Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 711 insertions, 0 deletions

diff --git a/xpcom/reflect/xptinfo/xptinfo.h b/xpcom/reflect/xptinfo/xptinfo.h
new file mode 100644
index 0000000000..2456c2c2b5
--- /dev/null
+++ b/xpcom/reflect/xptinfo/xptinfo.h
@@ -0,0 +1,711 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+/**
+ * Structures and methods with information about XPCOM interfaces for use by
+ * XPConnect. The static backing data structures used by this file are generated
+ * from xpidl interfaces by the jsonxpt.py and xptcodegen.py scripts.
+ */
+
+#ifndef xptinfo_h
+#define xptinfo_h
+
+#include <stdint.h>
+#include "nsID.h"
+#include "mozilla/Assertions.h"
+#include "jsapi.h"
+#include "js/Symbol.h"
+#include "js/Value.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+// Forward Declarations
+namespace mozilla {
+namespace dom {
+struct NativePropertyHooks;
+}  // namespace dom
+}  // namespace mozilla
+
+struct nsXPTInterfaceInfo;
+struct nsXPTType;
+struct nsXPTParamInfo;
+struct nsXPTMethodInfo;
+struct nsXPTConstantInfo;
+struct nsXPTDOMObjectInfo;
+
+enum class nsXPTInterface : uint16_t;
+
+// Internal helper methods.
+namespace xpt {
+namespace detail {
+
+inline const nsXPTInterfaceInfo* GetInterface(uint16_t aIndex);
+inline const nsXPTType& GetType(uint16_t aIndex);
+inline const nsXPTParamInfo& GetParam(uint16_t aIndex);
+inline const nsXPTMethodInfo& GetMethod(uint16_t aIndex);
+inline const nsXPTConstantInfo& GetConstant(uint16_t aIndex);
+inline const nsXPTDOMObjectInfo& GetDOMObjectInfo(uint16_t aIndex);
+inline const char* GetString(uint32_t aIndex);
+
+const nsXPTInterfaceInfo* InterfaceByIID(const nsIID& aIID);
+const nsXPTInterfaceInfo* InterfaceByName(const char* aName);
+
+extern const uint16_t sInterfacesSize;
+
+}  // namespace detail
+}  // namespace xpt
+
+/*
+ * An Interface describes a single XPCOM interface, including all of its
+ * methods. We don't record non-scriptable interfaces.
+ */
+struct nsXPTInterfaceInfo {
+  // High efficiency getters for Interfaces based on perfect hashes.
+  static const nsXPTInterfaceInfo* ByIID(const nsIID& aIID) {
+    return xpt::detail::InterfaceByIID(aIID);
+  }
+  static const nsXPTInterfaceInfo* ByName(const char* aName) {
+    return xpt::detail::InterfaceByName(aName);
+  }
+
+  static const nsXPTInterfaceInfo* Get(nsXPTInterface aID) {
+    return ByIndex(uint16_t(aID));
+  }
+
+  // These are only needed for Components_interfaces's enumerator.
+  static const nsXPTInterfaceInfo* ByIndex(uint16_t aIndex) {
+    // NOTE: We add 1 here, as the internal index 0 is reserved for null.
+    return xpt::detail::GetInterface(aIndex + 1);
+  }
+  static uint16_t InterfaceCount() { return xpt::detail::sInterfacesSize; }
+
+  // Interface flag getters
+  bool IsFunction() const { return mFunction; }
+  bool IsBuiltinClass() const { return mBuiltinClass; }
+  bool IsMainProcessScriptableOnly() const {
+    return mMainProcessScriptableOnly;
+  }
+
+  const char* Name() const { return xpt::detail::GetString(mName); }
+  const nsIID& IID() const { return mIID; }
+
+  // Get the parent interface, or null if this interface doesn't have a parent.
+  const nsXPTInterfaceInfo* GetParent() const {
+    return xpt::detail::GetInterface(mParent);
+  }
+
+  // Do we have an ancestor interface with the given IID?
