# `Tezex.Zarith`
[🔗](https://github.com/objkt-com/tezex/blob/v4.0.0/lib/zarith.ex#L1)

Provides encoding and decoding functions for Zarith numbers.

A Zarith number is an integer encoded as a variable length sequence of bytes.

Each byte has a running unary size bit:
  - The most significant bit of each byte tells if this is the last byte in the sequence (0) or if there is more to read (1)
  - The second most significant bit of the first byte is reserved for the sign (positive if zero)

Size and sign bits ignored, data is then the binary representation of the absolute value of the number in little endian order.

# `decoded_zarith`

```elixir
@type decoded_zarith() :: integer()
```

Represents a decoded Zarith number as an Elixir integer.

# `zarith_hex`

```elixir
@type zarith_hex() :: String.t()
```

Represents a Zarith-encoded integer as a hexadecimal string.

# `consume`

```elixir
@spec consume(zarith_hex()) :: {%{int: String.t()}, pos_integer()}
```

Consumes a Zarith-encoded integer.

Takes a hexadecimal string and returns the decoded integer in base 10 along with how many characters of the input string
were used to decode the integer.

## Parameters

  * `binary_input` - A hexadecimal string representing the Zarith-encoded integer.

## Returns

  A tuple containing:
  - A map with the key `:int` and the decoded integer as a string value.
  - The number of characters consumed from the input string.

## Examples

    iex> Tezex.Zarith.consume("a1d22c")
    {%{int: "365729"}, 6}

    iex> Tezex.Zarith.consume("e1d22c")
    {%{int: "-365729"}, 6}

# `decode`

```elixir
@spec decode(zarith_hex()) :: decoded_zarith()
```

Decodes a Zarith-encoded integer.

Takes a hexadecimal string representation of a Zarith-encoded number and returns the integer in base 10.

## Parameters

  * `binary_input` - A hexadecimal string representing the Zarith-encoded integer.

## Returns

  The decoded integer.

## Examples

    iex> Tezex.Zarith.decode("a1d22c")
    365_729

    iex> Tezex.Zarith.decode("e1d22c")
    -365_729

# `encode`

```elixir
@spec encode(decoded_zarith()) :: zarith_hex()
```

Encodes an integer to a Zarith-encoded hexadecimal string.

Takes an integer in base 10 and returns the Zarith-encoded hexadecimal string.

Implementation based on [anchorageoss/tezosprotocol (MIT License - Copyright (c) 2019 Anchor Labs, Inc.)](https://github.com/anchorageoss/tezosprotocol/blob/23a051d34fcfda8393940141f8151113a1aca10b/zarith/zarith.go#L153)

## Parameters

  * `integer` - The integer to be encoded.

## Returns

  A hexadecimal string representing the Zarith-encoded integer.

## Examples

    iex> Tezex.Zarith.encode(365_729)
    "a1d22c"

    iex> Tezex.Zarith.encode(-365_729)
    "e1d22c"

---

*Consult [api-reference.md](api-reference.md) for complete listing*