44 lines
1.3 KiB
Rust
44 lines
1.3 KiB
Rust
mod builder;
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mod iterator;
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pub use builder::BlockBuilder;
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use bytes::{Buf, BufMut, Bytes};
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pub use iterator::BlockIterator;
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pub(crate) const SIZEOF_U16: usize = std::mem::size_of::<u16>();
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/// A block is the smallest unit of read and caching in LSM tree. It is a collection of sorted
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/// key-value pairs.
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pub struct Block {
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pub(crate) data: Vec<u8>,
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pub(crate) offsets: Vec<u16>,
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}
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impl Block {
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pub fn encode(&self) -> Bytes {
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let mut buf = self.data.clone();
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let offsets_len = self.offsets.len();
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for offset in &self.offsets {
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buf.put_u16(*offset);
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}
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// Adds number of elements at the end of the block
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buf.put_u16(offsets_len as u16);
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buf.into()
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}
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pub fn decode(data: &[u8]) -> Self {
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// get number of elements in the block
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let entry_offsets_len = (&data[data.len() - SIZEOF_U16..]).get_u16() as usize;
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let data_end = data.len() - SIZEOF_U16 - entry_offsets_len * SIZEOF_U16;
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let offsets_raw = &data[data_end..data.len() - SIZEOF_U16];
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// get offset array
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let offsets = offsets_raw
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.chunks(SIZEOF_U16)
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.map(|mut x| x.get_u16())
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.collect();
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// retrieve data
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let data = data[0..data_end].to_vec();
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Self { data, offsets }
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}
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}
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