275 	TInt err = newChain.Alloc(len + aHdrReserve, *this);

   275 // Suppress the "follow-the-leader" behaviour of preserving the buffer sizing of the

   276 // existing chain. The goal of preserving buffer characteristics remains desirable but

   277 // not at the cost of having TCP use unnecessarily small buffers - this area needs 

   278 // rework once the Comms stack really adopts buffer pools and zero copy  	

   279 //	TInt err = newChain.Alloc(len + aHdrReserve, *this);

   280 	TInt err;

   281     if(First())

   282         {

   283         newChain.iNext = First()->Pool()->Pond().Alloc(len + aHdrReserve, 0, KMaxTInt);

   284         err = iNext ? KErrNone : KErrNoMBufs;      

   285         }

   286     else

   287         {

   288         RMBufAllocator allocator;

   289         err = newChain.Alloc(aLen + aHdrReserve, allocator);  

   290         }

   291 	

   535 	User::LeaveIfError(RCommsBufChain::Split(anOffset, newChain));

   551 	User::LeaveIfError(Split(anOffset, newChain));

   536 	}

   552 	}

   537 

   553 

   538 EXPORT_C TInt RMBufChain::Split(TInt anOffset, RMBufChain& newChain)

   554 EXPORT_C TInt RMBufChain::Split(TInt aOffset, RMBufChain& aNewChain)

   547 	return RCommsBufChain::Split(anOffset, newChain);		

   563     // RCommsBuf::Split() will not allocate a smaller buffer size than the current, as part of its approach of (trying to)

   548 	}

   564     // support zero-copy transfer by respecting the buffer pool in use. This work is incomplete (needs support throughout

   565     // the stack and probably a cleverer idea of what constitutes an acceptable buffer than simply size), so in the meantime

   566     // having MBufMgr reflect this behaviour by refusing to Split() a big buf into smaller bufs is unnecessarily purist.

   567     // Hence the functionality is implemented directly here

   568     

   569     __ASSERT_ALWAYS(iNext!=NULL, CommsBuf::Panic(EMBuf_EmptyChain));

   570     __ASSERT_ALWAYS(aOffset>=0, CommsBuf::Panic(EMBuf_NegativeOffset));

   571     

   572     // For testing post-conditions

   573 #ifdef _DEBUG

   574     TInt origLen = Length();

   575 #endif

   576     TInt splitBufOffset;

   577     TInt splitBufRemainder;

   578     RMBuf* splitBuf;

   579     RMBuf* splitBufPrev;

   580     

   581     if(!Goto(aOffset, splitBuf, splitBufOffset, splitBufRemainder, splitBufPrev))

   582         {

   583         aNewChain.Init();

   584         return KErrNone;

   585         }

   586     

   587     if(splitBufOffset != splitBuf->Offset()) // Not on an mbuf boundary

   588         {

   589         // Copy tail of splitBuf out to a new chain (hopefully a single buf, but needn't be)

   590         TInt splitDataOffset = splitBufOffset - splitBuf->Offset();

   591         TInt err = RMBufChain(splitBuf).Copy(aNewChain, splitDataOffset, splitBufRemainder);

   592         if(err != KErrNone)

   593             {

   594             return err;

   595             }

   596         splitBuf->AdjustDataEnd(-splitBufRemainder);

   597         RMBufChain splitTail(splitBuf->Next());

   598         aNewChain.Append(splitTail);

   599         splitBuf->SetNext(NULL);

   600         }

   601     else

   602         {

   603         // Split cleaves chain between bufs

   604         aNewChain = splitBuf;

   605         if(splitBufPrev)

   606             {

   607             splitBufPrev->Unlink();

   608             }

   609         }

   610     

   611     // Check post-conditions

   612 #ifdef _DEBUG

   613     TInt frag1Len = Length(); 

   614     TInt frag2Len = aNewChain.Length();

   615     ASSERT(origLen == frag1Len + frag2Len);

   616     ASSERT(frag1Len == aOffset);

   617 #endif

   618     return KErrNone;

   619 	}