<a id="nupp.data"></a>
# Module: `nupp.data`

# Data and text

`nupp.data` groups serialization, Unicode, identifiers and byte digests. Reach it
directly from the global [`nupp` namespace](stdlib.md); the C and Rust providers remain
hidden.

## JSON

`encodeJSON` and `decodeJSON` use the mature cjson implementation without exposing its
module name:

```nupp
local encoded = nupp.data.encodeJSON({name = "Nupp", ready = true})
local decoded = nupp.data.decodeJSON(encoded)
assert(decoded.name == "Nupp")
```

`null`, `emptyArray`, `arrayMt`, and `emptyArrayMt` preserve distinctions Lua tables
cannot express by themselves. The configuration methods match cjson's established
semantics, but live on `nupp.data`. `newJSON()` returns an independent `nupp.data.JSON`
encoder/decoder with its own settings:

```nupp
local compact = nupp.data.newJSON()
compact.encodeKeepBuffer(false)
local text = compact.encodeJSON({1, 2, 3})
```

JSON selects the `cjson` native feature. No `require("cjson")` is needed or recommended.

| Member | Result | Purpose |
| --- | --- | --- |
| `encodeJSON(value)` | `string` | Encode one Lua value. |
| `decodeJSON(text)` | `any` | Decode one JSON document. |
| `newJSON()` | `nupp.data.JSON` | Create an independently configured codec. |
| `null`, `emptyArray` | sentinel values | Represent JSON values that plain Lua tables cannot distinguish. |
| `arrayMt`, `emptyArrayMt` | metatables | Mark array-shaped tables explicitly. |

Both `nupp.data` and an object returned by `newJSON` provide the configuration
methods `encodeEmptyTableAsObject`, `decodeArrayWithArrayMt`,
`decodeAllowComment`, `encodeSparseArray`, `encodeMaxDepth`,
`decodeMaxDepth`, `encodeNumberPrecision`, `encodeKeepBuffer`,
`encodeInvalidNumbers`, `decodeInvalidNumbers`,
`encodeEscapeForwardSlash`, `encodeSkipUnsupportedValueTypes`, and
`encodeIndent`. Omitting a method's setting reads the current value where the
provider supports that form; passing a setting changes only that codec.

## UTF-8

`nupp.data.utf8` treats strings and [`nupp.io.ByteView`](io.md#byte-views) values as byte
sequences. Byte offsets are 1-based here so they compose with Lua string positions.
Invalid input decodes as U+FFFD while validation remains explicit.

```nupp
local utf8 = nupp.data.utf8
assert(utf8.length("A€") == 2)

local codepoint, nextByte = utf8.decodeAt("A€", 2)
assert(codepoint == 0x20ac and nextByte == 5)

codepoint, nextByte = utf8.decodeBefore("A€", nextByte)
assert(codepoint == 0x20ac and nextByte == 2)

assert(utf8.encode(0x20ac) == "€")
assert(utf8.isValid("café"))
assert(not utf8.isValid("\xff"))
assert(utf8.truncate("A€B", 4) == "A€")
```

`validPrefixLength(value, maxBytes)` returns the largest valid prefix no longer than the
byte budget. `truncate` applies that operation to a string. The underlying lua-utf8
provider loads only when this namespace is selected and reached.

| Member | Result | Position rule |
| --- | --- | --- |
| `length(value)` | `integer` | Counts decoded scalar values, replacing malformed bytes individually. |
| `decodeAt(value, byteOffset)` | `integer?, integer` | Decodes forward from a 1-based byte offset and returns the next offset. |
| `decodeBefore(value, byteOffset)` | `integer?, integer` | Decodes the scalar ending before a 1-based byte offset. |
| `encode(codepoint)` | `string` | Encodes one Unicode scalar value. |
| `isValid(value)` | `boolean` | Validates the complete byte sequence. |
| `validPrefixLength(value, maxBytes)` | `integer` | Finds a valid prefix within a byte budget. |
| `truncate(text, maxBytes)` | `string` | Copies that valid prefix. |

## UUIDs

`uuid4()` returns a random RFC 9562 version 4 identifier. `uuid7()` returns a
time-ordered version 7 identifier, useful when identifier order should roughly follow
creation order:

```nupp
local objectID = nupp.data.uuid4()
local eventID = nupp.data.uuid7()
```

Both are lowercase canonical strings. They share one `uuid` feature and never expose a
native UUID object.

