format with rustfmt

5 files changed, 419 insertions, 197 deletions

diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000..768d2e3
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1,8 @@
+edition = "2018"
+unstable_features = true
+max_width = 80
+binop_separator = "Back"
+inline_attribute_width = 80
+fn_params_layout = "Compressed"
+hard_tabs = false
+tab_spaces = 4
diff --git a/src/lib.rs b/src/lib.rs
index 7635dab..1db80e8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,2 +1,3 @@
-#[macro_use] extern crate scan_fmt;
+#[macro_use]
+extern crate scan_fmt;
 pub mod wal;
diff --git a/src/wal.rs b/src/wal.rs
index fe85c41..39c4390 100644
--- a/src/wal.rs
+++ b/src/wal.rs
@@ -7,7 +7,7 @@ enum WALRingType {
     Full,
     First,
     Middle,
-    Last
+    Last,
 }
 
 #[repr(packed)]
@@ -25,18 +25,27 @@ pub type WALPos = u64;
 #[derive(Eq, PartialEq, Copy, Clone, Debug, Hash)]
 pub struct WALRingId {
     start: WALPos,
-    end: WALPos
+    end: WALPos,
 }
 
 impl WALRingId {
-    pub fn empty_id() -> Self { WALRingId { start: 0, end: 0 } }
-    pub fn get_start(&self) -> WALPos { self.start }
-    pub fn get_end(&self) -> WALPos { self.end }
+    pub fn empty_id() -> Self {
+        WALRingId { start: 0, end: 0 }
+    }
+    pub fn get_start(&self) -> WALPos {
+        self.start
+    }
+    pub fn get_end(&self) -> WALPos {
+        self.end
+    }
 }
 
 impl Ord for WALRingId {
     fn cmp(&self, other: &WALRingId) -> std::cmp::Ordering {
-        other.start.cmp(&self.start).then_with(|| other.end.cmp(&self.end))
+        other
+            .start
+            .cmp(&self.start)
+            .then_with(|| other.end.cmp(&self.end))
     }
 }
 
@@ -68,14 +77,22 @@ pub trait WALFile {
     /// should be _atomic_ (the entire single write should be all or nothing).
     fn write(&self, offset: WALPos, data: WALBytes) -> Result<(), ()>;
     /// Read data with offset.
-    fn read(&self, offset: WALPos, length: usize) -> Result<Option<WALBytes>, ()>;
+    fn read(
+        &self,
+        offset: WALPos,
+        length: usize,
+    ) -> Result<Option<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(&mut self, filename: &str, touch: bool) -> Result<Box<dyn WALFile>, ()>;
+    fn open_file(
+        &mut self,
+        filename: &str,
+        touch: bool,
+    ) -> Result<Box<dyn WALFile>, ()>;
     /// Unlink a file given the filename.
     fn remove_file(&mut self, filename: &str) -> Result<(), ()>;
     /// Enumerate all WAL filenames. It should include all WAL files that are previously opened
@@ -84,7 +101,11 @@ pub trait WALStore {
     /// Apply the payload during recovery. An invocation of the callback waits the application for
     /// redoing the given operation to ensure its state is consistent. We assume the necessary
     /// changes by the payload has already been persistent when the callback returns.
-    fn apply_payload(&mut self, payload: WALBytes, ringid: WALRingId) -> Result<(), ()>;
+    fn apply_payload(
+        &mut self,
+        payload: WALBytes,
+        ringid: WALRingId,
+    ) -> Result<(), ()>;
 }
 
 /// The middle layer that manages WAL file handles and invokes public trait functions to actually
@@ -114,15 +135,22 @@ impl<F: WALStore> WALFilePool<F> {
         format!("{:08x}.log", fid)
     }
 
-    fn get_file(&mut self, fid: u64, touch: bool) -> Result<&'static dyn WALFile, ()> {
+    fn get_file(
+        &mut self,
+        fid: u64,
+        touch: bool,
+    ) -> Result<&'static dyn WALFile, ()> {
         let h = match self.handles.get(&fid) {
             Some(h) => &**h,
             None => {
-                self.handles.put(fid, self.store.open_file(&Self::get_fname(fid), touch)?);
+                self.handles.put(
+                    fid,
+                    self.store.open_file(&Self::get_fname(fid), touch)?,
+                );
                 &**self.handles.get(&fid).unwrap()
             }
         };
-        Ok(unsafe {&*(h as *const dyn WALFile)})
+        Ok(unsafe { &*(h as *const dyn WALFile) })
     }
 
