How does Memcached internally use 'item' structures?

[Nicola Licheri]

Hi. 

For my thesis, I'm working on a fork of Memcached, a C++ reimplementation without libevent. 

To do this, I need to know how Memcached use items to store key and values. 

Particularly, I'm interested to know in detail what each field is used for. 

The item type has been defined in memcached.h as

typedef struct _stritem {
    struct _stritem *next;
    struct _stritem *prev;
    struct _stritem *h_next;    /* hash chain next */
    rel_time_t      time;       /* least recent access */
    rel_time_t      exptime;    /* expire time */
    int             nbytes;     /* size of data */
    unsigned short  refcount;
    uint8_t         nsuffix;    /* length of flags-and-length string */
    uint8_t         it_flags;   /* ITEM_* above */
    uint8_t         slabs_clsid;/* which slab class we're in */
    uint8_t         nkey;       /* key length, w/terminating null and padding */
    /* this odd type prevents type-punning issues when we do
     * the little shuffle to save space when not using CAS. */
    union {
        uint64_t cas;
        char end;
    } data[];
    /* if it_flags & ITEM_CAS we have 8 bytes CAS */
    /* then null-terminated key */
    /* then " flags length\r\n" (no terminating null) */
    /* then data with terminating \r\n (no terminating null; it's binary!) */
} item;

Can you explain to me how populate each field of this structure to memorize, for example, key = "mickey" - value = "mouse" ?  

Thanks for helping me! 
Nicola

[Toru Maesaka]

Getting straight to the point -- this would be a good start.

https://github.com/memcached/memcached/blob/master/items.c#L88-L216

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