mfbt/FloatingPoint.cpp
author Kent Tamura <tkent@chromium.org>
Tue, 05 Mar 2019 12:13:23 +0000
changeset 464535 9af6b8db40bd483d631ba7535aa16a3de3ae345f
parent 448947 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1528029 [wpt PR 15376] - Remove a special handling for XLink namespace in XMLSerializer, a=testonly Automatic update from web-platform-tests Remove a special handling for XLink namespace in XMLSerializer The new behavior matches to the standard, Firefox, and Safari. Bug: 927626 Change-Id: Ifc6687992c10fbca13faaaeb4a56e59f5469f594 Reviewed-on: https://chromium-review.googlesource.com/c/1469843 Reviewed-by: Yoshifumi Inoue <yosin@chromium.org> Commit-Queue: Kent Tamura <tkent@chromium.org> Cr-Commit-Position: refs/heads/master@{#631984} -- wpt-commits: 6fb30bc55bf721c87d2ff32640deefc1b01061ab wpt-pr: 15376

/* -*- 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 http://mozilla.org/MPL/2.0/. */

/* Implementations of FloatingPoint functions */

#include "mozilla/FloatingPoint.h"

#include <cfloat>  // for FLT_MAX

namespace mozilla {

bool IsFloat32Representable(double aValue) {
  // NaNs and infinities are representable.
  if (!IsFinite(aValue)) {
    return true;
  }

  // If it exceeds finite |float| range, casting to |double| is always undefined
  // behavior per C++11 [conv.double]p1 last sentence.
  if (Abs(aValue) > FLT_MAX) {
    return false;
  }

  // But if it's within finite range, then either it's 1) an exact value and so
  // representable, or 2) it's "between two adjacent destination values" and
  // safe to cast to "an implementation-defined choice of either of those
  // values".
  auto valueAsFloat = static_cast<float>(aValue);

  // Per [conv.fpprom] this never changes value.
  auto valueAsFloatAsDouble = static_cast<double>(valueAsFloat);

  // Finally, in 1) exact representable value equals exact representable value,
  // or 2) *changed* value does not equal original value, ergo unrepresentable.
  return valueAsFloatAsDouble == aValue;
}

} /* namespace mozilla */