Most statically-allocated, non-list-based circular buffers operate on items of a fixed size. If we are storing elements of arbirary length, this forces us to either write one byte at a time and parse the output stream, or dedicate a known "max size" element and assume all elements fit in this max. This latter option is a huge waste of space if you're allocating for a potential worst case.
In this implementation, a fixed size buffer is used to hold data circularly in blobs. When a new blob is written that would cause an overrun of existing data, one or more entire blobs are deleted to make the necessary space. The write function can be set to return an error instead of overwrite.
Also included is a mode (enabled by CBUF_ALLOW_PARTIAL) where a blob can be opened and written to in multiple sequential writes. It
will still be read as a single blob. This is useful, for example, to hold incoming serial data until an EOL delimiter is received.