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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use crate::decoder::{VariantBasicType, VariantPrimitiveType};
use crate::{
ShortString, Variant, VariantDecimal16, VariantDecimal4, VariantDecimal8, VariantList,
VariantMetadata, VariantObject,
};
use arrow_schema::ArrowError;
use chrono::Timelike;
use indexmap::{IndexMap, IndexSet};
use std::collections::HashSet;
const BASIC_TYPE_BITS: u8 = 2;
const UNIX_EPOCH_DATE: chrono::NaiveDate = chrono::NaiveDate::from_ymd_opt(1970, 1, 1).unwrap();
fn primitive_header(primitive_type: VariantPrimitiveType) -> u8 {
(primitive_type as u8) << 2 | VariantBasicType::Primitive as u8
}
fn short_string_header(len: usize) -> u8 {
(len as u8) << 2 | VariantBasicType::ShortString as u8
}
fn array_header(large: bool, offset_size: u8) -> u8 {
let large_bit = if large { 1 } else { 0 };
(large_bit << (BASIC_TYPE_BITS + 2))
| ((offset_size - 1) << BASIC_TYPE_BITS)
| VariantBasicType::Array as u8
}
fn object_header(large: bool, id_size: u8, offset_size: u8) -> u8 {
let large_bit = if large { 1 } else { 0 };
(large_bit << (BASIC_TYPE_BITS + 4))
| ((id_size - 1) << (BASIC_TYPE_BITS + 2))
| ((offset_size - 1) << BASIC_TYPE_BITS)
| VariantBasicType::Object as u8
}
fn int_size(v: usize) -> u8 {
match v {
0..=0xFF => 1,
0x100..=0xFFFF => 2,
0x10000..=0xFFFFFF => 3,
_ => 4,
}
}
/// Write little-endian integer to buffer
fn write_offset(buf: &mut Vec<u8>, value: usize, nbytes: u8) {
let bytes = value.to_le_bytes();
buf.extend_from_slice(&bytes[..nbytes as usize]);
}
/// Write little-endian integer to buffer at a specific position
fn write_offset_at_pos(buf: &mut [u8], start_pos: usize, value: usize, nbytes: u8) {
let bytes = value.to_le_bytes();
buf[start_pos..start_pos + nbytes as usize].copy_from_slice(&bytes[..nbytes as usize]);
}
/// Append `value_size` bytes of given `value` into `dest`.
fn append_packed_u32(dest: &mut Vec<u8>, value: u32, value_size: usize) {
let n = dest.len() + value_size;
dest.extend(value.to_le_bytes());
dest.truncate(n);
}
/// Wrapper around a `Vec<u8>` that provides methods for appending
/// primitive values, variant types, and metadata.
///
/// This is used internally by the builders to construct the
/// the `value` field for [`Variant`] values.
