Thanks for all good explanation.
On Tue, Jul 9, 2013 at 11:24 PM, Sebastian Huber < sebastian.hu...@embedded-brains.de> wrote: > On 07/09/2013 05:29 AM, Ashi wrote: > >> Hi, Sebastian, thanks for your review! >> >> 在 2013-7-7 下午9:49，"Sebastian Huber" >> <sebastian.huber@embedded-**brains.de<sebastian.hu...@embedded-brains.de> >> <mailto:sebastian.huber@**embedded-brains.de<sebastian.hu...@embedded-brains.de> >> >>写道： >> >> > >> > Hello Ashi, >> > >> > >> > On 06/07/13 09:17, Ashi wrote: >> >> >> >> Hi all, >> >> >> >> this patch adds a data structure called freelist to score, there are >> no >> >> test cases yet and should be added later. >> > >> > >> > I would appreciate to have the test for this new stuff included in the >> patch. >> >> >> sure, I will update the patch with test cases. >> > >> > >> >> >> >> Freelist is a structure, which contains a chain of nodes. It supports >> 2 >> >> operation: >> >> - get node from freelist >> >> - put node to freelist. >> >> And when there is no enough node in freelist, it will automatically >> >> increase itself's size by allocate more nodes from heap or >> workspace(which >> >> is specified by user). >> > >> > >> > What can I do if I like to get the nodes from a magic space? >> >> >> sorry for the unclear, you can get nodes from freelist by 'get' >> operation. And >> if you mean get nodes from heap or workspace, it's done by >> _Freelist_Get_node(), which calls _Freelist_Bump() when there is no free >> node left. >> > > Yes, the problem is that you limit your Freelist to the heap and > workspace. If you use a handler function (or virtual method if you like) > then you can avoid this limitation. > > [...] > > >> +/** >> >> + * @typedef freelist_callout >> >> + */ >> >> +typedef void (*freelist_callout)( >> >> + Freelist_Control *fc, >> >> + void *nodes >> >> +); >> >> + >> >> +/** >> >> + * @typedef Freelist_Control_struct >> >> + * >> >> + * This is used to manage each element. >> >> + */ >> >> +struct Freelist_Control_struct { >> >> + Chain_Control Freelist; >> >> + size_t free_count; >> > >> > >> > Why do we need the free_count? >> >> free_count is used to keep track how many nodes there is in freelist. And >> if >> free_count is 0 when you try to get node from freelist by call >> _Freelist_Get_node(), _Freelist_Get_node() will call _Freelist_Bump() to >> allocate more node from heap or workspace. >> > > The list knows if it is empty. There is not need to store this > information in two ways. > > > > >> >> + size_t bump_count; >> >> + size_t node_size; >> > >> > >> >> + freelist_callout callout; >> >> + bool use_workspace; >> >> +}; >> > >> > >> > I would replace this with an extend handler. >> > >> > /** >> > * @brief Extends the freelist. >> > * >> > * @param[in] freelist The freelist control. >> > * >> > * @return The count of new nodes. >> > */ >> > typedef size_t ( *Freelist_Extend )( Freelist_Control *freelist ); >> > >> > This is much more flexible since you only specify the interface and >> don't >> limit this to heap/workspace. >> > >> > You can provide a _Freelist_Extend_with_nothing(**) which simply >> returns 0. >> >> Yeah, this Freelist_Extend is very flexible, but I feel the >> Freelist_Extend is >> a little complex. As it shows in _Freelist_Bump(), if users provides >> their own >> extension function, they have to append there new nodes to freelist's >> internal >> chain and call their callout function on new nodes. And since >> _Freelist_Initialize() also would call Freelist_Extend(), if we provided >> _Freelist_Extend_with_nothing(**), the initialization may fail. >> > > Since the Freelist_Extend gets the Freelist as a first argument it can set > the extend handler to _Freelist_Extend_with_nothing(**) after the first > invocation. > > Example: > > > /** > * @brief Extends the freelist. > * > * @param[in] freelist The freelist control. > */ > typedef void ( *Freelist_Extend )( Freelist_Control *freelist ); > > typedef struct { > Objects_Control obj; > int x; > } my_obj; > > void my_extend( Freelist_Control *freelist ) > { > size_t bump_count = freelist->bump_count; > size_t size = bump_count * sizeof(my_obj); > my_obj *objs = malloc(size); > > _Freelist_Set_extend_handler( freelist, _Freelist_Extend_with_nothing ); > _Chain_Initialize( > _Freelist_Get_list( freelist ), > objs, > bump_count, > size > ); > > } > I'm a little confused by my_extend() function, is it only called after calling _Freelist_Initialize() by user? > > [...] > > -- > Sebastian Huber, embedded brains GmbH > > Address : Dornierstr. 4, D-82178 Puchheim, Germany > Phone : +49 89 189 47 41-16 > Fax : +49 89 189 47 41-09 > E-Mail : > sebastian.huber@embedded-**brains.de<sebastian.hu...@embedded-brains.de> > PGP : Public key available on request. > > Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG. > Cheers, Zhongwei
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