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AK: Implement FlyString for the new String class

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This implements a FlyString that will de-duplicate String instances. The
FlyString will store the raw encoded data of the String instance: If the
String is a short string, FlyString holds the String::ShortString bytes;
otherwise FlyString holds a pointer to the Detail::StringData.

FlyString itself does not know about String's storage or how to refcount
its Detail::StringData. It defers to String to implement these details.
This commit is contained in:
Timothy Flynn 2023-01-11 08:26:49 -05:00 • committed by Andreas Kling
parent f49a65cb28
commit 1d4f287582
8 changed files with 445 additions and 1 deletions
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120
Tests/AK/TestFlyString.cpp Normal file
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/*
* Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibTest/TestCase.h>
#include <AK/FlyString.h>
#include <AK/String.h>
#include <AK/Try.h>
TEST_CASE(empty_string)
{
FlyString fly {};
EXPECT(fly.is_empty());
EXPECT_EQ(fly, ""sv);
// Short strings do not get stored in the fly string table.
EXPECT_EQ(FlyString::number_of_fly_strings(), 0u);
}
TEST_CASE(short_string)
{
FlyString fly1 { MUST(String::from_utf8("foo"sv)) };
EXPECT_EQ(fly1, "foo"sv);
FlyString fly2 { MUST(String::from_utf8("foo"sv)) };
EXPECT_EQ(fly2, "foo"sv);
FlyString fly3 { MUST(String::from_utf8("bar"sv)) };
EXPECT_EQ(fly3, "bar"sv);
EXPECT_EQ(fly1, fly2);
EXPECT_NE(fly1, fly3);
EXPECT_NE(fly2, fly3);
EXPECT(fly1.to_string().is_short_string());
EXPECT(fly2.to_string().is_short_string());
EXPECT(fly3.to_string().is_short_string());
// Short strings do not get stored in the fly string table.
EXPECT_EQ(FlyString::number_of_fly_strings(), 0u);
}
TEST_CASE(long_string)
{
FlyString fly1 { MUST(String::from_utf8("thisisdefinitelymorethan7bytes"sv)) };
EXPECT_EQ(fly1, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
FlyString fly2 { MUST(String::from_utf8("thisisdefinitelymorethan7bytes"sv)) };
EXPECT_EQ(fly2, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
FlyString fly3 { MUST(String::from_utf8("thisisalsoforsuremorethan7bytes"sv)) };
EXPECT_EQ(fly3, "thisisalsoforsuremorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 2u);
EXPECT_EQ(fly1, fly2);
EXPECT_NE(fly1, fly3);
EXPECT_NE(fly2, fly3);
EXPECT(!fly1.to_string().is_short_string());
EXPECT(!fly2.to_string().is_short_string());
EXPECT(!fly3.to_string().is_short_string());
}
TEST_CASE(from_string_view)
{
auto fly1 = MUST(FlyString::from_utf8("thisisdefinitelymorethan7bytes"sv));
EXPECT_EQ(fly1, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
auto fly2 = MUST(FlyString::from_utf8("thisisdefinitelymorethan7bytes"sv));
EXPECT_EQ(fly2, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
auto fly3 = MUST(FlyString::from_utf8("foo"sv));
EXPECT_EQ(fly3, "foo"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
EXPECT_EQ(fly1, fly2);
EXPECT_NE(fly1, fly3);
EXPECT_NE(fly2, fly3);
}
TEST_CASE(fly_string_keep_string_data_alive)
{
EXPECT_EQ(FlyString::number_of_fly_strings(), 0u);
{
FlyString fly {};
{
auto string = MUST(String::from_utf8("thisisdefinitelymorethan7bytes"sv));
fly = FlyString { string };
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
}
EXPECT_EQ(fly, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
}
EXPECT_EQ(FlyString::number_of_fly_strings(), 0u);
}
TEST_CASE(moved_fly_string_becomes_empty)
{
FlyString fly1 {};
EXPECT(fly1.is_empty());
FlyString fly2 { MUST(String::from_utf8("thisisdefinitelymorethan7bytes"sv)) };
EXPECT_EQ(fly2, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
fly1 = move(fly2);
EXPECT(fly2.is_empty());
EXPECT_EQ(fly1, "thisisdefinitelymorethan7bytes"sv);
EXPECT_EQ(FlyString::number_of_fly_strings(), 1u);
}