     fn get_fid(&mut self, fname: &str) -> WALFileId {
@@ -135,14 +163,19 @@ impl<F: WALStore> WALFilePool<F> {
         let mut fid = writes[0].0 >> self.file_nbit;
         let mut alloc_start = writes[0].0 & (self.file_size - 1);
         let mut alloc_end = alloc_start + writes[0].1.len() as u64;
-        let files = writes.iter().map(|(off, _)|
-            self.get_file((*off) >> self.file_nbit, true)).collect::<Result<Vec<&dyn WALFile>, ()>>()?;
+        let files = writes
+            .iter()
+            .map(|(off, _)| self.get_file((*off) >> self.file_nbit, true))
+            .collect::<Result<Vec<&dyn WALFile>, ()>>()?;
         // prepare file handles
         let mut last_h = files[0];
         for ((off, w), h) in writes[1..].iter().zip(files[1..].iter()) {
             let next_fid = off >> self.file_nbit;
             if next_fid != fid {
-                last_h.allocate(alloc_start, (alloc_end - alloc_start) as usize)?;
+                last_h.allocate(
+                    alloc_start,
+                    (alloc_end - alloc_start) as usize,
+                )?;
                 last_h = *h;
                 alloc_start = 0;
                 alloc_end = alloc_start + w.len() as u64;
@@ -153,7 +186,8 @@ impl<F: WALStore> WALFilePool<F> {
         }
         last_h.allocate(alloc_start, (alloc_end - alloc_start) as usize)?;
         for (off, w) in writes.into_iter() {
-            self.get_file(off >> self.file_nbit, true)?.write(off & (self.file_size - 1), w)?;
+            self.get_file(off >> self.file_nbit, true)?
+                .write(off & (self.file_size - 1), w)?;
         }
         Ok(())
     }
@@ -162,7 +196,9 @@ impl<F: WALStore> WALFilePool<F> {
         self.store.remove_file(&Self::get_fname(fid))
     }
 
-    fn reset(&mut self) { self.handles.clear() }
+    fn reset(&mut self) {
+        self.handles.clear()
+    }
 }
 
 pub struct WALWriter<F: WALStore> {
@@ -172,7 +208,7 @@ pub struct WALWriter<F: WALStore> {
     block_size: u32,
     next_complete: WALPos,
     io_complete: BinaryHeap<WALRingId>,
-    msize: usize
+    msize: usize,
 }
 
 impl<F: WALStore> WALWriter<F> {
@@ -181,21 +217,24 @@ impl<F: WALStore> WALWriter<F> {
         let block_size = 1 << file_pool.block_nbit as u32;
         let msize = std::mem::size_of::<WALRingBlob>();
         b.resize(block_size as usize, 0);
-        WALWriter{
+        WALWriter {
             state,
             file_pool,
             block_buffer: b.into_boxed_slice(),
             block_size,
             next_complete: 0,
             io_complete: BinaryHeap::new(),
-            msize
+            msize,
         }
     }
 
