/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef vm_StringType_inl_h
#define vm_StringType_inl_h

#include "vm/StringType.h"

#include "mozilla/PodOperations.h"
#include "mozilla/Range.h"
#include "mozilla/StringBuffer.h"

#include "gc/GCEnum.h"
#include "gc/MaybeRooted.h"
#include "gc/StoreBuffer.h"
#include "js/UniquePtr.h"
#include "vm/StaticStrings.h"

#include "gc/GCContext-inl.h"
#include "gc/Marking-inl.h"
#include "gc/StoreBuffer-inl.h"
#include "vm/JSContext-inl.h"

namespace js {

// Allocate a thin inline string if possible, and a fat inline string if not.
template <AllowGC allowGC, typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString* AllocateInlineString(
    JSContext* cx, size_t len, CharT** chars, js::gc::Heap heap) {
  MOZ_ASSERT(JSInlineString::lengthFits<CharT>(len));

  if (JSThinInlineString::lengthFits<CharT>(len)) {
    return cx->newCell<JSThinInlineString, allowGC>(heap, len, chars);
  }
  return cx->newCell<JSFatInlineString, allowGC>(heap, len, chars);
}

template <typename CharT>
static MOZ_ALWAYS_INLINE JSAtom* AllocateInlineAtom(JSContext* cx, size_t len,
                                                    CharT** chars,
                                                    js::HashNumber hash) {
  MOZ_ASSERT(JSAtom::lengthFitsInline<CharT>(len));
  if constexpr (js::ThinInlineAtom::EverInstantiated) {
    if (js::ThinInlineAtom::lengthFits<CharT>(len)) {
      return cx->newCell<js::ThinInlineAtom, js::NoGC>(len, chars, hash);
    }
  }
  return cx->newCell<js::FatInlineAtom, js::NoGC>(len, chars, hash);
}

// Create a thin inline string if possible, and a fat inline string if not.
template <AllowGC allowGC, typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString* NewInlineString(
    JSContext* cx, mozilla::Range<const CharT> chars,
    js::gc::Heap heap = js::gc::Heap::Default) {
  /*
   * Don't bother trying to find a static atom; measurement shows that not
   * many get here (for one, Atomize is catching them).
   */

  size_t len = chars.length();
  CharT* storage;
  JSInlineString* str = AllocateInlineString<allowGC>(cx, len, &storage, heap);
  if (!str) {
    return nullptr;
  }

  mozilla::PodCopy(storage, chars.begin().get(), len);
  return str;
}

// Create a thin inline string if possible, and a fat inline string if not.
template <AllowGC allowGC, typename CharT, size_t N>
static MOZ_ALWAYS_INLINE JSInlineString* NewInlineString(
    JSContext* cx, const CharT (&chars)[N], size_t len,
    js::gc::Heap heap = js::gc::Heap::Default) {
  MOZ_ASSERT(len <= N);

  /*
   * Don't bother trying to find a static atom; measurement shows that not
   * many get here (for one, Atomize is catching them).
   */

  CharT* storage;
  JSInlineString* str = AllocateInlineString<allowGC>(cx, len, &storage, heap);
  if (!str) {
    return nullptr;
  }

  if (JSThinInlineString::lengthFits<CharT>(len)) {
    constexpr size_t MaxLength = std::is_same_v<CharT, Latin1Char>
                                     ? JSThinInlineString::MAX_LENGTH_LATIN1
                                     : JSThinInlineString::MAX_LENGTH_TWO_BYTE;

    // memcpy with a constant length can be optimized more easily by compilers.
    constexpr size_t toCopy = std::min(N, MaxLength) * sizeof(CharT);
    std::memcpy(storage, chars, toCopy);
  } else {
    constexpr size_t MaxLength = std::is_same_v<CharT, Latin1Char>
                                     ? JSFatInlineString::MAX_LENGTH_LATIN1
                                     : JSFatInlineString::MAX_LENGTH_TWO_BYTE;

