goral09 / kv-storage-contract

How to understand the contract

Refer to this guide to understand how the Key-Value contract works, in addition to some detail on how the Casperlabs Contract DSL works.

Online IDE

Follow this link to execute this contract in an online IDE.

Deploying to the Testnet and Interacting with the Contract

There is a standalone python cli application that you can use for the kvstorage contract. When working with the testnet, create an account in CLarity and fund it using the faucet. Download the private key and use the key to sign the deployment. It's possible to create keys using the python client as well.

**Note, that this client was designed specifically for this contract. **

Deploy the Contract

The first step is actually to deploy the compiled wasm to the network, if you are using the python kv-client you must use the command deploy_kv_storage_contract. Once the contract is deployed, the client will retrieve the contract session hash as well as the blockhash where the contract is deployed.

python cli.py deploy_kv_storage_contract -f "29acb007dfa4f92fa5155cc2f3ae008b4ff234acf95b00c649e2eb77447f47ca" -p "../../kvkey.private.key" -c "../target/wasm32-unknown-unknown/release/contract.wasm" -b True

Invoke an Entry Point & Set a value

Once the contract is deployed, we can create another deploy, which calls one of the entry points within the contract. To call an entry point, you must first know the name of the entry point and the session hash, which we retrieved from the previous step. The kv-client, has four distinct commands to set key-values for u64, String, U512 and AccountHash.

python cli.py insert_u64 -f "29acb007dfa4f92fa5155cc2f3ae008b4ff234acf95b00c649e2eb77447f47ca" -p "../../kvkey.private.key" -s "0e82027493b88db434e85f82f6bcf48a30e0c1db15cf55fb87b73461b8aef20b" -k "test" -v 1 -b True

Query the Contract On Chain

Contracts can be executed under different contexts. In this example, when the contract is deployed, it runs in the context of a Contract and not a Session. This means that all stored keys are not stored under the account hash, but within the context of the contract. Therefore when we query to retrieve the value under a key, we are actually querying AccountHash/kvstorage_contract/<key-name> and not just AccountHash/<key-name>.

Reading a value is simple enough, after you insert a value, the command retrieves the block hash under which the value, is stored. Using that block hash, and the read-key command you can easily retrieve and value that was previously stored under a named key.

python cli.py read_key -b "cb08a634c9bbea695fbd92e2ddbeec6fe6a374db807b36fea35077a9c1d720df" -p "29acb007dfa4f92fa5155cc2f3ae008b4ff234acf95b00c649e2eb77447f47ca" -k "test"

More information on the kv-client, is available via the --help command. There is detailed information on each of the commands available with the client.

NOTE: The session hash is retrieved from the the chain by using a simple time delay, if processing the deploy takes longer than expected, it is likely that the kv-client will error out and not retrieve the session hash. In such cases, you can retrieve the session hash using the python casperlabs_client.

You must first find the block hash for the block that contains your deploy. Once you have the requisite block hash, then you can use the python shell to retrieve the session hash

Import casperlabs_client
client = casperlabs_client.CasperLabsClient(‘deploy.casperlabs.io’, 40401)
Session_code = client.queryState(<block-hash>, <account-hash>, “kvstorage_contract_hash”,’address’)
Session_hash = session_code.cl_value.value.bytes_value.hex()