charconv_test.cc - mozsearch

// Copyright 2018 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include "absl/strings/charconv.h"

#include <cfloat>

#include <cmath>

#include <cstdlib>

#include <functional>

#include <limits>

#include <string>

#include <system_error>  // NOLINT(build/c++11)

#include "gtest/gtest.h"

#include "absl/strings/internal/pow10_helper.h"

#include "absl/strings/str_cat.h"

#include "absl/strings/str_format.h"

#include "absl/strings/string_view.h"

#ifdef _MSC_FULL_VER

#define ABSL_COMPILER_DOES_EXACT_ROUNDING 0

#define ABSL_STRTOD_HANDLES_NAN_CORRECTLY 0

#else

#define ABSL_COMPILER_DOES_EXACT_ROUNDING 1

#define ABSL_STRTOD_HANDLES_NAN_CORRECTLY 1

#endif

namespace {

using absl::strings_internal::Pow10;

#if ABSL_COMPILER_DOES_EXACT_ROUNDING

// Tests that the given string is accepted by absl::from_chars, and that it

// converts exactly equal to the given number.

void TestDoubleParse(absl::string_view str, double expected_number) {

  SCOPED_TRACE(str);

  double actual_number = 0.0;

  absl::from_chars_result result =

      absl::from_chars(str.data(), str.data() + str.length(), actual_number);

  EXPECT_EQ(result.ec, std::errc());

  EXPECT_EQ(result.ptr, str.data() + str.length());

  EXPECT_EQ(actual_number, expected_number);

void TestFloatParse(absl::string_view str, float expected_number) {

  SCOPED_TRACE(str);

  float actual_number = 0.0;

  absl::from_chars_result result =

      absl::from_chars(str.data(), str.data() + str.length(), actual_number);

  EXPECT_EQ(result.ec, std::errc());

  EXPECT_EQ(result.ptr, str.data() + str.length());

  EXPECT_EQ(actual_number, expected_number);

// Tests that the given double or single precision floating point literal is

// parsed correctly by absl::from_chars.

//

// These convenience macros assume that the C++ compiler being used also does

// fully correct decimal-to-binary conversions.

#define FROM_CHARS_TEST_DOUBLE(number)     \

  {                                        \

    TestDoubleParse(#number, number);      \

    TestDoubleParse("-" #number, -number); \

#define FROM_CHARS_TEST_FLOAT(number)        \

  {                                          \

    TestFloatParse(#number, number##f);      \

    TestFloatParse("-" #number, -number##f); \

TEST(FromChars, NearRoundingCases) {

  // Cases from "A Program for Testing IEEE Decimal-Binary Conversion"

  // by Vern Paxson.

  // Forms that should round towards zero.  (These are the hardest cases for

  // each decimal mantissa size.)

  FROM_CHARS_TEST_DOUBLE(5.e125);

  FROM_CHARS_TEST_DOUBLE(69.e267);

  FROM_CHARS_TEST_DOUBLE(999.e-026);

  FROM_CHARS_TEST_DOUBLE(7861.e-034);

  FROM_CHARS_TEST_DOUBLE(75569.e-254);

  FROM_CHARS_TEST_DOUBLE(928609.e-261);

  FROM_CHARS_TEST_DOUBLE(9210917.e080);

  FROM_CHARS_TEST_DOUBLE(84863171.e114);

  FROM_CHARS_TEST_DOUBLE(653777767.e273);

  FROM_CHARS_TEST_DOUBLE(5232604057.e-298);

  FROM_CHARS_TEST_DOUBLE(27235667517.e-109);

  FROM_CHARS_TEST_DOUBLE(653532977297.e-123);

  FROM_CHARS_TEST_DOUBLE(3142213164987.e-294);

  FROM_CHARS_TEST_DOUBLE(46202199371337.e-072);

  FROM_CHARS_TEST_DOUBLE(231010996856685.e-073);

  FROM_CHARS_TEST_DOUBLE(9324754620109615.e212);

  FROM_CHARS_TEST_DOUBLE(78459735791271921.e049);

  FROM_CHARS_TEST_DOUBLE(272104041512242479.e200);

  FROM_CHARS_TEST_DOUBLE(6802601037806061975.e198);

  FROM_CHARS_TEST_DOUBLE(20505426358836677347.e-221);

  FROM_CHARS_TEST_DOUBLE(836168422905420598437.e-234);

  FROM_CHARS_TEST_DOUBLE(4891559871276714924261.e222);

  FROM_CHARS_TEST_FLOAT(5.e-20);

  FROM_CHARS_TEST_FLOAT(67.e14);

  FROM_CHARS_TEST_FLOAT(985.e15);

  FROM_CHARS_TEST_FLOAT(7693.e-42);

  FROM_CHARS_TEST_FLOAT(55895.e-16);

  FROM_CHARS_TEST_FLOAT(996622.e-44);

  FROM_CHARS_TEST_FLOAT(7038531.e-32);

  FROM_CHARS_TEST_FLOAT(60419369.e-46);

  FROM_CHARS_TEST_FLOAT(702990899.e-20);

  FROM_CHARS_TEST_FLOAT(6930161142.e-48);

  FROM_CHARS_TEST_FLOAT(25933168707.e-13);

  FROM_CHARS_TEST_FLOAT(596428896559.e20);

  // Similarly, forms that should round away from zero.