+  bool HasAncestor(const nsIID& aIID) const;
+
+  // Get methods & constants
+  uint16_t ConstantCount() const { return mNumConsts; }
+  const nsXPTConstantInfo& Constant(uint16_t aIndex) const;
+  uint16_t MethodCount() const { return mNumMethods; }
+  const nsXPTMethodInfo& Method(uint16_t aIndex) const;
+
+  nsresult GetMethodInfo(uint16_t aIndex, const nsXPTMethodInfo** aInfo) const;
+  nsresult GetConstant(uint16_t aIndex, JS::MutableHandle<JS::Value> constant,
+                       char** aName) const;
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsID mIID;
+  uint32_t mName;  // Index into xpt::detail::sStrings
+
+  uint16_t mParent : 14;
+  uint16_t mBuiltinClass : 1;
+  // XXX(nika): Do we need this if we don't have addons anymore?
+  uint16_t mMainProcessScriptableOnly : 1;
+
+  uint16_t mMethods;  // Index into xpt::detail::sMethods
+
+  uint16_t mConsts : 14;  // Index into xpt::detail::sConsts
+  uint16_t mFunction : 1;
+  // uint16_t unused : 1;
+
+  uint8_t mNumMethods;  // NOTE(24/04/18): largest=nsIDocShell (193)
+  uint8_t mNumConsts;   // NOTE(24/04/18): largest=nsIAccessibleRole (175)
+};
+
+// The fields in nsXPTInterfaceInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTInterfaceInfo) == 28, "wrong size?");
+
+/*
+ * The following enum represents contains the different tag types which
+ * can be found in nsXPTTypeInfo::mTag.
+ *
+ * WARNING: mTag is 5 bits wide, supporting at most 32 tags.
+ */
+enum nsXPTTypeTag : uint8_t {
+  // Arithmetic (POD) Types
+  //  - Do not require cleanup,
+  //  - All bit patterns are valid,
+  //  - Outparams may be uninitialized by caller,
+  //  - Directly supported in xptcall.
+  //
+  // NOTE: The name 'Arithmetic' comes from Harbison/Steele. Despite being a tad
+  // unclear, it is used frequently in xptcall, so is unlikely to be changed.
+  TD_INT8 = 0,
+  TD_INT16 = 1,
+  TD_INT32 = 2,
+  TD_INT64 = 3,
+  TD_UINT8 = 4,
+  TD_UINT16 = 5,
+  TD_UINT32 = 6,
+  TD_UINT64 = 7,
+  TD_FLOAT = 8,
+  TD_DOUBLE = 9,
+  TD_BOOL = 10,
+  TD_CHAR = 11,
+  TD_WCHAR = 12,
+  _TD_LAST_ARITHMETIC = TD_WCHAR,
+
+  // Pointer Types
+  //  - Require cleanup unless NULL,
+  //  - All-zeros (NULL) bit pattern is valid,
+  //  - Outparams may be uninitialized by caller,
+  //  - Supported in xptcall as raw pointer.
+  TD_VOID = 13,
+  TD_NSIDPTR = 14,
+  TD_PSTRING = 15,
+  TD_PWSTRING = 16,
+  TD_INTERFACE_TYPE = 17,
+  TD_INTERFACE_IS_TYPE = 18,
+  TD_LEGACY_ARRAY = 19,
+  TD_PSTRING_SIZE_IS = 20,
+  TD_PWSTRING_SIZE_IS = 21,
+  TD_DOMOBJECT = 22,
+  TD_PROMISE = 23,
+  _TD_LAST_POINTER = TD_PROMISE,
+
+  // Complex Types
+  //  - Require cleanup,
+  //  - Always passed indirectly,
+  //  - Outparams must be initialized by caller,
+  //  - Supported in xptcall due to indirection.
+  TD_UTF8STRING = 24,
+  TD_CSTRING = 25,
+  TD_ASTRING = 26,
+  TD_NSID = 27,
+  TD_JSVAL = 28,
+  TD_ARRAY = 29,
+  _TD_LAST_COMPLEX = TD_ARRAY
+};
+
+static_assert(_TD_LAST_COMPLEX < 32, "nsXPTTypeTag must fit in 5 bits");
+
+/*
+ * A nsXPTType is a union used to identify the type of a method argument or
+ * return value. The internal data is stored as an 5-bit tag, and two 8-bit
+ * integers, to keep alignment requirements low.
+ *
+ * nsXPTType contains 3 extra bits, reserved for use by nsXPTParamInfo.
