This page is used to describe all the additional APIs which exists as part of the Contract SDK.

To use the `Env`

package, you need to import it:

import ("github.com/orbs-network/orbs-contract-sdk/go/sdk/v1/env")

It provides the following functions:

Used to get the block height which will be the one this transaction be a part of

GetBlockHeight() uint64

It returns the block height in decimal values:

Used to get the block timestamp (creation time) which will be the one this transaction be a part of:

GetBlockTimestamp() uint64

It returns the block timestamp representing the Unix epoch in nanoseconds.

Used to get the virtual chain id this contract is executing on.

GetVirtualChainId() uint32

It returns the virtual chain id in decimal values.

To use the `Safemath`

package, you need to import it:

import ("github.com/orbs-network/orbs-contract-sdk/go/sdk/v1/safemath/safeuint256""github.com/orbs-network/orbs-contract-sdk/go/sdk/v1/safemath/safeuint64""github.com/orbs-network/orbs-contract-sdk/go/sdk/v1/safemath/safeuint32")

It gives the ability to work with 32, 64, and 256 bit unsigned integers in a 'safe' way meaning there is an overflow/underflow and illegal operation protection around the arithmetic operation done.

The API is uniform between the different variants and consist of the following functions:

Adds two numbers and returns the result. The numbers are validated so that they do not overflow after the addition.

Add(x *big.Int, y *big.Int) *big.IntAdd(x uint32, y uint32) uint32Add(x uint64, y uint64) uint64

Subtract `y`

from `x`

. The result is validated, so if it becomes negative, an error is returned.

Sub(x *big.Int, y *big.Int) *big.IntSub(x uint32, y uint32) uint32Sub(x uint64, y uint64) uint64

Multiplies the values and returns the new number. The result is validated so that it does not overflow.

Mul(x *big.Int, y *big.Int) *big.IntMul(x uint32, y uint32) uint32Mul(x uint64, y uint64) uint64

Performs an integer division of `x`

by `y`

. The remainder is discarded as it should in integer arithmetic, and the input (`y`

) is validated not to be zero.

Div(x *big.Int, y *big.Int) *big.IntDiv(x uint32, y uint32) uint32Div(x uint64, y uint64) uint64

Performs the modulo operation of `x`

by `y`

. The input is validated to be valid (meaning `y`

is not zero). The resulting number is the reminder.

Mod(x *big.Int, y *big.Int) *big.IntMod(x uint32, y uint32) uint32Mod(x uint64, y uint64) uint64

Only relevant for `safeuint256`

The function validates that the number is not negative, and did not overflow. If the validation fails, the code panics with the appropriate message.

Validate(n *big.Int)

Note that `validate`

is called automatically on each operation, meaning after using `Add`

or `Sub`

or any operation of the safemath library, so there is no need to call it manually.