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//! Writing a table.
use std::cmp::Ordering;
use std::sync::Arc;
use super::block::{BlockBuilder, Compare};
use super::filter::{BloomBuilder, Probing};
use super::handle::{Footer, write_block};
use super::{Compression, TableOptions};
use crate::error::{Error, Result};
use crate::seal::{FileSealer, SealHeader};
/// The properties block's key for the entry count.
pub(super) const ENTRIES_PROPERTY: &[u8] = b"entries";
/// The properties block's key for the handle of the range-delete block, present when the table
/// holds range deletes.
pub(super) const RANGE_DELETES_PROPERTY: &[u8] = b"range_deletes";
/// Builds a table from entries added in strictly increasing key order.
#[derive(Debug)]
pub struct TableBuilder {
options: TableOptions,
compare: Compare,
filter_key: fn(&[u8]) -> &[u8],
/// Finished bytes not yet taken; they follow the `drained` bytes taken before.
out: Vec<u8>,
drained: u64,
data: BlockBuilder,
index: BlockBuilder,
filter: BloomBuilder,
last_key: Vec<u8>,
entries: u64,
range_deletes: BlockBuilder,
last_range_key: Vec<u8>,
sealer: Option<Arc<FileSealer>>,
}
impl TableBuilder {
/// An empty table ordered by `compare`, whose filter holds `filter_key` of each key (the
/// part a point lookup knows exactly, such as the user key of an internal key).
pub fn new(options: TableOptions, compare: Compare, filter_key: fn(&[u8]) -> &[u8]) -> Self {
Self {
options,
compare,
filter_key,
out: Vec::new(),
drained: 0,
data: BlockBuilder::new(options.restart_interval, compare),
index: BlockBuilder::new(1, compare),
filter: BloomBuilder::new(options.bloom_bits_per_key),
last_key: Vec::new(),
entries: 0,
range_deletes: BlockBuilder::new(options.restart_interval, compare),
last_range_key: Vec::new(),
sealer: None,
}
}
/// An empty sealed table, as [`TableBuilder::new`]: the file starts with `header`, and each
/// block and the footer are encrypted by `sealer`, the key `header` derives for a table.
pub fn sealed(
options: TableOptions,
compare: Compare,
filter_key: fn(&[u8]) -> &[u8],
sealer: Arc<FileSealer>,
header: &SealHeader,
) -> Self {
let mut builder = Self::new(options, compare, filter_key);
builder.out.extend_from_slice(&header.encode());
builder.sealer = Some(sealer);
builder
}
/// Appends an entry.
///
/// # Errors
///
/// [`Error::Malformed`] when `key` does not sort after the previous key;
/// [`Error::TooLarge`] for a key or value longer than a u32 length.
pub fn add(&mut self, key: &[u8], value: &[u8]) -> Result<()> {
if self.entries > 0 && (self.compare)(key, &self.last_key) != Ordering::Greater {
return Err(Error::Malformed {
what: "table",
reason: "keys are not strictly increasing",
});
}
if !self.data.is_empty() && self.data.estimated_size() >= self.options.block_bytes {
self.close_data_block()?;
}
self.data.add(key, value)?;
self.filter.add((self.filter_key)(key));
self.last_key.clear();
self.last_key.extend_from_slice(key);
self.entries = self.entries.saturating_add(1);
Ok(())
}
/// Appends a range delete: `key` is where it starts (in the table's key order, as for
/// [`TableBuilder::add`]), `end` where it stops. Range deletes are kept in a block of their
/// own, apart from the entries.
///
/// # Errors
///
/// [`Error::Malformed`] when `key` does not sort after the previous range delete's key;
/// [`Error::TooLarge`] as for [`TableBuilder::add`].
pub fn add_range_delete(&mut self, key: &[u8], end: &[u8]) -> Result<()> {
if !self.range_deletes.is_empty()
&& (self.compare)(key, &self.last_range_key) != Ordering::Greater
{
return Err(Error::Malformed {
what: "table",
reason: "range deletes are not strictly increasing",
});
}
self.range_deletes.add(key, end)?;
self.last_range_key.clear();
self.last_range_key.extend_from_slice(key);
Ok(())
}
/// Entries added so far.
pub fn entries(&self) -> u64 {
self.entries
}
/// Bytes the table would take if finished now, roughly.
pub fn estimated_size(&self) -> usize {
usize::try_from(self.drained)
.unwrap_or(usize::MAX)
.saturating_add(self.out.len())
.saturating_add(self.data.estimated_size())
}
/// The bytes of the table finished so far and not yet taken, which continue the file
/// after the [`TableBuilder::drained`] bytes taken before. A writer that appends each piece
/// as it comes, and finally what [`TableBuilder::finish`] returns, writes the same file as
/// one built whole, while holding only the block being filled and the index and filter.
pub fn take_finished(&mut self) -> Vec<u8> {
let taken = std::mem::take(&mut self.out);
self.drained = self
.drained
.saturating_add(u64::try_from(taken.len()).unwrap_or(u64::MAX));
taken
}
/// Bytes taken so far by [`TableBuilder::take_finished`]: where the next piece, or what
/// [`TableBuilder::finish`] returns, begins in the file.
pub fn drained(&self) -> u64 {
self.drained
}
/// The rest of the table file: all of it when nothing was taken before.
///
/// # Errors
///
/// [`Error::TooLarge`] when a block outgrows the format's length fields.
pub fn finish(mut self) -> Result<Vec<u8>> {
if !self.data.is_empty() {
self.close_data_block()?;
}
let filter = write_block(
&mut self.out,
self.drained,
&self.filter.finish(),
Compression::None,
self.sealer.as_deref(),
)?;
let index = write_block(
&mut self.out,
self.drained,
&self.index.finish(),
Compression::None,
self.sealer.as_deref(),
)?;
let range_deletes = (!self.range_deletes.is_empty()).then(|| {
write_block(
&mut self.out,
self.drained,
&self.range_deletes.finish(),
Compression::None,
self.sealer.as_deref(),
)
});
let range_deletes = range_deletes.transpose()?;
let mut properties = BlockBuilder::new(1, |left, right| left.cmp(right));
properties.add(ENTRIES_PROPERTY, &self.entries.to_le_bytes())?;
if let Some(handle) = range_deletes {
properties.add(RANGE_DELETES_PROPERTY, &handle.encode())?;
}
let properties = write_block(
&mut self.out,
self.drained,
&properties.finish(),
Compression::None,
self.sealer.as_deref(),
)?;
let footer = Footer {
filter,
index,
properties,
probing: Probing::Remixed,
};
let footer = footer.encode();
match &self.sealer {
Some(sealer) => {
let at = self
.drained
.saturating_add(u64::try_from(self.out.len()).unwrap_or(u64::MAX));
self.out.extend_from_slice(&sealer.seal(at, &footer)?);
}
None => self.out.extend_from_slice(&footer),
}
Ok(self.out)
}
/// Writes the current data block and indexes it under its last key.
fn close_data_block(&mut self) -> Result<()> {
let payload = self.data.finish();
let handle = write_block(
&mut self.out,
self.drained,
&payload,
self.options.compression,
self.sealer.as_deref(),
)?;
self.index.add(&self.last_key, &handle.encode())
}
}