ReadNestedTlv Method

ReadNestedTlv(Int32)

Read the TLV at the current position as a NestedTlv. Return a new TlvReader object whose position is the beginning of the NestedTlv's value, which is the tag of the NestedTlv's first sub-element. Move the position of the original reader to the byte beyond the current TLV.

public TlvReader ReadNestedTlv(int expectedTag)

Parameters

Type	Name	Description
System.Int32	expectedTag	The tag that should be at the current position, the NestedTlv's tag.

Returns

TlvReader

A new TlvReader object that contains the sub-elements of the NestedTlv, with the position set at the first sub-element.

Exceptions

Type	Condition
TlvException	The tag was not the expected value, the tag or length is unsupported, or there was not enough data for the lengths given.

Remarks

The new object returned will contain the encoding of the sub-elements only.

If the tag at the current position in the encoding is not what was given as the expectedTag, or if the tag and/or length make up an invalid encoding, or if there are not enough bytes left in the encoding to read the tag, length, and value, this method will throw an exception.

For example, suppose the encoding is the following.

   7C 0D 01 01 14 02 02 01 80 05 04 00 89 2C 33
   This is a NestedTlv
   7C 0D
      01 01
         14
      02 02
         01 80
      05 04
         00 89 2C 33

Suppose the internal position is at 0, the beginning of full encoding.

  TlvReader newReader = reader.ReadNestedTlv(0x7C);
   This will return a new TlvReader object:
    new reader: 01 01 14 02 02 01 80 05 04 00 89 2C 33
                ^
                +--current position
   After the call, the internal position of the original reader is at
   the position just after the NestedTlv's value.
    original: 7C 0D 01 01 14 02 02 01 80 05 04 00 89 2C 33
                                                           ^
                                                           +--current position

Suppose the original reader is parsing something like this:

   01 01 14 7A 07 31 02 01 00 32 01 20 05 04 00 89 2C 33
 This is a concatenation with a NestedTlv as one of the elements.
      01 01
         14
      7A 07
         31 02
            01 00
         32 01
            20
      05 04
         00 89 2C 33

Suppose the internal position is at 0, the beginning of full encoding.

  ReadOnlyMemory<byte> value = reader.ReadValue(0x01);
   This returned a new ReadOnlyMemory object with the contents of the
   first TLV, namely the byte array { 0x14 }. It moved the pointer to
   the next TLV.
   01 01 14 7A 07 31 02 01 00 32 01 20 05 04 00 89 2C 33
            ^
            +--current position
  TlvReader newReader = reader.ReadNestedTlv(0x7A);
   This will return a new TlvReader object:
    new reader: 31 02 01 00 32 01 20
                ^
                +--current position
   After the call, the internal position of the original reader is at
   the position just after the NestedTlv's value.
   01 01 14 7A 07 31 02 01 00 32 01 20 05 04 00 89 2C 33
                                       ^
                                       +--current position