# parquet.convert

> A module of parquet's API.

Physical Parquet values to Arrow buffers.

A Parquet leaf's physical type and its Arrow type are often different widths:
an `INT32` annotated `Int(8, true)` is one byte in Arrow, a `DECIMAL` over
`FIXED_LEN_BYTE_ARRAY(7)` is a sign-extended little-endian 16-byte integer, and
`INT96` is a nanosecond timestamp built from a Julian day and a time of day.
`append_value` and `append_null` do that translation one value at a time,
straight into the destination `ArrayData`'s buffers.

## Functions

### `int96_to_nanos`

```mojo
def int96_to_nanos(src: Span[UInt8]) -> Int64
```

`INT96`: 8 little-endian bytes of nanoseconds within the day, then a little-endian Julian day number.

### `append_null`

```mojo
def append_null(mut out: ArrayData, leaf: LeafColumn)
```

Append a null slot, keeping every buffer the right length.

Validity is the caller's business — `parquet.assemble` maintains it, and
only materialises a bitmap once a null actually turns up.

### `append_value`

```mojo
def append_value(mut out: ArrayData, leaf: LeafColumn, vals: PhysBuffer, vi: Int)
```

Append value `vi` of `vals`, translated to `out`'s Arrow type.

## Aliases

### `JULIAN_UNIX_EPOCH`

```mojo
comptime JULIAN_UNIX_EPOCH = 2440588
```

### `NANOS_PER_DAY`

```mojo
comptime NANOS_PER_DAY = 86400000000000
```