///
/// You can reuse an existing `Vec<u8>` by using the `from` impl
#[derive(Debug, Default)]
struct ValueBuffer(Vec<u8>);
impl ValueBuffer {
/// Construct a ValueBuffer that will write to a new underlying `Vec`
fn new() -> Self {
Default::default()
}
}
impl From<Vec<u8>> for ValueBuffer {
fn from(value: Vec<u8>) -> Self {
Self(value)
}
}
impl From<ValueBuffer> for Vec<u8> {
fn from(value_buffer: ValueBuffer) -> Self {
value_buffer.0
}
}
impl ValueBuffer {
fn append_u8(&mut self, term: u8) {
self.0.push(term);
}
fn append_slice(&mut self, other: &[u8]) {
self.0.extend_from_slice(other);
}
fn append_primitive_header(&mut self, primitive_type: VariantPrimitiveType) {
self.0.push(primitive_header(primitive_type));
}
fn into_inner(self) -> Vec<u8> {
self.into()
}
fn inner_mut(&mut self) -> &mut Vec<u8> {
&mut self.0
}
// Variant types below
fn append_null(&mut self) {
self.append_primitive_header(VariantPrimitiveType::Null);
}
fn append_bool(&mut self, value: bool) {
let primitive_type = if value {
VariantPrimitiveType::BooleanTrue
} else {
VariantPrimitiveType::BooleanFalse
};
self.append_primitive_header(primitive_type);
}
fn append_int8(&mut self, value: i8) {
self.append_primitive_header(VariantPrimitiveType::Int8);
self.append_u8(value as u8);
}
fn append_int16(&mut self, value: i16) {
self.append_primitive_header(VariantPrimitiveType::Int16);
self.append_slice(&value.to_le_bytes());
}
fn append_int32(&mut self, value: i32) {
self.append_primitive_header(VariantPrimitiveType::Int32);
self.append_slice(&value.to_le_bytes());
}
fn append_int64(&mut self, value: i64) {
self.append_primitive_header(VariantPrimitiveType::Int64);
self.append_slice(&value.to_le_bytes());
}
fn append_float(&mut self, value: f32) {
self.append_primitive_header(VariantPrimitiveType::Float);
self.append_slice(&value.to_le_bytes());
}
fn append_double(&mut self, value: f64) {
self.append_primitive_header(VariantPrimitiveType::Double);
self.append_slice(&value.to_le_bytes());
}
fn append_date(&mut self, value: chrono::NaiveDate) {
self.append_primitive_header(VariantPrimitiveType::Date);
let days_since_epoch = value.signed_duration_since(UNIX_EPOCH_DATE).num_days() as i32;
self.append_slice(&days_since_epoch.to_le_bytes());
}
fn append_timestamp_micros(&mut self, value: chrono::DateTime<chrono::Utc>) {
self.append_primitive_header(VariantPrimitiveType::TimestampMicros);
let micros = value.timestamp_micros();
self.append_slice(µs.to_le_bytes());
}
fn append_timestamp_ntz_micros(&mut self, value: chrono::NaiveDateTime) {
self.append_primitive_header(VariantPrimitiveType::TimestampNtzMicros);
let micros = value.and_utc().timestamp_micros();
self.append_slice(µs.to_le_bytes());
}
fn append_time_micros(&mut self, value: chrono::NaiveTime) {
self.append_primitive_header(VariantPrimitiveType::Time);
let micros_from_midnight = value.num_seconds_from_midnight() as u64 * 1_000_000
+ value.nanosecond() as u64 / 1_000;
self.append_slice(µs_from_midnight.to_le_bytes());
}
fn append_decimal4(&mut self, decimal4: VariantDecimal4) {
self.append_primitive_header(VariantPrimitiveType::Decimal4);
self.append_u8(decimal4.scale());
self.append_slice(&decimal4.integer().to_le_bytes());
}
fn append_decimal8(&mut self, decimal8: VariantDecimal8) {
self.append_primitive_header(VariantPrimitiveType::Decimal8);
self.append_u8(decimal8.scale());
self.append_slice(&decimal8.integer().to_le_bytes());
}
fn append_decimal16(&mut self, decimal16: VariantDecimal16) {
self.append_primitive_header(VariantPrimitiveType::Decimal16);
self.append_u8(decimal16.scale());
self.append_slice(&decimal16.integer().to_le_bytes());
}
fn append_binary(&mut self, value: &[u8]) {
self.append_primitive_header(VariantPrimitiveType::Binary);
self.append_slice(&(value.len() as u32).to_le_bytes());
self.append_slice(value);
}
fn append_short_string(&mut self, value: ShortString) {
