Cursor is another ABC star-type. One may understand it as a "heavy iterator" or "non-owning buffer". To make the distinctions more clear:
- ABC slice is
T *s[2], an array of two pointers denoting an[a,b)memory range to be consumed. - ABC iterator is same as an ABC slice. That is
contrary to the C++ tradition that equates an
iterator and a pointer. A C++ iterator alone is
mostly useless as one needs to check the
end()pointer each time to advance the iterator. - ABC buffer is
T *b[4], a memory range divided into three slices (typically, PAST, DATA and IDLE). A buffer owns the memory, its DATA and IDLE slices serve as built-in iterators tracking used/empty parts of the buffer. - ABC cursor is
T* c[4], an iterator that still keeps track of the original memory range. Most typically, a cursor is a copy of a buffer, but its DATA slice is positioned differently.
Using a cursor makes a lot of sense when data iteration is not trivial. For example, one may want to use references to jump back and forth in the data, or refer to some metadata dictionary or simply to rewind an iterator.
Again, these are conventions, as all of the star types are just arrays of pointers demarcating memory ranges.