IOST Blockchain API

There objects below can be used directly inside contract codes.

storage object

All variables will be stored in memory in runtime. IOST provides storage object to help developers persist data in smart contracts. APIs without 'global' prefix are used to get/set storage of the calling contract. APIs with 'global' prefix are used to get storage of other contracts.

Storage API

put(key, value, payer=contractOwner)

Simply put a key-value pair into storage.

Parameter List	Parameter Type	Remark
key	string	cannot be longer than 65536 bytes
value	string	cannot be longer than 65536 bytes
payer	string(optional)	it determines who will pay for the ram usage. This parameter is optional. If it is empty, the contract publisher will pay for the ram usage.

Returns: none

example:

// insert a k-v pair into storage and cost ram from contract owner
storage.put("test-key", "test-value");

// insert a k-v pair into storage and cost ram from transaction publisher
storage.put("test-key", "test-value", tx.publisher);

get(key)

Simply retrieve the value from storage using key.

Parameter List	Parameter Type	Remark
key	string

Returns: value in string type if exists; null if not exists.

example:

let v = storage.get("test-key");
if (v !== null) {
    ...
}

has(key)

Check if the key exists in the storage.

Parameter List	Parameter Type	Remark
key	string

Returns: bool (true if exists, false if not exists)

example:

if (storage.has("test-key")) {
    ...
}

del(key)

Simply delete a key-value pair from storage using key.

Parameter List	Parameter Type	Remark
key	string

Returns: none

example:

storage.del("test-key")

mapPut(key, field, value, payer=contractOwner)

Map put a (key, field, value) pair. use key+field to find value.

Parameter List	Parameter Type	Remark
key	string	cannot be longer than 65536 bytes
field	string	cannot be longer than 65536 bytes
value	string	cannot be longer than 65536 bytes
payer	string(optional)	it determines who will pay for the ram usage. This parameter is optional. If it is empty, the contract publisher will pay for the ram usage.

Returns: none

example:

// insert a key-field-value pair into storage and cost ram from contract owner
storage.mapPut("test-key", "test-field", "test-value");

// insert a key-field-value pair into storage and cost ram from transaction publisher
storage.mapPut("test-key", "test-field", "test-value", tx.publisher);

mapGet(key, field)

Map Get a (key, field) pair, use key + field to find value

Parameter List	Parameter Type	Remark
key	string
field	string

Returns: value in string type if exists; null if not exists.

example:

let v = storage.mapGet("test-key", "test-field");
if (v !== null) {
    ...
}

mapHas(key, field)

Map check a (key, field) pair existence, use key+field to check.

Parameter List	Parameter Type	Remark
key	string
field	string

Returns: bool (true if exists, false if not exists)

example:

if (storage.mapHas("test-key", "test-field")) {
    ...
}

mapKeys(key)

Map Get fields inside a key.

Attention:

1. This API only stores 256 fields at most, and the field exceeded will not be stored and will not be returned in this API.
2. If you need to get all keys of a map, it is recommended that you maintain them yourself and not use this API.

Parameter List	Parameter Type	Remark
key	string

Returns: array[string] (array of fields)

mapLen(key)

Return len(mapKeys()).

The attention is the same as mapKeys.

Parameter List	Parameter Type	Remark
key	string

Returns: int (number of fields)

mapDel(key, field)

Map Delete a (key, field, value) pair, use key+field to delete value.

Parameter List	Parameter Type	Remark
key	string
field	string

Returns: none

Global Storage API

APIs used to get storage of other contracts.

globalHas(contract, key)

Check if the key exists in the given contract's storage.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string

Returns: bool (true if exists, false if not exists)

example:

if (storage.globalHas("Contractxxxxxx", "test-key")) {
    ...
}

globalGet(contract, key)

Get value from the given contract's storage using key.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string

Returns: string of value if exists, null if not exists

example:

let v = storage.globalGet("Contractxxxxxx", "test-key");
if (v !== null) {
    ...
}

globalMapHas(contract, key, field)

Map check if a (key, field) pair exists in the given contract's storage, use key+field to check.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string
field	string

Returns: bool (true if exists, false if not exists)

example:

// read auth.iost contract's storage to judge whether an account exists
accountExists(account) {
    return storage.globalMapHas("auth.iost", "auth", account);
}

globalMapGet(contract, key, field)

Map get a (key, field) pair from global storage, use key+field to check.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string
field	string

Returns: string of value if exists, null if not exists

example:

let v = storage.globalMapGet("Contractxxxxxx", "test-key", "test-field");
if (v !== null) {
       ...
}

globalMapLen(contract, key)

Map count number of fields inside a key from global storage.