## Hashes and checksums

Each function accepts a string or immutable [`nupp.io.ByteView`](io.md#byte-views).

```nupp
assert(nupp.data.fnv1a64("hello") == "a430d84680aabd0b")
assert(nupp.data.sha256("abc") ==
    "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad")

local checksum = nupp.data.crc32(header)
checksum = nupp.data.crc32(body, checksum)
```

`fnv1a64` is a fast non-cryptographic identity rendered as 16 lowercase hexadecimal
digits. `sha256` is a cryptographic digest rendered as 64 lowercase hexadecimal digits.
`adler32` and `crc32` return unsigned 32-bit numbers and accept a previous result for
incremental checksumming. Checksums detect accidental damage; they do not authenticate
data. A supplied previous checksum must itself be an unsigned 32-bit integer.

FNV-1a, Adler-32 and CRC-32 are pure generated Lua. SHA-256 is independently gated in
the shared Rust provider. See [automatic native selection](tooling/build.md#compiler-native-features).

| Member | Result | Native provider |
| --- | --- | --- |
| `uuid4()` | canonical UUID string | shared provider, `uuid` feature |
| `uuid7()` | canonical UUID string | shared provider, `uuid` feature |
| `fnv1a64(value)` | 16 lowercase hex digits | none |
| `sha256(value)` | 64 lowercase hex digits | shared provider, `sha256` feature |
| `adler32(value, previous?)` | unsigned 32-bit number | none |
| `crc32(value, previous?)` | unsigned 32-bit number | none |


JSON, UTF-8, UUIDs, hashes and checksums.

## Submodules

| Module | Description |
| --- | --- |
| `nupp.data.utf8` | UTF-8 codepoint operations over strings and byte views. |

## Constructors

<a id="nupp.data.newJSON"></a>
### `newJSON` _constructor_

Creates an independent JSON codec with its own settings.

```nupp
local newJSON: function(): JSON
```

#### Returns

| Type | Description |
| --- | --- |
| `JSON` | the new codec |

## Types

<a id="nupp.data.JSON"></a>
### `JSON` _interface_

One independently configured JSON encoder and decoder.

```nupp
interface JSON
    encodeJSON: function(value: any): string
    decodeJSON: function(text: string): any
    null: any
    emptyArray: any
    arrayMt: metatable<{any}>
    emptyArrayMt: metatable<{any}>
    encodeEmptyTableAsObject: function(setting: boolean | string?): boolean
    decodeArrayWithArrayMt: function(setting: boolean | string?): boolean
    decodeAllowComment: function(setting: boolean | string?): boolean
    encodeSparseArray: function(convert: boolean?, ratio: integer?, safe: integer?): (boolean, integer, integer)
    encodeMaxDepth: function(depth: integer?): integer
    decodeMaxDepth: function(depth: integer?): integer
    encodeNumberPrecision: function(precision: integer?): integer
    encodeKeepBuffer: function(keep: boolean | string?): boolean
    encodeInvalidNumbers: function(setting: boolean | string?): boolean | string
    decodeInvalidNumbers: function(setting: boolean | string?): boolean
    encodeEscapeForwardSlash: function(setting: boolean | string?): boolean
    encodeSkipUnsupportedValueTypes: function(setting: boolean | string?): boolean
    encodeIndent: function(indent: string?): string
end
```

#### Methods

<a id="nupp.data.JSON.encodeJSON"></a>
##### `encodeJSON`

Encodes a Lua value as JSON text.

```nupp
encodeJSON: function(value: any): string
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `any` | the value to encode |

###### Returns

| Type | Description |
| --- | --- |
| `string` | the encoded JSON document |

<a id="nupp.data.JSON.decodeJSON"></a>
##### `decodeJSON`

Decodes one JSON document into Lua values.

```nupp
decodeJSON: function(text: string): any
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `text` | `string` | the JSON document to decode |

###### Returns

| Type | Description |
| --- | --- |
| `any` | the decoded value |

<a id="nupp.data.JSON.encodeEmptyTableAsObject"></a>
##### `encodeEmptyTableAsObject`

Sets whether an empty table encodes as an object, or reads the current
setting when omitted.

```nupp
encodeEmptyTableAsObject: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | true or "on" for `{}`, false or "off" for `[]` |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether empty tables encode as objects |

<a id="nupp.data.JSON.decodeArrayWithArrayMt"></a>
##### `decodeArrayWithArrayMt`

Sets whether decoded arrays carry `arrayMt`, or reads the current setting
when omitted.