    // memcpy with a constant length can be optimized more easily by compilers.
    constexpr size_t toCopy = std::min(N, MaxLength) * sizeof(CharT);
    std::memcpy(storage, chars, toCopy);
  }
  return str;
}

template <typename CharT>
static MOZ_ALWAYS_INLINE JSAtom* NewInlineAtom(JSContext* cx,
                                               const CharT* chars,
                                               size_t length,
                                               js::HashNumber hash) {
  CharT* storage;
  JSAtom* str = AllocateInlineAtom(cx, length, &storage, hash);
  if (!str) {
    return nullptr;
  }

  mozilla::PodCopy(storage, chars, length);
  return str;
}

// Create a thin inline string if possible, and a fat inline string if not.
template <typename CharT>
static MOZ_ALWAYS_INLINE JSInlineString* NewInlineString(
    JSContext* cx, Handle<JSLinearString*> base, size_t start, size_t length,
    js::gc::Heap heap) {
  MOZ_ASSERT(JSInlineString::lengthFits<CharT>(length));

  CharT* chars;
  JSInlineString* s = AllocateInlineString<CanGC>(cx, length, &chars, heap);
  if (!s) {
    return nullptr;
  }

  JS::AutoCheckCannotGC nogc;
  mozilla::PodCopy(chars, base->chars<CharT>(nogc) + start, length);
  return s;
}

template <typename CharT>
static MOZ_ALWAYS_INLINE JSLinearString* TryEmptyOrStaticString(
    JSContext* cx, const CharT* chars, size_t n) {
  // Measurements on popular websites indicate empty strings are pretty common
  // and most strings with length 1 or 2 are in the StaticStrings table. For
  // length 3 strings that's only about 1%, so we check n <= 2.
  if (n <= 2) {
    if (n == 0) {
      return cx->emptyString();
    }

    if (JSLinearString* str = cx->staticStrings().lookup(chars, n)) {
      return str;
    }
  }

  return nullptr;
}

} /* namespace js */

template <typename CharT>
JSString::OwnedChars<CharT>::OwnedChars(CharT* chars, size_t length, Kind kind)
    : chars_(chars, length), kind_(kind) {
  MOZ_ASSERT(kind != Kind::Uninitialized);
  MOZ_ASSERT(length > 0);
  MOZ_ASSERT(chars);
#ifdef DEBUG
  bool inNursery = js::TlsContext.get()->nursery().isInside(chars);
  MOZ_ASSERT((kind == Kind::Nursery) == inNursery);
#endif
}

template <typename CharT>
JSString::OwnedChars<CharT>::OwnedChars(JSString::OwnedChars<CharT>&& other)
    : chars_(other.chars_), kind_(other.kind_) {
  other.release();
}

template <typename CharT>
JSString::OwnedChars<CharT>& JSString::OwnedChars<CharT>::operator=(
    JSString::OwnedChars<CharT>&& other) {
  reset();
  chars_ = other.chars_;
  kind_ = other.kind_;
  other.release();
  return *this;
}

template <typename CharT>
CharT* JSString::OwnedChars<CharT>::release() {
  CharT* chars = chars_.data();
  chars_ = {};
  kind_ = Kind::Uninitialized;
  return chars;
}

template <typename CharT>
void JSString::OwnedChars<CharT>::reset() {
  switch (kind_) {
    case Kind::Uninitialized:
    case Kind::Nursery:
      break;
    case Kind::Malloc:
      js_free(chars_.data());
      break;
    case Kind::StringBuffer:
      mozilla::StringBuffer::FromData(chars_.data())->Release();
      break;
  }
  chars_ = {};
  kind_ = Kind::Uninitialized;
}

template <typename CharT>
void JSString::OwnedChars<CharT>::ensureNonNursery() {
  if (kind_ != Kind::Nursery) {
    return;
  }

  js::AutoEnterOOMUnsafeRegion oomUnsafe;
  CharT* oldPtr = data();
  size_t length = chars_.Length();
  CharT* ptr = js_pod_arena_malloc<CharT>(js::StringBufferArena, length);
  if (!ptr) {
    oomUnsafe.crash(chars_.size(), "moving nursery buffer to heap");
  }
  mozilla::PodCopy(ptr, oldPtr, length);
  chars_ = mozilla::Span<CharT>(ptr, length);
  kind_ = Kind::Malloc;
}