  FROM_CHARS_TEST_DOUBLE(9.e-265);

  FROM_CHARS_TEST_DOUBLE(85.e-037);

  FROM_CHARS_TEST_DOUBLE(623.e100);

  FROM_CHARS_TEST_DOUBLE(3571.e263);

  FROM_CHARS_TEST_DOUBLE(81661.e153);

  FROM_CHARS_TEST_DOUBLE(920657.e-023);

  FROM_CHARS_TEST_DOUBLE(4603285.e-024);

  FROM_CHARS_TEST_DOUBLE(87575437.e-309);

  FROM_CHARS_TEST_DOUBLE(245540327.e122);

  FROM_CHARS_TEST_DOUBLE(6138508175.e120);

  FROM_CHARS_TEST_DOUBLE(83356057653.e193);

  FROM_CHARS_TEST_DOUBLE(619534293513.e124);

  FROM_CHARS_TEST_DOUBLE(2335141086879.e218);

  FROM_CHARS_TEST_DOUBLE(36167929443327.e-159);

  FROM_CHARS_TEST_DOUBLE(609610927149051.e-255);

  FROM_CHARS_TEST_DOUBLE(3743626360493413.e-165);

  FROM_CHARS_TEST_DOUBLE(94080055902682397.e-242);

  FROM_CHARS_TEST_DOUBLE(899810892172646163.e283);

  FROM_CHARS_TEST_DOUBLE(7120190517612959703.e120);

  FROM_CHARS_TEST_DOUBLE(25188282901709339043.e-252);

  FROM_CHARS_TEST_DOUBLE(308984926168550152811.e-052);

  FROM_CHARS_TEST_DOUBLE(6372891218502368041059.e064);

  FROM_CHARS_TEST_FLOAT(3.e-23);

  FROM_CHARS_TEST_FLOAT(57.e18);

  FROM_CHARS_TEST_FLOAT(789.e-35);

  FROM_CHARS_TEST_FLOAT(2539.e-18);

  FROM_CHARS_TEST_FLOAT(76173.e28);

  FROM_CHARS_TEST_FLOAT(887745.e-11);

  FROM_CHARS_TEST_FLOAT(5382571.e-37);

  FROM_CHARS_TEST_FLOAT(82381273.e-35);

  FROM_CHARS_TEST_FLOAT(750486563.e-38);

  FROM_CHARS_TEST_FLOAT(3752432815.e-39);

  FROM_CHARS_TEST_FLOAT(75224575729.e-45);

  FROM_CHARS_TEST_FLOAT(459926601011.e15);

#undef FROM_CHARS_TEST_DOUBLE

#undef FROM_CHARS_TEST_FLOAT

#endif

float ToFloat(absl::string_view s) {

  float f;

  absl::from_chars(s.data(), s.data() + s.size(), f);

  return f;

double ToDouble(absl::string_view s) {

  double d;

  absl::from_chars(s.data(), s.data() + s.size(), d);

  return d;

// A duplication of the test cases in "NearRoundingCases" above, but with

// expected values expressed with integers, using ldexp/ldexpf.  These test

// cases will work even on compilers that do not accurately round floating point

// literals.

TEST(FromChars, NearRoundingCasesExplicit) {

  EXPECT_EQ(ToDouble("5.e125"), ldexp(6653062250012735, 365));

  EXPECT_EQ(ToDouble("69.e267"), ldexp(4705683757438170, 841));

  EXPECT_EQ(ToDouble("999.e-026"), ldexp(6798841691080350, -129));

  EXPECT_EQ(ToDouble("7861.e-034"), ldexp(8975675289889240, -153));

  EXPECT_EQ(ToDouble("75569.e-254"), ldexp(6091718967192243, -880));

  EXPECT_EQ(ToDouble("928609.e-261"), ldexp(7849264900213743, -900));

  EXPECT_EQ(ToDouble("9210917.e080"), ldexp(8341110837370930, 236));

  EXPECT_EQ(ToDouble("84863171.e114"), ldexp(4625202867375927, 353));

  EXPECT_EQ(ToDouble("653777767.e273"), ldexp(5068902999763073, 884));

  EXPECT_EQ(ToDouble("5232604057.e-298"), ldexp(5741343011915040, -1010));