+ */
+struct nsXPTType {
+  nsXPTTypeTag Tag() const { return static_cast<nsXPTTypeTag>(mTag); }
+
+  // The index in the function argument list which should be used when
+  // determining the iid_is or size_is properties of this dependent type.
+  uint8_t ArgNum() const {
+    MOZ_ASSERT(Tag() == TD_INTERFACE_IS_TYPE || Tag() == TD_PSTRING_SIZE_IS ||
+               Tag() == TD_PWSTRING_SIZE_IS || Tag() == TD_LEGACY_ARRAY);
+    return mData1;
+  }
+
+ private:
+  // Helper for reading 16-bit data values split between mData1 and mData2.
+  uint16_t Data16() const {
+    return static_cast<uint16_t>(mData1 << 8) | mData2;
+  }
+
+ public:
+  // Get the type of the element in the current array or sequence. Arrays only
+  // fit 8 bits of type data, while sequences support up to 16 bits of type data
+  // due to not needing to store an ArgNum.
+  const nsXPTType& ArrayElementType() const {
+    if (Tag() == TD_LEGACY_ARRAY) {
+      return xpt::detail::GetType(mData2);
+    }
+    MOZ_ASSERT(Tag() == TD_ARRAY);
+    return xpt::detail::GetType(Data16());
+  }
+
+  // We store the 16-bit iface value as two 8-bit values in order to
+  // avoid 16-bit alignment requirements for XPTTypeDescriptor, which
+  // reduces its size and also the size of XPTParamDescriptor.
+  const nsXPTInterfaceInfo* GetInterface() const {
+    MOZ_ASSERT(Tag() == TD_INTERFACE_TYPE);
+    return xpt::detail::GetInterface(Data16());
+  }
+
+  const nsXPTDOMObjectInfo& GetDOMObjectInfo() const {
+    MOZ_ASSERT(Tag() == TD_DOMOBJECT);
+    return xpt::detail::GetDOMObjectInfo(Data16());
+  }
+
+  // See the comments in nsXPTTypeTag for an explanation as to what each of
+  // these categories mean.
+  bool IsArithmetic() const { return Tag() <= _TD_LAST_ARITHMETIC; }
+  bool IsPointer() const {
+    return !IsArithmetic() && Tag() <= _TD_LAST_POINTER;
+  }
+  bool IsComplex() const { return Tag() > _TD_LAST_POINTER; }
+
+  bool IsInterfacePointer() const {
+    return Tag() == TD_INTERFACE_TYPE || Tag() == TD_INTERFACE_IS_TYPE;
+  }
+
+  bool IsDependent() const {
+    return (Tag() == TD_ARRAY && InnermostType().IsDependent()) ||
+           Tag() == TD_INTERFACE_IS_TYPE || Tag() == TD_LEGACY_ARRAY ||
+           Tag() == TD_PSTRING_SIZE_IS || Tag() == TD_PWSTRING_SIZE_IS;
+  }
+
+  // Unwrap a nested type to its innermost value (e.g. through arrays).
+  const nsXPTType& InnermostType() const {
+    if (Tag() == TD_LEGACY_ARRAY || Tag() == TD_ARRAY) {
+      return ArrayElementType().InnermostType();
+    }
+    return *this;
+  }
+
+  // In-memory size of native type in bytes.
+  inline size_t Stride() const;
+
+  // Offset the given base pointer to reference the element at the given index.
+  void* ElementPtr(const void* aBase, uint32_t aIndex) const {
+    return (char*)aBase + (aIndex * Stride());
+  }
+
+  // Zero out a native value of the given type. The type must not be 'complex'.
+  void ZeroValue(void* aValue) const {
+    MOZ_RELEASE_ASSERT(!IsComplex(), "Cannot zero a complex value");
+    memset(aValue, 0, Stride());
+  }
+
+  // Indexes into the extra types array of a small set of known types.
+  enum class Idx : uint8_t {
+    INT8 = 0,
+    UINT8,
+    INT16,
+    UINT16,
+    INT32,
+    UINT32,
+    INT64,
+    UINT64,
+    FLOAT,
+    DOUBLE,
+    BOOL,
+    CHAR,
+    WCHAR,
+    NSIDPTR,
+    PSTRING,
+    PWSTRING,
+    INTERFACE_IS_TYPE
+  };
+
+  // Helper methods for fabricating nsXPTType values used by xpconnect.