template <typename CharT>
JSString::OwnedChars<CharT>::OwnedChars(
    js::UniquePtr<CharT[], JS::FreePolicy>&& chars, size_t length)
    : OwnedChars(chars.release(), length, Kind::Malloc) {}

template <typename CharT>
JSString::OwnedChars<CharT>::OwnedChars(RefPtr<mozilla::StringBuffer>&& buffer,
                                        size_t length)
    : OwnedChars(static_cast<CharT*>(buffer->Data()), length,
                 Kind::StringBuffer) {
  // Transfer the reference from |buffer| to this OwnedChars.
  mozilla::StringBuffer* buf;
  buffer.forget(&buf);
}

MOZ_ALWAYS_INLINE bool JSString::validateLength(JSContext* cx, size_t length) {
  return validateLengthInternal<js::CanGC>(cx, length);
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE bool JSString::validateLengthInternal(JSContext* cx,
                                                        size_t length) {
  if (MOZ_UNLIKELY(length > JSString::MAX_LENGTH)) {
    if constexpr (allowGC) {
      js::ReportOversizedAllocation(cx, JSMSG_ALLOC_OVERFLOW);
    }
    return false;
  }

  return true;
}

template <>
MOZ_ALWAYS_INLINE const char16_t* JSString::nonInlineCharsRaw() const {
  return d.s.u2.nonInlineCharsTwoByte;
}

template <>
MOZ_ALWAYS_INLINE const JS::Latin1Char* JSString::nonInlineCharsRaw() const {
  return d.s.u2.nonInlineCharsLatin1;
}

bool JSString::ownsMallocedChars() const {
  if (!hasOutOfLineChars() || asLinear().hasStringBuffer()) {
    return false;
  }

  js::gc::StoreBuffer* sb = storeBuffer();
  if (!sb) {
    // Tenured strings always own out-of-line chars.
    return true;
  }

  // Return whether the chars are malloced. Note: this allows the data to be in
  // a different nursery chunk than the Cell itself, at the performance cost of
  // iterating over all chunks.
  return !sb->nursery().isInside(asLinear().nonInlineCharsRaw());
}

template <typename CharT>
inline size_t JSLinearString::maybeMallocCharsOnPromotion(
    js::Nursery* nursery) {
  const void** chars;
  if constexpr (std::is_same_v<CharT, char16_t>) {
    chars = reinterpret_cast<const void**>(&d.s.u2.nonInlineCharsTwoByte);
  } else {
    chars = reinterpret_cast<const void**>(&d.s.u2.nonInlineCharsLatin1);
  }

  size_t bytesUsed = length() * sizeof(CharT);
  size_t bytesCapacity =
      isExtensible() ? (asExtensible().capacity() * sizeof(CharT)) : bytesUsed;
  MOZ_ASSERT(bytesUsed <= bytesCapacity);

  if (nursery->maybeMoveNurseryOrMallocBufferOnPromotion(
          const_cast<void**>(chars), this, bytesUsed, bytesCapacity,
          js::MemoryUse::StringContents,
          js::StringBufferArena) == js::Nursery::BufferMoved) {
    MOZ_ASSERT(allocSize() == bytesCapacity);
    return bytesCapacity;
  }

  return 0;
}

inline size_t JSLinearString::allocSize() const {
  MOZ_ASSERT(ownsMallocedChars() || hasStringBuffer());

  size_t charSize =
      hasLatin1Chars() ? sizeof(JS::Latin1Char) : sizeof(char16_t);
  size_t count = isExtensible() ? asExtensible().capacity() : length();
  return count * charSize;
}

inline size_t JSString::allocSize() const {
  if (ownsMallocedChars() || hasStringBuffer()) {
    return asLinear().allocSize();
  }
  return 0;
}

inline JSRope::JSRope(JSString* left, JSString* right, size_t length) {
  // JITs expect rope children aren't empty.
  MOZ_ASSERT(!left->empty() && !right->empty());

  // |length| must be the sum of the length of both child nodes.
  MOZ_ASSERT(left->length() + right->length() == length);

