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• Public:
  • IBuf: Single buffer in a linked chain
  • IBufChain: Linked chain of IBufs
  • IBufQueue; Queue container for IBufChains
  • Buf (IBuf in shared pointer)
  • BufChain (IBufChain in shared pointer)
  • BufQueue (IBufQueue in shared pointer)
• Private:
  • CBufImpl: Implementation of IBuf with ability to be a CFreeListNode
  • CBufChainImpl: Implementation of IBufChain with ability to be a CFreeListNode
  • BufImpl (CBufImpl in shared pointer)
  • BufChainImpl (CBufChainImpl in shared pointer)

Buf

IBuf class methods implemented in CBufImpl:

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• void addToChain(BufChainImpl c); Add this buffer, and the rest of the list, to an empty chain
• void reinit(): Reset the payload pointers (beg = end = HEADROOM)
• BufImpl getNextImpl(): Get next entry
• BufImpl getPrevImpl(): Get prev entry
• BufChainImpl getChainImpl(): Get chain pointer
• unlinkCheap(CBufChainImpl::key k): 

BufChain

IBufChain class methods implemented in CBufChainImpl:

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• BufImpl getHeadImpl(): get head of list
• BufImpl getTailImpl(): get tail of list
• void addSIze(ssize_t s) add bytes to total size
• void addLen(int l) add entries to total length
• setSize(size_t s): set total size in bytes
• setLen(unsigned l): set buffer length
  
  

BufQueue

IBufQueue class methods:

• BufQueue create(unsigned size): create an object
  
  

IBufQueue virtual methods:

• BufChain pop(const CTimeout *abs_timeout): Pop an entry from the queue with timeout
• BufChain tryPop(): try to pop without timeout?
• bool push(BufChain b, const CTimeout *abs_timeout): add an entry to the queue with timeout
• bool tryPush(BufChain b): add an entry without timeout?
• getAbsTimeoutPop(const CTimeout *rel_timeout): ?????
• getAbsTimeoutPush(const CTimeout *rel_timeout): ????
• IEventSource getReadEventSource(): ????
• IEventSource getWriteEventSource(): ????
• bool isFull(): queue is full
• bool isEmpty() queue is full
• void shutdown(): ????
• void startup(): ????
  
  

Questions:

Till,

I am going through the CPSW code and have some questions and comments, starting with the CPSW buffer implementation. BTW I like the approach to the buffer chains which minimizes the number of copies to the copy from the UDP receive and the copy to user space. 

1. It appears you base the buffer size constants and container variables around the assumption that we will limit each buffer element size to 64K. I am not sure if that is a safe assumption once we add support for interfaces that are not TCP/IP or UDP. With PGP or axi-stream we can have much larger buffers. Also you seem to hardcode some ethernet based constants in the .h file and I am not sure that is the best place for a generic implementation. (more notes on size later)

2. In adjPayload you have this line:

if ( delta > beg || delta > old_size )
return false;

Why do you care if the shift size is greater than the beginning payload offset? Should this be an unsigned compare to check for left shifts beyond the beginning of the buffer?

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