  EXPECT_EQ(ToDouble("27235667517.e-109"), ldexp(6707124626673586, -380));

  EXPECT_EQ(ToDouble("653532977297.e-123"), ldexp(7078246407265384, -422));

  EXPECT_EQ(ToDouble("3142213164987.e-294"), ldexp(8219991337640559, -988));

  EXPECT_EQ(ToDouble("46202199371337.e-072"), ldexp(5224462102115359, -246));

  EXPECT_EQ(ToDouble("231010996856685.e-073"), ldexp(5224462102115359, -247));

  EXPECT_EQ(ToDouble("9324754620109615.e212"), ldexp(5539753864394442, 705));

  EXPECT_EQ(ToDouble("78459735791271921.e049"), ldexp(8388176519442766, 166));

  EXPECT_EQ(ToDouble("272104041512242479.e200"), ldexp(5554409530847367, 670));

  EXPECT_EQ(ToDouble("6802601037806061975.e198"), ldexp(5554409530847367, 668));

  EXPECT_EQ(ToDouble("20505426358836677347.e-221"),

            ldexp(4524032052079546, -722));

  EXPECT_EQ(ToDouble("836168422905420598437.e-234"),

            ldexp(5070963299887562, -760));

  EXPECT_EQ(ToDouble("4891559871276714924261.e222"),

            ldexp(6452687840519111, 757));

  EXPECT_EQ(ToFloat("5.e-20"), ldexpf(15474250, -88));

  EXPECT_EQ(ToFloat("67.e14"), ldexpf(12479722, 29));

  EXPECT_EQ(ToFloat("985.e15"), ldexpf(14333636, 36));

  EXPECT_EQ(ToFloat("7693.e-42"), ldexpf(10979816, -150));

  EXPECT_EQ(ToFloat("55895.e-16"), ldexpf(12888509, -61));

  EXPECT_EQ(ToFloat("996622.e-44"), ldexpf(14224264, -150));

  EXPECT_EQ(ToFloat("7038531.e-32"), ldexpf(11420669, -107));

  EXPECT_EQ(ToFloat("60419369.e-46"), ldexpf(8623340, -150));

  EXPECT_EQ(ToFloat("702990899.e-20"), ldexpf(16209866, -61));

  EXPECT_EQ(ToFloat("6930161142.e-48"), ldexpf(9891056, -150));

  EXPECT_EQ(ToFloat("25933168707.e-13"), ldexpf(11138211, -32));

  EXPECT_EQ(ToFloat("596428896559.e20"), ldexpf(12333860, 82));

  EXPECT_EQ(ToDouble("9.e-265"), ldexp(8168427841980010, -930));

  EXPECT_EQ(ToDouble("85.e-037"), ldexp(6360455125664090, -169));

  EXPECT_EQ(ToDouble("623.e100"), ldexp(6263531988747231, 289));

  EXPECT_EQ(ToDouble("3571.e263"), ldexp(6234526311072170, 833));

  EXPECT_EQ(ToDouble("81661.e153"), ldexp(6696636728760206, 472));

  EXPECT_EQ(ToDouble("920657.e-023"), ldexp(5975405561110124, -109));

  EXPECT_EQ(ToDouble("4603285.e-024"), ldexp(5975405561110124, -110));

  EXPECT_EQ(ToDouble("87575437.e-309"), ldexp(8452160731874668, -1053));

  EXPECT_EQ(ToDouble("245540327.e122"), ldexp(4985336549131723, 381));

  EXPECT_EQ(ToDouble("6138508175.e120"), ldexp(4985336549131723, 379));

  EXPECT_EQ(ToDouble("83356057653.e193"), ldexp(5986732817132056, 625));

  EXPECT_EQ(ToDouble("619534293513.e124"), ldexp(4798406992060657, 399));

  EXPECT_EQ(ToDouble("2335141086879.e218"), ldexp(5419088166961646, 713));

  EXPECT_EQ(ToDouble("36167929443327.e-159"), ldexp(8135819834632444, -536));

  EXPECT_EQ(ToDouble("609610927149051.e-255"), ldexp(4576664294594737, -850));

  EXPECT_EQ(ToDouble("3743626360493413.e-165"), ldexp(6898586531774201, -549));

  EXPECT_EQ(ToDouble("94080055902682397.e-242"), ldexp(6273271706052298, -800));

  EXPECT_EQ(ToDouble("899810892172646163.e283"), ldexp(7563892574477827, 947));

  EXPECT_EQ(ToDouble("7120190517612959703.e120"), ldexp(5385467232557565, 409));

  EXPECT_EQ(ToDouble("25188282901709339043.e-252"),

            ldexp(5635662608542340, -825));

  EXPECT_EQ(ToDouble("308984926168550152811.e-052"),

            ldexp(5644774693823803, -157));

