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AK: Add an optional starting offset to CircularBuffer::offset_of

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This parameter allows to start searching after an offset. For example,
to resume a search.

It is unfortunately a breaking change in API so this patch also modifies
one user and one test.
This commit is contained in:
Lucas CHOLLET 2023-01-07 13:09:20 -05:00 committed by Andrew Kaster
parent 34922c0cc0
commit 9a7accddb7
Notes: sideshowbarker 2024-07-17 12:02:22 +09:00 
Author: https://github.com/LucasChollet
Commit: https://github.com/SerenityOS/serenity/commit/9a7accddb7
Pull-request: https://github.com/SerenityOS/serenity/pull/16544
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/timschumi ✅
4 changed files with 57 additions and 9 deletions
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22
AK/CircularBuffer.cpp
View file

@ -52,19 +52,29 @@ bool CircularBuffer::is_wrapping_around() const
return capacity() <= m_reading_head + m_used_space;
}
Optional<size_t> CircularBuffer::offset_of(StringView needle, Optional<size_t> until) const
Optional<size_t> CircularBuffer::offset_of(StringView needle, Optional<size_t> from, Optional<size_t> until) const
{
auto const read_from = from.value_or(0);
auto const read_until = until.value_or(m_used_space);
VERIFY(read_from <= read_until);
Array<ReadonlyBytes, 2> spans {};
spans[0] = next_read_span();
if (spans[0].size() > read_until)
spans[0] = spans[0].trim(read_until);
else if (is_wrapping_around())
spans[1] = m_buffer.span().slice(0, read_until - spans[0].size());
if (read_from > 0)
spans[0] = spans[0].slice(min(spans[0].size(), read_from));
return AK::memmem(spans.begin(), spans.end(), needle.bytes());
if (spans[0].size() + read_from > read_until)
spans[0] = spans[0].trim(read_until - read_from);
if (is_wrapping_around())
spans[1] = m_buffer.span().slice(max(spans[0].size(), read_from) - spans[0].size(), min(read_until, m_used_space) - spans[0].size());
auto maybe_found = AK::memmem(spans.begin(), spans.end(), needle.bytes());
if (maybe_found.has_value())
*maybe_found += read_from;
return maybe_found;
}
void CircularBuffer::clear()

2
AK/CircularBuffer.h
View file

@ -36,7 +36,7 @@ public:
[[nodiscard]] size_t used_space() const;
[[nodiscard]] size_t capacity() const;
Optional<size_t> offset_of(StringView needle, Optional<size_t> until = {}) const;
Optional<size_t> offset_of(StringView needle, Optional<size_t> from = {}, Optional<size_t> until = {}) const;
void clear();

40
Tests/AK/TestCircularBuffer.cpp
View file

@ -272,6 +272,44 @@ TEST_CASE(offset_of)
EXPECT(result.has_value());
EXPECT_EQ(result.value(), 13ul);
result = circular_buffer.offset_of("!Well"sv, 12);
result = circular_buffer.offset_of("!Well"sv, {}, 12);
EXPECT(!result.has_value());
result = circular_buffer.offset_of("e"sv, 2);
EXPECT(result.has_value());
EXPECT_EQ(result.value(), 9ul);
}
TEST_CASE(offset_of_with_until_and_after)
{
auto const source = "Well Hello Friends!"sv;
auto byte_buffer_or_error = ByteBuffer::copy(source.bytes());
EXPECT(!byte_buffer_or_error.is_error());
auto byte_buffer = byte_buffer_or_error.release_value();
auto circular_buffer_or_error = CircularBuffer::create_initialized(byte_buffer);
EXPECT(!circular_buffer_or_error.is_error());
auto circular_buffer = circular_buffer_or_error.release_value();
auto result = circular_buffer.offset_of("Well Hello Friends!"sv, 0, 19);
EXPECT_EQ(result.value_or(42), 0ul);
result = circular_buffer.offset_of(" Hello"sv, 4, 10);
EXPECT_EQ(result.value_or(42), 4ul);
result = circular_buffer.offset_of("el"sv, 3, 10);
EXPECT_EQ(result.value_or(42), 6ul);
safe_discard(circular_buffer, 5);
auto written_bytes = circular_buffer.write(byte_buffer.span().trim(5));
EXPECT_EQ(written_bytes, 5ul);
result = circular_buffer.offset_of("Hello Friends!Well "sv, 0, 19);
EXPECT_EQ(result.value_or(42), 0ul);
result = circular_buffer.offset_of("o Frie"sv, 4, 10);
EXPECT_EQ(result.value_or(42), 4ul);
result = circular_buffer.offset_of("el"sv, 3, 14);
EXPECT_EQ(result.value_or(42), 15ul);
}

2
Userland/Libraries/LibCore/Stream.h
View file

@ -719,7 +719,7 @@ public:
Optional<size_t> longest_match;
size_t match_size = 0;
for (auto& candidate : candidates) {
auto const result = m_buffer.offset_of(candidate, readable_size);
auto const result = m_buffer.offset_of(candidate, {}, readable_size);
if (result.has_value()) {
auto previous_match = longest_match.value_or(*result);
if ((previous_match < *result) || (previous_match == *result && match_size < candidate.length())) {