. This led to visible performance regressions in µ-benchmarks.
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template <typename CharT>
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class MOZ_NON_PARAM InlineCharBuffer
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{
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using CharPtr = UniquePtr<CharT[], JS::FreePolicy>;
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static constexpr size_t InlineCapacity = MaximumInlineLength<CharT>::value;
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CharT inlineStorage[InlineCapacity];
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CharPtr heapStorage;
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#ifdef DEBUG
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// In debug mode, we keep track of the requested string lengths to ensure
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// all character buffer methods are called in the correct order and with
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// the expected argument values.
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size_t lastRequestedLength = 0;
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void assertValidRequest(size_t expectedLastLength, size_t length) {
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MOZ_ASSERT(length > expectedLastLength, "cannot shrink requested length");
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MOZ_ASSERT(lastRequestedLength == expectedLastLength);
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lastRequestedLength = length;
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}
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#else
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void assertValidRequest(size_t expectedLastLength, size_t length) {}
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#endif
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public:
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CharT* get()
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{
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return heapStorage ? heapStorage.get() : inlineStorage;
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}
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bool maybeAlloc(JSContext* cx, size_t length)
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{
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assertValidRequest(0, length);
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if (length <= InlineCapacity)
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return true;
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MOZ_ASSERT(!heapStorage, "heap storage already allocated");
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heapStorage = cx->make_pod_array<CharT>(length + 1);
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return !!heapStorage;
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}
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bool maybeRealloc(JSContext* cx, size_t oldLength, size_t newLength)
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{
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assertValidRequest(oldLength, newLength);
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if (newLength <= InlineCapacity)
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return true;
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if (!heapStorage) {
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heapStorage = cx->make_pod_array<CharT>(newLength + 1);
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if (!heapStorage)
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return false;
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MOZ_ASSERT(oldLength <= InlineCapacity);
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PodCopy(heapStorage.get(), inlineStorage, oldLength);
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return true;
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}
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CharT* oldChars = heapStorage.release();
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CharT* newChars = cx->pod_realloc(oldChars, oldLength + 1, newLength + 1);
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if (!newChars) {
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js_free(oldChars);
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return false;
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}
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heapStorage.reset(newChars);
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return true;
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}
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JSString* toString(JSContext* cx, size_t length)
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{
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MOZ_ASSERT(length == lastRequestedLength);
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if (JSInlineString::lengthFits<CharT>(length)) {
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MOZ_ASSERT(!heapStorage,
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"expected only inline storage when length fits in inline string");
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mozilla::Range<const CharT> range(inlineStorage, length);
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return NewInlineString<CanGC>(cx, range);
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}
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MOZ_ASSERT(heapStorage, "heap storage was not allocated for non-inline string");
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heapStorage.get()[length] = '\0'; // Null-terminate
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JSString* res = NewStringDontDeflate<CanGC>(cx, heapStorage.get(), length);
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if (!res)
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return nullptr;
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mozilla::Unused << heapStorage.release();
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return res;
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}
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};
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/**
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* U+03A3 GREEK CAPITAL LETTER SIGMA has two different lower case mappings
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* depending on its context:
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