scovich commented on code in PR #8031:
URL: https://github.com/apache/arrow-rs/pull/8031#discussion_r2673509425
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parquet-variant/src/builder/object.rs:
##########
@@ -24,14 +24,50 @@ use crate::{
use arrow_schema::ArrowError;
use indexmap::IndexMap;
-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)
+fn object_header<const LARGE_BIT: u8, const ID_SIZE: u8, const OFFSET_SIZE:
u8>() -> u8 {
+ (LARGE_BIT << (BASIC_TYPE_BITS + 4))
+ | ((ID_SIZE - 1) << (BASIC_TYPE_BITS + 2))
+ | ((OFFSET_SIZE - 1) << BASIC_TYPE_BITS)
| VariantBasicType::Object as u8
}
+struct ObjectHeaderWriter<const OFFSET_SIZE: u8, const ID_SIZE: u8>();
+
+impl<const OFFSET_SIZE: u8, const ID_SIZE: u8> ObjectHeaderWriter<OFFSET_SIZE,
ID_SIZE> {
+ fn write(
+ dst: &mut Vec<u8>,
+ num_fields: usize,
+ field_ids: impl Iterator<Item = u32>,
+ offsets: impl Iterator<Item = usize>,
+ data_size: usize,
+ ) {
+ let is_large = num_fields > u8::MAX as usize;
+ // num_fields will consume 4 bytes when it is larger than u8::MAX
+ if is_large {
Review Comment:
nit: I'm not sure `is_large` as a val is really helpful -- if field count is
too large to fit in a byte, of course it will need more bytes to store? (but
definitely a matter of preference)
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