let inner = value.0;
self.append_u8(short_string_header(inner.len()));
self.append_slice(inner.as_bytes());
}
fn append_string(&mut self, value: &str) {
self.append_primitive_header(VariantPrimitiveType::String);
self.append_slice(&(value.len() as u32).to_le_bytes());
self.append_slice(value.as_bytes());
}
fn append_object(&mut self, metadata_builder: &mut MetadataBuilder, obj: VariantObject) {
let mut object_builder = self.new_object(metadata_builder);
for (field_name, value) in obj.iter() {
object_builder.insert(field_name, value);
}
object_builder.finish().unwrap();
}
fn try_append_object(
&mut self,
metadata_builder: &mut MetadataBuilder,
obj: VariantObject,
) -> Result<(), ArrowError> {
let mut object_builder = self.new_object(metadata_builder);
for res in obj.iter_try() {
let (field_name, value) = res?;
object_builder.try_insert(field_name, value)?;
}
object_builder.finish()?;
Ok(())
}
fn append_list(&mut self, metadata_builder: &mut MetadataBuilder, list: VariantList) {
let mut list_builder = self.new_list(metadata_builder);
for value in list.iter() {
list_builder.append_value(value);
}
list_builder.finish();
}
fn try_append_list(
&mut self,
metadata_builder: &mut MetadataBuilder,
list: VariantList,
) -> Result<(), ArrowError> {
let mut list_builder = self.new_list(metadata_builder);
for res in list.iter_try() {
let value = res?;
list_builder.try_append_value(value)?;
}
list_builder.finish();
Ok(())
}
fn offset(&self) -> usize {
self.0.len()
}
fn new_object<'a>(
&'a mut self,
metadata_builder: &'a mut MetadataBuilder,
) -> ObjectBuilder<'a> {
let parent_state = ParentState::Variant {
buffer: self,
metadata_builder,
};
let validate_unique_fields = false;
ObjectBuilder::new(parent_state, validate_unique_fields)
}
fn new_list<'a>(&'a mut self, metadata_builder: &'a mut MetadataBuilder) -> ListBuilder<'a> {
let parent_state = ParentState::Variant {
buffer: self,
metadata_builder,
};
let validate_unique_fields = false;
ListBuilder::new(parent_state, validate_unique_fields)
}
/// Appends a variant to the buffer.
///
/// # Panics
///
/// This method will panic if the variant contains duplicate field names in objects
/// when validation is enabled. For a fallible version, use [`ValueBuffer::try_append_variant`]
fn append_variant<'m, 'd>(
&mut self,
variant: Variant<'m, 'd>,
metadata_builder: &mut MetadataBuilder,
) {
match variant {
Variant::Null => self.append_null(),
Variant::BooleanTrue => self.append_bool(true),
Variant::BooleanFalse => self.append_bool(false),
Variant::Int8(v) => self.append_int8(v),
Variant::Int16(v) => self.append_int16(v),
Variant::Int32(v) => self.append_int32(v),
Variant::Int64(v) => self.append_int64(v),
Variant::Date(v) => self.append_date(v),
Variant::TimestampMicros(v) => self.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => self.append_timestamp_ntz_micros(v),
Variant::Decimal4(decimal4) => self.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => self.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => self.append_decimal16(decimal16),
Variant::Float(v) => self.append_float(v),
Variant::Double(v) => self.append_double(v),
Variant::Binary(v) => self.append_binary(v),
Variant::String(s) => self.append_string(s),
Variant::ShortString(s) => self.append_short_string(s),
Variant::Object(obj) => self.append_object(metadata_builder, obj),
Variant::List(list) => self.append_list(metadata_builder, list),
Variant::Time(v) => self.append_time_micros(v),
}
}
/// Appends a variant to the buffer
fn try_append_variant<'m, 'd>(
&mut self,
variant: Variant<'m, 'd>,
metadata_builder: &mut MetadataBuilder,
) -> Result<(), ArrowError> {
match variant {
Variant::Null => self.append_null(),
Variant::BooleanTrue => self.append_bool(true),
Variant::BooleanFalse => self.append_bool(false),
Variant::Int8(v) => self.append_int8(v),
Variant::Int16(v) => self.append_int16(v),