  EXPECT_EQ(ToDouble("6372891218502368041059.e064"),

            ldexp(4616868614322430, 233));

  EXPECT_EQ(ToFloat("3.e-23"), ldexpf(9507380, -98));

  EXPECT_EQ(ToFloat("57.e18"), ldexpf(12960300, 42));

  EXPECT_EQ(ToFloat("789.e-35"), ldexpf(10739312, -130));

  EXPECT_EQ(ToFloat("2539.e-18"), ldexpf(11990089, -72));

  EXPECT_EQ(ToFloat("76173.e28"), ldexpf(9845130, 86));

  EXPECT_EQ(ToFloat("887745.e-11"), ldexpf(9760860, -40));

  EXPECT_EQ(ToFloat("5382571.e-37"), ldexpf(11447463, -124));

  EXPECT_EQ(ToFloat("82381273.e-35"), ldexpf(8554961, -113));

  EXPECT_EQ(ToFloat("750486563.e-38"), ldexpf(9975678, -120));

  EXPECT_EQ(ToFloat("3752432815.e-39"), ldexpf(9975678, -121));

  EXPECT_EQ(ToFloat("75224575729.e-45"), ldexpf(13105970, -137));

  EXPECT_EQ(ToFloat("459926601011.e15"), ldexpf(12466336, 65));

// Common test logic for converting a string which lies exactly halfway between

// two target floats.

//

// mantissa and exponent represent the precise value between two floating point

// numbers, `expected_low` and `expected_high`.  The floating point

// representation to parse in `StrCat(mantissa, "e", exponent)`.

//

// This function checks that an input just slightly less than the exact value

// is rounded down to `expected_low`, and an input just slightly greater than

// the exact value is rounded up to `expected_high`.

//

// The exact value should round to `expected_half`, which must be either

// `expected_low` or `expected_high`.

template <typename FloatType>

void TestHalfwayValue(const std::string& mantissa, int exponent,

                      FloatType expected_low, FloatType expected_high,

                      FloatType expected_half) {

  std::string low_rep = mantissa;

  low_rep[low_rep.size() - 1] -= 1;

  absl::StrAppend(&low_rep, std::string(1000, '9'), "e", exponent);

  FloatType actual_low = 0;

  absl::from_chars(low_rep.data(), low_rep.data() + low_rep.size(), actual_low);

  EXPECT_EQ(expected_low, actual_low);

  std::string high_rep =

      absl::StrCat(mantissa, std::string(1000, '0'), "1e", exponent);

  FloatType actual_high = 0;

  absl::from_chars(high_rep.data(), high_rep.data() + high_rep.size(),

                   actual_high);

  EXPECT_EQ(expected_high, actual_high);

  std::string halfway_rep = absl::StrCat(mantissa, "e", exponent);

  FloatType actual_half = 0;

  absl::from_chars(halfway_rep.data(), halfway_rep.data() + halfway_rep.size(),

                   actual_half);

  EXPECT_EQ(expected_half, actual_half);

TEST(FromChars, DoubleRounding) {

  const double zero = 0.0;

  const double first_subnormal = nextafter(zero, 1.0);

  const double second_subnormal = nextafter(first_subnormal, 1.0);

  const double first_normal = DBL_MIN;

  const double last_subnormal = nextafter(first_normal, 0.0);

  const double second_normal = nextafter(first_normal, 1.0);

  const double last_normal = DBL_MAX;

  const double penultimate_normal = nextafter(last_normal, 0.0);

  // Various test cases for numbers between two representable floats.  Each

  // call to TestHalfwayValue tests a number just below and just above the

  // halfway point, as well as the number exactly between them.

  // Test between zero and first_subnormal.  Round-to-even tie rounds down.

  TestHalfwayValue(

      "2."

      "470328229206232720882843964341106861825299013071623822127928412503377536"

      "351043759326499181808179961898982823477228588654633283551779698981993873"

      "980053909390631503565951557022639229085839244910518443593180284993653615"

      "250031937045767824921936562366986365848075700158576926990370631192827955"

      "855133292783433840935197801553124659726357957462276646527282722005637400"

      "648549997709659947045402082816622623785739345073633900796776193057750674"

      "017632467360096895134053553745851666113422376667860416215968046191446729"

      "184030053005753084904876539171138659164623952491262365388187963623937328"

      "042389101867234849766823508986338858792562830275599565752445550725518931"

      "369083625477918694866799496832404970582102851318545139621383772282614543"

      "7693412532098591327667236328125",

      -324, zero, first_subnormal, zero);

  // first_subnormal and second_subnormal.  Round-to-even tie rounds up.

  TestHalfwayValue(

      "7."