+  static nsXPTType MkArrayType(Idx aInner) {
+    MOZ_ASSERT(aInner <= Idx::INTERFACE_IS_TYPE);
+    return {TD_LEGACY_ARRAY, false, false, false, 0, (uint8_t)aInner};
+  }
+  static const nsXPTType& Get(Idx aInner) {
+    MOZ_ASSERT(aInner <= Idx::INTERFACE_IS_TYPE);
+    return xpt::detail::GetType((uint8_t)aInner);
+  }
+
+  ///////////////////////////////////////
+  // nsXPTType backwards compatibility //
+  ///////////////////////////////////////
+
+  nsXPTType& operator=(nsXPTTypeTag aPrefix) {
+    mTag = aPrefix;
+    return *this;
+  }
+  operator nsXPTTypeTag() const { return Tag(); }
+
+#define TD_ALIAS_(name_, value_) static constexpr nsXPTTypeTag name_ = value_
+  TD_ALIAS_(T_I8, TD_INT8);
+  TD_ALIAS_(T_I16, TD_INT16);
+  TD_ALIAS_(T_I32, TD_INT32);
+  TD_ALIAS_(T_I64, TD_INT64);
+  TD_ALIAS_(T_U8, TD_UINT8);
+  TD_ALIAS_(T_U16, TD_UINT16);
+  TD_ALIAS_(T_U32, TD_UINT32);
+  TD_ALIAS_(T_U64, TD_UINT64);
+  TD_ALIAS_(T_FLOAT, TD_FLOAT);
+  TD_ALIAS_(T_DOUBLE, TD_DOUBLE);
+  TD_ALIAS_(T_BOOL, TD_BOOL);
+  TD_ALIAS_(T_CHAR, TD_CHAR);
+  TD_ALIAS_(T_WCHAR, TD_WCHAR);
+  TD_ALIAS_(T_VOID, TD_VOID);
+  TD_ALIAS_(T_NSIDPTR, TD_NSIDPTR);
+  TD_ALIAS_(T_CHAR_STR, TD_PSTRING);
+  TD_ALIAS_(T_WCHAR_STR, TD_PWSTRING);
+  TD_ALIAS_(T_INTERFACE, TD_INTERFACE_TYPE);
+  TD_ALIAS_(T_INTERFACE_IS, TD_INTERFACE_IS_TYPE);
+  TD_ALIAS_(T_LEGACY_ARRAY, TD_LEGACY_ARRAY);
+  TD_ALIAS_(T_PSTRING_SIZE_IS, TD_PSTRING_SIZE_IS);
+  TD_ALIAS_(T_PWSTRING_SIZE_IS, TD_PWSTRING_SIZE_IS);
+  TD_ALIAS_(T_UTF8STRING, TD_UTF8STRING);
+  TD_ALIAS_(T_CSTRING, TD_CSTRING);
+  TD_ALIAS_(T_ASTRING, TD_ASTRING);
+  TD_ALIAS_(T_NSID, TD_NSID);
+  TD_ALIAS_(T_JSVAL, TD_JSVAL);
+  TD_ALIAS_(T_DOMOBJECT, TD_DOMOBJECT);
+  TD_ALIAS_(T_PROMISE, TD_PROMISE);
+  TD_ALIAS_(T_ARRAY, TD_ARRAY);
+#undef TD_ALIAS_
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint8_t mTag : 5;
+
+  // Parameter bitflags are packed into the XPTTypeDescriptor to save space.
+  // When the TypeDescriptor is not in a parameter, these flags are ignored.
+  uint8_t mInParam : 1;
+  uint8_t mOutParam : 1;
+  uint8_t mOptionalParam : 1;
+
+  // The data for the different variants is stored in these two data fields.
+  // These should only be accessed via the getter methods above, which will
+  // assert if the tag is invalid.
+  uint8_t mData1;
+  uint8_t mData2;
+};
+
+// The fields in nsXPTType were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTType) == 3, "wrong size");
+
+/*
+ * A nsXPTParamInfo is used to describe either a single argument to a method or
+ * a method's result. It stores its flags in the type descriptor to save space.
