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AK: Cache all the line positions in LineTrackingLexer

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Also updates a LibWeb text test that used to report the wrong line
number.
This commit is contained in:
Ali Mohammad Pur 2024-10-10 09:58:31 +02:00 • committed by Tim Ledbetter
commit 02b50d463b
Notes: github-actions[bot] 2024-10-10 22:54:58 +00:00
4 changed files with 42 additions and 31 deletions
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43
AK/GenericLexer.cpp
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@ -175,27 +175,32 @@ ErrorOr<T> GenericLexer::consume_decimal_integer()
LineTrackingLexer::Position LineTrackingLexer::position_for(size_t index) const
{
auto& [cached_index, cached_line, cached_column] = m_cached_position;
if (cached_index <= index) {
for (size_t i = cached_index; i < index; ++i) {
if (m_input[i] == '\n')
++cached_line, cached_column = 0;
else
++cached_column;
}
} else {
auto lines_backtracked = m_input.substring_view(index, cached_index - index).count('\n');
cached_line -= lines_backtracked;
if (lines_backtracked == 0) {
cached_column -= cached_index - index;
} else {
auto current_line_start = m_input.substring_view(0, index).find_last('\n').value_or(0);
cached_column = index - current_line_start;
// Sad case: we have no idea where the nearest newline is, so we have to
// scan ahead a bit.
while (index > m_largest_known_line_start_position) {
auto next_newline = m_input.find('\n', m_largest_known_line_start_position);
if (!next_newline.has_value()) {
// No more newlines, add the end of the input as a line start to avoid searching again.
m_line_start_positions->insert(m_input.length(), m_line_start_positions->size());
m_largest_known_line_start_position = m_input.length();
break;
}
m_line_start_positions->insert(next_newline.value() + 1, m_line_start_positions->size());
m_largest_known_line_start_position = next_newline.value() + 1;
}
cached_index = index;
return m_cached_position;
// We should always have at least the first line start position.
auto previous_line_it = m_line_start_positions->find_largest_not_above_iterator(index);
auto previous_line_index = previous_line_it.key();
auto line = *previous_line_it;
auto column = index - previous_line_index;
if (line == 0) {
// First line, take into account the start position.
column += m_first_line_start_position.column;
}
line += m_first_line_start_position.line;
return { index, line, column };
}
template ErrorOr<u8> GenericLexer::consume_decimal_integer<u8>();