```nupp
decodeArrayWithArrayMt: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether decoded arrays carry `arrayMt` |

<a id="nupp.data.JSON.decodeAllowComment"></a>
##### `decodeAllowComment`

Sets whether the decoder accepts comments, or reads the current setting
when omitted.

```nupp
decodeAllowComment: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether comments are accepted |

<a id="nupp.data.JSON.encodeSparseArray"></a>
##### `encodeSparseArray`

Configures how excessively sparse arrays are encoded, or reads the current
settings when every argument is omitted.

```nupp
encodeSparseArray: function(convert: boolean?, ratio: integer?, safe: integer?): (boolean, integer, integer)
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `convert` | `boolean?` | whether sparse arrays become JSON objects instead of raising |
| `ratio` | `integer?` | the maximum ratio between the highest index and item count |
| `safe` | `integer?` | the array size below which sparsity is always accepted |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether sparse arrays are converted |
| `integer` | the current ratio limit |
| `integer` | the current safe size |

<a id="nupp.data.JSON.encodeMaxDepth"></a>
##### `encodeMaxDepth`

Sets the maximum nested-container depth accepted by the encoder, or reads
the current limit when omitted.

```nupp
encodeMaxDepth: function(depth: integer?): integer
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `depth` | `integer?` | the new maximum depth |

###### Returns

| Type | Description |
| --- | --- |
| `integer` | the current maximum depth |

<a id="nupp.data.JSON.decodeMaxDepth"></a>
##### `decodeMaxDepth`

Sets the maximum nested-container depth accepted by the decoder, or reads
the current limit when omitted.

```nupp
decodeMaxDepth: function(depth: integer?): integer
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `depth` | `integer?` | the new maximum depth |

###### Returns

| Type | Description |
| --- | --- |
| `integer` | the current maximum depth |

<a id="nupp.data.JSON.encodeNumberPrecision"></a>
##### `encodeNumberPrecision`

Sets the significant-digit precision used to encode numbers, or reads the
current precision when omitted.

```nupp
encodeNumberPrecision: function(precision: integer?): integer
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `precision` | `integer?` | the new number of significant digits |

###### Returns

| Type | Description |
| --- | --- |
| `integer` | the current precision |

<a id="nupp.data.JSON.encodeKeepBuffer"></a>
##### `encodeKeepBuffer`

Sets whether the encoder reuses its internal buffer, or reads the current
setting when omitted.

```nupp
encodeKeepBuffer: function(keep: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `keep` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether the internal buffer is retained |

<a id="nupp.data.JSON.encodeInvalidNumbers"></a>
##### `encodeInvalidNumbers`

Configures encoding of NaN and infinities, or reads the current setting
when omitted.

```nupp
encodeInvalidNumbers: function(setting: boolean | string?): boolean | string
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | false to reject them, true to emit them, or "null" to emit null |

###### Returns

| Type | Description |
| --- | --- |
| `boolean | string` | the active invalid-number setting |

<a id="nupp.data.JSON.decodeInvalidNumbers"></a>
##### `decodeInvalidNumbers`

Sets whether the decoder accepts NaN and infinities, or reads the current
setting when omitted.

```nupp
decodeInvalidNumbers: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether invalid numbers are accepted |

<a id="nupp.data.JSON.encodeEscapeForwardSlash"></a>
##### `encodeEscapeForwardSlash`

Sets whether `/` is escaped in JSON strings, or reads the current setting
when omitted.

```nupp
encodeEscapeForwardSlash: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether forward slashes are escaped |

<a id="nupp.data.JSON.encodeSkipUnsupportedValueTypes"></a>
##### `encodeSkipUnsupportedValueTypes`

Sets whether unsupported values are skipped instead of raising, or reads the
current setting when omitted.

```nupp
encodeSkipUnsupportedValueTypes: function(setting: boolean | string?): boolean
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

###### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether unsupported values are skipped |

<a id="nupp.data.JSON.encodeIndent"></a>
##### `encodeIndent`

Sets the indentation used for encoded containers, or reads the current
indentation when omitted.

```nupp
encodeIndent: function(indent: string?): string
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `indent` | `string?` | the indentation string |

###### Returns

| Type | Description |
| --- | --- |
| `string` | the current indentation string |

#### Fields

| Name | Type | Description |
| --- | --- | --- |
| `null` | `any` | Sentinel that decodes from and encodes as JSON null. |
| `emptyArray` | `any` | Sentinel that always encodes as an empty JSON array. |
| `arrayMt` | `metatable\<{any}\>` | Metatable marking a table to encode as a JSON array. |
| `emptyArrayMt` | `metatable\<{any}\>` | Metatable marking a table to encode as an empty JSON array. |

<a id="nupp.data.JSONEncodable"></a>
### `JSONEncodable` _interface_

Values that can encode themselves as JSON text.