     /// Submit a sequence of records to WAL; WALStore/WALFile callbacks are invoked before the
     /// function returns.  The caller then has the knowledge of WAL writes so it should defer
     /// actual data writes after WAL writes.
-    pub fn grow<T: AsRef<[WALBytes]>>(&mut self, records: T) -> (Box<[WALRingId]>, Result<(), ()>) {
+    pub fn grow<T: AsRef<[WALBytes]>>(
+        &mut self,
+        records: T,
+    ) -> (Box<[WALRingId]>, Result<(), ()>) {
         let mut res = Vec::new();
         let mut writes = Vec::new();
         let msize = self.msize as u32;
@@ -213,9 +252,14 @@ impl<F: WALStore> WALWriter<F> {
                 let remain = self.block_size - bbuff_cur;
                 if remain > msize {
                     let d = remain - msize;
-                    let rs0 = self.state.next + (bbuff_cur - bbuff_start) as u64;
-                    let blob = unsafe {std::mem::transmute::<*mut u8, &mut WALRingBlob>(
-                        (&mut self.block_buffer[bbuff_cur as usize..]).as_mut_ptr())};
+                    let rs0 =
+                        self.state.next + (bbuff_cur - bbuff_start) as u64;
+                    let blob = unsafe {
+                        std::mem::transmute::<*mut u8, &mut WALRingBlob>(
+                            (&mut self.block_buffer[bbuff_cur as usize..])
+                                .as_mut_ptr(),
+                        )
+                    };
                     bbuff_cur += msize;
                     if d >= rsize {
                         // the remaining rec fits in the block
@@ -228,25 +272,28 @@ impl<F: WALStore> WALWriter<F> {
                             (rs0, WALRingType::Full)
                         };
                         blob.rtype = rt;
-                        &mut self.block_buffer[
-                            bbuff_cur as usize..
-                            bbuff_cur as usize + payload.len()].copy_from_slice(payload);
+                        &mut self.block_buffer[bbuff_cur as usize..
+                            bbuff_cur as usize + payload.len()]
+                            .copy_from_slice(payload);
                         bbuff_cur += rsize;
                         rsize = 0;
-                        let end = self.state.next + (bbuff_cur - bbuff_start) as u64;
-                        res.push(WALRingId{start: rs, end });
+                        let end =
+                            self.state.next + (bbuff_cur - bbuff_start) as u64;
+                        res.push(WALRingId { start: rs, end });
                     } else {
                         // the remaining block can only accommodate partial rec
                         let payload = &rec[..d as usize];
                         blob.crc32 = crc::crc32::checksum_ieee(payload);
                         blob.rsize = d;
-                        blob.rtype = if ring_start.is_some() {WALRingType::Middle} else {
+                        blob.rtype = if ring_start.is_some() {
+                            WALRingType::Middle
+                        } else {
                             ring_start = Some(rs0);
                             WALRingType::First
                         };
-                        &mut self.block_buffer[
-                            bbuff_cur as usize..
-                            bbuff_cur as usize + payload.len()].copy_from_slice(payload);
+                        &mut self.block_buffer[bbuff_cur as usize..
+                            bbuff_cur as usize + payload.len()]
+                            .copy_from_slice(payload);
                         bbuff_cur += d;
                         rsize -= d;
                         rec = &rec[d as usize..];
@@ -256,9 +303,12 @@ impl<F: WALStore> WALWriter<F> {
                     bbuff_cur = self.block_size;
                 }
                 if bbuff_cur == self.block_size {
-                    writes.push((self.state.next,
-                             self.block_buffer[bbuff_start as usize..]
-                                .to_vec().into_boxed_slice()));
+                    writes.push((
+                        self.state.next,
+                        self.block_buffer[bbuff_start as usize..]
+                            .to_vec()
+                            .into_boxed_slice(),
+                    ));
                     self.state.next += (self.block_size - bbuff_start) as u64;
                     bbuff_start = 0;
                     bbuff_cur = 0;
@@ -266,9 +316,12 @@ impl<F: WALStore> WALWriter<F> {
             }
         }
         if bbuff_cur > bbuff_start {
-            writes.push((self.state.next,
-                     self.block_buffer[bbuff_start as usize..bbuff_cur as usize]
-                        .to_vec().into_boxed_slice()));
+            writes.push((
+                self.state.next,
+                self.block_buffer[bbuff_start as usize..bbuff_cur as usize]
+                    .to_vec()
+                    .into_boxed_slice(),
+            ));
             self.state.next += (bbuff_cur - bbuff_start) as u64;
         }
 
@@ -277,16 +330,20 @@ impl<F: WALStore> WALWriter<F> {
 
     /// Inform the WALWriter that data writes (specified by a slice of (offset, length) tuples) are
     /// complete so that it could automatically remove obsolete WAL files.
-    pub fn peel<T: AsRef<[WALRingId]>>(&mut self, records: T) -> Result<(), ()> {
+    pub fn peel<T: AsRef<[WALRingId]>>(
+        &mut self,
+        records: T,
+    ) -> Result<(), ()> {
         let msize = self.msize as u64;
         let block_size = self.block_size as u64;
         for rec in records.as_ref() {
             self.io_complete.push(*rec);
         }
         let orig_fid = self.state.first_fid;
-        while let Some(s) = self.io_complete.peek().and_then(|&e| Some(e.start)) {
+        while let Some(s) = self.io_complete.peek().and_then(|&e| Some(e.start))
+        {
             if s != self.next_complete {
-                break
+                break;
             }
             let mut m = self.io_complete.pop().unwrap();
             let block_remain = block_size - (m.end & (block_size - 1));
@@ -309,7 +366,7 @@ pub struct WALLoader {
     block_nbit: u8,
     cache_size: usize,
     msize: usize,
-    filename_fmt: regex::Regex
+    filename_fmt: regex::Regex,
 }
 
 impl WALLoader {
@@ -318,17 +375,30 @@ impl WALLoader {
         assert!(file_nbit > block_nbit);
         assert!(msize < 1 << block_nbit);
         let filename_fmt = regex::Regex::new(r"[0-9a-f]+\.log").unwrap();
-        WALLoader{ file_nbit, block_nbit, cache_size, msize, filename_fmt }
+        WALLoader {
+            file_nbit,
+            block_nbit,
+            cache_size,
+            msize,
+            filename_fmt,
+        }
     }
 
