Parsing contract endpoint output

Question

A contract endpoint on Ropsten returns a set like this:

(uint256 _assetId, address _assetOwner, address _issuer, string _content, uint256 _sellPrice, uint256 _status)

The endpoint is getAssetById at can be queried at:

https://ropsten.etherscan.io/address/0xd42e3ac7f89f5904a41cfd19d6505dec77fc2bcd#readContract

I am trying to parse the output for the cases where input is 1 and 2 with the following results:

asset 1:
0000000000000000000000000000000000000000000000000000000000000001 // uint256 _assetId
0000000000000000000000004b0897b0513fdc7c541b6d9d7e929c4e5364d2db // address _assetOwner
0000000000000000000000009b9731b07b9b5f982289bab87097eade6a4bc25d // address _issuer
00000000000000000000000000000000000000000000000000000000000000c0 // string _content ???
0000000000000000000000000000000000000000000000000000000000000000 // uint256 _sellPrice
0000000000000000000000000000000000000000000000000000000000000002 // uint256 _status
0000000000000000000000000000000000000000000000000000000000000016
43726f6d6f20646520546f6e69204d6f72616c2c206e00000000000000000000



asset 2:
0000000000000000000000000000000000000000000000000000000000000002 // uint256 _assetId
0000000000000000000000004b0897b0513fdc7c541b6d9d7e929c4e5364d2db // address _assetOwner
0000000000000000000000009b9731b07b9b5f982289bab87097eade6a4bc25d // address _issuer
00000000000000000000000000000000000000000000000000000000000000c0 // string _content ???
0000000000000000000000000000000000000000000000000000000000000000 // uint256 _sellPrice
0000000000000000000000000000000000000000000000000000000000000002 // uint256 _status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But the string is messing up things.

Where can I find the length of the string?

Why is part of the string on fourth line and the rest on seventh and nexts?

Any clue to interpret these results? Thx!

Refs.:

Parsing contract method output as an array of fields

Answer 1

The length of the string is the word after the one you have identified as status. So for asset1 it is 0x16 = 22 in decimal, and for asset2 it is 0xc9 = 201 decimal.

Strings are dynamic types and have a particular ABI representation as described in the ABI spec. Dynamic data appears after the rest of the data: your string_content ??? word is a pointer to where the string data begins within the returned data, i.e. at byte 0xc0. The string is then represented by a word containing its length in bytes, followed by the string character data itself.

asset 1:
0x00 0000000000000000000000000000000000000000000000000000000000000001 // uint256 _assetId
0x20 0000000000000000000000004b0897b0513fdc7c541b6d9d7e929c4e5364d2db // address _assetOwner
0x40 0000000000000000000000009b9731b07b9b5f982289bab87097eade6a4bc25d // address _issuer
0x60 00000000000000000000000000000000000000000000000000000000000000c0 // pointer to string data starting at 0xc0
0x80 0000000000000000000000000000000000000000000000000000000000000000 // uint256 _sellPrice
0xa0 0000000000000000000000000000000000000000000000000000000000000002 // uint256 _status
0xc0 0000000000000000000000000000000000000000000000000000000000000016 // the length of the string data
0xe0 43726f6d6f20646520546f6e69204d6f72616c2c206e00000000000000000000 // the content of the string data