Fe_

fn Fe_(comptime bits: comptime_int) type

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Code

fn Fe_(comptime bits: comptime_int) type {
    return struct {
        const Self = @This();

        const FeUint = Uint(bits);

        /// The element value as a `Uint`.
        v: FeUint,

        /// `true` if the element is in Montgomery form.
        montgomery: bool = false,

        /// The maximum number of bytes required to encode a field element.
        pub const encoded_bytes = FeUint.encoded_bytes;

        // The number of active limbs to represent the field element.
        fn limbs_count(self: Self) usize {
            return self.v.limbs_len;
        }

        /// Creates a field element from a primitive.
        /// This function may not run in constant time.
        pub fn fromPrimitive(comptime T: type, m: Modulus(bits), x: T) (OverflowError || FieldElementError)!Self {
            comptime assert(@bitSizeOf(T) <= bits); // Primitive type is larger than the modulus type.
            const v = try FeUint.fromPrimitive(T, x);
            var fe = Self{ .v = v };
            try m.shrink(&fe);
            try m.rejectNonCanonical(fe);
            return fe;
        }

        /// Converts the field element to a primitive.
        /// This function may not run in constant time.
        /// Returns an error if the element is in Montgomery form.
        pub fn toPrimitive(self: Self, comptime T: type) (OverflowError || RepresentationError)!T {
            if (self.montgomery) {
                return error.UnexpectedRepresentation;
            }
            return self.v.toPrimitive(T);
        }

        /// Creates a field element from a byte string.
        pub fn fromBytes(m: Modulus(bits), bytes: []const u8, comptime endian: Endian) (OverflowError || FieldElementError)!Self {
            const v = try FeUint.fromBytes(bytes, endian);
            var fe = Self{ .v = v };
            try m.shrink(&fe);
            try m.rejectNonCanonical(fe);
            return fe;
        }

        /// Converts the field element to a byte string.
        /// Returns an error if the element is in Montgomery form.
        pub fn toBytes(self: Self, bytes: []u8, comptime endian: Endian) (OverflowError || RepresentationError)!void {
            if (self.montgomery) {
                return error.UnexpectedRepresentation;
            }
            return self.v.toBytes(bytes, endian);
        }

        /// Returns `true` if the field elements are equal, in constant time.
        pub fn eql(x: Self, y: Self) bool {
            return x.v.eql(y.v);
        }

        /// Compares two field elements in constant time.
        pub fn compare(x: Self, y: Self) math.Order {
            return x.v.compare(y.v);
        }

        /// Returns `true` if the element is zero.
        pub fn isZero(self: Self) bool {
            return self.v.isZero();
        }

        /// Returns `true` is the element is odd.
        pub fn isOdd(self: Self) bool {
            return self.v.isOdd();
        }
    };
}