      "410984687618698162648531893023320585475897039214871466383785237510132609"

      "053131277979497545424539885696948470431685765963899850655339096945981621"

      "940161728171894510697854671067917687257517734731555330779540854980960845"

      "750095811137303474765809687100959097544227100475730780971111893578483867"

      "565399878350301522805593404659373979179073872386829939581848166016912201"

      "945649993128979841136206248449867871357218035220901702390328579173252022"

      "052897402080290685402160661237554998340267130003581248647904138574340187"

      "552090159017259254714629617513415977493871857473787096164563890871811984"

      "127167305601704549300470526959016576377688490826798697257336652176556794"

      "107250876433756084600398490497214911746308553955635418864151316847843631"

      "3080237596295773983001708984375",

      -324, first_subnormal, second_subnormal, second_subnormal);

  // last_subnormal and first_normal.  Round-to-even tie rounds up.

  TestHalfwayValue(

      "2."

      "225073858507201136057409796709131975934819546351645648023426109724822222"

      "021076945516529523908135087914149158913039621106870086438694594645527657"

      "207407820621743379988141063267329253552286881372149012981122451451889849"

      "057222307285255133155755015914397476397983411801999323962548289017107081"

      "850690630666655994938275772572015763062690663332647565300009245888316433"

      "037779791869612049497390377829704905051080609940730262937128958950003583"

      "799967207254304360284078895771796150945516748243471030702609144621572289"

      "880258182545180325707018860872113128079512233426288368622321503775666622"

      "503982534335974568884423900265498198385487948292206894721689831099698365"

      "846814022854243330660339850886445804001034933970427567186443383770486037"

      "86162277173854562306587467901408672332763671875",

      -308, last_subnormal, first_normal, first_normal);

  // first_normal and second_normal.  Round-to-even tie rounds down.

  TestHalfwayValue(

      "2."

      "225073858507201630123055637955676152503612414573018013083228724049586647"

      "606759446192036794116886953213985520549032000903434781884412325572184367"

      "563347617020518175998922941393629966742598285899994830148971433555578567"

      "693279306015978183162142425067962460785295885199272493577688320732492479"

      "924816869232247165964934329258783950102250973957579510571600738343645738"

      "494324192997092179207389919761694314131497173265255020084997973676783743"

      "155205818804439163810572367791175177756227497413804253387084478193655533"

      "073867420834526162513029462022730109054820067654020201547112002028139700"

      "141575259123440177362244273712468151750189745559978653234255886219611516"

      "335924167958029604477064946470184777360934300451421683607013647479513962"

      "13837722826145437693412532098591327667236328125",

      -308, first_normal, second_normal, first_normal);

  // penultimate_normal and last_normal.  Round-to-even rounds down.

  TestHalfwayValue(

      "1."

      "797693134862315608353258760581052985162070023416521662616611746258695532"

      "672923265745300992879465492467506314903358770175220871059269879629062776"

      "047355692132901909191523941804762171253349609463563872612866401980290377"

      "995141836029815117562837277714038305214839639239356331336428021390916694"

      "57927874464075218944",

      308, penultimate_normal, last_normal, penultimate_normal);

// Same test cases as DoubleRounding, now with new and improved Much Smaller

// Precision!

TEST(FromChars, FloatRounding) {

  const float zero = 0.0;

  const float first_subnormal = nextafterf(zero, 1.0);

  const float second_subnormal = nextafterf(first_subnormal, 1.0);

  const float first_normal = FLT_MIN;

  const float last_subnormal = nextafterf(first_normal, 0.0);

  const float second_normal = nextafterf(first_normal, 1.0);

  const float last_normal = FLT_MAX;

  const float penultimate_normal = nextafterf(last_normal, 0.0);

  // Test between zero and first_subnormal.  Round-to-even tie rounds down.

  TestHalfwayValue(

      "7."

      "006492321624085354618647916449580656401309709382578858785341419448955413"

      "42930300743319094181060791015625",

      -46, zero, first_subnormal, zero);

  // first_subnormal and second_subnormal.  Round-to-even tie rounds up.

  TestHalfwayValue(

      "2."

      "101947696487225606385594374934874196920392912814773657635602425834686624"

      "028790902229957282543182373046875",

      -45, first_subnormal, second_subnormal, second_subnormal);

  // last_subnormal and first_normal.  Round-to-even tie rounds up.

  TestHalfwayValue(

      "1."

      "175494280757364291727882991035766513322858992758990427682963118425003064"

      "9651730385585324256680905818939208984375",

      -38, last_subnormal, first_normal, first_normal);

  // first_normal and second_normal.  Round-to-even tie rounds down.

  TestHalfwayValue(

      "1."

      "175494420887210724209590083408724842314472120785184615334540294131831453"

      "9442813071445925743319094181060791015625",

      -38, first_normal, second_normal, first_normal);

  // penultimate_normal and last_normal.  Round-to-even rounds down.

