mycodecrafting/cborutil

CLI Utility to decode or update data in a CBOR payload located at a specific data path

CBOR Utility

This utility can decode data in a CBOR payload located at a specific data path.

This utility can also be used to update data in a CBOR payload at a specific data path.

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Building

make build

This builds a binary in bin/cborutil

Usage

Decoding CBOR Data

bin/cborutil decode -cbor <payload> [ -path data.path -base64 -json ]

• -cbor CBOR payload in hex or base64 format
• -path Data path to decode using dot notation
• -base64 Payload is in base64 format
• -json Return decoded result in JSON format?

Examples

Decoding from hex:

$ bin/cborutil decode -cbor a26161016162820203 -path b.0
2

Decoding from base64:

$ bin/cborutil decode -cbor omFhAWFiggID -base64 -path b.0
2

Decoding to JSON:

$ bin/cborutil decode -cbor omFhAWFiggID -base64 -path b -json
[2,3]

Can you also omit the -path arg to decode the whole payload:

$ bin/cborutil decode -cbor omFhAWFiggID -base64 -json
{"a":1,"b":[2,3]}

Updating CBOR Data

bin/cborutil update -cbor <payload> -data <input> -path data.path [ -base64 -json ]

• -cbor CBOR payload in hex or base64 format
• -data Input data
• -path Data path to update using dot notation
• -base64 Payload is in base64 format
• -json Input data is in JSON format?

Examples

Updating a hex payload

$ bin/cborutil update -cbor a26161016162820203 -data "changed me" -path a
a261616a6368616e676564206d656162820203

Updating a base64 payload

$ bin/cborutil update -cbor omFhAWFiggID -base64 -data "changed me" -path a
omFhamNoYW5nZWQgbWVhYoICAw==

Updating using JSON

$ bin/cborutil update -cbor omFhAWFiggID -base64 -data '{"aa":"AAA"}' -json -path a
omFhoWJhYWNBQUFhYoICAw==

Dot Notation

This utility uses dot notation to specify the path to a node in the data. For example, let's take a look at the following JSON data:

{
  "Student": {
    "Name": "Eve",
    "Parents": [
      {
        "Name": "Alice"
      },
      {
        "Name": "Bob"
      }
    ]
  }
}

Here, if we want to get the student's name, we could reference Student.Name

Arrays are referenced by their integer index, starting from 0. For example to get the Student's Parent's names, we would use Student.Parents.0.Name and Student.Parents.1.Name

Let's use the utility to update the CBOR data for Eve. Her father wants his name to be listed as Robert instead of Bob.

$ bin/cborutil update \
-cbor oWdTdHVkZW50omROYW1lY0V2ZWdQYXJlbnRzgqFkTmFtZWVBbGljZaFkTmFtZWNCb2I= \
-base64 -path Student.Parents.1.Name -data Robert
oWdTdHVkZW50omROYW1lY0V2ZWdQYXJlbnRzgqFkTmFtZWVBbGljZaFkTmFtZWZSb2JlcnQ=

We can also use the utility to confirm the update happened correctly:

$ bin/cborutil decode \
-cbor oWdTdHVkZW50omROYW1lY0V2ZWdQYXJlbnRzgqFkTmFtZWVBbGljZaFkTmFtZWZSb2JlcnQ= \
-base64 -json
{"Student":{"Name":"Eve","Parents":[{"Name":"Alice"},{"Name":"Robert"}]}}

Note You can couple cborutil update with the -json flag to not just update individual values, but to replace entire portions of the data tree.

For example, we entered the wrong student data. Let's go ahead and correct it:

$ bin/cborutil update \
-cbor oWdTdHVkZW50omROYW1lY0V2ZWdQYXJlbnRzgqFkTmFtZWVBbGljZaFkTmFtZWNCb2I= \
-base64 -path Student \
-data '{"Name":"John","Interests":["Gaming","Blockchain","Piano"]}' \
-json
oWdTdHVkZW50omROYW1lZEpvaG5pSW50ZXJlc3Rzg2ZHYW1pbmdqQmxvY2tjaGFpbmVQaWFubw==

And again we can use the utility to verify the data tree was updated:

$ bin/cborutil decode \
-cbor oWdTdHVkZW50omROYW1lZEpvaG5pSW50ZXJlc3Rzg2ZHYW1pbmdqQmxvY2tjaGFpbmVQaWFubw== \
-base64 -json
{"Student":{"Interests":["Gaming","Blockchain","Piano"],"Name":"John"}}