sqlite3_pcache_page,
  sqlite3_pcache_page —
Custom Page Cache Object
typedef struct sqlite3_pcache_page sqlite3_pcache_page;
struct sqlite3_pcache_page;
The sqlite3_pcache_page object represents a single page in the page cache. The
  page cache will allocate instances of this object. Various methods of the page
  cache use pointers to instances of this object as parameters or as their
  return value.
See sqlite3_pcache_methods2 for additional information.