  TestHalfwayValue("3.40282336497324057985868971510891282432", 38,

                   penultimate_normal, last_normal, penultimate_normal);

TEST(FromChars, Underflow) {

  // Check that underflow is handled correctly, according to the specification

  // in DR 3081.

  double d;

  float f;

  absl::from_chars_result result;

  std::string negative_underflow = "-1e-1000";

  const char* begin = negative_underflow.data();

  const char* end = begin + negative_underflow.size();

  d = 100.0;

  result = absl::from_chars(begin, end, d);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_TRUE(std::signbit(d));  // negative

  EXPECT_GE(d, -std::numeric_limits<double>::min());

  f = 100.0;

  result = absl::from_chars(begin, end, f);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_TRUE(std::signbit(f));  // negative

  EXPECT_GE(f, -std::numeric_limits<float>::min());

  std::string positive_underflow = "1e-1000";

  begin = positive_underflow.data();

  end = begin + positive_underflow.size();

  d = -100.0;

  result = absl::from_chars(begin, end, d);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_FALSE(std::signbit(d));  // positive

  EXPECT_LE(d, std::numeric_limits<double>::min());

  f = -100.0;

  result = absl::from_chars(begin, end, f);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_FALSE(std::signbit(f));  // positive

  EXPECT_LE(f, std::numeric_limits<float>::min());

TEST(FromChars, Overflow) {

  // Check that overflow is handled correctly, according to the specification

  // in DR 3081.

  double d;

  float f;

  absl::from_chars_result result;

  std::string negative_overflow = "-1e1000";

  const char* begin = negative_overflow.data();

  const char* end = begin + negative_overflow.size();

  d = 100.0;

  result = absl::from_chars(begin, end, d);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_TRUE(std::signbit(d));  // negative

  EXPECT_EQ(d, -std::numeric_limits<double>::max());

  f = 100.0;

  result = absl::from_chars(begin, end, f);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_TRUE(std::signbit(f));  // negative

  EXPECT_EQ(f, -std::numeric_limits<float>::max());

  std::string positive_overflow = "1e1000";

  begin = positive_overflow.data();

  end = begin + positive_overflow.size();

  d = -100.0;

  result = absl::from_chars(begin, end, d);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_FALSE(std::signbit(d));  // positive

  EXPECT_EQ(d, std::numeric_limits<double>::max());

  f = -100.0;

  result = absl::from_chars(begin, end, f);

  EXPECT_EQ(result.ptr, end);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_FALSE(std::signbit(f));  // positive

  EXPECT_EQ(f, std::numeric_limits<float>::max());

TEST(FromChars, RegressionTestsFromFuzzer) {

  absl::string_view src = "0x21900000p00000000099";

  float f;

  auto result = absl::from_chars(src.data(), src.data() + src.size(), f);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

TEST(FromChars, ReturnValuePtr) {

  // Check that `ptr` points one past the number scanned, even if that number

  // is not representable.

  double d;

  absl::from_chars_result result;

  std::string normal = "3.14@#$%@#$%";

  result = absl::from_chars(normal.data(), normal.data() + normal.size(), d);

  EXPECT_EQ(result.ec, std::errc());

  EXPECT_EQ(result.ptr - normal.data(), 4);

  std::string overflow = "1e1000@#$%@#$%";

  result = absl::from_chars(overflow.data(),

                            overflow.data() + overflow.size(), d);

  EXPECT_EQ(result.ec, std::errc::result_out_of_range);

  EXPECT_EQ(result.ptr - overflow.data(), 6);

  std::string garbage = "#$%@#$%";

  result = absl::from_chars(garbage.data(),

                            garbage.data() + garbage.size(), d);

  EXPECT_EQ(result.ec, std::errc::invalid_argument);

  EXPECT_EQ(result.ptr - garbage.data(), 0);

// Check for a wide range of inputs that strtod() and absl::from_chars() exactly

// agree on the conversion amount.

//

// This test assumes the platform's strtod() uses perfect round_to_nearest

// rounding.

TEST(FromChars, TestVersusStrtod) {

  for (int mantissa = 1000000; mantissa <= 9999999; mantissa += 501) {

    for (int exponent = -300; exponent < 300; ++exponent) {

      std::string candidate = absl::StrCat(mantissa, "e", exponent);

      double strtod_value = strtod(candidate.c_str(), nullptr);

      double absl_value = 0;

      absl::from_chars(candidate.data(), candidate.data() + candidate.size(),

                       absl_value);

      ASSERT_EQ(strtod_value, absl_value) << candidate;

// Check for a wide range of inputs that strtof() and absl::from_chars() exactly

// agree on the conversion amount.

//

// This test assumes the platform's strtof() uses perfect round_to_nearest

// rounding.