Variant::Int32(v) => self.append_int32(v),
Variant::Int64(v) => self.append_int64(v),
Variant::Date(v) => self.append_date(v),
Variant::TimestampMicros(v) => self.append_timestamp_micros(v),
Variant::TimestampNtzMicros(v) => self.append_timestamp_ntz_micros(v),
Variant::Decimal4(decimal4) => self.append_decimal4(decimal4),
Variant::Decimal8(decimal8) => self.append_decimal8(decimal8),
Variant::Decimal16(decimal16) => self.append_decimal16(decimal16),
Variant::Float(v) => self.append_float(v),
Variant::Double(v) => self.append_double(v),
Variant::Binary(v) => self.append_binary(v),
Variant::String(s) => self.append_string(s),
Variant::ShortString(s) => self.append_short_string(s),
Variant::Object(obj) => self.try_append_object(metadata_builder, obj)?,
Variant::List(list) => self.try_append_list(metadata_builder, list)?,
Variant::Time(v) => self.append_time_micros(v),
}
Ok(())
}
/// Writes out the header byte for a variant object or list, from the starting position
/// of the buffer, will return the position after this write
fn append_header_start_from_buf_pos(
&mut self,
start_pos: usize, // the start position where the header will be inserted
header_byte: u8,
is_large: bool,
num_fields: usize,
) -> usize {
let buffer = self.inner_mut();
// Write header at the original start position
let mut header_pos = start_pos;
// Write header byte
buffer[header_pos] = header_byte;
header_pos += 1;
// Write number of fields
if is_large {
buffer[header_pos..header_pos + 4].copy_from_slice(&(num_fields as u32).to_le_bytes());
header_pos += 4;
} else {
buffer[header_pos] = num_fields as u8;
header_pos += 1;
}
header_pos
}
/// Writes out the offsets for an array of offsets, including the final offset (data size).
/// from the starting position of the buffer, will return the position after this write
fn append_offset_array_start_from_buf_pos(
&mut self,
start_pos: usize,
offsets: impl IntoIterator<Item = usize>,
data_size: Option<usize>,
nbytes: u8,
) -> usize {
let buf = self.inner_mut();
let mut current_pos = start_pos;
for relative_offset in offsets {
write_offset_at_pos(buf, current_pos, relative_offset, nbytes);
current_pos += nbytes as usize;
}
// Write data_size
if let Some(data_size) = data_size {
// Write data_size at the end of the offsets
write_offset_at_pos(buf, current_pos, data_size, nbytes);
current_pos += nbytes as usize;
}
current_pos
}
}
/// Builder for constructing metadata for [`Variant`] values.
///
/// This is used internally by the [`VariantBuilder`] to construct the metadata
///
/// You can use an existing `Vec<u8>` as the metadata buffer by using the `from` impl.
#[derive(Default, Debug)]
struct MetadataBuilder {
// Field names -- field_ids are assigned in insert order
field_names: IndexSet<String>,
// flag that checks if field names by insertion order are also lexicographically sorted
is_sorted: bool,
/// Output buffer. Metadata is written to the end of this buffer
metadata_buffer: Vec<u8>,
}
/// Create a new MetadataBuilder that will write to the specified metadata buffer
impl From<Vec<u8>> for MetadataBuilder {
fn from(metadata_buffer: Vec<u8>) -> Self {
Self {
metadata_buffer,
..Default::default()
}
}
}
impl MetadataBuilder {
/// Upsert field name to dictionary, return its ID
fn upsert_field_name(&mut self, field_name: &str) -> u32 {
let (id, new_entry) = self.field_names.insert_full(field_name.to_string());
if new_entry {
let n = self.num_field_names();
// Dictionary sort order tracking:
// - An empty dictionary is unsorted (ambiguous in spec but required by interop tests)
// - A single-entry dictionary is trivially sorted
// - Otherwise, an already-sorted dictionary becomes unsorted if the new entry breaks order
self.is_sorted =
n == 1 || self.is_sorted && (self.field_names[n - 2] < self.field_names[n - 1]);
}
id as u32
}
/// Returns the number of field names stored in the metadata builder.
