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indexedlog: make Index.file optional

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Summary:
This makes it possible to create an Index instance without providing a
file. It's used in later changes.

Reviewed By: xavierd

Differential Revision: D16044035

fbshipit-source-id: e7b52b9cb342cc82567c6583902eecd003ac0949
This commit is contained in:
Jun Wu 2019-07-18 15:04:30 -07:00 committed by Facebook Github Bot
parent 82b6c96907
commit ec4ff4a2d2
1 changed files with 24 additions and 6 deletions
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30
lib/indexedlog/src/index.rs
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@ -66,7 +66,7 @@ use crate::base16::{base16_to_base256, single_hex_to_base16, Base16Iter};
use crate::checksum_table::ChecksumTable;
use crate::errors::{data_error, parameter_error};
use crate::lock::ScopedFileLock;
use crate::utils::mmap_readonly;
use crate::utils::{mmap_empty, mmap_readonly};
use byteorder::{ByteOrder, LittleEndian, WriteBytesExt};
use failure::{self, Fallible};
@ -1418,7 +1418,7 @@ impl IterState {
/// non-radix-trees). Though none of them are implemented.
pub struct Index {
// For locking and low-level access.
file: File,
file: Option<File>,
// For efficient and shared random reading.
buf: Mmap,
@ -1617,7 +1617,7 @@ impl OpenOptions {
let key_buf = self.key_buf.clone();
Ok(Index {
file,
file: Some(file),
buf: mmap,
read_only,
root,
@ -1637,8 +1637,13 @@ impl OpenOptions {
impl Index {
/// Return a cloned [`Index`].
pub(crate) fn clone(&self) -> Fallible<Index> {
let file = self.file.duplicate()?;
let mmap = mmap_readonly(&file, Some(self.len))?.0;
let (file, mmap) = match &self.file {
Some(f) => (Some(f.duplicate()?), mmap_readonly(&f, Some(self.len))?.0),
None => {
assert_eq!(self.len, 0);
(None, mmap_empty()?)
}
};
let checksum = match self.checksum {
Some(ref table) => Some(table.clone()?),
None => None,
@ -1701,6 +1706,19 @@ impl Index {
let err: io::Error = io::ErrorKind::PermissionDenied.into();
return Err(err.into());
}
if self.file.is_none() {
// Why is this Ok, not Err?
//
// An in-memory Index does not share data with anybody else,
// therefore no need to flush. In other words, whether flush
// happens or not does not change the result of other APIs on
// this Index instance.
//
// Another way to think about it, an in-memory Index is similar
// to a private anonymous mmap, and msync on that mmap would
// succeed.
return Ok(0);
}
let mut new_len = self.len;
if !self.root.radix_offset.is_dirty() {
@ -1712,7 +1730,7 @@ impl Index {
{
let mut offset_map = OffsetMap::empty_for_index(self);
let estimated_dirty_bytes = self.dirty_links.len() * 50;
let mut lock = ScopedFileLock::new(&mut self.file, true)?;
let mut lock = ScopedFileLock::new(self.file.as_mut().unwrap(), true)?;
let len = lock.as_mut().seek(SeekFrom::End(0))?;
let mut buf = Vec::with_capacity(estimated_dirty_bytes);