+ */
+struct nsXPTParamInfo {
+  bool IsIn() const { return mType.mInParam; }
+  bool IsOut() const { return mType.mOutParam; }
+  bool IsOptional() const { return mType.mOptionalParam; }
+  bool IsShared() const { return false; }  // XXX remove (backcompat)
+
+  // Get the type of this parameter.
+  const nsXPTType& Type() const { return mType; }
+  const nsXPTType& GetType() const {
+    return Type();
+  }  // XXX remove (backcompat)
+
+  // Whether this parameter is passed indirectly on the stack. All out/inout
+  // params are passed indirectly, and complex types are always passed
+  // indirectly.
+  bool IsIndirect() const { return IsOut() || Type().IsComplex(); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsXPTType mType;
+};
+
+// The fields in nsXPTParamInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTParamInfo) == 3, "wrong size");
+
+/*
+ * A nsXPTMethodInfo is used to describe a single interface method.
+ */
+struct nsXPTMethodInfo {
+  bool IsGetter() const { return mGetter; }
+  bool IsSetter() const { return mSetter; }
+  bool IsReflectable() const { return mReflectable; }
+  bool IsSymbol() const { return mIsSymbol; }
+  bool WantsOptArgc() const { return mOptArgc; }
+  bool WantsContext() const { return mContext; }
+  uint8_t ParamCount() const { return mNumParams; }
+
+  const char* Name() const {
+    MOZ_ASSERT(!IsSymbol());
+    return xpt::detail::GetString(mName);
+  }
+  const nsXPTParamInfo& Param(uint8_t aIndex) const {
+    MOZ_ASSERT(aIndex < mNumParams);
+    return xpt::detail::GetParam(mParams + aIndex);
+  }
+
+  bool HasRetval() const { return mHasRetval; }
+  const nsXPTParamInfo* GetRetval() const {
+    return mHasRetval ? &Param(mNumParams - 1) : nullptr;
+  }
+
+  // If this is an [implicit_jscontext] method, returns the index of the
+  // implicit JSContext* argument in the C++ method's argument list.
+  // Otherwise returns UINT8_MAX.
+  uint8_t IndexOfJSContext() const {
+    if (!WantsContext()) {
+      return UINT8_MAX;
+    }
+    if (IsGetter() || IsSetter()) {
+      // Getters/setters always have the context as first argument.
+      return 0;
+    }
+    // The context comes before the return value, if there is one.
+    MOZ_ASSERT_IF(HasRetval(), ParamCount() > 0);
+    return ParamCount() - uint8_t(HasRetval());
+  }
+
+  JS::SymbolCode GetSymbolCode() const {
+    MOZ_ASSERT(IsSymbol());
+    return JS::SymbolCode(mName);
+  }
+
+  JS::Symbol* GetSymbol(JSContext* aCx) const {
+    return JS::GetWellKnownSymbol(aCx, GetSymbolCode());
+  }
+
+  const char* SymbolDescription() const;
+
+  const char* NameOrDescription() const {
+    if (IsSymbol()) {
+      return SymbolDescription();
+    }
+    return Name();
+  }
+
+  bool GetId(JSContext* aCx, jsid& aId) const;
+
+  /////////////////////////////////////////////
+  // nsXPTMethodInfo backwards compatibility //
+  /////////////////////////////////////////////
+
+  const char* GetName() const { return Name(); }
+
+  uint8_t GetParamCount() const { return ParamCount(); }
+  const nsXPTParamInfo& GetParam(uint8_t aIndex) const { return Param(aIndex); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint32_t mName;    // Index into xpt::detail::sStrings.
+  uint16_t mParams;  // Index into xpt::detail::sParams.
+  uint8_t mNumParams;
+
+  uint8_t mGetter : 1;
+  uint8_t mSetter : 1;
+  uint8_t mReflectable : 1;
+  uint8_t mOptArgc : 1;
+  uint8_t mContext : 1;
+  uint8_t mHasRetval : 1;
+  uint8_t mIsSymbol : 1;
+};
+
+// The fields in nsXPTMethodInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTMethodInfo) == 8, "wrong size");
+
+// This number is chosen to be no larger than the maximum number of parameters
+// any XPIDL-defined function needs; there is a static assert in the generated
+// code from xptcodegen.py to verify that decision.  It is therefore also the
+// maximum number of stack allocated nsXPTCMiniVariant structures for argument
+// passing purposes in PrepareAndDispatch implementations.
