The standard library

The standard library is unstable. Function signatures and behavior are going to be changed in future releases.

Most of the functions described here are special, as they accept arrays of arbitrary size. Since there are only fixed-size arrays in Zinc now, it would be challenging to create a function for arrays of every possible size. It is not possible to write such a function yourself using the language type system, but std makes an exception to simplify development for now.

Definitions

  • {scalar} - a scalar type, which can be bool, u{N}, i{N}, field
  • u{N} - an unsigned integer of bitlength N
  • i{N} - a signed integer of bitlength N
  • field - a field element of bitlength 254

std::crypto module

std::crypto::sha256

Computes the sha256 hash of a given bit array.

Will cause a compile-error if either:

  • preimage length is zero
  • preimage length is not multiple of 8

Arguments:

  • preimage bit array [bool; N]

Returns: 256-bit hash [bool; 256]

std::crypto::pedersen

Maps a bit array to a point on an elliptic curve.

Will cause a compile-error if either:

  • preimage length is zero
  • preimage length is greater than 512 bits

To understand what is under the hood, see this article.

Arguments:

  • preimage bit array [bool; N]

Returns: elliptic curve point coordinates (field, field)

std::crypto::ecc::Point

The elliptic curve point.

struct Point {
    x: field,
    y: field,
}

std::crypto::schnorr::Signature

The Schnorr EDDSA signature structure.

struct Signature {
    r: std::crypto::ecc::Point,
    s: field,
    pk: std::crypto::ecc::Point,
}

std::crypto::schnorr::Signature::verify

Verifies the EDDSA signature.

Will cause a compile-error if either:

  • message length is zero
  • message length is greater than 248 bits

Arguments:

  • the signature: std::crypto::schnorr::Signature
  • the message: [bool; N]

Returns: the boolean result

std::convert module

std::convert::to_bits

Converts a scalar value to a bit array of its bitlength.

Arguments:

  • scalar value: u{N}, or i{N}, or field

Returns: [bool; N]

std::convert::from_bits_unsigned

Converts a bit array to an unsigned integer of the array's bitlength.

Will cause a compile-error if either:

  • bit array size is zero
  • bit array size is greater than 248 bits
  • bit array size is not multiple of 8

Arguments:

  • bit array: [bool; N]

Returns: u{N}

std::convert::from_bits_signed

Converts a bit array to a signed integer of the array's bitlength.

Will cause a compile-error if either:

  • bit array size is zero
  • bit array size is greater than 248 bits
  • bit array size is not multiple of 8

Arguments:

  • bit array: [bool; N]

Returns: i{N}

std::convert::from_bits_unsigned

Converts a bit array to a field element.

Arguments:

  • bit array: [bool; 254]

Returns: field

std::array module

std::array::reverse

Reverses a given array.

Arguments:

  • array: [{scalar}; N]

Returns: [{scalar}; N]

std::array::truncate

Truncates an array of size N to an array of size new_length.

Will cause a compile-error if either:

  • array size is less than new length
  • new length is not a constant expression

Arguments:

  • array: [{scalar}; N]
  • new_length: u{N} or field

Returns: [{scalar}; new_length]

std::array::pad

Pads a given array with the given values.

Will cause a compile-error if either:

  • array size is greater than new length
  • new length is not a constant expression

Arguments:

  • array: [{scalar}; N]
  • new_length: u{N} or field
  • fill_value: {scalar}

Returns: [{scalar}; new_length]

std::ff module

std::ff::invert

Inverts a finite field.

Arguments:

  • value: field

Returns: field

std::collections module

std::collections::MTreeMap<K, V>

The map type, which can only be a contract storage field and accessed via the methods below.

std::collections::MTreeMap::get

Gets the value from the map. Returns the value and presence flag. If the presence flag is false, the value is filled with zeros.

Arguments:

  • key: K

Returns: (V, bool)

std::collections::MTreeMap::contains

Checks if the value exists in the map. Returns the presence flag.

Arguments:

  • key: K

Returns: bool

std::collections::MTreeMap::insert

Inserts the value into the map. Returns the old value and presence flag. If the presence flag is false, the old value is filled with zeros.

Arguments:

  • key: K
  • value: V

Returns: (V, bool)

std::collections::MTreeMap::remove

Removes the value from the map. Returns the removed value and presence flag. If the presence flag is false, the removed value is filled with zeros.

Arguments:

  • key: K

Returns: (V, bool)