tvl-depot/absl/strings/internal/charconv_bigint_test.cc
Abseil Team bd40a41cc1 --
f28d30df5769bb832dec3ff36d2fcd2bcdf494a3 by Shaindel Schwartz <shaindel@google.com>:

Internal change

PiperOrigin-RevId: 201046831

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711715a78b7e53dfaafd4d7f08a74e76db22af88 by Mark Barolak <mbar@google.com>:

Internal fix

PiperOrigin-RevId: 201043684

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64b53edd6bf1fa48f74e7f5d33f00f80d5089147 by Shaindel Schwartz <shaindel@google.com>:

Remove extra whitespace

PiperOrigin-RevId: 201041989

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0bdd2a0b33657b688e4a04aeba9ebba47e4dc6ca by Shaindel Schwartz <shaindel@google.com>:

Whitespace fix.

PiperOrigin-RevId: 201034413

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3deb0ac296ef1b74c4789e114a8a8bf53253f26b by Shaindel Schwartz <shaindel@google.com>:

Scrub build tags. No functional changes.

PiperOrigin-RevId: 201032927

--
da75d0f8b73baa7e8f4e9a092bba546012ed3b71 by Alex Strelnikov <strel@google.com>:

Internal change.

PiperOrigin-RevId: 201026131

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6815d80caa19870d0c441b6b9816c68db41393a5 by Tom Manshreck <shreck@google.com>:

Add documentation for our LTS snapshot branches

PiperOrigin-RevId: 201025191

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64c3b02006f39e6a8127bbabf9ec947fb45b6504 by Greg Falcon <gfalcon@google.com>:

Provide absl::from_chars for double and float types.  This is a forward-compatible implementation of std::from_chars from C++17.

This provides exact "round_to_nearest" conversions, and has some nice properties:

* Works with string_view (it can convert numbers from non-NUL-terminated buffers)
* Never allocates memory
* Faster than the standard library strtod() in our toolchain
* Uses integer math in its calculations, so is unaffected by floating point environment
* Unaffected by C locale

Also change SimpleAtod/SimpleAtoi to use this new API under the hood.

PiperOrigin-RevId: 201003324

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542869258eb100779497c899103dc96aced52749 by Greg Falcon <gfalcon@google.com>:

Internal change

PiperOrigin-RevId: 200999200

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3aba192775c7f80e2cd7f221b0a73537823c54ea by Gennadiy Rozental <rogeeff@google.com>:

Internal change

PiperOrigin-RevId: 200947470

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daf9b9feedd748d5364a4c06165b7cb7604d3e1e by Mark Barolak <mbar@google.com>:

Add an absl:: qualification to a usage of base_internal::SchedulingMode outside of an absl:: namespace.

PiperOrigin-RevId: 200748234

--
a8d265290a22d629f3d9bf9f872c204200bfe8c8 by Mark Barolak <mbar@google.com>:

Add a missing namespace closing comment to optional.h.

PiperOrigin-RevId: 200739934

--
f05af8ee1c6b864dad2df7c907d424209a3e3202 by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 200719115
GitOrigin-RevId: f28d30df5769bb832dec3ff36d2fcd2bcdf494a3
Change-Id: Ie4fa601078fd4aa57286372611f1d114fdec82c0
2018-06-18 16:20:03 -04:00