The attention is the same as mapKeys.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string

Returns: int (number of fields)

globalMapKeys(contract, key)

Map Get fields inside a key from global storage.

The attention is the same as mapKeys.

Parameter List	Parameter Type	Remark
contract	string	the contract id
key	string

Returns: array[string] (array of fields)

blockchain object

blockchain object is used to call system API, and call other contract's abi.

transfer(from, to, amount, memo)

Transfer iost token.

Parameter List	Parameter Type	Remark
from	string	account who sends token
to	string	account who receives token
amount	string	the amount of token transferred
memo	string	additional information

Returns: none

example:

// transfer transaction publisher's 1.23 iost to testacc
blockchain.transfer(tx.publisher, "testacc", "1.23", "this is memo")

withdraw(to, amount, memo)

Withdraw iost token from contract. It equals to:

blockchain.transfer(blockchain.contractName(), to, amount, memo)

Parameter List	Parameter Type	Remark
to	string	account who receives token
amount	string	the amount of token transferred
memo	string	additional information

Returns: none

example:

// transfer 1.23 iost to testacc from this contract
blockchain.withdraw(tx.publisher, "1.23", "this is memo")

deposit(from, amount, memo)

Deposit iost token to contract. It equals to:

blockchain.transfer(from, blockchain.contractName(), amount, memo)

Parameter List	Parameter Type	Remark
from	string	account who receives token
amount	string	the amount of token transferred
memo	string	additional information

Returns: none

example:

// transfer 1.23 iost to contract from transaction publisher
blockchain.deposit(tx.publisher, "1.23", "this is memo")

contractName()

Get contract id.

Parameters: none

Returns: string of contract id

publisher()

Get transaction publisher.

Parameters: none

Returns: string of tx publisher

contractOwner()

Get contract owner.

Parameters: none

Returns: string of contract publisher

call(contract, abi, args)

Call contract's abi using args.

Parameter List	Parameter Type	Remark
contract	string	contract id
abi	string
args	array/string	the array of arguments, or the json string of it

Returns: Array containing a string which is the json string of what the called contract returns.

example:

// query admin's iost balance by calling balanceOf of token.iost 
let ret = blockchain.call("token.iost", "balanceOf", ["iost", "admin"])
console.log(ret[0]) // attention: ret[0] is what balanceOf returns

// get a vote result by calling getResult of vote.iost
let ret = blockchain.call("vote.iost", "getResult", ["1"])
let voteRes = JSON.parse(ret[0]) // what getResult of vote.iost returns is an array, so we have to json parse it.

callWithAuth(contract, abi, args)

Call contract's abi using args with the contract's authority.

Parameter List	Parameter Type	Remark
contract	string	contract id
abi	string
args	array/string	the array of arguments, or the json string of it

Returns: Array containing a string which is the json string of what the called contract returns.

example:

// transfer 20 iost to testacc
blockchain.callWithAuth("token.iost", "transfer", ["iost", blockchain.contractName(), "testacc", "20", ""]);

// if we use call, it will throw an error since transferring contract's token needs its authority 
blockchain.call("token.iost", "transfer", ["iost", blockchain.contractName(), "testacc", "20", ""]); // throw error

requireAuth(account, permission)

Check whether a given account's given permission is provided.

Parameter List	Parameter Type	Remark
account	string
permission	string

Returns: bool (true if the permission is provided, false if not)

example:

// check whether testacc's active permission is provided
// that means whether the transaction contains the signature of testacc's active key
const ret = blockchain.requireAuth('testacc', 'active');
if (ret !== true) {
    throw new Error("require auth failed");
}

receipt(data)

Generate receipt.

Parameter List	Parameter Type	Remark
data	string

Returns: none

example:

testReceipt() {
    blockchain.receipt("some receipt content")
}

After calling testReceipt of this contract, there will be a such record in TxReceipt:

"receipts": [
    {
        "funcName": "Contractxxxxx/testReceipt",
        "content": "some receipt content"
    }
]

event(data)

Post event.