/// Note: this method should be the only place to call `self.field_names.len()`
///
/// # Panics
///
/// If the number of field names exceeds the maximum allowed value for `u32`.
fn num_field_names(&self) -> usize {
let n = self.field_names.len();
assert!(n <= u32::MAX as usize);
n
}
fn field_name(&self, i: usize) -> &str {
&self.field_names[i]
}
fn metadata_size(&self) -> usize {
self.field_names.iter().map(|k| k.len()).sum()
}
fn finish(self) -> Vec<u8> {
let nkeys = self.num_field_names();
// Calculate metadata size
let total_dict_size: usize = self.metadata_size();
let Self {
field_names,
is_sorted,
mut metadata_buffer,
} = self;
// Determine appropriate offset size based on the larger of dict size or total string size
let max_offset = std::cmp::max(total_dict_size, nkeys);
let offset_size = int_size(max_offset);
let offset_start = 1 + offset_size as usize;
let string_start = offset_start + (nkeys + 1) * offset_size as usize;
let metadata_size = string_start + total_dict_size;
metadata_buffer.reserve(metadata_size);
// Write header: version=1, field names are sorted, with calculated offset_size
metadata_buffer.push(0x01 | (is_sorted as u8) << 4 | ((offset_size - 1) << 6));
// Write dictionary size
write_offset(&mut metadata_buffer, nkeys, offset_size);
// Write offsets
let mut cur_offset = 0;
for key in field_names.iter() {
write_offset(&mut metadata_buffer, cur_offset, offset_size);
cur_offset += key.len();
}
// Write final offset
write_offset(&mut metadata_buffer, cur_offset, offset_size);
// Write string data
for key in field_names {
metadata_buffer.extend_from_slice(key.as_bytes());
}
metadata_buffer
}
/// Return the inner buffer, without finalizing any in progress metadata.
pub(crate) fn take_buffer(self) -> Vec<u8> {
self.metadata_buffer
}
}
impl<S: AsRef<str>> FromIterator<S> for MetadataBuilder {
fn from_iter<T: IntoIterator<Item = S>>(iter: T) -> Self {
let mut this = Self::default();
this.extend(iter);
this
}
}
impl<S: AsRef<str>> Extend<S> for MetadataBuilder {
fn extend<T: IntoIterator<Item = S>>(&mut self, iter: T) {
let iter = iter.into_iter();
let (min, _) = iter.size_hint();
self.field_names.reserve(min);
for field_name in iter {
self.upsert_field_name(field_name.as_ref());
}
}
}
/// Tracks information needed to correctly finalize a nested builder, for each parent builder type.
///
/// A child builder has no effect on its parent unless/until its `finalize` method is called, at
/// which point the child appends the new value to the parent. As a (desirable) side effect,
/// creating a parent state instance captures mutable references to a subset of the parent's fields,
/// rendering the parent object completely unusable until the parent state goes out of scope. This
/// ensures that at most one child builder can exist at a time.
///
/// The redundancy in buffer and metadata_builder is because all the references come from the
/// parent, and we cannot "split" a mutable reference across two objects (parent state and the child
/// builder that uses it). So everything has to be here. Rust layout optimizations should treat the
/// variants as a union, so that accessing a `buffer` or `metadata_builder` is branch-free.
enum ParentState<'a> {
Variant {
buffer: &'a mut ValueBuffer,
metadata_builder: &'a mut MetadataBuilder,
},
List {
buffer: &'a mut ValueBuffer,
metadata_builder: &'a mut MetadataBuilder,
parent_value_offset_base: usize,
offsets: &'a mut Vec<usize>,
},
Object {
buffer: &'a mut ValueBuffer,
metadata_builder: &'a mut MetadataBuilder,
fields: &'a mut IndexMap<u32, usize>,
field_name: &'a str,
parent_value_offset_base: usize,
},
}
impl ParentState<'_> {
fn buffer(&mut self) -> &mut ValueBuffer {
match self {
ParentState::Variant { buffer, .. } => buffer,
ParentState::List { buffer, .. } => buffer,
ParentState::Object { buffer, .. } => buffer,
}
}
fn metadata_builder(&mut self) -> &mut MetadataBuilder {
match self {
ParentState::Variant {
metadata_builder, ..