TEST(FromChars, TestVersusStrtof) {

  for (int mantissa = 1000000; mantissa <= 9999999; mantissa += 501) {

    for (int exponent = -43; exponent < 32; ++exponent) {

      std::string candidate = absl::StrCat(mantissa, "e", exponent);

      float strtod_value = strtof(candidate.c_str(), nullptr);

      float absl_value = 0;

      absl::from_chars(candidate.data(), candidate.data() + candidate.size(),

                       absl_value);

      ASSERT_EQ(strtod_value, absl_value) << candidate;

// Tests if two floating point values have identical bit layouts.  (EXPECT_EQ

// is not suitable for NaN testing, since NaNs are never equal.)

template <typename Float>

bool Identical(Float a, Float b) {

  return 0 == memcmp(&a, &b, sizeof(Float));

// Check that NaNs are parsed correctly.  The spec requires that

// std::from_chars on "NaN(123abc)" return the same value as std::nan("123abc").

// How such an n-char-sequence affects the generated NaN is unspecified, so we

// just test for symmetry with std::nan and strtod here.

//

// (In Linux, this parses the value as a number and stuffs that number into the

// free bits of a quiet NaN.)

TEST(FromChars, NaNDoubles) {

  for (std::string n_char_sequence :

       {"", "1", "2", "3", "fff", "FFF", "200000", "400000", "4000000000000",

        "8000000000000", "abc123", "legal_but_unexpected",

        "99999999999999999999999", "_"}) {

    std::string input = absl::StrCat("nan(", n_char_sequence, ")");

    SCOPED_TRACE(input);

    double from_chars_double;

    absl::from_chars(input.data(), input.data() + input.size(),

                     from_chars_double);

    double std_nan_double = std::nan(n_char_sequence.c_str());

    EXPECT_TRUE(Identical(from_chars_double, std_nan_double));

    // Also check that we match strtod()'s behavior.  This test assumes that the

    // platform has a compliant strtod().

#if ABSL_STRTOD_HANDLES_NAN_CORRECTLY

    double strtod_double = strtod(input.c_str(), nullptr);

    EXPECT_TRUE(Identical(from_chars_double, strtod_double));

#endif  // ABSL_STRTOD_HANDLES_NAN_CORRECTLY

    // Check that we can parse a negative NaN

    std::string negative_input = "-" + input;

    double negative_from_chars_double;

    absl::from_chars(negative_input.data(),

                     negative_input.data() + negative_input.size(),

                     negative_from_chars_double);

    EXPECT_TRUE(std::signbit(negative_from_chars_double));

    EXPECT_FALSE(Identical(negative_from_chars_double, from_chars_double));

    from_chars_double = std::copysign(from_chars_double, -1.0);

    EXPECT_TRUE(Identical(negative_from_chars_double, from_chars_double));

TEST(FromChars, NaNFloats) {

  for (std::string n_char_sequence :

       {"", "1", "2", "3", "fff", "FFF", "200000", "400000", "4000000000000",

        "8000000000000", "abc123", "legal_but_unexpected",

        "99999999999999999999999", "_"}) {

    std::string input = absl::StrCat("nan(", n_char_sequence, ")");

    SCOPED_TRACE(input);

    float from_chars_float;

    absl::from_chars(input.data(), input.data() + input.size(),

                     from_chars_float);

    float std_nan_float = std::nanf(n_char_sequence.c_str());

    EXPECT_TRUE(Identical(from_chars_float, std_nan_float));

    // Also check that we match strtof()'s behavior.  This test assumes that the

    // platform has a compliant strtof().

#if ABSL_STRTOD_HANDLES_NAN_CORRECTLY

    float strtof_float = strtof(input.c_str(), nullptr);

    EXPECT_TRUE(Identical(from_chars_float, strtof_float));

#endif  // ABSL_STRTOD_HANDLES_NAN_CORRECTLY

    // Check that we can parse a negative NaN

    std::string negative_input = "-" + input;

    float negative_from_chars_float;

    absl::from_chars(negative_input.data(),

                     negative_input.data() + negative_input.size(),

                     negative_from_chars_float);

    EXPECT_TRUE(std::signbit(negative_from_chars_float));

    EXPECT_FALSE(Identical(negative_from_chars_float, from_chars_float));

    // Use the (float, float) overload of std::copysign to prevent narrowing;

    // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98251.

    from_chars_float = std::copysign(from_chars_float, -1.0f);

    EXPECT_TRUE(Identical(negative_from_chars_float, from_chars_float));

// Returns an integer larger than step.  The values grow exponentially.

int NextStep(int step) {

  return step + (step >> 2) + 1;

// Test a conversion on a family of input strings, checking that the calculation

// is correct for in-bounds values, and that overflow and underflow are done

// correctly for out-of-bounds values.

//

// input_generator maps from an integer index to a string to test.