  // |isLatin1| is set when both children are guaranteed to contain only Latin-1
  // characters. Note that flattening either rope child can clear the Latin-1
  // flag of that child, so it's possible that a Latin-1 rope can end up with
  // both children being two-byte (dependent) strings.
  bool isLatin1 = left->hasLatin1Chars() && right->hasLatin1Chars();

  // Do not try to make a rope that could fit inline.
  MOZ_ASSERT_IF(!isLatin1, !JSInlineString::lengthFits<char16_t>(length));
  MOZ_ASSERT_IF(isLatin1, !JSInlineString::lengthFits<JS::Latin1Char>(length));

  js::CharEncoding encoding = js::CharEncodingFromIsLatin1(isLatin1);
  uint32_t flags = StringFlags::ropeFlags(encoding);
  initLengthAndFlags(length, flags);
  d.s.u2.left = left;
  d.s.u3.right = right;

  // Post-barrier by inserting into the whole cell buffer if either
  // this -> left or this -> right is a tenured -> nursery edge.
  if (isTenured()) {
    js::gc::StoreBuffer* sb = left->storeBuffer();
    if (!sb) {
      sb = right->storeBuffer();
    }
    if (sb) {
      sb->putWholeCell(this);
    }
  }
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSRope* JSRope::new_(
    JSContext* cx,
    typename js::MaybeRooted<JSString*, allowGC>::HandleType left,
    typename js::MaybeRooted<JSString*, allowGC>::HandleType right,
    size_t length, js::gc::Heap heap) {
  if (MOZ_UNLIKELY(!validateLengthInternal<allowGC>(cx, length))) {
    return nullptr;
  }
  return cx->newCell<JSRope, allowGC>(heap, left, right, length);
}

inline JSDependentString::JSDependentString(JSLinearString* base, size_t start,
                                            size_t length) {
  MOZ_ASSERT(start + length <= base->length());
  JS::AutoCheckCannotGC nogc;
  js::CharEncoding encoding =
      js::CharEncodingFromIsLatin1(base->hasLatin1Chars());
  uint32_t flags = StringFlags::dependentStringFlags(encoding);
  initLengthAndFlags(length, flags);
  if (encoding == js::CharEncoding::Latin1) {
    d.s.u2.nonInlineCharsLatin1 = base->latin1Chars(nogc) + start;
  } else {
    d.s.u2.nonInlineCharsTwoByte = base->twoByteChars(nogc) + start;
  }
  base->setDependedOn();
  d.s.u3.base = base;
  if (isTenured() && !base->isTenured()) {
    base->storeBuffer()->putWholeCell(this);
  }
}

template <JS::ContractBaseChain contract>
MOZ_ALWAYS_INLINE JSLinearString* JSDependentString::newImpl_(
    JSContext* cx, JSLinearString* baseArg, size_t start, size_t length,
    js::gc::Heap heap) {
  // Not passed in as a Handle because `base` is reassigned.
  JS::Rooted<JSLinearString*> base(cx, baseArg);

  // Do not try to make a dependent string that could fit inline.
  MOZ_ASSERT_IF(base->hasTwoByteChars(),
                !JSInlineString::lengthFits<char16_t>(length));
  MOZ_ASSERT_IF(!base->hasTwoByteChars(),
                !JSInlineString::lengthFits<JS::Latin1Char>(length));

  // Invariant: if a tenured dependent string points to chars in the nursery,
  // then the string must be in the store buffer.
  //
  // Refuse to create a chain tenured -> tenured -> nursery (with nursery
  // chars). The same holds for anything else that might create length > 1
  // chains of dependent strings.
  bool mustContract;
  if constexpr (contract == JS::ContractBaseChain::Contract) {
    mustContract = true;
  } else {
    auto& nursery = cx->runtime()->gc.nursery();
    mustContract = nursery.isInside(base->nonInlineCharsRaw());
  }

  if (mustContract) {
    // Try to avoid long chains of dependent strings. We can't avoid these
    // entirely, however, due to how ropes are flattened.
    if (base->isDependent()) {
      start += base->asDependent().baseOffset();
      base = base->asDependent().base();
    }
  }

  MOZ_ASSERT(start + length <= base->length());