+#if defined(MOZ_THUNDERBIRD) || defined(MOZ_SUITE)
+#  define PARAM_BUFFER_COUNT 18
+#else
+#  define PARAM_BUFFER_COUNT 14
+#endif
+
+/**
+ * A nsXPTConstantInfo is used to describe a single interface constant.
+ */
+struct nsXPTConstantInfo {
+  const char* Name() const { return xpt::detail::GetString(mName); }
+
+  JS::Value JSValue() const {
+    if (mSigned || mValue <= uint32_t(INT32_MAX)) {
+      return JS::Int32Value(int32_t(mValue));
+    }
+    return JS::DoubleValue(mValue);
+  }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  uint32_t mName : 31;  // Index into xpt::detail::mStrings.
+
+  // Whether the value should be interpreted as a int32_t or uint32_t.
+  uint32_t mSigned : 1;
+  uint32_t mValue;  // The value stored as a u32
+};
+
+// The fields in nsXPTConstantInfo were carefully ordered to minimize size.
+static_assert(sizeof(nsXPTConstantInfo) == 8, "wrong size");
+
+/**
+ * Object representing the information required to wrap and unwrap DOMObjects.
+ *
+ * This object will not live in rodata as it contains relocations.
+ */
+struct nsXPTDOMObjectInfo {
+  nsresult Unwrap(JS::Handle<JS::Value> aHandle, void** aObj,
+                  JSContext* aCx) const {
+    return mUnwrap(aHandle, aObj, aCx);
+  }
+
+  bool Wrap(JSContext* aCx, void* aObj,
+            JS::MutableHandle<JS::Value> aHandle) const {
+    return mWrap(aCx, aObj, aHandle);
+  }
+
+  void Cleanup(void* aObj) const { return mCleanup(aObj); }
+
+  ////////////////////////////////////////////////////////////////
+  // Ensure these fields are in the same order as xptcodegen.py //
+  ////////////////////////////////////////////////////////////////
+
+  nsresult (*mUnwrap)(JS::Handle<JS::Value> aHandle, void** aObj,
+                      JSContext* aCx);
+  bool (*mWrap)(JSContext* aCx, void* aObj,
+                JS::MutableHandle<JS::Value> aHandle);
+  void (*mCleanup)(void* aObj);
+};
+
+namespace xpt {
+namespace detail {
+
+// The UntypedTArray type allows low-level access from XPConnect to nsTArray
+// internals without static knowledge of the array element type in question.
+class UntypedTArray : public nsTArray_base<nsTArrayFallibleAllocator,
+                                           nsTArray_RelocateUsingMemutils> {
+ public:
+  void* Elements() const { return static_cast<void*>(Hdr() + 1); }
+
+  // Changes the length and capacity to be at least large enough for aTo
+  // elements.
+  bool SetLength(const nsXPTType& aEltTy, uint32_t aTo) {
+    if (!EnsureCapacity<nsTArrayFallibleAllocator>(aTo, aEltTy.Stride())) {
+      return false;
+    }
+
+    if (mHdr != EmptyHdr()) {
+      mHdr->mLength = aTo;
+    }
+
+    return true;
+  }
+
+  // Free backing memory for the nsTArray object.
+  void Clear() {
+    if (mHdr != EmptyHdr() && !UsesAutoArrayBuffer()) {
+      nsTArrayFallibleAllocator::Free(mHdr);
+    }
+    mHdr = EmptyHdr();
+  }
+};
+
+//////////////////////////////////////////////
+// Raw typelib data stored in const statics //
+//////////////////////////////////////////////
+
+// XPIDL information
+extern const nsXPTInterfaceInfo sInterfaces[];
+extern const nsXPTType sTypes[];
+extern const nsXPTParamInfo sParams[];
+extern const nsXPTMethodInfo sMethods[];
+extern const nsXPTConstantInfo sConsts[];
+extern const nsXPTDOMObjectInfo sDOMObjects[];
+
+extern const char sStrings[];
+
+//////////////////////////////////////
+// Helper Methods for fetching data //
+//////////////////////////////////////
+
+inline const nsXPTInterfaceInfo* GetInterface(uint16_t aIndex) {
+  if (aIndex > 0 && aIndex <= sInterfacesSize) {
+    return &sInterfaces[aIndex - 1];  // 1-based as 0 is a marker.
