How to choose a descriptor

How to choose a descriptor

Taken from Netqin

Do you need to modify the content of the description
Yes			no
Whether the memory of the descriptor has been allocated			Whether the memory of the descriptor has been allocated
Yes	no		Yes	no
TPtr	Can the line size be less than 256 bytes		TPtrC	Can the line size be less than 256 bytes
	Yes	no		Yes	no
	TBuf	HBufC: Use TPtr when you need to change the content HBufC* buf=HBufC::New(1024); TPtr temp（buf->Des()); temp.Format(_L("test"));		TBufC	HBufC

If the descriptor contains binary content, an 8-bit descriptor should be used.
If the descriptor contains wide characters, a 16-bit descriptor should be used.
Otherwise, a descriptor without a specified bit should be used.