     /// Recover by reading the WAL log files.
     pub fn recover<F: WALStore>(self, store: F) -> Result<WALWriter<F>, ()> {
-        let mut file_pool = WALFilePool::new(store, self.file_nbit, self.block_nbit, self.cache_size);
+        let mut file_pool = WALFilePool::new(
+            store,
+            self.file_nbit,
+            self.block_nbit,
+            self.cache_size,
+        );
         let block_size = 1 << file_pool.block_nbit;
-        let msize = std::mem::size_of::<WALRingBlob>() as u32;
-        let mut logfiles: Vec<String> = file_pool.store
+        let msize = self.msize as u32;
+        let mut logfiles: Vec<String> = file_pool
+            .store
             .enumerate_files()?
-            .filter(|f| self.filename_fmt.is_match(f)).collect();
+            .filter(|f| self.filename_fmt.is_match(f))
+            .collect();
         // TODO: check for missing logfiles
         logfiles.sort();
         let mut chunks = None;
@@ -340,7 +410,10 @@ impl WALLoader {
                 let ringid_start = (fid << file_pool.file_nbit) + off;
                 off += msize as u64;
                 let header = unsafe {
-                    std::mem::transmute::<*const u8, &WALRingBlob>(header_raw.as_ptr())};
+                    std::mem::transmute::<*const u8, &WALRingBlob>(
+                        header_raw.as_ptr(),
+                    )
+                };
                 let rsize = header.rsize;
                 match header.rtype {
                     WALRingType::Full => {
@@ -351,26 +424,36 @@ impl WALLoader {
                             payload,
                             WALRingId {
                                 start: ringid_start,
-                                end: (fid << file_pool.file_nbit) + off
-                            })?;
-                    },
+                                end: (fid << file_pool.file_nbit) + off,
+                            },
+                        )?;
+                    }
                     WALRingType::First => {
                         assert!(chunks.is_none());
-                        chunks = Some((vec![f.read(off, rsize as usize)?.ok_or(())?], ringid_start));
+                        chunks = Some((
+                            vec![f.read(off, rsize as usize)?.ok_or(())?],
+                            ringid_start,
+                        ));
                         off += rsize as u64;
-                    },
+                    }
                     WALRingType::Middle => {
                         if let Some((chunks, _)) = &mut chunks {
-                            chunks.push(f.read(off, rsize as usize)?.ok_or(())?);
+                            chunks
+                                .push(f.read(off, rsize as usize)?.ok_or(())?);
                         } // otherwise ignore the leftover
                         off += rsize as u64;
-                    },
+                    }
                     WALRingType::Last => {
-                        if let Some((mut chunks, ringid_start)) = chunks.take() {
-                            chunks.push(f.read(off, rsize as usize)?.ok_or(())?);
+                        if let Some((mut chunks, ringid_start)) = chunks.take()
+                        {
+                            chunks
+                                .push(f.read(off, rsize as usize)?.ok_or(())?);
                             off += rsize as u64;
                             let mut payload = Vec::new();
-                            payload.resize(chunks.iter().fold(0, |acc, v| acc + v.len()), 0);
+                            payload.resize(
+                                chunks.iter().fold(0, |acc, v| acc + v.len()),
+                                0,
+                            );
                             let mut ps = &mut payload[..];
                             for c in chunks {
                                 ps[..c.len()].copy_from_slice(&*c);
@@ -380,11 +463,15 @@ impl WALLoader {
                                 payload.into_boxed_slice(),
                                 WALRingId {
                                     start: ringid_start,
-                                    end: (fid << file_pool.file_nbit) + off
-                                })?;
-                        } // otherwise ignore the leftover
-                        else { off += rsize as u64; }
-                    },
+                                    end: (fid << file_pool.file_nbit) + off,
+                                },
+                            )?;
+                        }
+                        // otherwise ignore the leftover
+                        else {
+                            off += rsize as u64;
+                        }
+                    }
                     WALRingType::Null => break,
                 }
                 let block_remain = block_size - (off & (block_size - 1));
@@ -396,10 +483,13 @@ impl WALLoader {
             file_pool.remove_file(fid)?;
         }
         file_pool.reset();
-        Ok(WALWriter::new(WALState {
-            first_fid: 0,
-            next: 0,
-            file_nbit: file_pool.file_nbit,
-        }, file_pool))
+        Ok(WALWriter::new(
+            WALState {
+                first_fid: 0,
+                next: 0,
+                file_nbit: file_pool.file_nbit,
+            },
+            file_pool,
+        ))
     }
 }
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 76533eb..f230edb 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -1,81 +1,92 @@
 #[cfg(test)]
 #[allow(dead_code)]
-
 extern crate growthring;
-use growthring::wal::{WALFile, WALStore, WALLoader, WALPos, WALBytes, WALRingId};
-use indexmap::{IndexMap, map::Entry};
+use growthring::wal::{
+    WALBytes, WALFile, WALLoader, WALPos, WALRingId, WALStore,
+};
+use indexmap::{map::Entry, IndexMap};
 use rand::Rng;
-use std::collections::{HashMap, hash_map};
 use std::cell::RefCell;
-use std::rc::Rc;
-use std::convert::TryInto;
 use std::collections::VecDeque;
+use std::collections::{hash_map, HashMap};
+use std::convert::TryInto;
+use std::rc::Rc;
 