+  }
+  return nullptr;
+}
+
+inline const nsXPTType& GetType(uint16_t aIndex) { return sTypes[aIndex]; }
+
+inline const nsXPTParamInfo& GetParam(uint16_t aIndex) {
+  return sParams[aIndex];
+}
+
+inline const nsXPTMethodInfo& GetMethod(uint16_t aIndex) {
+  return sMethods[aIndex];
+}
+
+inline const nsXPTConstantInfo& GetConstant(uint16_t aIndex) {
+  return sConsts[aIndex];
+}
+
+inline const nsXPTDOMObjectInfo& GetDOMObjectInfo(uint16_t aIndex) {
+  return sDOMObjects[aIndex];
+}
+
+inline const char* GetString(uint32_t aIndex) { return &sStrings[aIndex]; }
+
+}  // namespace detail
+}  // namespace xpt
+
+#define XPT_FOR_EACH_ARITHMETIC_TYPE(MACRO) \
+  MACRO(TD_INT8, int8_t)                    \
+  MACRO(TD_INT16, int16_t)                  \
+  MACRO(TD_INT32, int32_t)                  \
+  MACRO(TD_INT64, int64_t)                  \
+  MACRO(TD_UINT8, uint8_t)                  \
+  MACRO(TD_UINT16, uint16_t)                \
+  MACRO(TD_UINT32, uint32_t)                \
+  MACRO(TD_UINT64, uint64_t)                \
+  MACRO(TD_FLOAT, float)                    \
+  MACRO(TD_DOUBLE, double)                  \
+  MACRO(TD_BOOL, bool)                      \
+  MACRO(TD_CHAR, char)                      \
+  MACRO(TD_WCHAR, char16_t)
+
+#define XPT_FOR_EACH_POINTER_TYPE(MACRO)    \
+  MACRO(TD_VOID, void*)                     \
+  MACRO(TD_NSIDPTR, nsID*)                  \
+  MACRO(TD_PSTRING, char*)                  \
+  MACRO(TD_PWSTRING, wchar_t*)              \
+  MACRO(TD_INTERFACE_TYPE, nsISupports*)    \
+  MACRO(TD_INTERFACE_IS_TYPE, nsISupports*) \
+  MACRO(TD_LEGACY_ARRAY, void*)             \
+  MACRO(TD_PSTRING_SIZE_IS, char*)          \
+  MACRO(TD_PWSTRING_SIZE_IS, wchar_t*)      \
+  MACRO(TD_DOMOBJECT, void*)                \
+  MACRO(TD_PROMISE, mozilla::dom::Promise*)
+
+#define XPT_FOR_EACH_COMPLEX_TYPE(MACRO) \
+  MACRO(TD_UTF8STRING, nsCString)        \
+  MACRO(TD_CSTRING, nsCString)           \
+  MACRO(TD_ASTRING, nsString)            \
+  MACRO(TD_NSID, nsID)                   \
+  MACRO(TD_JSVAL, JS::Value)             \
+  MACRO(TD_ARRAY, xpt::detail::UntypedTArray)
+
+#define XPT_FOR_EACH_TYPE(MACRO)      \
+  XPT_FOR_EACH_ARITHMETIC_TYPE(MACRO) \
+  XPT_FOR_EACH_POINTER_TYPE(MACRO)    \
+  XPT_FOR_EACH_COMPLEX_TYPE(MACRO)
+
+inline size_t nsXPTType::Stride() const {
+  // Compute the stride to use when walking an array of the given type.
+  switch (Tag()) {
+#define XPT_TYPE_STRIDE(tag, type) \
+  case tag:                        \
+    return sizeof(type);
+    XPT_FOR_EACH_TYPE(XPT_TYPE_STRIDE)
+#undef XPT_TYPE_STRIDE
+  }
+
+  MOZ_CRASH("Unknown type");
+}
+
+#endif /* xptinfo_h */