mongoose/docs/c-api/mbuf.h/struct_mbuf.md

title	decl_name	symbol_kind	signature
struct mbuf	struct mbuf	struct	struct mbuf { char *buf; /* Buffer pointer */ size_t len; /* Data length. Data is located between offset 0 and len. */ size_t size; /* Buffer size allocated by realloc(1). Must be >= len */ };

Memory buffer descriptor