When committing an undo group, run an optimization pass on it
With incremntal insertion, undo groups tends to be a lot of single character insertion/deletions at the same point, but the end result is most of the time a single string insertion. Buffer now tries to optimize the undo group.
This commit is contained in:
Maxime Coste
parent
b16c967f9c
commit
7ce3212fb2
219
src/buffer.cc
219
src/buffer.cc
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@ -177,24 +177,6 @@ String Buffer::string(const BufferIterator& begin, const BufferIterator& end) co
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return res;
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}
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void Buffer::commit_undo_group()
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{
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if (m_flags & Flags::NoUndo)
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return;
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if (m_current_undo_group.empty())
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return;
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m_history.erase(m_history_cursor, m_history.end());
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m_history.push_back(std::move(m_current_undo_group));
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m_current_undo_group.clear();
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m_history_cursor = m_history.end();
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if (m_history.size() < m_last_save_undo_index)
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m_last_save_undo_index = -1;
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}
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// A Modification holds a single atomic modification to Buffer
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struct Buffer::Modification
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{
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@ -220,6 +202,207 @@ struct Buffer::Modification
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}
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};
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class UndoGroupOptimizer
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{
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static constexpr auto Insert = Buffer::Modification::Type::Insert;
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static constexpr auto Erase = Buffer::Modification::Type::Erase;
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static BufferCoord advance(BufferCoord coord, const String& str)
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{
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for (auto c : str)
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{
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if (c == '\n')
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{
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++coord.line;
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coord.column = 0;
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}
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else
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++coord.column;
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}
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return coord;
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}
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static ByteCount count_byte_to(BufferCoord pos, const BufferCoord& endpos, const String& str)
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{
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ByteCount count = 0;
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for (auto it = str.begin(); it != str.end() and pos != endpos; ++it)
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{
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if (*it == '\n')
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{
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++pos.line;
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pos.column = 0;
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}
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else
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++pos.column;
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++count;
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}
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assert(pos == endpos);
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return count;
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}
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static const ByteCount overlaps(const String& lhs, const String& rhs)
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{
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if (lhs.empty() or rhs.empty())
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return -1;
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char c = rhs.front();
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ByteCount pos = 0;
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while ((pos = (int)lhs.find_first_of(c, (int)pos)) != -1)
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{
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ByteCount i = pos, j = 0;
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while (i != lhs.length() and j != rhs.length() and lhs[i] == rhs[j])
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++i, ++j;
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if (i == lhs.length())
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break;
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++pos;
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}
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return pos;
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}
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static bool merge_contiguous(Buffer::UndoGroup& undo_group)
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{
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bool progress = false;
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auto it = undo_group.begin();
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auto it_next = it+1;
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while (it_next != undo_group.end())
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{
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ByteCount pos;
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auto& coord = it->coord;
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auto& next_coord = it_next->coord;
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// reorders modification doing a kind of custom bubble sort
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// so we have a O(n²) worst case complexity of the undo group optimization
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if (next_coord < coord)
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{
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BufferCoord next_end = advance(next_coord, it_next->content);
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if (it_next->type == Insert)
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{
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if (coord.line == next_coord.line)
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coord.column += next_end.column - next_coord.column;
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coord.line += next_end.line - next_coord.line;
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}
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else if (it->type == Insert)
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{
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if (next_end > coord)
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{
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ByteCount start = count_byte_to(next_coord, coord, it_next->content);
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ByteCount len = std::min(it->content.length(), it_next->content.length() - start);
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it->coord = it_next->coord;
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it->content = it->content.substr(len);
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it_next->content = it_next->content.substr(0,start) + it_next->content.substr(start + len);
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}
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else
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{
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if (next_end.line == coord.line)
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{
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coord.line = next_coord.line;
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coord.column = next_coord.column + coord.column - next_end.column;
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}
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else
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coord.line -= next_end.line - next_coord.line;
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}
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}
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else if (it->type == Erase and next_end > coord)
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{
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ByteCount start = count_byte_to(next_coord, coord, it_next->content);
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it_next->content = it_next->content.substr(0, start) + it->content + it_next->content.substr(start);
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it->coord = it_next->coord;
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it->content.clear();
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}
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std::swap(*it, *it_next);
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progress = true;
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}
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if (it->type == Erase and it_next->type == Erase and coord == next_coord)
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{
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it->content += it_next->content;
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it_next = undo_group.erase(it_next);
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progress = true;
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}
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else if (it->type == Insert and it_next->type == Insert and
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is_in_range(next_coord, coord, advance(coord, it->content)))
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{
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ByteCount prefix_len = count_byte_to(coord, next_coord, it->content);
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it->content = it->content.substr(0, prefix_len) + it_next->content
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+ it->content.substr(prefix_len);
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it_next = undo_group.erase(it_next);
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progress = true;
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}
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else if (it->type == Insert and it_next->type == Erase and
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coord <= next_coord and next_coord < advance(coord, it->content))
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{
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ByteCount insert_len = it->content.length();
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ByteCount erase_len = it_next->content.length();
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ByteCount prefix_len = count_byte_to(coord, next_coord, it->content);
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it->content = it->content.substr(0, prefix_len) +
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((prefix_len + erase_len < insert_len) ?
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it->content.substr(prefix_len + erase_len) : "");
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it_next->content = (insert_len - prefix_len < erase_len) ?
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it_next->content.substr(insert_len - prefix_len) : "";
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++it, ++it_next;
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progress = true;
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}
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else if (it->type == Erase and it_next->type == Insert and coord == next_coord and
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(pos = overlaps(it->content, it_next->content)) != -1)
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{
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ByteCount overlaps_len = it->content.length() - pos;
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it->content = it->content.substr(0, pos);
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it_next->content = it_next->content.substr(overlaps_len);
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++it, ++it_next;
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progress = true;
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}
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else
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++it, ++it_next;
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}
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return progress;
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}
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static bool erase_empty(Buffer::UndoGroup& undo_group)
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{
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auto it = std::remove_if(begin(undo_group), end(undo_group),
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[](Buffer::Modification& m) { return m.content.empty(); });
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if (it != end(undo_group))
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{
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undo_group.erase(it, end(undo_group));
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return true;
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}
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return false;
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}
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public:
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static void optimize(Buffer::UndoGroup& undo_group)
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{
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while (undo_group.size() > 1)
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{
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bool progress = false;
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progress |= merge_contiguous(undo_group);
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progress |= erase_empty(undo_group);
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if (not progress)
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break;
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}
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}
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};
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void Buffer::commit_undo_group()
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{
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if (m_flags & Flags::NoUndo)
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return;
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UndoGroupOptimizer::optimize(m_current_undo_group);
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if (m_current_undo_group.empty())
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return;
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m_history.erase(m_history_cursor, m_history.end());
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m_history.push_back(std::move(m_current_undo_group));
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m_current_undo_group.clear();
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m_history_cursor = m_history.end();
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if (m_history.size() < m_last_save_undo_index)
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m_last_save_undo_index = -1;
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}
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bool Buffer::undo()
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{
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commit_undo_group();
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@ -202,6 +202,7 @@ private:
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struct Modification;
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typedef std::vector<Modification> UndoGroup;
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friend class UndoGroupOptimizer;
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std::vector<UndoGroup> m_history;
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std::vector<UndoGroup>::iterator m_history_cursor;
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