# `SpanId`

A span's id (W3C Trace Context): 16 lower-case hexadecimal digits, not all zero.

[Software](types.md#software); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `SpanId("00f067aa0ba902b7")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: SpanId)` reads one from its text; text that isn't one at all fails `malformed`, such as `0000000000000000`, `00F067AA0BA902B7` or `00f067aa0ba902b`.

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `00f067aa0ba902b7` | `"00f067aa0ba902b7"` |
| `ffffffffffffffff` | `"ffffffffffffffff"` |

It is stored in one column named for the field, of type `text`. `ffffffffffffffff` is stored as `'ffffffffffffffff'`.

## Shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `00f067aa0ba902b7` | `00f067aa0ba902b7` |
| `ffffffffffffffff` | `ffffffffffffffff` |

## Operations

It has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It isn't ordered, so `<` and sorting don't take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.