# `Digest`

A content digest (the OCI image specification): its algorithm, `:` and the encoded hash, `sha256:` and 64 lower-case hexadecimal digits.

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

## Make one

Build one from its text, `Digest("sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: Digest)` reads one from its text; text that isn't one at all fails `malformed`, such as `sha256:` or `""`.

## 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 |
|---|---|
| `sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b` | `"sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b"` |
| `sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1` | `"sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1"` |
| `multihash+base58:QmRZxt2b1FVZPNqd8hsiykDL3TdBDeTSPX9Kv46HmX4Gx8` | `"multihash+base58:QmRZxt2b1FVZPNqd8hsiykDL3TdBDeTSPX9Kv46HmX4Gx8"` |

It is stored in one column named for the field, of type `text`. `sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1` is stored as `'sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1'`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b` | `sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b` |
| `sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1` | `sha512:401b09eab3c013d4ca54922bb802bec8fd5318192b0a75f201d8b3727429080fb337591abd3e44453b954555b7a0812e1081c39b740293f765eae731f5a65ed1` |
| `multihash+base58:QmRZxt2b1FVZPNqd8hsiykDL3TdBDeTSPX9Kv46HmX4Gx8` | `multihash+base58:QmRZxt2b1FVZPNqd8hsiykDL3TdBDeTSPX9Kv46HmX4Gx8` |

## 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.