  JSDependentString* str;
  if constexpr (contract == JS::ContractBaseChain::Contract) {
    return cx->newCell<JSDependentString>(heap, base, start, length);
  }

  str = cx->newCell<JSDependentString>(heap, base, start, length);
  if (str && base->isDependent() && base->isTenured()) {
    // Tenured dependent -> nursery base string edges are problematic for
    // deduplication if the tenured dependent string can itself have strings
    // dependent on it. Whenever such a thing can be created, the nursery base
    // must be marked as non-deduplicatable.
    JSString* rootBase = base;
    while (rootBase->isDependent()) {
      rootBase = rootBase->base();
    }
    if (!rootBase->isTenured()) {
      rootBase->setNonDeduplicatable();
    }
  }

  return str;
}

/* static */
inline JSLinearString* JSDependentString::new_(JSContext* cx,
                                               JSLinearString* base,
                                               size_t start, size_t length,
                                               js::gc::Heap heap) {
  return newImpl_<JS::ContractBaseChain::Contract>(cx, base, start, length,
                                                   heap);
}

inline JSLinearString::JSLinearString(const char16_t* chars, size_t length,
                                      bool hasBuffer) {
  uint32_t flags =
      StringFlags::linearStringFlags(js::CharEncoding::TwoByte, hasBuffer);
  initLengthAndFlags(length, flags);
  // Check that the new buffer is located in the StringBufferArena.
  checkStringCharsArena(chars, hasBuffer);
  d.s.u2.nonInlineCharsTwoByte = chars;
}

inline JSLinearString::JSLinearString(const JS::Latin1Char* chars,
                                      size_t length, bool hasBuffer) {
  uint32_t flags =
      StringFlags::linearStringFlags(js::CharEncoding::Latin1, hasBuffer);
  initLengthAndFlags(length, flags);
  // Check that the new buffer is located in the StringBufferArena.
  checkStringCharsArena(chars, hasBuffer);
  d.s.u2.nonInlineCharsLatin1 = chars;
}

template <typename CharT>
inline JSLinearString::JSLinearString(
    JS::MutableHandle<JSString::OwnedChars<CharT>> chars) {
  // Note that it is possible that the chars may have been moved from the
  // nursery to the malloc heap when allocating the Cell that this constructor
  // is initializing.
  MOZ_ASSERT(chars.data());
  checkStringCharsArena(chars.data(), chars.hasStringBuffer());
  if (isTenured()) {
    chars.ensureNonNursery();
  }
  constexpr js::CharEncoding encoding = js::CharEncodingFromType<CharT>();
  uint32_t flags =
      StringFlags::linearStringFlags(encoding, chars.hasStringBuffer());
  initLengthAndFlags(chars.length(), flags);
  if constexpr (encoding == js::CharEncoding::Latin1) {
    d.s.u2.nonInlineCharsLatin1 = chars.data();
  } else {
    d.s.u2.nonInlineCharsTwoByte = chars.data();
  }
}

void JSLinearString::disownCharsBecauseError() {
  setLengthAndFlags(
      0, StringFlags::linearStringFlags(js::CharEncoding::Latin1,
                                        /* hasStringBuffer = */ false));
  d.s.u2.nonInlineCharsLatin1 = nullptr;
}

template <js::AllowGC allowGC, typename CharT>
MOZ_ALWAYS_INLINE JSLinearString* JSLinearString::new_(
    JSContext* cx, JS::MutableHandle<JSString::OwnedChars<CharT>> chars,
    js::gc::Heap heap) {
  if (MOZ_UNLIKELY(!validateLengthInternal<allowGC>(cx, chars.length()))) {
    return nullptr;
  }

  return newValidLength<allowGC>(cx, chars, heap);
}

template <js::AllowGC allowGC, typename CharT>
MOZ_ALWAYS_INLINE JSLinearString* JSLinearString::newValidLength(
    JSContext* cx, JS::MutableHandle<JSString::OwnedChars<CharT>> chars,
    js::gc::Heap heap) {
  MOZ_ASSERT(!cx->zone()->isAtomsZone());
  MOZ_ASSERT(!JSInlineString::lengthFits<CharT>(chars.length()));
  JSLinearString* str = cx->newCell<JSLinearString, allowGC>(heap, chars);
  if (!str) {
    return nullptr;
  }