```nupp
interface JSONEncodable
    toJSON: function(self): string
end
```

#### Methods

<a id="nupp.data.JSONEncodable.toJSON"></a>
##### `toJSON`

```nupp
toJSON: function(self): string
```

###### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `?` | `self` |  |

###### Returns

| Type | Description |
| --- | --- |
| `string` |  |

## Functions

<a id="nupp.data.adler32"></a>
### `adler32` _function_

Computes or continues an Adler-32 checksum.

```nupp
local adler32: function(value: string | nupp.io.ByteView, previous: integer?): integer
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `string | nupp.io.ByteView` | the bytes to checksum |
| `previous` | `integer?` | a previous Adler-32 value, or 1 to start |

#### Returns

| Type | Description |
| --- | --- |
| `integer` | the unsigned 32-bit checksum |

<a id="nupp.data.crc32"></a>
### `crc32` _function_

Computes or continues a CRC-32 checksum.

```nupp
local crc32: function(value: string | nupp.io.ByteView, previous: integer?): integer
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `string | nupp.io.ByteView` | the bytes to checksum |
| `previous` | `integer?` | a previous CRC-32 value, or 0 to start |

#### Returns

| Type | Description |
| --- | --- |
| `integer` | the unsigned 32-bit checksum |

<a id="nupp.data.decodeAllowComment"></a>
### `decodeAllowComment` _function_

Sets whether the decoder accepts comments, or reads the current setting
when omitted.

```nupp
local decodeAllowComment: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether comments are accepted |

<a id="nupp.data.decodeArrayWithArrayMt"></a>
### `decodeArrayWithArrayMt` _function_

Sets whether decoded arrays carry `arrayMt`, or reads the current setting
when omitted.

```nupp
local decodeArrayWithArrayMt: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether decoded arrays carry `arrayMt` |

<a id="nupp.data.decodeInvalidNumbers"></a>
### `decodeInvalidNumbers` _function_

Sets whether the decoder accepts NaN and infinities, or reads the current
setting when omitted.

```nupp
local decodeInvalidNumbers: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether invalid numbers are accepted |

<a id="nupp.data.decodeJSON"></a>
### `decodeJSON` _function_

Decodes one JSON document into Lua values.

```nupp
local decodeJSON: function(text: string): any
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `text` | `string` | the JSON document to decode |

#### Returns

| Type | Description |
| --- | --- |
| `any` | the decoded value |

<a id="nupp.data.decodeMaxDepth"></a>
### `decodeMaxDepth` _function_

Sets the maximum nested-container depth accepted by the decoder, or reads
the current limit when omitted.

```nupp
local decodeMaxDepth: function(depth: integer?): integer
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `depth` | `integer?` | the new maximum depth |

#### Returns

| Type | Description |
| --- | --- |
| `integer` | the current maximum depth |

<a id="nupp.data.encodeEmptyTableAsObject"></a>
### `encodeEmptyTableAsObject` _function_

Sets whether an empty table encodes as an object, or reads the current
setting when omitted.

```nupp
local encodeEmptyTableAsObject: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | true or "on" for `{}`, false or "off" for `[]` |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether empty tables encode as objects |

<a id="nupp.data.encodeEscapeForwardSlash"></a>
### `encodeEscapeForwardSlash` _function_

Sets whether `/` is escaped in JSON strings, or reads the current setting
when omitted.

```nupp
local encodeEscapeForwardSlash: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether forward slashes are escaped |

<a id="nupp.data.encodeIndent"></a>
### `encodeIndent` _function_

Sets the indentation used for encoded containers, or reads the current
indentation when omitted.

```nupp
local encodeIndent: function(indent: string?): string
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `indent` | `string?` | the indentation string |

#### Returns

| Type | Description |
| --- | --- |
| `string` | the current indentation string |

<a id="nupp.data.encodeInvalidNumbers"></a>
### `encodeInvalidNumbers` _function_

Configures encoding of NaN and infinities, or reads the current setting
when omitted.

