oracle

Documentation

Overview

Package oracle provides interface to OracleContract native contract. Oracles allow you to get external (non-blockchain) data using HTTPS or NeoFS protocols.

Index

• Constants
• func GetPrice() int
• func Request(url string, filter []byte, cb string, userData interface{}, gasForResponse int)
• func SetPrice(amount int)

Constants

const (
	Success              = 0x00
	ProtocolNotSupported = 0x10
	ConsensusUnreachable = 0x12
	NotFound             = 0x14
	Timeout              = 0x16
	Forbidden            = 0x18
	ResponseTooLarge     = 0x1a
	InsufficientFunds    = 0x1c
	Error                = 0xff
)

These are potential response codes you get in your callback completing oracle request. Resulting data is only passed with Success code, it's nil otherwise.

const Hash = "\x58\x87\x17\x11\x7e\x0a\xa8\x10\x72\xaf\xab\x71\xd2\xdd\x89\xfe\x7c\x4b\x92\xfe"

Hash represents Oracle contract hash.

const MinimumResponseGas = 10_000_000

MinimumResponseGas is the minimum response fee permitted for request (that is you can't attach less than that to your request). It's 0.1 GAS at the moment.

Functions

func GetPrice

func GetPrice() int

GetPrice returns current oracle request price.

func Request

func Request(url string, filter []byte, cb string, userData interface{}, gasForResponse int)

Request makes an oracle request. It can only be successfully invoked by deployed contract and it takes the following parameters:

url
    URL to fetch, only https and neofs URLs are supported like
    https://example.com/some.json or
    neofs:6pJtLUnGqDxE2EitZYLsDzsfTDVegD6BrRUn8QAFZWyt/5Cyxb3wrHDw5pqY63hb5otCSsJ24ZfYmsA8NAjtho2gr

filter
    JSONPath filter to process the result, if specified it will be
    applied to the data returned from HTTP/NeoFS and you'll only get
    filtered data in your callback method.

cb
    name of the method that will process oracle data, it must be a method
    of the same contract that invokes Request and it must have the following
    signature for correct invocation:

        Method(url string, userData interface{}, code int, result []byte)

    where url is the same url specified for Request, userData is anything
    passed in the next parameter, code is the status of the reply and
    result is data returned from request if any.

userData
    data to pass to the callback function.

gasForResponse
    GAS attached to this request for reply callback processing,
    note that it's different from the oracle request price, this
    GAS is used for oracle transaction's network and system fees,
    so it should be enough to pay for reply data as well as
    its processing.

func SetPrice

func SetPrice(amount int)

SetPrice allows to set oracle request price. This method can only be successfully invoked by the committee.