  if (!str->isTenured()) {
    // If the following registration fails, the string is partially initialized
    // and must be made valid, or its finalizer may attempt to free
    // uninitialized memory.
    bool ok = true;
    if (chars.isMalloced()) {
      ok = cx->nursery().registerMallocedBuffer(chars.data(), chars.size());
    } else if (chars.hasStringBuffer()) {
      ok = cx->nursery().addStringBuffer(str);
    }
    if (!ok) {
      str->disownCharsBecauseError();
      if (allowGC) {
        ReportOutOfMemory(cx);
      }
      return nullptr;
    }
  } else {
    // Note: this will overcount if the same StringBuffer is used by multiple JS
    // strings. Unfortunately we don't have a good way to avoid this.
    cx->zone()->addCellMemory(str, chars.size(), js::MemoryUse::StringContents);
  }

  // Either the tenured Cell or the nursery's registry owns the chars now.
  chars.release();

  return str;
}

template <typename CharT>
MOZ_ALWAYS_INLINE JSAtom* JSAtom::newValidLength(JSContext* cx,
                                                 OwnedChars<CharT>& chars,
                                                 js::HashNumber hash) {
  size_t length = chars.length();
  MOZ_ASSERT(validateLength(cx, length));
  MOZ_ASSERT(cx->zone()->isAtomsZone());

  // Note: atom allocation can't GC. The unrooted |chars| argument relies on
  // this.
  JSAtom* str = cx->newCell<js::NormalAtom, js::NoGC>(chars, hash);
  if (!str) {
    return nullptr;
  }

  // The atom now owns the chars.
  chars.release();

  MOZ_ASSERT(str->isTenured());
  cx->zone()->addCellMemory(str, length * sizeof(CharT),
                            js::MemoryUse::StringContents);

  return str;
}

inline js::PropertyName* JSLinearString::toPropertyName(JSContext* cx) {
#ifdef DEBUG
  uint32_t dummy;
  MOZ_ASSERT(!isIndex(&dummy));
#endif
  JSAtom* atom = js::AtomizeString(cx, this);
  if (!atom) {
    return nullptr;
  }
  return atom->asPropertyName();
}

// String characters are movable in the following cases:
//
// 1. Inline nursery strings (moved during promotion)
// 2. Nursery strings with nursery chars (moved during promotion)
// 3. Nursery strings that are deduplicated (moved during promotion)
// 4. Inline tenured strings (moved during compaction)
//
// This method does not consider #3, because if this method returns true and the
// caller does not want the characters to move, it can fix them in place by
// setting the nondeduplicatable bit. (If the bit were already taken into
// consideration, then the caller wouldn't know whether the movability is
// "fixable" or not. If it is *only* movable because of the lack of the bit
// being set, then it is fixable by setting the bit.)
bool JSLinearString::hasMovableChars() const {
  const JSLinearString* topBase = this;
  while (topBase->hasBase()) {
    topBase = topBase->base();
  }
  if (topBase->isInline()) {
    return true;
  }
  if (topBase->isTenured()) {
    return false;
  }
  return topBase->storeBuffer()->nursery().isInside(
      topBase->nonInlineCharsRaw());
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSThinInlineString* JSThinInlineString::new_(
    JSContext* cx, js::gc::Heap heap) {
  MOZ_ASSERT(!cx->zone()->isAtomsZone());
  return cx->newCell<JSThinInlineString, allowGC>(heap);
}

template <js::AllowGC allowGC>
MOZ_ALWAYS_INLINE JSFatInlineString* JSFatInlineString::new_(
    JSContext* cx, js::gc::Heap heap) {
  MOZ_ASSERT(!cx->zone()->isAtomsZone());
  return cx->newCell<JSFatInlineString, allowGC>(heap);
}

inline JSThinInlineString::JSThinInlineString(size_t length,
                                              JS::Latin1Char** chars) {
  MOZ_ASSERT(lengthFits<JS::Latin1Char>(length));
  uint32_t flags = StringFlags::thinInlineStringFlags(js::CharEncoding::Latin1);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageLatin1;
}

