Buffer: add iterator_at_line_{begin,end} methods

src/buffer.cc

@@ -96,6 +96,17 @@ BufferCoord Buffer::clamp(const BufferCoord& line_and_column) const
     return result;
 }
 
+BufferIterator Buffer::iterator_at_line_begin(const BufferIterator& iterator) const
+{
+    return BufferIterator(*this, m_lines[line_at(iterator)]);
+}
+
+BufferIterator Buffer::iterator_at_line_end(const BufferIterator& iterator) const
+{
+    BufferPos line = line_at(iterator) + 1;
+    return line < m_lines.size() ? BufferIterator(*this, m_lines[line]) : end();
+}
+
 void Buffer::compute_lines()
 {
     m_lines.clear();

src/buffer.hh

@@ -149,6 +149,15 @@ public:
     void register_modification_listener(BufferModificationListener* listener);
     void unregister_modification_listener(BufferModificationListener* listener);
 
+    // returns an iterator pointing to the first character of the line
+    // iterator is on
+    BufferIterator iterator_at_line_begin(const BufferIterator& iterator) const;
+
+    // returns an iterator pointing to the character after the last of the
+    // line iterator is on (which is the first of the next line if iterator is
+    // not on the last one)
+    BufferIterator iterator_at_line_end(const BufferIterator& iterator) const;
+
 private:
     BufferChar at(BufferPos position) const;