-thread_local! {
-    //pub static RNG: RefCell<rand::rngs::StdRng> = RefCell::new(<rand::rngs::StdRng as rand::SeedableRng>::from_seed([0; 32]));
-    pub static RNG: RefCell<rand::rngs::ThreadRng> = RefCell::new(rand::thread_rng());
-}
-
-/*
-pub fn gen_rand_letters(i: usize) -> String {
-    RNG.with(|rng| {
-        (0..i).map(|_| (rng.borrow_mut().gen_range(0, 26) + 'a' as u8) as char).collect()
-    })
+pub trait FailGen {
+    fn next_fail(&self) -> bool;
 }
-*/
 
 struct FileContentEmul(RefCell<Vec<u8>>);
 
 impl FileContentEmul {
-    pub fn new() -> Self { FileContentEmul(RefCell::new(Vec::new())) }
+    pub fn new() -> Self {
+        FileContentEmul(RefCell::new(Vec::new()))
+    }
 }
 
 impl std::ops::Deref for FileContentEmul {
     type Target = RefCell<Vec<u8>>;
-    fn deref(&self) -> &Self::Target {&self.0}
-}
-
-pub trait FailGen {
-    fn next_fail(&self) -> bool;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
 }
 
 /// Emulate the a virtual file handle.
 pub struct WALFileEmul<G: FailGen> {
     file: Rc<FileContentEmul>,
-    fgen: Rc<G>
+    fgen: Rc<G>,
 }
 
 impl<G: FailGen> WALFile for WALFileEmul<G> {
     fn allocate(&self, offset: WALPos, length: usize) -> Result<(), ()> {
-        if self.fgen.next_fail() { return Err(()) }
+        if self.fgen.next_fail() {
+            return Err(());
+        }
         let offset = offset as usize;
         if offset + length > self.file.borrow().len() {
             self.file.borrow_mut().resize(offset + length, 0)
         }
-        for v in &mut self.file.borrow_mut()[offset..offset + length] { *v = 0 }
+        for v in &mut self.file.borrow_mut()[offset..offset + length] {
+            *v = 0
+        }
         Ok(())
     }
 
     fn truncate(&self, length: usize) -> Result<(), ()> {
-        if self.fgen.next_fail() { return Err(()) }
+        if self.fgen.next_fail() {
+            return Err(());
+        }
         self.file.borrow_mut().resize(length, 0);
         Ok(())
     }
 
     fn write(&self, offset: WALPos, data: WALBytes) -> Result<(), ()> {
-        if self.fgen.next_fail() { return Err(()) }
+        if self.fgen.next_fail() {
+            return Err(());
+        }
         let offset = offset as usize;
-        &self.file.borrow_mut()[offset..offset + data.len()].copy_from_slice(&data);
+        &self.file.borrow_mut()[offset..offset + data.len()]
+            .copy_from_slice(&data);
         Ok(())
     }
 
