Storage

Algorand smart contracts can utilise three different types of on-chain storage: Global storage, Local storage, and Box Storage. They also have access to a transient form of storage in Scratch space.

Global storage

Global or Application storage is a key/value store of bytes or uint64 values stored against a smart contract application. The number of values used must be declared when the application is first created and will affect the minimum balance requirement for the application. For ARC4 contracts, this information is captured in the ARC32 and ARC56 specification files and automatically included in deployments.

Global storage values are declared using the GlobalState function to create a GlobalState proxy object.

import {
  GlobalState,
  Contract,
  uint64,
  bytes,
  Uint64,
  contract,
} from '@algorandfoundation/algorand-typescript';

class DemoContract extends Contract {
  // The property name 'globalInt' will be used as the key
  globalInt = GlobalState<uint64>({ initialValue: Uint64(1) });
  // Explicitly override the key
  globalBytes = GlobalState<bytes>({ key: 'alternativeKey' });
}

// If using dynamic keys, state must be explicitly reserved
@contract({ stateTotals: { globalBytes: 5 } })
class DynamicAccessContract extends Contract {
  test(key: string, value: string) {
    // Interact with state using a dynamic key
    const dynamicAccess = GlobalState<string>({ key });
    dynamicAccess.value = value;
  }
}

Local storage

Local or Account storage is a key/value store of bytes or uint64 stored against a smart contract application and a single account which has opted into that contract. The number of values used must be declared when the application is first created and will affect the minimum balance requirement of an account which opts into the contract. For ARC4 contracts, this information is captured in the ARC32 and ARC56 specification files and automatically included in deployments.

import type { bytes, uint64 } from '@algorandfoundation/algorand-typescript';
import { abimethod, Contract, LocalState, Txn } from '@algorandfoundation/algorand-typescript';
import type { StaticArray, UintN } from '@algorandfoundation/algorand-typescript/arc4';

type SampleArray = StaticArray<UintN<64>, 10>;

export class LocalStateDemo extends Contract {
  localUint = LocalState<uint64>({ key: 'l1' });
  localUint2 = LocalState<uint64>();
  localBytes = LocalState<bytes>({ key: 'b1' });
  localBytes2 = LocalState<bytes>();
  localEncoded = LocalState<SampleArray>();

  @abimethod({ allowActions: 'OptIn' })
  optIn() {}

  public setState({ a, b }: { a: uint64; b: bytes }, c: SampleArray) {
    this.localUint(Txn.sender).value = a;
    this.localUint2(Txn.sender).value = a;
    this.localBytes(Txn.sender).value = b;
    this.localBytes2(Txn.sender).value = b;
    this.localEncoded(Txn.sender).value = c.copy();
  }

  public getState() {
    return {
      localUint: this.localUint(Txn.sender).value,
      localUint2: this.localUint2(Txn.sender).value,
      localBytes: this.localBytes(Txn.sender).value,
      localBytes2: this.localBytes2(Txn.sender).value,
      localEncoded: this.localEncoded(Txn.sender).value.copy(),
    };
  }

  public clearState() {
    this.localUint(Txn.sender).delete();
    this.localUint2(Txn.sender).delete();
    this.localBytes(Txn.sender).delete();
    this.localBytes2(Txn.sender).delete();
    this.localEncoded(Txn.sender).delete();
  }
}

Box storage

We provide two different types for accessing box storage: Box and BoxMap. We also expose raw operations via the AVM ops module.

Before using box storage, be sure to familiarise yourself with the requirements and restrictions of the underlying API.

The Box type provides an abstraction over storing a single value in a single box. A box can be declared as a class field (in which case the key must be a compile-time constant), or as a local variable within any subroutine. Box proxy instances can be passed around like any other value.

BoxMap is similar to the Box type, but allows for grouping a set of boxes with a common key and content type. A keyPrefix is specified when the BoxMap is created and the item key can be a Bytes value, or anything that can be converted to Bytes. The final box name is the combination of keyPrefix + key. The BoxMap proxy is a function which takes a key argument and returns you a Box proxy object for that item.

import type { Account, uint64 } from '@algorandfoundation/algorand-typescript';
import { Box, BoxMap, Contract, Txn, assert } from '@algorandfoundation/algorand-typescript';
import { bzero } from '@algorandfoundation/algorand-typescript/op';

export class BoxContract extends Contract {
  boxOne = Box<string>({ key: 'one' });
  boxMapTwo = BoxMap<Account, uint64>({ keyPrefix: 'two' });
  boxRefThree = Box<bytes>({ key: 'three' });

  test(): void {
    if (!this.boxOne.exists) {
      this.boxOne.value = 'Hello World';
    }
    this.boxMapTwo(Txn.sender).value = Txn.sender.balance;
    const boxForSender = this.boxMapTwo(Txn.sender);
    assert(boxForSender.exists);
    if (this.boxRefThree.exists) {
      this.boxRefThree.resize(8000);
    } else {
      this.boxRefThree.create({ size: 8000 });
    }

    this.boxRefThree.replace(0, bzero(0).bitwiseInvert());
    this.boxRefThree.replace(4000, bzero(0));
  }
}

Scratch storage

Scratch storage persists for the lifetime of a group transaction and can be used to pass values between multiple calls and/or applications in the same group. Scratch storage for logic signatures is separate from that of the application calls, and logic signatures do not have access to the scratch space of other transactions in the group.

Values can be written to scratch space using the Scratch.store(...) method and read from using Scratch.loadUint64(...) or Scratch.loadBytes(...) methods. These all take a scratch slot number between 0 and 255 inclusive, and that scratch slot must be explicitly reserved by the contract using the contract options decorator.

import { assert, BaseContract, Bytes, contract } from '@algorandfoundation/algorand-typescript';
import { Scratch } from '@algorandfoundation/algorand-typescript/op';

@contract({ scratchSlots: [0, 1, { from: 10, to: 20 }] })
export class ReserveScratchAlgo extends BaseContract {
  setThings() {
    Scratch.store(0, 1);
    Scratch.store(1, Bytes('hello'));
    Scratch.store(15, 45);
  }

  approvalProgram(): boolean {
    this.setThings();

    assert(Scratch.loadUint64(0) === 1);
    assert(Scratch.loadBytes(1) === Bytes('hello'));
    assert(Scratch.loadUint64(15) === 45);
    return true;
  }
}

Scratch space can be read from group transactions using the gloadUint64 and gloadBytes ops. These ops take the group index of the target transaction and a scratch slot number.

import { gloadBytes, gloadUint64 } from '@algorandfoundation/algorand-typescript/op';

function test() {
  const b = gloadBytes(0, 1);
  const u = gloadUint64(1, 2);
}