Implement VersionEdit (#8)

This implements VersionEdit, which holds metadata for a Version in the
DB. A version in LevelDB is like a snapshot which roughly is a
collection of sstable files. This change is a prerequisite towards it.

src/config.rs

@@ -0,0 +1,27 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+pub const NUM_LEVELS: i32 = 7;
+
+/// Level-0 compaction is triggered when we hit this many files.
+pub const L0_COMPACTION_TRIGGER: i32 = 4;
+
+/// Soft limit on number of level-0 files. We slow down writes at this point.
+pub const L0_SLOWDOWN_WRITES_TRIGGER: i32 = 8;
+
+/// Maximum number of level-0 files. We stop writes at this point.
+pub const L0_STOP_WRITES_TRIGGER: i32 = 12;

src/dbformat.rs

@@ -17,6 +17,7 @@
 
 use std::cmp::Ordering;
 use std::convert::TryFrom;
+use std::fmt::{Debug, Display, Formatter, Result as DebugResult};
 use std::rc::Rc;
 
 use slice::Slice;
@@ -35,6 +36,15 @@ pub enum ValueType {
  VALUE = 0x1
 }
 
+impl Display for ValueType {
+ fn fmt(&self, f: &mut Formatter) -> DebugResult {
+ match self {
+ &ValueType::DELETION => write!(f, "ValueType::Deletion"),
+ &ValueType::VALUE => write!(f, "ValueType::Value")
+ }
+ }
+}
+
 impl TryFrom<u8> for ValueType {
  type Error = super::result::Error;
  fn try_from(v: u8) -> Result<ValueType> {
@@ -213,6 +223,29 @@ impl InternalKey {
  }
 }
 
+impl Debug for InternalKey {
+ fn fmt(&self, f: &mut Formatter) -> DebugResult {
+ if let Ok(parsed) = ParsedInternalKey::try_from(&self.rep) {
+ write!(f, "{:?}", parsed)
+ } else {
+ let s = unsafe {
+ ::std::str::from_utf8_unchecked(&self.rep[..])
+ };
+ write!(f, "(bad){}", s)
+ }
+ }
+}
+
+impl<'a> From<&'a Slice> for InternalKey {
+ fn from(s: &'a Slice) -> InternalKey {
+ let mut v = Vec::new();
+ v.extend_from_slice(s.data());
+ InternalKey {
+ rep: v
+ }
+ }
+}
+
 fn append_internal_key(result: &mut Vec<u8>, key: &ParsedInternalKey) {
  result.extend_from_slice(&key.user_key.data());
  let key_len = result.len();
@@ -250,6 +283,13 @@ impl ParsedInternalKey {
  }
 }
 
+impl Debug for ParsedInternalKey {
+ fn fmt(&self, f: &mut Formatter) -> DebugResult {
+ write!(f, "'{}' @ {} : {}", self.user_key.as_str(), self.seqno, self.value_type)
+ }
+}
+
+
 impl<'a> TryFrom<&'a Slice> for ParsedInternalKey {
  type Error = super::result::Error;
 
@@ -266,6 +306,14 @@ impl<'a> TryFrom<&'a Slice> for ParsedInternalKey {
  }
 }
 
+impl<'a> TryFrom<&'a Vec<u8>> for ParsedInternalKey {
+ type Error = super::result::Error;
+
+ fn try_from(s: &Vec<u8>) -> Result<ParsedInternalKey> {
+ ParsedInternalKey::try_from(&Slice::from(s))
+ }
+}
+
 #[cfg(test)]
 mod tests {
  use super::*;

src/lib.rs

@@ -35,10 +35,12 @@ pub mod result;
 pub mod slice;
 pub mod comparator;
 pub mod dbformat;
+pub mod config;
 pub mod skiplist;
 pub mod iterator;
 pub mod memtable;
 pub mod write_batch;
 pub mod log_format;
 pub mod log_writer;
 pub mod log_reader;
+pub mod version_edit;

src/slice.rs

@@ -141,6 +141,13 @@ impl<'a> From<&'a [u8]> for Slice {
  }
 }
 
+impl<'a> From<&'a Vec<u8>> for Slice {
+ #[inline]
+ fn from(v: &'a Vec<u8>) -> Self {
+ Slice::new(v[..].as_ptr(), v.len())
+ }
+}
+
 impl<'a> From<&'a str> for Slice {
  #[inline]
  fn from(s: &'a str) -> Self {