From 7b84f3676b37a85e84b1364e5252283b16f4cb8b Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jan@jantuomi.fi>
Date: Wed, 2 Oct 2024 12:26:20 +0300
Subject: Refactor modules

---
 src/lib.rs | 129 +++----------------------------------------------------------
 1 file changed, 5 insertions(+), 124 deletions(-)

(limited to 'src/lib.rs')

diff --git a/src/lib.rs b/src/lib.rs
index 3aae5fb..4afeb4c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,17 +3,18 @@ extern crate log;
 extern crate rev_buf_reader;
 
 mod common;
+mod log_reader;
 mod primary_memtable;
 mod secondary_memtable;
 
 pub use common::*;
 use fs2::FileExt;
+pub use log_reader::LogReader;
 use primary_memtable::PrimaryMemtable;
-use rev_buf_reader::RevBufReader;
 use secondary_memtable::SecondaryMemtable;
 use std::fmt::Debug;
 use std::fs::{self};
-use std::io::{self, BufRead, Read, Seek, Write};
+use std::io::{self, Write};
 use std::path::{Path, PathBuf};
 
 pub struct ConfigBuilder<'a, Field: Eq + Clone + Debug> {
@@ -130,18 +131,11 @@ struct Config<Field: Eq + Clone> {
     pub memtable_evict_policy: MemtableEvictPolicy,
 }
 
-trait Memtable<Field: Eq + Clone + Debug, T: Debug> {
-    fn field(&self) -> &Field;
-    fn new(field: &Field, capacity: usize, evict_policy: MemtableEvictPolicy) -> Self;
-    fn set(&mut self, key: &IndexableValue, value: &T);
-    fn get(&mut self, key: &IndexableValue) -> Option<&T>;
-}
-
 pub struct DB<Field: Eq + Clone + Debug> {
     config: Config<Field>,
     log_path: PathBuf,
     primary_key_index: usize,
-    primary_memtable: PrimaryMemtable<Field>,
+    primary_memtable: PrimaryMemtable,
     secondary_memtables: Vec<SecondaryMemtable<Field>>,
 }
 
@@ -204,7 +198,6 @@ impl<Field: Eq + Clone + Debug> DB<Field> {
             }
         }
         let primary_memtable = PrimaryMemtable::new(
-            &config.primary_key,
             config.memtable_capacity,
             config.memtable_evict_policy.clone(),
         );
@@ -473,8 +466,7 @@ impl<Field: Eq + Clone + Debug> DB<Field> {
 
         debug!("Lock acquired, searching log file for record");
 
-        let mut log_reader = LogReader::new(&mut file)?;
-        let result = log_reader
+        let result = LogReader::new(&mut file)?
             .filter(|record| {
                 let record_key = record.values[key_index]
                     .as_indexable()
@@ -499,114 +491,3 @@ impl<Field: Eq + Clone + Debug> DB<Field> {
         Ok(result)
     }
 }
-
-#[derive(Debug, Eq, PartialEq)]
-enum SpecialSequence {
-    RecordSeparator,
-    LiteralFieldSeparator,
-    LiteralEscape,
-}
-
-pub struct LogReader<'a> {
-    rev_reader: RevBufReader<&'a mut fs::File>,
-}
-
-impl<'a> LogReader<'a> {
-    pub fn new(file: &mut fs::File) -> Result<LogReader, io::Error> {
-        let rev_reader = RevBufReader::new(file);
-        Ok(LogReader { rev_reader })
-    }
-
-    fn read_record(&mut self) -> Result<Option<Record>, io::Error> {
-        if self.rev_reader.stream_position()? == 0 {
-            return Ok(None);
-        }
-
-        // Check that the record starts with the record separator
-        if self.read_special_sequence()? != SpecialSequence::RecordSeparator {
-            return Err(io::Error::new(
-                io::ErrorKind::InvalidData,
-                "Record candidate does not end with record separator",
-            ));
-        }
-
-        // The buffer that stores all the bytes of the record read so far in reverse order.
-        let mut result_buf: Vec<u8> = Vec::new();
-        // The buffer that stores the bytes read from the file.
-        let mut read_buf: Vec<u8> = Vec::new();
-
-        loop {
-            read_buf.clear();
-            self.rev_reader
-                .read_until(ESCAPE_CHARACTER, &mut read_buf)?;
-
-            result_buf.extend(read_buf.iter().rev());
-
-            if self.rev_reader.stream_position()? == 0 {
-                // If we've reached the beginning of the file, we've read the entire record.
-                break;
-            }
-
-            // Otherwise, we must have encountered an escape character.
-            match self.read_special_sequence()? {
-                SpecialSequence::RecordSeparator => {
-                    // The record is complete, so we can break out of the loop.
-                    // Move the cursor back to the beginning of the special sequence.
-                    self.rev_reader.seek_relative(3)?;
-                    break;
-                }
-                SpecialSequence::LiteralFieldSeparator => {
-                    // The field separator is escaped, so we need to add it to the result buffer.
-                    result_buf.push(FIELD_SEPARATOR);
-                }
-                SpecialSequence::LiteralEscape => {
-                    // The escape character is escaped, so we need to add it to the result buffer.
-                    result_buf.push(ESCAPE_CHARACTER);
-                }
-            }
-        }
-
-        result_buf.reverse();
-        let record = Record::deserialize(&result_buf);
-        Ok(Some(record))
-    }
-
-    fn read_special_sequence(&mut self) -> Result<SpecialSequence, io::Error> {
-        let mut special_buf: Vec<u8> = vec![0; 3];
-        self.rev_reader.read_exact(&mut special_buf)?;
-
-        match validate_special(&special_buf.as_slice()) {
-            Some(special) => Ok(special),
-            None => Err(io::Error::new(
-                io::ErrorKind::InvalidData,
-                "Not a special sequence",
-            )),
-        }
-    }
-}
-
-impl Iterator for LogReader<'_> {
-    type Item = Record;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self.read_record() {
-            Ok(Some(record)) => Some(record),
-            Ok(None) => None,
-            Err(err) => panic!("Error reading record: {:?}", err),
-        }
-    }
-}
-
-/// There are three special characters that need to be handled:
-/// Here: SC = escape char, FS = field separator.
-/// - FS FS SC  -> actual record separator
-/// - SC FS SC  -> literal FS
-/// - SC SC SC  -> literal SC
-fn validate_special(buf: &[u8]) -> Option<SpecialSequence> {
-    match buf {
-        SEQ_RECORD_SEP => Some(SpecialSequence::RecordSeparator),
-        SEQ_LIT_FIELD_SEP => Some(SpecialSequence::LiteralFieldSeparator),
-        SEQ_LIT_ESCAPE => Some(SpecialSequence::LiteralEscape),
-        _ => None,
-    }
-}
-- 
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