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LibCore: Keep track of file offset to avoid system call for tell()

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This optimization makes the new test run 2x faster.
This commit is contained in:
kleines Filmröllchen 2023-07-06 13:41:38 +02:00 • committed by Jelle Raaijmakers
parent 111fd1e5fe
commit 10edd38543
3 changed files with 33 additions and 1 deletions
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19
Tests/LibCore/TestLibCoreStream.cpp
View file

@ -92,6 +92,25 @@ TEST_CASE(file_seeking_around)
EXPECT_EQ(buffer_contents, expected_seek_contents3);
}
BENCHMARK_CASE(file_tell)
{
auto file = TRY_OR_FAIL(Core::File::open("/usr/Tests/LibCore/10kb.txt"sv, Core::File::OpenMode::Read));
auto expected_file_offset = 0u;
auto ten_byte_buffer = TRY_OR_FAIL(ByteBuffer::create_uninitialized(1));
for (auto i = 0u; i < 4000; ++i) {
TRY_OR_FAIL(file->read_until_filled(ten_byte_buffer));
expected_file_offset += 1u;
EXPECT_EQ(expected_file_offset, TRY_OR_FAIL(file->tell()));
}
for (auto i = 0u; i < 4000; ++i) {
auto seek_file_offset = TRY_OR_FAIL(file->seek(-1, SeekMode::FromCurrentPosition));
expected_file_offset -= 1;
EXPECT_EQ(seek_file_offset, TRY_OR_FAIL(file->tell()));
EXPECT_EQ(expected_file_offset, TRY_OR_FAIL(file->tell()));
}
}
TEST_CASE(file_adopt_fd)
{
int rc = ::open("/usr/Tests/LibCore/long_lines.txt", O_RDONLY);

12
Userland/Libraries/LibCore/File.cpp
View file

@ -117,6 +117,7 @@ ErrorOr<Bytes> File::read_some(Bytes buffer)
ssize_t nread = TRY(System::read(m_fd, buffer));
m_last_read_was_eof = nread == 0;
m_file_offset += nread;
return buffer.trim(nread);
}
@ -135,7 +136,9 @@ ErrorOr<size_t> File::write_some(ReadonlyBytes buffer)
return Error::from_errno(EBADF);
}
return TRY(System::write(m_fd, buffer));
auto nwritten = TRY(System::write(m_fd, buffer));
m_file_offset += nwritten;
return nwritten;
}
bool File::is_eof() const { return m_last_read_was_eof; }
@ -177,15 +180,22 @@ ErrorOr<size_t> File::seek(i64 offset, SeekMode mode)
}
size_t seek_result = TRY(System::lseek(m_fd, offset, syscall_mode));
m_file_offset = seek_result;
m_last_read_was_eof = false;
return seek_result;
}
ErrorOr<size_t> File::tell() const
{
return m_file_offset;
}
ErrorOr<void> File::truncate(size_t length)
{
if (length > static_cast<size_t>(NumericLimits<off_t>::max()))
return Error::from_string_literal("Length is larger than the maximum supported length");
m_file_offset = min(length, m_file_offset);
return System::ftruncate(m_fd, length);
}

3
Userland/Libraries/LibCore/File.h
View file

@ -67,6 +67,7 @@ public:
virtual bool is_open() const override;
virtual void close() override;
virtual ErrorOr<size_t> seek(i64 offset, SeekMode) override;
virtual ErrorOr<size_t> tell() const override;
virtual ErrorOr<void> truncate(size_t length) override;
// Sets the blocking mode of the file. If blocking mode is disabled, reads
@ -109,6 +110,8 @@ private:
int m_fd { -1 };
bool m_last_read_was_eof { false };
ShouldCloseFileDescriptor m_should_close_file_descriptor { ShouldCloseFileDescriptor::Yes };
size_t m_file_offset { 0 };
};
AK_ENUM_BITWISE_OPERATORS(File::OpenMode)