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Fix performance of diff-based reloading of buffers

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It turns out diffing was pretty fast, but applying the diff was
sub-optimal as it was constantly inserting/erasing lines which
led to lots of unnecessary shifting. Fix this by manually tracking
a read/write iterator and only shifting when necessary (on keeps,
and inserts).
This commit is contained in:
Maxime Coste 2023-12-26 20:55:47 +11:00
parent 68e73d8a24
commit 43e8aadcaa
1 changed files with 26 additions and 11 deletions
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37
src/buffer.cc
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@ -219,40 +219,55 @@ void Buffer::reload(BufferLines lines, ByteOrderMark bom, EolFormat eolformat, F
[](const StringDataPtr& lhs, const StringDataPtr& rhs)
{ return lhs->strview() == rhs->strview(); });
auto it = m_lines.begin();
auto read_it = m_lines.begin();
auto write_it = m_lines.begin();
auto new_it = lines.begin();
for (auto& [op, len] : diff)
for (auto [op, len] : diff)
{
kak_assert(read_it >= write_it);
if (op == DiffOp::Keep)
{
it += len;
if (read_it != write_it)
std::move(read_it, read_it + len, write_it);
write_it += len;
read_it += len;
new_it += len;
}
else if (op == DiffOp::Add)
{
const LineCount cur_line = (int)(it - m_lines.begin());
const LineCount cur_line = (int)(write_it - m_lines.begin());
for (LineCount line = 0; line < len; ++line)
m_current_undo_group.push_back({Modification::Insert, cur_line + line, *(new_it + (int)line)});
m_changes.push_back({Change::Insert, cur_line, cur_line + len});
m_lines.insert(it, new_it, new_it + len);
it = m_lines.begin() + (int)(cur_line + len);
if (read_it != write_it)
{
auto count = std::min(len, static_cast<int>(read_it - write_it));
write_it = std::copy(new_it, new_it + count, write_it);
new_it += count;
if (len == count)
continue;
len -= count;
}
auto read_pos = read_it - m_lines.begin();
write_it = m_lines.insert(write_it, new_it, new_it + len) + len;
read_it = m_lines.begin() + read_pos + len;
new_it += len;
}
else if (op == DiffOp::Remove)
{
const LineCount cur_line = (int)(it - m_lines.begin());
const LineCount cur_line = (int)(write_it - m_lines.begin());
for (LineCount line = len-1; line >= 0; --line)
m_current_undo_group.push_back({
Modification::Erase, cur_line + line,
m_lines.get_storage(cur_line + line)});
it = m_lines.erase(it, it + len);
read_it += len;
m_changes.push_back({ Change::Erase, cur_line, cur_line + len });
}
}
m_lines.erase(write_it, m_lines.end());
}
commit_undo_group();