} => metadata_builder,
ParentState::List {
metadata_builder, ..
} => metadata_builder,
ParentState::Object {
metadata_builder, ..
} => metadata_builder,
}
}
// Performs any parent-specific aspects of finishing, after the child has appended all necessary
// bytes to the parent's value buffer. ListBuilder records the new value's starting offset;
// ObjectBuilder associates the new value's starting offset with its field id; VariantBuilder
// doesn't need anything special.
fn finish(&mut self, starting_offset: usize) {
match self {
ParentState::Variant { .. } => (),
ParentState::List {
offsets,
parent_value_offset_base,
..
} => offsets.push(starting_offset - *parent_value_offset_base),
ParentState::Object {
metadata_builder,
fields,
field_name,
parent_value_offset_base,
..
} => {
let field_id = metadata_builder.upsert_field_name(field_name);
let shifted_start_offset = starting_offset - *parent_value_offset_base;
fields.insert(field_id, shifted_start_offset);
}
}
}
/// Return mutable references to the buffer and metadata builder that this
/// parent state is using.
fn buffer_and_metadata_builder(&mut self) -> (&mut ValueBuffer, &mut MetadataBuilder) {
match self {
ParentState::Variant {
buffer,
metadata_builder,
}
| ParentState::List {
buffer,
metadata_builder,
..
}
| ParentState::Object {
buffer,
metadata_builder,
..
} => (buffer, metadata_builder),
}
}
// Return the offset of the underlying buffer at the time of calling this method.
fn buffer_current_offset(&self) -> usize {
match self {
ParentState::Variant { buffer, .. }
| ParentState::Object { buffer, .. }
| ParentState::List { buffer, .. } => buffer.offset(),
}
}
// Return the current index of the undelying metadata buffer at the time of calling this method.
fn metadata_current_offset(&self) -> usize {
match self {
ParentState::Variant {
metadata_builder, ..
}
| ParentState::Object {
metadata_builder, ..
}
| ParentState::List {
metadata_builder, ..
} => metadata_builder.metadata_buffer.len(),
}
}
}
/// Top level builder for [`Variant`] values
///
/// # Example: create a Primitive Int8
/// ```
/// # use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
/// builder.append_value(Variant::Int8(42));
/// // Finish the builder to get the metadata and value
/// let (metadata, value) = builder.finish();
/// // use the Variant API to verify the result
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// assert_eq!(variant, Variant::Int8(42));
/// ```
///
/// # Example: Create a [`Variant::Object`]
///
/// This example shows how to create an object with two fields:
/// ```json
/// {
/// "first_name": "Jiaying",
/// "last_name": "Li"
/// }
/// ```
///
/// ```
/// # use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
/// // Create an object builder that will write fields to the object
/// let mut object_builder = builder.new_object();
/// object_builder.insert("first_name", "Jiaying");
/// object_builder.insert("last_name", "Li");
/// object_builder.finish(); // call finish to finalize the object
/// // Finish the builder to get the metadata and value
/// let (metadata, value) = builder.finish();
/// // use the Variant API to verify the result
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// let variant_object = variant.as_object().unwrap();
/// assert_eq!(
/// variant_object.get("first_name"),
/// Some(Variant::from("Jiaying"))
/// );
/// assert_eq!(
/// variant_object.get("last_name"),
/// Some(Variant::from("Li"))
/// );
/// ```
///
///
/// You can also use the [`ObjectBuilder::with_field`] to add fields to the
/// object
/// ```
/// # use parquet_variant::{Variant, VariantBuilder};
/// // build the same object as above
/// let mut builder = VariantBuilder::new();
/// builder.new_object()
/// .with_field("first_name", "Jiaying")
/// .with_field("last_name", "Li")
/// .finish();
/// let (metadata, value) = builder.finish();
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// let variant_object = variant.as_object().unwrap();
/// assert_eq!(
/// variant_object.get("first_name"),
/// Some(Variant::from("Jiaying"))
/// );
/// assert_eq!(
/// variant_object.get("last_name"),
/// Some(Variant::from("Li"))
/// );
/// ```
/// # Example: Create a [`Variant::List`] (an Array)
///
/// This example shows how to create an array of integers: `[1, 2, 3]`.
