length and offset is 0 ?

[oznfc]

I'm using flipper examle for solana. if ı call flip and get function together my codes is working. but ı tried different way.
first step ı call only Flip function.
second step ı call only get function . When ı called only get fuction after the first step my ofset and length is "0" .
I have to use the flip and get functions together. Why ?

[seanyoung]

The flip function has no return values, so the length will be zero. It might make sense for the flip function to return the current state. Does that explain what is happening?

[oznfc]

I know flip has no return values.already ı tried for get function. error :

UnhandledPromiseRejectionWarning: Error: Returned values aren't valid, did it run Out of Gas? You might also see this error if you are not using the correct ABI for the contract you are retrieving data from, requesting data from a block number that does not exist, or querying a node which is not fully synced.

I tried at new contract , simple name get- set functions . same error.

[seanyoung]

Would you mind sharing your code so I can reproduce this issue? I don't know how this can happen without seeing your code. Thanks

[oznfc]

yes sure.

contract Events {
    string public name;
    string public surname;

    event NameChanced(string message, string newName);
    event SurnameChanced(string message, string newSurname);

    constructor() public {
        name = 'myName';
        surname = 'mySurname';
    }

    function setName(string memory _name) public {
        name = _name;
        emit NameChanced('Name Chanced', _name);
    }

    function setSurname(string memory _surname) public {
        surname = _surname;
        emit SurnameChanced('Surname Chanced', _surname);
    }

    function getNames() public view returns (string memory _name , string memory _surname ) {
        return (name ,surname);
    }


    function getName() public view returns (string memory _name ) {
        return name ;
    }

     function getSurname() public view returns (string memory _surname ) {
        return surname ;
    }

}

[seanyoung]

Would you mind sharing the client-side code too? Thanks

[oznfc]

I already using solang library. if ı using this style (2 function together. ) ı can see account data.

        let res = await prog.call_function(conn, "setName", ["ozan"]);
        let res2 = await prog.call_function(conn, "getName", []);

but if I use only await prog.call_function(conn, "setName", ["ozan"]); than ı call await prog.call_function(conn, "getName", []); function than ı cant see account data.

            const accountInfo = await test.connection.getAccountInfo(this.contractStorageAccount.publicKey);
            let length = Number(accountInfo!.data.readUInt32LE(4));
            let offset = Number(accountInfo!.data.readUInt32LE(8));

length and offset are zero.

[seanyoung]

I think I can reproduce an issue. Let me get back to you..

[oksanassss]

Ok. I am waiting.

[seanyoung]

Would you mind testing this again with the latest solang? Also note that I have turned your example into a test case.

[oksanassss]

did you test it? length and offset are 0 after the setName() function. so ı can't read data.

[seanyoung]

Yes, the tes runs and the tests get run by github actions at every pull request as well.

Note that setName will clear the offset/length because the function has no return values.

Would you mind sharing your entire test case so I can reproduce the problem?

[oksanassss]

hmm , understood. now running . I misunderstood some things. another question. :
if ı want not use getName() .
Because

    string public name;
    string public surname;

is public data. Do I have to use the call_function function again? can ı read public datas in accounData ?

[seanyoung]

A public variable will have an accessor function generated. This means you do call_funtion('name', []) and there is no need for the getName() function.

[oksanassss]

I know but call_function wants gas fee. I should not pay gass fee to read public data.

[seanyoung]

Yes, you're absolutely right. So this should be done via an RPC call, which does not charge any gas at all. However, since this function writes to account data, it cannot be an RPC call.

The way to fix this is to provide an alternate way of returning data in Solana. This is why solana-labs/solana#19318 exists. Hopefully this will be approved soon and then it can be implemented.

[oksanassss]

Hopefully. Actually what I'm looking for is something like this:

contractStorageAccount = new PublicKey("24QoA3yefopzVxNuGFGKdcmbSebheZaFt9XBKJKarFur");
    const accountInfo = await connection.getAccountInfo(contractStorageAccount);
    const data = Buffer.from(accountInfo.data);
    const DataInfoLayout = BufferLayout.struct([
        BufferLayout.u8("data1"),
        BufferLayout.u8("data2"),
    ]);
    const tokenInfo = DataInfoLayout.decode(data);
    console.log(tokenInfo)
   // output { data1: 0, data2: 1 }

When I try with this method, I can read data from a normal solana program. I don't know if I can read from Solang this way. I tried, it didn't work.

[seanyoung]

For the first string, you need to read the u32 at offset 16 (let's call this V). If V is 0, the string is empty; if is not zero, then it is the offset at which the string is stored. The length can be fetched the u32 at V - 8.

Ideally we need a node library that can do this. There is a plan for a npm package here solana-labs/solana-solidity.js#1, I will add an entry for reading the storage.

[oksanassss]

I'm looking forward.

[seanyoung]

That solana-solidity.js project has just received funding from Solana (25k USD). Hopefully it will move quickly.

[seanyoung]

@oznfc @oksanassss anything else I can help with or can I close this issue?