Sequences of bytes

Bytes are used for serializing data, for example to compute signature hashes. Conversely, they can be used to deserialise external data, in which case the expected LIGO type needs to be specified.

Literals

Byte literals are sequences of bytes (eight-bit values, also known as octets), defined using the prefix 0x followed by hexadecimal digits, or none if the denoted literal is zero:

const a : bytes = 0x70FF;

const zero : bytes = 0x;

const zero_too = 0x00;

Clearly, this means that literal bytes are always comprised of an even number of hexadecimal digits (because one hexadecimal digit requires up to four bits in binary, and eight are needed to make up a byte).

From numbers to bytes and back

Some other numerals can be converted to bytes by means of calling the predefined function bytes, which is overloaded. The reverse conversion is done by the predefined functions int and nat. For instance, here how to create bytes from natural numbers and integers:

const b: bytes = bytes(123n); // 7B in hexadecimal

const c: bytes = bytes(123);

const d: bytes = bytes(-123); // Two's complement

const n: nat = nat(0x7B); // n == 123n

const i: int = int(0x7B); // i == 123

Note: See Two's complement.

From strings

A string literal can be converted to bytes in two ways:

1. by interpreting the ASCII code of each character (which spans over two hexadecimal digits) as one byte;
2. by interpreting directly each character as one hexadecimal digit.

In the former case, the syntax is somewhat odd -- as opposed to simply calling the function bytes:

const from_ascii: bytes = bytes`foo`; // Not a call

The latter case is implemented as a type cast:

// raw == from_ascii

const raw: bytes = ("666f6f" as bytes);

Note that both syntaxes apply respectively only to verbatim string literals and general strings, not general expressions of type string. In other words, the contents of the strings must be available at compile-time. (This actually reveals that ("666f6f" as bytes) is not really a cast, as casts are non-operations.)