From 81eb9ce9299b2e31471db3f00457ff3c1a41fb60 Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Wed, 10 Jun 2020 12:45:25 -0400
Subject: filter out other non-WAL files

---
 Cargo.lock        |  1 +
 Cargo.toml        |  1 +
 examples/demo1.rs |  6 ++++--
 src/wal.rs        | 26 +++++++++++++++++++-------
 4 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 7b26bbc..34e5a1d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -98,6 +98,7 @@ dependencies = [
  "lru",
  "nix",
  "rand",
+ "regex",
  "scan_fmt",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index 1593173..1a60577 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@ edition = "2018"
 crc = "1.8.1"
 lru = "0.5.1"
 scan_fmt = "0.2.5"
+regex = "1"
 
 [dev-dependencies]
 hex = "0.4.2"
diff --git a/examples/demo1.rs b/examples/demo1.rs
index 104c3b0..e0c7d58 100644
--- a/examples/demo1.rs
+++ b/examples/demo1.rs
@@ -87,6 +87,8 @@ impl Drop for WALStoreTest {
 }
 
 impl WALStore for WALStoreTest {
+    type FileNameIter = std::vec::IntoIter<String>;
+
     fn open_file(&self, filename: &str, touch: bool) -> Option<Box<dyn WALFile>> {
         println!("open_file(filename={}, touch={})", filename, touch);
         let filename = filename.to_string();
@@ -98,13 +100,13 @@ impl WALStore for WALStoreTest {
         unlinkat(Some(self.rootfd), filename, UnlinkatFlags::NoRemoveDir).or_else(|_| Err(()))
     }
 
-    fn enumerate_files(&self) -> Box<[String]> {
+    fn enumerate_files(&self) -> Self::FileNameIter {
         println!("enumerate_files()");
         let mut logfiles = Vec::new();
         for fname in std::fs::read_dir(&self.rootpath).unwrap() {
             logfiles.push(fname.unwrap().file_name().into_string().unwrap())
         }
-        logfiles.into_boxed_slice()
+        logfiles.into_iter()
     }
 
     fn apply_payload(&self, payload: WALBytes) {
diff --git a/src/wal.rs b/src/wal.rs
index 05ffd01..0ba35fb 100644
--- a/src/wal.rs
+++ b/src/wal.rs
@@ -55,20 +55,29 @@ pub trait WALFile {
     fn allocate(&self, offset: WALPos, length: usize) -> Result<(), ()>;
     /// Truncate a file to a specified length.
     fn truncate(&self, length: usize) -> Result<(), ()>;
-    /// Write data with offset.
+    /// Write data with offset. We assume the actual writes on the storage medium are _strictly
+    /// ordered_ the same way as this callback is invoked. We also assume all previous
+    /// `allocate/truncate` invocation should be visible if ordered earlier (should be guaranteed
+    /// by most OS).  Additionally, the final write caused by each invocation of this function
+    /// should be _atomic_ (the entire single write should be all or nothing).
     fn write(&self, offset: WALPos, data: WALBytes);
     /// Read data with offset.
     fn read(&self, offset: WALPos, length: usize) -> WALBytes;
 }
 
 pub trait WALStore {
+    type FileNameIter: Iterator<Item = String>;
+
     /// Open a file given the filename, create the file if not exists when `touch` is `true`.
     fn open_file(&self, filename: &str, touch: bool) -> Option<Box<dyn WALFile>>;
     /// Unlink a file given the filename.
     fn remove_file(&self, filename: &str) -> Result<(), ()>;
-    /// Enumerate all WAL files.
-    fn enumerate_files(&self) -> Box<[String]>;
-    /// Apply (redo) the payload during recovery.
+    /// Enumerate all WAL filenames. It should include all WAL files that are previously opened
+    /// (created) but not removed. The list could be unordered.
+    fn enumerate_files(&self) -> Self::FileNameIter;
+    /// Apply the payload during recovery. This notifies the application should redo the given
+    /// operation to ensure its state is consistent (the major goal of having a WAL). We assume
+    /// the application applies the payload by the _order_ of this callback invocation.
     fn apply_payload(&self, payload: WALBytes);
 }
 
@@ -282,19 +291,22 @@ impl<F: WALStore> WALWriter<F> {
 
 pub struct WALLoader<F: WALStore> {
     file_pool: WALFilePool<F>,
+    filename_fmt: regex::Regex
 }
 
 impl<F: WALStore> WALLoader<F> {
     pub fn new(store: F, file_nbit: u8, block_nbit: u8, cache_size: usize) -> Self {
         let file_pool = WALFilePool::new(store, file_nbit, block_nbit, cache_size);
-        WALLoader{ file_pool }
+        let filename_fmt = regex::Regex::new(r"[0-9a-f]+\.log").unwrap();
+        WALLoader{ file_pool, filename_fmt }
     }
 
     pub fn recover(mut self) -> WALWriter<F> {
         let block_size = 1 << self.file_pool.block_nbit;
         let msize = std::mem::size_of::<WALRingBlob>() as u32;
-        let mut logfiles = self.file_pool.store.enumerate_files();
-        // TODO: use regex to filter out invalid files
+        let mut logfiles: Vec<String> = self.file_pool.store
+            .enumerate_files()
+            .filter(|f| self.filename_fmt.is_match(f)).collect();
         // TODO: check for missing logfiles
         logfiles.sort();
         let mut chunks = None;
-- 
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