inline JSThinInlineString::JSThinInlineString(size_t length, char16_t** chars) {
  MOZ_ASSERT(lengthFits<char16_t>(length));
  uint32_t flags =
      StringFlags::thinInlineStringFlags(js::CharEncoding::TwoByte);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageTwoByte;
}

inline JSFatInlineString::JSFatInlineString(size_t length,
                                            JS::Latin1Char** chars) {
  MOZ_ASSERT(lengthFits<JS::Latin1Char>(length));
  uint32_t flags = StringFlags::fatInlineStringFlags(js::CharEncoding::Latin1);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageLatin1;
}

inline JSFatInlineString::JSFatInlineString(size_t length, char16_t** chars) {
  MOZ_ASSERT(lengthFits<char16_t>(length));
  uint32_t flags = StringFlags::fatInlineStringFlags(js::CharEncoding::TwoByte);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageTwoByte;
}

inline JSExternalString::JSExternalString(
    const char16_t* chars, size_t length,
    const JSExternalStringCallbacks* callbacks) {
  MOZ_ASSERT(callbacks);
  uint32_t flags = StringFlags::externalStringFlags(js::CharEncoding::TwoByte);
  initLengthAndFlags(length, flags);
  d.s.u2.nonInlineCharsTwoByte = chars;
  d.s.u3.externalCallbacks = callbacks;
}

inline JSExternalString::JSExternalString(
    const JS::Latin1Char* chars, size_t length,
    const JSExternalStringCallbacks* callbacks) {
  MOZ_ASSERT(callbacks);
  uint32_t flags = StringFlags::externalStringFlags(js::CharEncoding::Latin1);
  initLengthAndFlags(length, flags);
  d.s.u2.nonInlineCharsLatin1 = chars;
  d.s.u3.externalCallbacks = callbacks;
}

template <typename CharT>
/* static */
MOZ_ALWAYS_INLINE JSExternalString* JSExternalString::newImpl(
    JSContext* cx, const CharT* chars, size_t length,
    const JSExternalStringCallbacks* callbacks) {
  if (MOZ_UNLIKELY(!validateLength(cx, length))) {
    return nullptr;
  }
  auto* str = cx->newCell<JSExternalString>(chars, length, callbacks);

  if (!str) {
    return nullptr;
  }
  size_t nbytes = length * sizeof(CharT);

  MOZ_ASSERT(str->isTenured());
  js::AddCellMemory(str, nbytes, js::MemoryUse::StringContents);

  return str;
}

/* static */
MOZ_ALWAYS_INLINE JSExternalString* JSExternalString::new_(
    JSContext* cx, const JS::Latin1Char* chars, size_t length,
    const JSExternalStringCallbacks* callbacks) {
  return newImpl(cx, chars, length, callbacks);
}

/* static */
MOZ_ALWAYS_INLINE JSExternalString* JSExternalString::new_(
    JSContext* cx, const char16_t* chars, size_t length,
    const JSExternalStringCallbacks* callbacks) {
  return newImpl(cx, chars, length, callbacks);
}

template <typename CharT>
inline js::NormalAtom::NormalAtom(const OwnedChars<CharT>& chars,
                                  js::HashNumber hash)
    : hash_(hash) {
  // Check that the new buffer is located in the StringBufferArena
  checkStringCharsArena(chars.data(), chars.hasStringBuffer());

  constexpr js::CharEncoding encoding = js::CharEncodingFromType<CharT>();
  uint32_t flags =
      StringFlags::normalAtomFlags(encoding, chars.hasStringBuffer());
  initLengthAndFlags(chars.length(), flags);

  if constexpr (std::is_same_v<CharT, char16_t>) {
    d.s.u2.nonInlineCharsTwoByte = chars.data();
  } else {
    d.s.u2.nonInlineCharsLatin1 = chars.data();
  }
}