-    fn read(&self, offset: WALPos, length: usize) -> Result<Option<WALBytes>, ()> {
-        if self.fgen.next_fail() { return Err(()) }
+    fn read(
+        &self,
+        offset: WALPos,
+        length: usize,
+    ) -> Result<Option<WALBytes>, ()> {
+        if self.fgen.next_fail() {
+            return Err(());
+        }
+
         let offset = offset as usize;
         let file = self.file.borrow();
-        if offset + length > file.len() { Ok(None) }
-        else {
-            Ok(Some((&file[offset..offset + length]).to_vec().into_boxed_slice()))
+        if offset + length > file.len() {
+            Ok(None)
+        } else {
+            Ok(Some(
+                (&file[offset..offset + length]).to_vec().into_boxed_slice(),
+            ))
         }
     }
 }
@@ -85,61 +96,87 @@ pub struct WALStoreEmulState {
 }
 
 impl WALStoreEmulState {
-    pub fn new() -> Self { WALStoreEmulState { files: HashMap::new() } }
+    pub fn new() -> Self {
+        WALStoreEmulState {
+            files: HashMap::new(),
+        }
+    }
 }
 
 /// Emulate the persistent storage state.
 pub struct WALStoreEmul<'a, G, F>
 where
     G: FailGen,
-    F: FnMut(WALBytes, WALRingId) {
+    F: FnMut(WALBytes, WALRingId),
+{
     state: &'a mut WALStoreEmulState,
     fgen: Rc<G>,
-    recover: F
+    recover: F,
 }
 
 impl<'a, G: FailGen, F: FnMut(WALBytes, WALRingId)> WALStoreEmul<'a, G, F> {
-    pub fn new(state: &'a mut WALStoreEmulState, fgen: Rc<G>,
-                recover: F) -> Self {
+    pub fn new(
+        state: &'a mut WALStoreEmulState,
+        fgen: Rc<G>,
+        recover: F,
+    ) -> Self {
         WALStoreEmul {
             state,
             fgen,
-            recover
+            recover,
         }
     }
 }
 
-impl<'a, G, F> WALStore for WALStoreEmul<'a, G, F> 
+impl<'a, G, F> WALStore for WALStoreEmul<'a, G, F>
 where
-    G: 'static + FailGen, F: FnMut(WALBytes, WALRingId) {
+    G: 'static + FailGen,
+    F: FnMut(WALBytes, WALRingId),
+{
     type FileNameIter = std::vec::IntoIter<String>;
 
-    fn open_file(&mut self, filename: &str, touch: bool) -> Result<Box<dyn WALFile>, ()> {
-        if self.fgen.next_fail() { return Err(()) }
+    fn open_file(
+        &mut self,
+        filename: &str,
+        touch: bool,
+    ) -> Result<Box<dyn WALFile>, ()> {
+        if self.fgen.next_fail() {
+            return Err(());
+        }
         match self.state.files.entry(filename.to_string()) {
             hash_map::Entry::Occupied(e) => Ok(Box::new(WALFileEmul {
                 file: e.get().clone(),
-                fgen: self.fgen.clone()
+                fgen: self.fgen.clone(),
             })),
-            hash_map::Entry::Vacant(e) => if touch {
-                Ok(Box::new(WALFileEmul {
-                    file: e.insert(Rc::new(FileContentEmul::new())).clone(),
-                    fgen: self.fgen.clone()
-                }))
-            } else {
-                Err(())
+            hash_map::Entry::Vacant(e) => {
+                if touch {
+                    Ok(Box::new(WALFileEmul {
+                        file: e.insert(Rc::new(FileContentEmul::new())).clone(),
+                        fgen: self.fgen.clone(),
+                    }))
+                } else {
+                    Err(())
+                }
             }
         }
     }
 
     fn remove_file(&mut self, filename: &str) -> Result<(), ()> {
         //println!("remove_file(filename={})", filename);
-        if self.fgen.next_fail() { return Err(()) }
-        self.state.files.remove(filename).ok_or(()).and_then(|_| Ok(()))
+        if self.fgen.next_fail() {
+            return Err(());
+        }
+        self.state
+            .files
+            .remove(filename)
+            .ok_or(())
+            .and_then(|_| Ok(()))
     }
 
     fn enumerate_files(&self) -> Result<Self::FileNameIter, ()> {
-        if self.fgen.next_fail() { return Err(()) }
+        if self.fgen.next_fail() {
+            return Err(());
+        }
         let mut logfiles = Vec::new();
         for (fname, _) in self.state.files.iter() {
             logfiles.push(fname.clone())
@@ -147,11 +184,19 @@ where
         Ok(logfiles.into_iter())
     }
 
