[CRIU] [PATCH 13/32] tools: cpt2 -- Introduce "object" abstraction

[Pavel Emelyanov]

On 03/31/2013 01:42 AM, Cyrill Gorcunov wrote:
> 
> Objects are aimed to carry real data read from dump files.
> Usually the data read is placed after the __payload pointer
> 
> [ though the object may carry another structures like a
>   container and in this case __payload is followed by
>   embedded data while image data addressed by o_image
>   member, will be explained later ].
> 
> For fast lookup of objects by their position read from dumpfile
> there is 16K object chain-hash. 16K should be enough for now,
> still if one day we see serious contention (which I quite doubt
> in) the hash size can be easily increased by tuning OBJS_HASH_BITS
> value.
> 
> Because of dumpfile format specifics objects types up to CPT_OBJ_MAX
> are linked to per-type lists, allowing a caller to walk over all
> of them via regular list helpers code. If possible try to not use
> @o_list member for anything else, until really needed.
> 
> When read, each object is assigned with unique 32 bit id.
> 
> Because objects on its own are not that usefull, the general
> idea of their presense is to carry other structures. For this
> sake a number of macros provided in obj.h header file.
> 
> Lets consider we need to work with the following structure
> 
> struct some_struct {
> 	struct list_head	list;
> 	struct cpt_image	image;
> } *entry;
> 
> where @list is a member we use for own linking (outside of objects'
> subsystem) and @image is some member from cpt-image.h file and
> represent a record in dumpfile.
> 
> First we allocate structure as
> 
> 	entry = obj_alloc_to(struct some_struct, image);
> 
> then we may read data to @image member with help of
> read_obj_cpt() macro.
> 
> Once object no longer needed, we can call to obj_free_to(entry)
> and get it destroyed.
> 
> For convenience helpers are postfixed with _to and _of names,
> _to is used when operate with pointer to a compound object, and
> _of operate with pointer to obj_t.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
> ---
>  tools/cpt2/src/Makefile      |   1 +
>  tools/cpt2/src/include/obj.h | 223 +++++++++++++++++++++++++++++++++++
>  tools/cpt2/src/obj.c         | 270 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 494 insertions(+)
>  create mode 100644 tools/cpt2/src/include/obj.h
>  create mode 100644 tools/cpt2/src/obj.c
> 


> +extern int read_obj_cont(int fd, void *p, size_t size);
> +
> +#define read_obj_cont(fd, p)						\
> +({									\
> +	int __ret = -1;							\
> +	void *__p = (void *)(p) + sizeof(struct cpt_object_hdr);	\
> +	u64 __size = sizeof(*p) - sizeof(struct cpt_object_hdr);	\
> +									\
> +	if (read_data(fd, __p, __size, false) == 0)			\
> +		__ret = 0;						\
> +	else								\
> +		pr_err("Can't read object payload\n");			\
> +									\
> +	__ret;								\
> +})

Huh?