Operation bytes parsing

Question

I am trying to query the RPC parse operation method and I found another question about it. But I can't figure out why operation bytes with the same data are different (58 vs 90 bytes), moreover: Query:

https://alphanet-node.tzscan.io/chains/main/blocks/head/helpers/parse/operations

Body:

{
"operations": [
    {
        "data": "0800002122d44d997e158c36c60649d198c4175dad425efa09d2a405f44e00f6f0b40201420eaa410ac21addf427211cddd6115cba385a94000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
        "branch": "BLpcXF8ADJbGuyUKNv7TypXRd5rqnoPn3PMqJLNBeRSr4VFeUuK"
    }
]}

Response:

[{
        "branch": "BLpcXF8ADJbGuyUKNv7TypXRd5rqnoPn3PMqJLNBeRSr4VFeUuK",
        "contents": [{
                "kind": "transaction",
                "source": "tz1NfEiS2uJsX43vowNjau5pdqg3Nvy8whvc",
                "fee": "1274",
                "counter": "86610",
                "gas_limit": "10100",
                "storage_limit": "0",
                "amount": "5060726",
                "destination": "KT1Ec3jNXyxyA54nezwcjGDRoutECJCQjpya"
            }
        ],
        "signature": "edsigtXomBKi5CTRf5cjATJWSyaRvhfYNHqSUGrn4SdbYRcGwQrUGjzEfQDTuqHhuA8b2d8NarZjz8TRf65WkpQmo423BtomS8Q"
    }
]

Then I'm trying to forge this data without signature:

{
"branch": "BLpcXF8ADJbGuyUKNv7TypXRd5rqnoPn3PMqJLNBeRSr4VFeUuK",
"contents": [{
        "kind": "transaction",
        "source": "tz1NfEiS2uJsX43vowNjau5pdqg3Nvy8whvc",
        "fee": "1274",
        "counter": "86610",
        "gas_limit": "10100",
        "storage_limit": "0",
        "amount": "5060726",
        "destination": "KT1Ec3jNXyxyA54nezwcjGDRoutECJCQjpya"
    }
]}

Response:

"92122a7e654cdff09e22a7be1b7d41bd279ffa197a0137e6fea0d3ed3ce95fc00800002122d44d997e158c36c60649d198c4175dad425efa09d2a405f44e00f6f0b40201420eaa410ac21addf427211cddd6115cba385a940000"

Response is much bigger than parsed data. And if I try to add to response 64 zero bytes or signature bytes I get "operation.cannot_parse" error.

Answer 1

If we put the hex strings next to each other and find out where they match it becomes easy to see why they differ.

__________________________Branch________________________________0800002122d44d997e158c36c60649d198c4175dad425efa09d2a405f44e00f6f0b40201420eaa410ac21addf427211cddd6115cba385a94000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
92122a7e654cdff09e22a7be1b7d41bd279ffa197a0137e6fea0d3ed3ce95fc00800002122d44d997e158c36c60649d198c4175dad425efa09d2a405f44e00f6f0b40201420eaa410ac21addf427211cddd6115cba385a940000_____________________________________________________Signature__________________________________________________________________

As you can see the first hex string consists of contents + signature and the second one of branch + contents. When we inject an operation, it should contain branch + contents + signature. That forge and parse isn't exactly each other’s opposites probably have to do with their intended use-cases. Forge is something you typically do before you append the signature, so it would be hard for it to return a signature at that stage.