/// ```
/// # use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
/// // Create a builder that will write elements to the list
/// let mut list_builder = builder.new_list();
/// list_builder.append_value(1i8);
/// list_builder.append_value(2i8);
/// list_builder.append_value(3i8);
/// // call finish to finalize the list
/// list_builder.finish();
/// // Finish the builder to get the metadata and value
/// let (metadata, value) = builder.finish();
/// // use the Variant API to verify the result
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// let variant_list = variant.as_list().unwrap();
/// // Verify the list contents
/// assert_eq!(variant_list.get(0).unwrap(), Variant::Int8(1));
/// assert_eq!(variant_list.get(1).unwrap(), Variant::Int8(2));
/// assert_eq!(variant_list.get(2).unwrap(), Variant::Int8(3));
/// ```
///
/// You can also use the [`ListBuilder::with_value`] to append values to the
/// list.
/// ```
/// # use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
/// builder.new_list()
/// .with_value(1i8)
/// .with_value(2i8)
/// .with_value(3i8)
/// .finish();
/// let (metadata, value) = builder.finish();
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// let variant_list = variant.as_list().unwrap();
/// assert_eq!(variant_list.get(0).unwrap(), Variant::Int8(1));
/// assert_eq!(variant_list.get(1).unwrap(), Variant::Int8(2));
/// assert_eq!(variant_list.get(2).unwrap(), Variant::Int8(3));
/// ```
///
/// # Example: [`Variant::List`] of [`Variant::Object`]s
///
/// This example shows how to create an list of objects:
/// ```json
/// [
/// {
/// "id": 1,
/// "type": "Cauliflower"
/// },
/// {
/// "id": 2,
/// "type": "Beets"
/// }
/// ]
/// ```
/// ```
/// use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
///
/// // Create a builder that will write elements to the list
/// let mut list_builder = builder.new_list();
///
/// {
/// let mut object_builder = list_builder.new_object();
/// object_builder.insert("id", 1);
/// object_builder.insert("type", "Cauliflower");
/// object_builder.finish();
/// }
///
/// {
/// let mut object_builder = list_builder.new_object();
/// object_builder.insert("id", 2);
/// object_builder.insert("type", "Beets");
/// object_builder.finish();
/// }
///
/// list_builder.finish();
/// // Finish the builder to get the metadata and value
/// let (metadata, value) = builder.finish();
/// // use the Variant API to verify the result
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// let variant_list = variant.as_list().unwrap();
///
///
/// let obj1_variant = variant_list.get(0).unwrap();
/// let obj1 = obj1_variant.as_object().unwrap();
/// assert_eq!(
/// obj1.get("id"),
/// Some(Variant::from(1))
/// );
/// assert_eq!(
/// obj1.get("type"),
/// Some(Variant::from("Cauliflower"))
/// );
///
/// let obj2_variant = variant_list.get(1).unwrap();
/// let obj2 = obj2_variant.as_object().unwrap();
///
/// assert_eq!(
/// obj2.get("id"),
/// Some(Variant::from(2))
/// );
/// assert_eq!(
/// obj2.get("type"),
/// Some(Variant::from("Beets"))
/// );
///
/// ```
/// # Example: Reusing Buffers
///
/// You can use the [`VariantBuilder`] to write into existing buffers (for
/// example to write multiple variants back to back in the same buffer)
///
/// ```
/// // we will write two variants back to back
/// use parquet_variant::{Variant, VariantBuilder};
/// // Append 12345
/// let mut builder = VariantBuilder::new();