// expected_generator maps from an integer index to an expected Float value.

// from_chars conversion of input_generator(i) should result in

// expected_generator(i).

//

// lower_bound and upper_bound denote the smallest and largest values for which

// the conversion is expected to succeed.

template <typename Float>

void TestOverflowAndUnderflow(

    const std::function<std::string(int)>& input_generator,

    const std::function<Float(int)>& expected_generator, int lower_bound,

    int upper_bound) {

  // test legal values near lower_bound

  int index, step;

  for (index = lower_bound, step = 1; index < upper_bound;

       index += step, step = NextStep(step)) {

    std::string input = input_generator(index);

    SCOPED_TRACE(input);

    Float expected = expected_generator(index);

    Float actual;

    auto result =

        absl::from_chars(input.data(), input.data() + input.size(), actual);

    EXPECT_EQ(result.ec, std::errc());

    EXPECT_EQ(expected, actual)

        << absl::StrFormat("%a vs %a", expected, actual);

  // test legal values near upper_bound

  for (index = upper_bound, step = 1; index > lower_bound;

       index -= step, step = NextStep(step)) {

    std::string input = input_generator(index);

    SCOPED_TRACE(input);

    Float expected = expected_generator(index);

    Float actual;

    auto result =

        absl::from_chars(input.data(), input.data() + input.size(), actual);

    EXPECT_EQ(result.ec, std::errc());

    EXPECT_EQ(expected, actual)

        << absl::StrFormat("%a vs %a", expected, actual);

  // Test underflow values below lower_bound

  for (index = lower_bound - 1, step = 1; index > -1000000;

       index -= step, step = NextStep(step)) {

    std::string input = input_generator(index);

    SCOPED_TRACE(input);

    Float actual;

    auto result =

        absl::from_chars(input.data(), input.data() + input.size(), actual);

    EXPECT_EQ(result.ec, std::errc::result_out_of_range);

    EXPECT_LT(actual, 1.0);  // check for underflow

  // Test overflow values above upper_bound

  for (index = upper_bound + 1, step = 1; index < 1000000;

       index += step, step = NextStep(step)) {

    std::string input = input_generator(index);

    SCOPED_TRACE(input);

    Float actual;

    auto result =

        absl::from_chars(input.data(), input.data() + input.size(), actual);

    EXPECT_EQ(result.ec, std::errc::result_out_of_range);

    EXPECT_GT(actual, 1.0);  // check for overflow

// Check that overflow and underflow are caught correctly for hex doubles.

//

// The largest representable double is 0x1.fffffffffffffp+1023, and the

// smallest representable subnormal is 0x0.0000000000001p-1022, which equals

// 0x1p-1074.  Therefore 1023 and -1074 are the limits of acceptable exponents

// in this test.

TEST(FromChars, HexdecimalDoubleLimits) {

  auto input_gen = [](int index) { return absl::StrCat("0x1.0p", index); };

  auto expected_gen = [](int index) { return std::ldexp(1.0, index); };

  TestOverflowAndUnderflow<double>(input_gen, expected_gen, -1074, 1023);

// Check that overflow and underflow are caught correctly for hex floats.

//

// The largest representable float is 0x1.fffffep+127, and the smallest

// representable subnormal is 0x0.000002p-126, which equals 0x1p-149.

// Therefore 127 and -149 are the limits of acceptable exponents in this test.

TEST(FromChars, HexdecimalFloatLimits) {

  auto input_gen = [](int index) { return absl::StrCat("0x1.0p", index); };

  auto expected_gen = [](int index) { return std::ldexp(1.0f, index); };

  TestOverflowAndUnderflow<float>(input_gen, expected_gen, -149, 127);

// Check that overflow and underflow are caught correctly for decimal doubles.

//

// The largest representable double is about 1.8e308, and the smallest

// representable subnormal is about 5e-324.  '1e-324' therefore rounds away from

// the smallest representable positive value.  -323 and 308 are the limits of

// acceptable exponents in this test.

TEST(FromChars, DecimalDoubleLimits) {

  auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };

  auto expected_gen = [](int index) { return Pow10(index); };

  TestOverflowAndUnderflow<double>(input_gen, expected_gen, -323, 308);

// Check that overflow and underflow are caught correctly for decimal floats.

//

// The largest representable float is about 3.4e38, and the smallest

// representable subnormal is about 1.45e-45.  '1e-45' therefore rounds towards

// the smallest representable positive value.  -45 and 38 are the limits of

// acceptable exponents in this test.

TEST(FromChars, DecimalFloatLimits) {

  auto input_gen = [](int index) { return absl::StrCat("1.0e", index); };

  auto expected_gen = [](int index) { return Pow10(index); };

  TestOverflowAndUnderflow<float>(input_gen, expected_gen, -45, 38);

}  // namespace

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