SAVITRI-721: NFT Standard

SAVITRI-721 (SNT1 -- Savitri Non-Fungible Token) is the NFT standard for the Savitri Network, equivalent to Ethereum's ERC-721. Each token has a unique ID and a single owner.

Interface

Function	Params	Returns	Description
balance_of	owner	u64	Number of NFTs owned by address
owner_of	token_id	address	Owner of a specific token
transfer_from	from, to, token_id	Result	Transfer an NFT
approve	to, token_id	Result	Approve address to transfer token
safe_transfer_from	from, to, token_id	Result	Transfer with safety checks
token_uri	token_id	String	Get token metadata URI
mint	to, token_id, uri	Result	Mint a new NFT

Storage Layout

Slot Range	Purpose	Derivation
0-99	BaseContract (reserved)	Direct
100+	Token owners	keccak256(100 || token_id)
200+	Token balances	keccak256(200 || address)
300+	Token approvals	keccak256(300 || token_id)
400+	Token URIs	keccak256(400 || token_id)

Keccak256 hashing prevents slot collisions between categories (e.g., token_id 100 won't collide with the balances base slot).

Minting an NFT

use savitri_contracts::contracts::standards::savitri721::SAVITRI721;

SAVITRI721::mint(
    &mut contract_storage,
    &storage,
    &recipient,             // [u8; 32]
    42,                     // token_id: u64
    "ipfs://Qm.../meta",   // token URI
    &mut event_system,
    Some(&mut gas_meter),
)?;

Transferring

// Direct transfer
SAVITRI721::transfer_from(
    &mut contract_storage,
    &storage,
    &from,          // current owner
    &to,            // new owner
    42,             // token_id
    &mut event_system,
    Some(&mut gas_meter),
)?;

Querying

// Who owns token #42?
let owner = SAVITRI721::owner_of(&contract_storage, &storage, 42)?;

// How many NFTs does this address own?
let count = SAVITRI721::balance_of(&contract_storage, &storage, &address)?;

// Get metadata URI
let uri = SAVITRI721::token_uri(&contract_storage, &storage, 42)?;

Events

Event	Fields	Description
Transfer	from, to, token_id	NFT transferred
Approval	owner, approved, token_id	Approval granted
Mint	to, token_id	New NFT minted

Via SDK

use savitri_sdk::{ContractClient, Wallet};

let contract = ContractClient::from_url_and_wallet("http://localhost:8545", wallet)?;

// Mint NFT via contract call
let tx = contract.call_contract(
    &nft_contract_address,
    b"mint",
    &encode_mint_args(recipient, token_id, uri),
    Some(0),
).await?;