Parameter List	Parameter Type	Remark
data	string

Returns: none

example:

testEvent() {
    blockchain.event("some event content")
}

After calling testEvent of this contract, there will be event which you could get by calling subscribe:

curl -X POST http://127.0.0.1:30001/subscribe -d '{"topics":["CONTRACT_EVENT"], "filter":{"contract_id":"Contractxxxxx"}}'

{"result":{"event":{"topic":"CONTRACT_EVENT","data":"some event content","time":"1557150634515314000"}}}

blockchain.contextInfo()

{"abi_name":"hello","caller":{"name":"admin","is_account":true},"contract_name":"ContractATrHLF6LnpzjwQ1iU4VB38cSCURYzeCSyH8nSFSw8Tnc","publisher":"admin"}

tx object and block object

tx object contains current transaction information. Here's its attributes:

{
    time: 1541541540000000000, // nano second
    hash: "4mBbjkCYJQZz7hGSdnRKCLgGEkuhen1FCb6YDD7oLmtP",
    expiration: 1541541540010000000, // nano second
    gasLimit: 100000,
    gasRatio: 100,
    authList: {"Gcv8c2tH8qZrUYnKdEEdTtASsxivic2834MQW6mgxqto":2}, // pubkey
    publisher: "user0"
}

example:

console.log(tx.publisher)

block object contrains current block information. Here's its attributes:

{
    number: 132,
    parentHash: "4mBbjkCYJQZz7hGSdnRKCLgGEkuhen1FCb6YDD7oLmtP", / parent block hash
    witness: "6sNQa7PV2SFzqCBtQUcQYJGGoU7XaB6R4xuCQVXNZe6b", // block producer pubkey. Producer key is not same as account key
    time: 1541541540000000000 // nano second
}

example:

console.log(block.time)

IOSTCrypto object

IOSTCrypto provides hash function and signature verification function.

sha3(data)

Calculate sha3-256 hash.

Parameter List	Parameter Type	Remark
data	string

Returns: string which is the result of base58 encode of hash byte array. (base58_encode(sha3_256(data)))

example:

IOSTCrypto.sha3("Fule will be expensive. Everyone will have a small car.") // result: EBNarfcGkAczpeiSJwtUfH9FEVd1xFhdZis83erU9WNu

Returns: base58_encode(sha3_256(data))

verify(algo, message, signature, pubkey)

Signature verification. Both ed25519 and secp256k1 algorithms are supported.

Parameter List	Parameter Type	Remark
algo	string	can only be "ed25519" or "secp256k1"
message	string	base58 encoded original text to be signed
signature	string	base58 encoded signature to be checked
pubkey	string	base58 encoded public key of the corresponding private key used for signing

Returns: int, 1 (succees) or 0 (failure)

example:

// choose ed25519 algorithm
// the base58 encoded private key is "4PTQW2hvwZoyuMdgKbo3iQ9mM7DTzxSV54RpeJyycD9b1R1oGgYT9hKoPpAGiLrhYA8sLQ3sAVFoNuMXRsUH7zw6"
// the base58 encoded public key is "2vSjKSXhepo7vmbPQHFcnEvx8mWRFrf46DaTX1Bp3TBi"
// the origial text is "hello world"
// "StV1DL6CwTryKyV" is base58 encoded result of "hello world"
// "38V8bZC4e78pU7zBN86CF8R8ip76Rhf3vyiwTQR2MVkqHesmUbZJVmN8AE6eWhQg6ekKaa2H4iB4JJibC5stBRrN" is base58 encoded signature signed by the private key above
// So the result of verification should be 1:
let v = IOSTCrypto.verify("ed25519", "StV1DL6CwTryKyV", "38V8bZC4e78pU7zBN86CF8R8ip76Rhf3vyiwTQR2MVkqHesmUbZJVmN8AE6eWhQg6ekKaa2H4iB4JJibC5stBRrN", "2vSjKSXhepo7vmbPQHFcnEvx8mWRFrf46DaTX1Bp3TBi"); // v = 1

Float64, Int64 and BigNumber object

In contract, we could use Float64, Int64 and BigNumber to do high precision calculation.
Float64 APIs can be found here.
Int64 APIs can be found here.
BigNumber APIs can be found here.

example:

let bonus = new Float64("1.0123456789");
let earning = bonus.div(2).toFixed(8); // earning is "0.50617283"
blockchain.withdraw("testacc", earning, "");

Disabled Javascript Methods

Some functions of Javascript is forbidden for security reasons.
This document gives a list of allowed and forbidden APIs.