48 lines
1.5 KiB
Rust
48 lines
1.5 KiB
Rust
//! Opaque row identifiers.
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//!
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//! Each backend assigns its own bytes for a [`RowId`]; the trait treats them
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//! opaquely. The in-memory backend and the KV backends use a big-endian `u64`
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//! row counter; the geomerge backend encodes its `(CommitHash, counter)`
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//! pair. Callers do not interpret the bytes: they hand a `RowId` back to the
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//! same backend to reference an existing row.
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//!
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//! Storage is inline up to 36 bytes (the geomerge `(CommitHash, counter)`
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//! width), which covers every encoding the workspace produces today. Wider
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//! row-id encodings spill to the heap automatically via [`SmallVec`].
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use smallvec::SmallVec;
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const INLINE_BYTES: usize = 36;
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#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
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pub struct RowId(SmallVec<[u8; INLINE_BYTES]>);
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impl RowId {
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/// Build a row id by copying the given bytes into inline storage when they
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/// fit (≤ 36 bytes) or onto the heap when they don't.
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pub fn new(bytes: impl AsRef<[u8]>) -> Self {
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Self(SmallVec::from_slice(bytes.as_ref()))
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}
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/// View the underlying bytes.
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#[must_use]
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pub fn as_bytes(&self) -> &[u8] {
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&self.0
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}
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}
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impl std::fmt::Display for RowId {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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for byte in &self.0 {
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write!(f, "{byte:02x}")?;
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}
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Ok(())
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}
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}
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impl From<u64> for RowId {
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fn from(value: u64) -> Self {
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Self(SmallVec::from_slice(&value.to_be_bytes()))
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}
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}
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