203 lines
6.2 KiB
C++

// 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
//
// http://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/internal/charconv_bigint.h"
#include <string>
#include "gtest/gtest.h"
namespace absl {
namespace strings_internal {
TEST(BigUnsigned, ShiftLeft) {
{
// Check that 3 * 2**100 is calculated correctly
BigUnsigned<4> num(3u);
num.ShiftLeft(100);
EXPECT_EQ(num, BigUnsigned<4>("3802951800684688204490109616128"));
}
{
// Test that overflow is truncated properly.
// 15 is 4 bits long, and BigUnsigned<4> is a 128-bit bigint.
// Shifting left by 125 bits should truncate off the high bit, so that
// 15 << 125 == 7 << 125
// after truncation.
BigUnsigned<4> a(15u);
BigUnsigned<4> b(7u);
BigUnsigned<4> c(3u);
a.ShiftLeft(125);
b.ShiftLeft(125);
c.ShiftLeft(125);
EXPECT_EQ(a, b);
EXPECT_NE(a, c);
}
{
// Same test, larger bigint:
BigUnsigned<84> a(15u);
BigUnsigned<84> b(7u);
BigUnsigned<84> c(3u);
a.ShiftLeft(84 * 32 - 3);
b.ShiftLeft(84 * 32 - 3);
c.ShiftLeft(84 * 32 - 3);
EXPECT_EQ(a, b);
EXPECT_NE(a, c);
}
{
// Check that incrementally shifting has the same result as doing it all at
// once (attempting to capture corner cases.)
const std::string seed = "1234567890123456789012345678901234567890";
BigUnsigned<84> a(seed);
for (int i = 1; i <= 84 * 32; ++i) {
a.ShiftLeft(1);
BigUnsigned<84> b(seed);
b.ShiftLeft(i);
EXPECT_EQ(a, b);
}
// And we should have fully rotated all bits off by now:
EXPECT_EQ(a, BigUnsigned<84>(0u));
}
}
TEST(BigUnsigned, MultiplyByUint32) {
const BigUnsigned<84> factorial_100(
"933262154439441526816992388562667004907159682643816214685929638952175999"
"932299156089414639761565182862536979208272237582511852109168640000000000"
"00000000000000");
BigUnsigned<84> a(1u);
for (uint32_t i = 1; i <= 100; ++i) {
a.MultiplyBy(i);
}
EXPECT_EQ(a, BigUnsigned<84>(factorial_100));
}
TEST(BigUnsigned, MultiplyByBigUnsigned) {
{
// Put the terms of factorial_200 into two bigints, and multiply them
// together.
const BigUnsigned<84> factorial_200(
"7886578673647905035523632139321850622951359776871732632947425332443594"
"4996340334292030428401198462390417721213891963883025764279024263710506"
"1926624952829931113462857270763317237396988943922445621451664240254033"
"2918641312274282948532775242424075739032403212574055795686602260319041"
"7032406235170085879617892222278962370389737472000000000000000000000000"
"0000000000000000000000000");
BigUnsigned<84> evens(1u);
BigUnsigned<84> odds(1u);
for (uint32_t i = 1; i < 200; i += 2) {
odds.MultiplyBy(i);
evens.MultiplyBy(i + 1);
}
evens.MultiplyBy(odds);
EXPECT_EQ(evens, factorial_200);
}
{
// Multiply various powers of 10 together.
for (int a = 0 ; a < 700; a += 25) {
SCOPED_TRACE(a);
BigUnsigned<84> a_value("3" + std::string(a, '0'));
for (int b = 0; b < (700 - a); b += 25) {
SCOPED_TRACE(b);
BigUnsigned<84> b_value("2" + std::string(b, '0'));
BigUnsigned<84> expected_product("6" + std::string(a + b, '0'));
b_value.MultiplyBy(a_value);
EXPECT_EQ(b_value, expected_product);
}
}
}
}
TEST(BigUnsigned, MultiplyByOverflow) {
{
// Check that multiplcation overflow predictably truncates.
// A big int with all bits on.
BigUnsigned<4> all_bits_on("340282366920938463463374607431768211455");
// Modulo 2**128, this is equal to -1. Therefore the square of this,
// modulo 2**128, should be 1.
all_bits_on.MultiplyBy(all_bits_on);
EXPECT_EQ(all_bits_on, BigUnsigned<4>(1u));
}
{
// Try multiplying a large bigint by 2**50, and compare the result to
// shifting.
BigUnsigned<4> value_1("12345678901234567890123456789012345678");
BigUnsigned<4> value_2("12345678901234567890123456789012345678");
BigUnsigned<4> two_to_fiftieth(1u);
two_to_fiftieth.ShiftLeft(50);
value_1.ShiftLeft(50);
value_2.MultiplyBy(two_to_fiftieth);
EXPECT_EQ(value_1, value_2);
}
}
TEST(BigUnsigned, FiveToTheNth) {
{
// Sanity check that MultiplyByFiveToTheNth gives consistent answers, up to
// and including overflow.
for (int i = 0; i < 1160; ++i) {
SCOPED_TRACE(i);
BigUnsigned<84> value_1(123u);
BigUnsigned<84> value_2(123u);
value_1.MultiplyByFiveToTheNth(i);
for (int j = 0; j < i; j++) {
value_2.MultiplyBy(5u);
}
EXPECT_EQ(value_1, value_2);
}
}
{
// Check that the faster, table-lookup-based static method returns the same
// result that multiplying in-place would return, up to and including
// overflow.
for (int i = 0; i < 1160; ++i) {
SCOPED_TRACE(i);
BigUnsigned<84> value_1(1u);
value_1.MultiplyByFiveToTheNth(i);
BigUnsigned<84> value_2 = BigUnsigned<84>::FiveToTheNth(i);
EXPECT_EQ(value_1, value_2);
}
}
}
TEST(BigUnsigned, TenToTheNth) {
{
// Sanity check MultiplyByTenToTheNth.
for (int i = 0; i < 800; ++i) {
SCOPED_TRACE(i);
BigUnsigned<84> value_1(123u);
BigUnsigned<84> value_2(123u);
value_1.MultiplyByTenToTheNth(i);
for (int j = 0; j < i; j++) {
value_2.MultiplyBy(10u);
}
EXPECT_EQ(value_1, value_2);
}
}
{
// Alternate testing approach, taking advantage of the decimal parser.
for (int i = 0; i < 200; ++i) {
SCOPED_TRACE(i);
BigUnsigned<84> value_1(135u);
value_1.MultiplyByTenToTheNth(i);
BigUnsigned<84> value_2("135" + std::string(i, '0'));
EXPECT_EQ(value_1, value_2);
}
}
}
} // namespace strings_internal
} // namespace absl