SAVITRI-1155: Multi-Asset Token Standard

SAVITRI-1155 (SMA -- Savitri Multi Asset) is the multi-asset token standard for the Savitri Network, equivalent to Ethereum's ERC-1155. It supports both fungible and non-fungible tokens in a single contract with efficient batch operations.

Interface

Function	Params	Returns	Description
balance_of	owner, id	u128	Balance of a specific token for an owner
balance_of_batch	owners[], ids[]	u128[]	Batch balance query
safe_transfer_from	from, to, id, amount, data	Result	Transfer tokens
safe_batch_transfer_from	from, to, ids[], amounts[], data	Result	Batch transfer
set_approval_for_all	operator, approved	Result	Approve operator for all tokens
is_approved_for_all	owner, operator	bool	Check operator approval

Storage Layout

Balance Storage (Slot 100+)

Nested mapping: balances[owner][id]

hash1 = keccak256(owner || 100)
hash2 = keccak256(id || hash1)
slot  = first 8 bytes of hash2 as u64

Operator Approval Storage (Slot 200+)

Nested mapping: operator_approvals[owner][operator]

hash1 = keccak256(owner || 200)
hash2 = keccak256(operator || hash1)
slot  = first 8 bytes of hash2 as u64

This layout provides:

• Uniform distribution: Keccak256 ensures uniform slot distribution
• No collisions: Negligible collision probability
• Efficient batch queries: Each slot is calculated independently
• Cache-friendly: ContractStorage caches reads

Usage

Single Transfer

use savitri_contracts::contracts::standards::savitri1155::SAVITRI1155;

SAVITRI1155::safe_transfer_from(
    &mut contract_storage,
    &storage,
    &from,          // [u8; 32]
    &to,            // [u8; 32]
    1,              // token id
    100,            // amount
    &[],            // data
    &mut event_system,
    Some(&mut gas_meter),
)?;

Batch Transfer

SAVITRI1155::safe_batch_transfer_from(
    &mut contract_storage,
    &storage,
    &from,
    &to,
    &[1, 2, 3],           // token ids
    &[100, 50, 1],        // amounts
    &[],                   // data
    &mut event_system,
    Some(&mut gas_meter),
)?;

Batch Balance Query

let balances = SAVITRI1155::balance_of_batch(
    &contract_storage,
    &storage,
    &[owner1, owner2, owner3],
    &[token_id_1, token_id_2, token_id_3],
)?;

Operator Approval

// Approve an operator for all tokens
SAVITRI1155::set_approval_for_all(
    &mut contract_storage,
    &storage,
    &owner,
    &operator,
    true,           // approved
    &mut event_system,
    Some(&mut gas_meter),
)?;

// Check approval
let approved = SAVITRI1155::is_approved_for_all(
    &contract_storage,
    &storage,
    &owner,
    &operator,
)?;

Events

Event	Fields	Description
TransferSingle	operator, from, to, id, amount	Single token transfer
TransferBatch	operator, from, to, ids[], amounts[]	Batch transfer
ApprovalForAll	owner, operator, approved	Operator approval changed

Use Cases

Scenario	Token Type	Example
In-game currency	Fungible (id=1)	1000 gold coins
Unique items	Non-fungible (amount=1)	Legendary sword #42
Semi-fungible	Limited supply	50 copies of a rare card
Rewards	Fungible	PoU reward tokens
Certificates	Non-fungible	Validator certification

Batch Optimization

The SAVITRI-1155 implementation optimizes batch operations by:

1. Pre-calculating all slots before reading storage
2. Leveraging ContractStorage cache to avoid repeated DB reads
3. Independent slot calculation enabling future parallel reads
4. Minimizing address decoding by reusing decoded addresses across operations