[CRIU] Re: [RFC 0/4] Lets try PB again

[Pavel Emelyanov]

On 07/06/2012 04:35 PM, Cyrill Gorcunov wrote:
> On Fri, Jul 06, 2012 at 04:21:25PM +0400, Pavel Emelyanov wrote:
>>
>> Is there a way to unpack an object into a static buffer rather than
>> allocating one dynamically?
> 
> Yes, previously I've been using 16K stack for that, I can bring it back ;)
> 
> +#define pbimg_write_obj(__fd, __object, __type, __get_packed_size, __pack)
> +({
> +	u8  ___buf[KILO(16)];
> +	u32 ___size = __get_packed_size(__object);
> +	int ___ret = -1;
> 
> that is from previous versions. If buffer is too small we will ge error.
> But in most case 16K is more than enough ;)

No, I meant a bit different thing. Instead of

FooEntry *foo;

foo = foo_entry__unpack();
...
foo_entry__free_unpacked();

write

FooEntry foo;

foo_entry__unpack_on_staack(&foo);

Is it possible? If no, then OK, let's proceed with this approach.

>>> +			fdinfo_entry__get_packed_size,
>>> +			fdinfo_entry__pack);
>>
>> I'd appreciate if this looked like
>>
>> pc_write(fd, &e, fdinfo_entry);
>>
>> where __get_packet_size and __pack are concatenated inside the macro
> 
> yeah, good point, will update
> 
>>> +#define pb_write(__fd, __obj_ptr, __get_pksize, __pack)				\
>>> +({										\
>>> +	u32 __size = __get_pksize(__obj_ptr);					\
>>> +	u8 *__buf = xmalloc(__size);						\
>>> +	int __ret = -1;								\
>>> +										\
>>> +	if (__buf) {								\
>>> +		__pack(__obj_ptr, __buf);					\
>>> +		__ret = write_img(__fd, &__size);				\
>>> +		if (!__ret)							\
>>> +			__ret = write_img_buf(__fd, __buf, __size);		\
>>> +		xfree(__buf);							\
>>> +	}									\
>>> +										\
>>> +	__ret;									\
>>> +})
>>
>> That's too big for a macro. Turn it into a macro + outlined function.
> 
> I've been trying, but the problem is that PB compiler generates pack/unpack
> prototypes with argument typed and I can't use some abstract function which
> has void* types as arguments, gcc complains. So I switched to macros.

Well, I think for _that_ case it's OK to use very abstract casting
like this (*)() ;)

> 	Cyrill
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