-    fn apply_payload(&mut self, payload: WALBytes, ringid: WALRingId) -> Result<(), ()> {
-        if self.fgen.next_fail() { return Err(()) }
-        //println!("apply_payload(payload=0x{}, ringid={:?})",
-        //        hex::encode(&payload),
-        //        ringid);
+    fn apply_payload(
+        &mut self,
+        payload: WALBytes,
+        ringid: WALRingId,
+    ) -> Result<(), ()> {
+        if self.fgen.next_fail() {
+            return Err(());
+        }
+        /*
+        println!("apply_payload(payload=0x{}, ringid={:?})",
+                hex::encode(&payload),
+                ringid);
+        */
         (self.recover)(payload, ringid);
         Ok(())
     }
@@ -159,14 +204,14 @@ where
 
 pub struct SingleFailGen {
     cnt: std::cell::Cell<usize>,
-    fail_point: usize
+    fail_point: usize,
 }
 
 impl SingleFailGen {
     pub fn new(fail_point: usize) -> Self {
         SingleFailGen {
             cnt: std::cell::Cell::new(0),
-            fail_point
+            fail_point,
         }
     }
 }
@@ -182,14 +227,20 @@ impl FailGen for SingleFailGen {
 pub struct ZeroFailGen;
 
 impl FailGen for ZeroFailGen {
-    fn next_fail(&self) -> bool { false }
+    fn next_fail(&self) -> bool {
+        false
+    }
 }
 
 pub struct CountFailGen(std::cell::Cell<usize>);
 
 impl CountFailGen {
-    pub fn new() -> Self { CountFailGen(std::cell::Cell::new(0)) }
-    pub fn get_count(&self) -> usize { self.0.get() }
+    pub fn new() -> Self {
+        CountFailGen(std::cell::Cell::new(0))
+    }
+    pub fn get_count(&self) -> usize {
+        self.0.get()
+    }
 }
 
 impl FailGen for CountFailGen {
@@ -203,8 +254,12 @@ impl FailGen for CountFailGen {
 pub struct PaintStrokes(Vec<(u32, u32, u32)>);
 
 impl PaintStrokes {
-    pub fn new() -> Self { PaintStrokes(Vec::new()) }
-    pub fn clone(&self) -> Self { PaintStrokes(self.0.clone()) }
+    pub fn new() -> Self {
+        PaintStrokes(Vec::new())
+    }
+    pub fn clone(&self) -> Self {
+        PaintStrokes(self.0.clone())
+    }
     pub fn to_bytes(&self) -> WALBytes {
         let mut res: Vec<u8> = Vec::new();
         let is = std::mem::size_of::<u32>();
@@ -233,31 +288,41 @@ impl PaintStrokes {
             let (s_raw, rest1) = rest.split_at(is);
             let (e_raw, rest2) = rest1.split_at(is);
             let (c_raw, rest3) = rest2.split_at(is);
-            res.push((u32::from_le_bytes(s_raw.try_into().unwrap()),
-                    u32::from_le_bytes(e_raw.try_into().unwrap()),
-                    u32::from_le_bytes(c_raw.try_into().unwrap())));
+            res.push((
+                u32::from_le_bytes(s_raw.try_into().unwrap()),
+                u32::from_le_bytes(e_raw.try_into().unwrap()),
+                u32::from_le_bytes(c_raw.try_into().unwrap()),
+            ));
             rest = rest3
         }
         PaintStrokes(res)
     }
 
-    pub fn gen_rand<R: rand::Rng>(max_pos: u32, max_len: u32,
-                                  max_col: u32, n: usize, rng: &mut R) -> PaintStrokes {
+    pub fn gen_rand<R: rand::Rng>(
+        max_pos: u32,
+        max_len: u32,
+        max_col: u32,
+        n: usize,
+        rng: &mut R,
+    ) -> PaintStrokes {
         assert!(max_pos > 0);
         let mut strokes = Self::new();
         for _ in 0..n {
             let pos = rng.gen_range(0, max_pos);
-            let len = rng.gen_range(1, std::cmp::min(max_len, max_pos - pos + 1));
+            let len =
+                rng.gen_range(1, std::cmp::min(max_len, max_pos - pos + 1));
             strokes.stroke(pos, pos + len, rng.gen_range(0, max_col))
         }
         strokes
     }
-    
+
     pub fn stroke(&mut self, start: u32, end: u32, color: u32) {
         self.0.push((start, end, color))
     }
 
