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LibCore: Calculate the correct seek offset for buffered streams

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This commit is contained in:
Tim Schumacher 2023-01-16 15:46:59 +01:00 • committed by Jelle Raaijmakers
parent caeb772894
commit bdf991fe76
2 changed files with 74 additions and 0 deletions
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70
Tests/LibCore/TestLibCoreStream.cpp
View file

@ -468,6 +468,76 @@ TEST_CASE(buffered_small_file_read)
EXPECT(!file->can_read_line().value());
}
TEST_CASE(buffered_file_tell_and_seek)
{
auto file = Core::Stream::File::open("/usr/Tests/LibCore/small.txt"sv, Core::Stream::OpenMode::Read).release_value();
auto buffered_file = Core::Stream::BufferedFile::create(move(file)).release_value();
// Initial state.
{
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 0);
}
// Read a character.
{
auto character = buffered_file->read_value<char>().release_value();
EXPECT_EQ(character, 'W');
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 1);
}
// Read one more character.
{
auto character = buffered_file->read_value<char>().release_value();
EXPECT_EQ(character, 'e');
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 2);
}
// Seek seven characters forward.
{
auto current_offset = buffered_file->seek(7, Core::Stream::SeekMode::FromCurrentPosition).release_value();
EXPECT_EQ(current_offset, 9);
}
// Read a character again.
{
auto character = buffered_file->read_value<char>().release_value();
EXPECT_EQ(character, 'o');
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 10);
}
// Seek five characters backwards.
{
auto current_offset = buffered_file->seek(-5, Core::Stream::SeekMode::FromCurrentPosition).release_value();
EXPECT_EQ(current_offset, 5);
}
// Read a character.
{
auto character = buffered_file->read_value<char>().release_value();
EXPECT_EQ(character, 'h');
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 6);
}
// Seek back to the beginning.
{
auto current_offset = buffered_file->seek(0, Core::Stream::SeekMode::SetPosition).release_value();
EXPECT_EQ(current_offset, 0);
}
// Read the first character.
{
auto character = buffered_file->read_value<char>().release_value();
EXPECT_EQ(character, 'W');
auto current_offset = buffered_file->tell().release_value();
EXPECT_EQ(current_offset, 1);
}
}
constexpr auto buffered_sent_data = "Well hello friends!\n:^)\nThis shouldn't be present. :^("sv;
constexpr auto first_line = "Well hello friends!"sv;
constexpr auto second_line = ":^)"sv;

4
Userland/Libraries/LibCore/Stream.h
View file

@ -875,8 +875,12 @@ public:
virtual void close() override { m_helper.stream().close(); }
virtual ErrorOr<off_t> seek(i64 offset, SeekMode mode) override
{
if (mode == SeekMode::FromCurrentPosition)
offset = offset - m_helper.buffered_data_size();
auto result = TRY(m_helper.stream().seek(offset, mode));
m_helper.clear_buffer();
return result;
}
virtual ErrorOr<void> truncate(off_t length) override