dom/bindings/ProxyHandlerUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_dom_ProxyHandlerUtils_h
   8 #define mozilla_dom_ProxyHandlerUtils_h
   9
  10 #include "mozilla/Likely.h"
  11 #include "mozilla/Maybe.h"
  12 #include "mozilla/TextUtils.h"
  13
  14 #include "js/Id.h"
  15 #include "js/Object.h"  // JS::GetClass
  16 #include "js/PropertyDescriptor.h"
  17 #include "js/String.h"  // JS::AtomToLinearString, JS::GetLinearString{CharAt,Length}
  18 #include "js/TypeDecls.h"
  19
  20 #include "jsfriendapi.h"  // js::StringIsArrayIndex
  21
  22 namespace mozilla::dom {
  23
  24 extern jsid s_length_id;
  25
  26 // A return value of UINT32_MAX indicates "not an array index".  Note, in
  27 // particular, that UINT32_MAX itself is not a valid array index in general.
  28 inline uint32_t GetArrayIndexFromId(JS::Handle<jsid> id) {
  29   // Much like js::IdIsIndex, except with a fast path for "length" and another
  30   // fast path for starting with a lowercase ascii char.  Is that second one
  31   // really needed?  I guess it is because StringIsArrayIndex is out of line...
  32   // as of now, use id.get() instead of id otherwise operands mismatch error
  33   // occurs.
  34   if (MOZ_LIKELY(id.isInt())) {
  35     return id.toInt();
  36   }
  37   if (MOZ_LIKELY(id.get() == s_length_id)) {
  38     return UINT32_MAX;
  39   }
  40   if (MOZ_UNLIKELY(!id.isAtom())) {
  41     return UINT32_MAX;
  42   }
  43
  44   JSLinearString* str = JS::AtomToLinearString(id.toAtom());
  45   if (MOZ_UNLIKELY(JS::GetLinearStringLength(str) == 0)) {
  46     return UINT32_MAX;
  47   }
  48
  49   char16_t firstChar = JS::GetLinearStringCharAt(str, 0);
  50   if (MOZ_LIKELY(IsAsciiLowercaseAlpha(firstChar))) {
  51     return UINT32_MAX;
  52   }
  53
  54   uint32_t i;
  55   return js::StringIsArrayIndex(str, &i) ? i : UINT32_MAX;
  56 }
  57
  58 inline bool IsArrayIndex(uint32_t index) { return index < UINT32_MAX; }
  59
  60 }  // namespace mozilla::dom
  61
  62 #endif /* mozilla_dom_ProxyHandlerUtils_h */