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struct nsID {
  /**
   * @name Identifier values
   */

  //@{
  uint32_t m0;
  uint16_t m1;
  uint16_t m2;
  uint8_t m3[8];
  //@}

  /**
   * @name Methods
   */

  //@{
  /**
   * Ensures everything is zeroed out.
   */
  void Clear();

  /**
   * Equivalency method. Compares this nsID with another.
   * @return true if they are the same, false if not.
   */

  inline bool Equals(const nsID& aOther) const {
    // At the time of this writing, modern compilers (namely Clang) inline this
    // memcmp call into a single SIMD operation on x86/x86-64 architectures (as
    // long as we compare to zero rather than returning the full integer return
    // value), which is measurably more efficient to any manual comparisons we
    // can do directly.
#if defined(__x86_64__) || defined(__i386__)
    return !memcmp(this, &aOther, sizeof *this);
#else
    // However, on ARM architectures, compilers still tend to generate a direct
    // memcmp call, which we'd like to avoid.
    return (((uint32_t*)&m0)[0] == ((uint32_t*)&aOther.m0)[0]) &&
           (((uint32_t*)&m0)[1] == ((uint32_t*)&aOther.m0)[1]) &&
           (((uint32_t*)&m0)[2] == ((uint32_t*)&aOther.m0)[2]) &&
           (((uint32_t*)&m0)[3] == ((uint32_t*)&aOther.m0)[3]);
#endif
  }

  inline bool operator==(const nsID& aOther) const { return Equals(aOther); }

  /**
   * nsID Parsing method. Turns a {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
   * string into an nsID
   */
  bool Parse(const char* aIDStr);

#ifndef XPCOM_GLUE_AVOID_NSPR
  /**
   * nsID string encoder. Returns an allocated string in
   * {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format. Caller should free string.
   * YOU SHOULD ONLY USE THIS IF YOU CANNOT USE ToProvidedString() BELOW.
   */
  char* ToString() const;

  /**
   * nsID string encoder. Builds a string in
   * {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format, into a char[NSID_LENGTH]
   * buffer provided by the caller (for instance, on the stack).
   */
  void ToProvidedString(char (&aDest)[NSID_LENGTH]) const;

#endif  // XPCOM_GLUE_AVOID_NSPR

  // Infallibly duplicate an nsID. Must be freed with free().
  nsID* Clone() const;

  //@}
};