-    pub fn into_vec(self) -> Vec<(u32, u32, u32)> { self.0 }
+    pub fn into_vec(self) -> Vec<(u32, u32, u32)> {
+        self.0
+    }
 }
 
 #[test]
@@ -268,7 +333,10 @@ fn test_paint_strokes() {
     }
     let pr = p.to_bytes();
     for ((s, e, c), i) in PaintStrokes::from_bytes(&pr)
-                            .into_vec().into_iter().zip(0..) {
+        .into_vec()
+        .into_iter()
+        .zip(0..)
+    {
         assert_eq!(s, i);
         assert_eq!(e, i + 3);
         assert_eq!(c, i + 10);
@@ -278,7 +346,7 @@ fn test_paint_strokes() {
 pub struct Canvas {
     waiting: HashMap<WALRingId, usize>,
     queue: IndexMap<u32, VecDeque<(u32, WALRingId)>>,
-    canvas: Box<[u32]>
+    canvas: Box<[u32]>,
 }
 
 impl Canvas {
@@ -290,7 +358,7 @@ impl Canvas {
         Canvas {
             waiting: HashMap::new(),
             queue: IndexMap::new(),
-            canvas
+            canvas,
         }
     }
 
@@ -309,14 +377,14 @@ impl Canvas {
     fn get_waiting(&mut self, rid: WALRingId) -> &mut usize {
         match self.waiting.entry(rid) {
             hash_map::Entry::Occupied(e) => e.into_mut(),
-            hash_map::Entry::Vacant(e) => e.insert(0)
+            hash_map::Entry::Vacant(e) => e.insert(0),
         }
     }
 
     fn get_queued(&mut self, pos: u32) -> &mut VecDeque<(u32, WALRingId)> {
         match self.queue.entry(pos) {
             Entry::Occupied(e) => e.into_mut(),
-            Entry::Vacant(e) => e.insert(VecDeque::new())
+            Entry::Vacant(e) => e.insert(VecDeque::new()),
         }
     }
 
@@ -335,8 +403,13 @@ impl Canvas {
     // TODO: allow customized scheduler
     /// Schedule to paint one position, randomly. It optionally returns a finished batch write
     /// identified by its start position of WALRingId.
-    pub fn rand_paint<R: rand::Rng>(&mut self, rng: &mut R) -> Option<(Option<WALRingId>, u32)> {
-        if self.is_empty() { return None }
+    pub fn rand_paint<R: rand::Rng>(
+        &mut self,
+        rng: &mut R,
+    ) -> Option<(Option<WALRingId>, u32)> {
+        if self.is_empty() {
+            return None;
+        }
         let idx = rng.gen_range(0, self.queue.len());
         let (pos, _) = self.queue.get_index_mut(idx).unwrap();
         let pos = *pos;
@@ -355,18 +428,24 @@ impl Canvas {
         self.clear_queued()
     }
 
-    pub fn is_empty(&self) -> bool { self.queue.is_empty() }
+    pub fn is_empty(&self) -> bool {
+        self.queue.is_empty()
+    }
 
     pub fn paint(&mut self, pos: u32) -> Option<WALRingId> {
         let q = self.queue.get_mut(&pos).unwrap();
         let (c, rid) = q.pop_front().unwrap();
-        if q.is_empty() { self.queue.remove(&pos); }
+        if q.is_empty() {
+            self.queue.remove(&pos);
+        }
         self.canvas[pos as usize] = c;
         let cnt = self.waiting.get_mut(&rid).unwrap();
         *cnt -= 1;
         if *cnt == 0 {
             Some(rid)
-        } else { None }
+        } else {
+            None
+        }
     }
 
     pub fn is_same(&self, other: &Canvas) -> bool {
@@ -387,15 +466,13 @@ impl Canvas {
 
 #[test]
 fn test_canvas() {
+    let mut rng = <rand::rngs::StdRng as rand::SeedableRng>::seed_from_u64(42);
     let mut canvas1 = Canvas::new(100);
     let mut canvas2 = Canvas::new(100);
     let canvas3 = Canvas::new(101);