How to Use Descriptors

Explains how to use descriptors for various use cases.

• How to use the non-modifiable buffer descriptor — TBufC<TInt>
  Non-modifiable buffer descriptors are useful for holding constant strings or data and providing safe ways to access that data.
• How to use modifiable buffer descriptor — TBuf<TInt>
  Modifiable buffer descriptors are useful for holding strings or data and providing safe ways to access and modify that data.
• How to use the non-modifiable pointer descriptor - TPtrC
  Non-modifiable pointer descriptors are useful for referencing constant strings or data; for example, accessing strings built into ROM resident code, or passing a reference to data in RAM which must not be modified through that reference.
• How to use the modifiable pointer descriptor — TPtr
  Modifiable pointer descriptors are useful for referencing strings or data which can be accessed and changed.
• How to use the heap descriptor - HBufC
  Heap descriptors provide a buffer of fixed length, allocated on the heap. Descriptors are useful for holding constant strings or data, when the length of the data may not be known until run time.
• How to use the resizable buffer descriptor - RBuf
  Use this descriptor to hold a string or binary data.
• Descriptors for function interfaces
  Descriptors to specify interfaces which use or manipulate text strings or general binary data use
• How to represent general binary data
  Construct an 8 bit variant descriptor to represent general binary data.
• Using TDes
  Use TDes for interfaces which take narrow or wide (Unicode) text, depending on the build variant.
• Using TDes16 class
  Use TDes16 for Interfaces which take wide (Unicode) text regardless of the build variant.
• Using TDes8 Class
  Use TDes8 for Interfaces which take binary data or narrow text regardless of the build variant.
• Using TDes8Overflow
  Use TDes8Overflow to handle overflow issues when calling the TDes8::AppendFormat() function.
• Using TDesC
  Use TDesC for interfaces which take narrow or wide (Unicode) text, depending on the build variant, but does not change the data.
• Using TDesC16 Class
  Use TDesC16 for interfaces which access Unicode text, regardless of the build variant, but which does not change the data.
• Using TDesC8 Class
  Use TDescC8 for interfaces which takes binary data or explicit narrow text, regardless of the build variant, but which does not need to change the data.
• Format string syntax
  TDes8::Format() , TDes16::Format() and some other functions take a format string containing literal text embedded with directives for converting a trailing list of arguments into text.