/// builder.append_value(12345);
/// let (metadata, value) = builder.finish();
/// // remember where the first variant ends
/// let (first_meta_offset, first_meta_len) = (0, metadata.len());
/// let (first_value_offset, first_value_len) = (0, value.len());
///
/// // now, append a second variant to the same buffers
/// let mut builder = VariantBuilder::new_with_buffers(metadata, value);
/// builder.append_value("Foo");
/// let (metadata, value) = builder.finish();
///
/// // The variants can be referenced in their appropriate location
/// let variant1 = Variant::new(
/// &metadata[first_meta_offset..first_meta_len],
/// &value[first_value_offset..first_value_len]
/// );
/// assert_eq!(variant1, Variant::Int32(12345));
///
/// let variant2 = Variant::new(
/// &metadata[first_meta_len..],
/// &value[first_value_len..]
/// );
/// assert_eq!(variant2, Variant::from("Foo"));
/// ```
///
/// # Example: Unique Field Validation
///
/// This example shows how enabling unique field validation will cause an error
/// if the same field is inserted more than once.
/// ```
/// use parquet_variant::VariantBuilder;
///
/// let mut builder = VariantBuilder::new().with_validate_unique_fields(true);
/// let mut obj = builder.new_object();
///
/// obj.insert("a", 1);
/// obj.insert("a", 2); // duplicate field
///
/// // When validation is enabled, finish will return an error
/// let result = obj.finish(); // returns Err
/// assert!(result.is_err());
/// ```
///
/// # Example: Sorted dictionaries
///
/// This example shows how to create a [`VariantBuilder`] with a pre-sorted field dictionary
/// to improve field access performance when reading [`Variant`] objects.
///
/// You can use [`VariantBuilder::with_field_names`] to add multiple field names at once:
/// ```
/// use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new()
/// .with_field_names(["age", "name", "score"].into_iter());
///
/// let mut obj = builder.new_object();
/// obj.insert("name", "Alice");
/// obj.insert("age", 30);
/// obj.insert("score", 95.5);
/// obj.finish().unwrap();
///
/// let (metadata, value) = builder.finish();
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// ```
///
/// Alternatively, you can use [`VariantBuilder::add_field_name`] to add field names one by one:
/// ```
/// use parquet_variant::{Variant, VariantBuilder};
/// let mut builder = VariantBuilder::new();
/// builder.add_field_name("age"); // field id = 0
/// builder.add_field_name("name"); // field id = 1
/// builder.add_field_name("score"); // field id = 2
///
/// let mut obj = builder.new_object();
/// obj.insert("name", "Bob"); // field id = 3
/// obj.insert("age", 25);
/// obj.insert("score", 88.0);
/// obj.finish().unwrap();
///
/// let (metadata, value) = builder.finish();
/// let variant = Variant::try_new(&metadata, &value).unwrap();
/// ```
#[derive(Default, Debug)]
pub struct VariantBuilder {
buffer: ValueBuffer,
metadata_builder: MetadataBuilder,
validate_unique_fields: bool,
}
impl VariantBuilder {
/// Create a new VariantBuilder with new underlying buffer
pub fn new() -> Self {
Self {
buffer: ValueBuffer::new(),
metadata_builder: MetadataBuilder::default(),
validate_unique_fields: false,
}
}
/// Create a new VariantBuilder with pre-existing [`VariantMetadata`].
pub fn with_metadata(mut self, metadata: VariantMetadata) -> Self {
self.metadata_builder.extend(metadata.iter());
self
}