48 lines
1.4 KiB
Rust
48 lines
1.4 KiB
Rust
use std::borrow::Cow;
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use std::convert::{TryFrom, TryInto};
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use std::mem::size_of;
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use std::str;
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use crate::TreeLevel;
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pub struct StrLevelPositionCodec;
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impl<'a> heed::BytesDecode<'a> for StrLevelPositionCodec {
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type DItem = (&'a str, TreeLevel, u32, u32);
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fn bytes_decode(bytes: &'a [u8]) -> Option<Self::DItem> {
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let footer_len = size_of::<u8>() + size_of::<u32>() * 2;
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if bytes.len() < footer_len {
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return None;
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}
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let (word, bytes) = bytes.split_at(bytes.len() - footer_len);
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let word = str::from_utf8(word).ok()?;
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let (level, bytes) = bytes.split_first()?;
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let left = bytes[..4].try_into().map(u32::from_be_bytes).ok()?;
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let right = bytes[4..].try_into().map(u32::from_be_bytes).ok()?;
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let level = TreeLevel::try_from(*level).ok()?;
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Some((word, level, left, right))
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}
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}
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impl<'a> heed::BytesEncode<'a> for StrLevelPositionCodec {
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type EItem = (&'a str, TreeLevel, u32, u32);
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fn bytes_encode((word, level, left, right): &Self::EItem) -> Option<Cow<[u8]>> {
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let left = left.to_be_bytes();
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let right = right.to_be_bytes();
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let mut bytes = Vec::with_capacity(word.len() + 1 + left.len() + right.len());
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bytes.extend_from_slice(word.as_bytes());
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bytes.push((*level).into());
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bytes.extend_from_slice(&left[..]);
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bytes.extend_from_slice(&right[..]);
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Some(Cow::Owned(bytes))
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}
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}
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