```nupp
local encodeInvalidNumbers: function(setting: boolean | string?): boolean | string
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | false to reject them, true to emit them, or "null" to emit null |

#### Returns

| Type | Description |
| --- | --- |
| `boolean | string` | the active invalid-number setting |

<a id="nupp.data.encodeJSON"></a>
### `encodeJSON` _function_

Encodes a Lua value as JSON text.

```nupp
local encodeJSON: function(value: any): string
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `any` | the value to encode |

#### Returns

| Type | Description |
| --- | --- |
| `string` | the encoded JSON document |

<a id="nupp.data.encodeKeepBuffer"></a>
### `encodeKeepBuffer` _function_

Sets whether the encoder reuses its internal buffer, or reads the current
setting when omitted.

```nupp
local encodeKeepBuffer: function(keep: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `keep` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether the internal buffer is retained |

<a id="nupp.data.encodeMaxDepth"></a>
### `encodeMaxDepth` _function_

Sets the maximum nested-container depth accepted by the encoder, or reads
the current limit when omitted.

```nupp
local encodeMaxDepth: function(depth: integer?): integer
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `depth` | `integer?` | the new maximum depth |

#### Returns

| Type | Description |
| --- | --- |
| `integer` | the current maximum depth |

<a id="nupp.data.encodeNumberPrecision"></a>
### `encodeNumberPrecision` _function_

Sets the significant-digit precision used to encode numbers, or reads the
current precision when omitted.

```nupp
local encodeNumberPrecision: function(precision: integer?): integer
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `precision` | `integer?` | the new number of significant digits |

#### Returns

| Type | Description |
| --- | --- |
| `integer` | the current precision |

<a id="nupp.data.encodeSkipUnsupportedValueTypes"></a>
### `encodeSkipUnsupportedValueTypes` _function_

Sets whether unsupported values are skipped instead of raising, or reads the
current setting when omitted.

```nupp
local encodeSkipUnsupportedValueTypes: function(setting: boolean | string?): boolean
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `setting` | `boolean | string?` | the new setting |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether unsupported values are skipped |

<a id="nupp.data.encodeSparseArray"></a>
### `encodeSparseArray` _function_

Configures how excessively sparse arrays are encoded, or reads the current
settings when every argument is omitted.

```nupp
local encodeSparseArray: function(convert: boolean?, ratio: integer?, safe: integer?): (boolean, integer, integer)
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `convert` | `boolean?` | whether sparse arrays become JSON objects instead of raising |
| `ratio` | `integer?` | the maximum ratio between the highest index and item count |
| `safe` | `integer?` | the array size below which sparsity is always accepted |

#### Returns

| Type | Description |
| --- | --- |
| `boolean` | whether sparse arrays are converted |
| `integer` | the current ratio limit |
| `integer` | the current safe size |

<a id="nupp.data.fnv1a64"></a>
### `fnv1a64` _function_

Computes the 64-bit FNV-1a digest of bytes.

```nupp
local fnv1a64: function(value: string | nupp.io.ByteView): string
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `string | nupp.io.ByteView` | the bytes to hash |

#### Returns

| Type | Description |
| --- | --- |
| `string` | the lowercase hexadecimal digest |

<a id="nupp.data.sha256"></a>
### `sha256` _function_

Computes the SHA-256 digest of bytes.

```nupp
local sha256: function(value: string | nupp.io.ByteView): string
```

#### Arguments

| Name | Type | Description |
| --- | --- | --- |
| `value` | `string | nupp.io.ByteView` | the bytes to hash |

#### Returns

| Type | Description |
| --- | --- |
| `string` | the lowercase hexadecimal digest |

<a id="nupp.data.uuid4"></a>
### `uuid4` _function_

Generates a random version 4 UUID.

```nupp
local uuid4: function(): string
```

#### Returns

| Type | Description |
| --- | --- |
| `string` | the canonical lowercase UUID text |

<a id="nupp.data.uuid7"></a>
### `uuid7` _function_

Generates a time-ordered version 7 UUID.

```nupp
local uuid7: function(): string
```

#### Returns

| Type | Description |
| --- | --- |
| `string` | the canonical lowercase UUID text |

## Values

<a id="nupp.data.arrayMt"></a>
### `arrayMt` _variable_

Metatable marking a table to encode as a JSON array.

```nupp
local arrayMt: metatable<{any}>
```

<a id="nupp.data.emptyArray"></a>
### `emptyArray` _variable_

Sentinel that always encodes as an empty JSON array.

```nupp
local emptyArray: any
```

<a id="nupp.data.emptyArrayMt"></a>
### `emptyArrayMt` _variable_

Metatable marking a table to encode as an empty JSON array.

```nupp
local emptyArrayMt: metatable<{any}>
```

<a id="nupp.data.null"></a>
### `null` _variable_

Sentinel that decodes from and encodes as JSON null.

```nupp
local null: any
```