#ifndef JS_64BIT
inline js::ThinInlineAtom::ThinInlineAtom(size_t length, JS::Latin1Char** chars,
                                          js::HashNumber hash)
    : NormalAtom(hash) {
  uint32_t flags = StringFlags::thinInlineAtomFlags(js::CharEncoding::Latin1);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageLatin1;
}

inline js::ThinInlineAtom::ThinInlineAtom(size_t length, char16_t** chars,
                                          js::HashNumber hash)
    : NormalAtom(hash) {
  uint32_t flags = StringFlags::thinInlineAtomFlags(js::CharEncoding::TwoByte);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageTwoByte;
}
#endif

inline js::FatInlineAtom::FatInlineAtom(size_t length, JS::Latin1Char** chars,
                                        js::HashNumber hash)
    : hash_(hash) {
  MOZ_ASSERT(lengthFits<JS::Latin1Char>(length));
  uint32_t flags = StringFlags::fatInlineAtomFlags(js::CharEncoding::Latin1);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageLatin1;
}

inline js::FatInlineAtom::FatInlineAtom(size_t length, char16_t** chars,
                                        js::HashNumber hash)
    : hash_(hash) {
  MOZ_ASSERT(lengthFits<char16_t>(length));
  uint32_t flags = StringFlags::fatInlineAtomFlags(js::CharEncoding::TwoByte);
  initLengthAndFlags(length, flags);
  *chars = d.inlineStorageTwoByte;
}

inline JSLinearString* js::StaticStrings::getUnitString(JSContext* cx,
                                                        char16_t c) {
  if (c < UNIT_STATIC_LIMIT) {
    return getUnit(c);
  }
  return js::NewInlineString<CanGC>(cx, {c}, 1);
}

inline JSLinearString* js::StaticStrings::getUnitStringForElement(
    JSContext* cx, JSString* str, size_t index) {
  MOZ_ASSERT(index < str->length());

  char16_t c;
  if (!str->getChar(cx, index, &c)) {
    return nullptr;
  }
  return getUnitString(cx, c);
}

inline JSLinearString* js::StaticStrings::getUnitStringForElement(
    JSContext* cx, const JSLinearString* str, size_t index) {
  MOZ_ASSERT(index < str->length());

  char16_t c = str->latin1OrTwoByteChar(index);
  return getUnitString(cx, c);
}

MOZ_ALWAYS_INLINE void JSString::finalize(JS::GCContext* gcx) {
  /* FatInline strings are in a different arena. */
  MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_STRING);
  MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_ATOM);

  if (isLinear()) {
    asLinear().finalize(gcx);
  } else {
    MOZ_ASSERT(isRope());
  }
}

inline void JSLinearString::finalize(JS::GCContext* gcx) {
  MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_STRING);
  MOZ_ASSERT(getAllocKind() != js::gc::AllocKind::FAT_INLINE_ATOM);

  if (!isInline() && !isDependent()) {
    size_t size = allocSize();
    if (hasStringBuffer()) {
      mozilla::StringBuffer* buffer = stringBuffer();
      buffer->Release();
      gcx->removeCellMemory(this, size, js::MemoryUse::StringContents);
    } else {
      gcx->free_(this, nonInlineCharsRaw(), size,
                 js::MemoryUse::StringContents);
    }
  }
}

inline void JSFatInlineString::finalize(JS::GCContext* gcx) {
  MOZ_ASSERT(getAllocKind() == js::gc::AllocKind::FAT_INLINE_STRING);
  MOZ_ASSERT(isInline());

  // Nothing to do.
}

inline void js::FatInlineAtom::finalize(JS::GCContext* gcx) {
  MOZ_ASSERT(JSString::isAtom());
  MOZ_ASSERT(getAllocKind() == js::gc::AllocKind::FAT_INLINE_ATOM);

  // Nothing to do.
}

inline void JSExternalString::finalize(JS::GCContext* gcx) {
  MOZ_ASSERT(JSString::isExternal());

  if (hasLatin1Chars()) {
    size_t nbytes = length() * sizeof(JS::Latin1Char);
    gcx->removeCellMemory(this, nbytes, js::MemoryUse::StringContents);

    callbacks()->finalize(const_cast<JS::Latin1Char*>(rawLatin1Chars()));
  } else {
    size_t nbytes = length() * sizeof(char16_t);
    gcx->removeCellMemory(this, nbytes, js::MemoryUse::StringContents);

    callbacks()->finalize(const_cast<char16_t*>(rawTwoByteChars()));
  }
}

#endif /* vm_StringType_inl_h */