From ba04108ee179b00c97708aa6ece6c6fff53101d0 Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Thu, 11 Jun 2020 18:20:42 -0400
Subject: tentatively add async fn

---
 src/wal.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

(limited to 'src/wal.rs')

diff --git a/src/wal.rs b/src/wal.rs
index 39c4390..85b144b 100644
--- a/src/wal.rs
+++ b/src/wal.rs
@@ -1,4 +1,6 @@
+use async_trait::async_trait;
 use std::collections::BinaryHeap;
+use std::future::Future;
 
 #[repr(u8)]
 enum WALRingType {
@@ -65,9 +67,10 @@ struct WALState {
     file_nbit: u64,
 }
 
+#[async_trait(?Send)]
 pub trait WALFile {
     /// Initialize the file space in [offset, offset + length) to zero.
-    fn allocate(&self, offset: WALPos, length: usize) -> Result<(), ()>;
+    async 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. We assume the actual writes on the storage medium are _strictly
@@ -75,8 +78,8 @@ pub trait WALFile {
     /// `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) -> Result<(), ()>;
-    /// Read data with offset.
+    async fn write(&self, offset: WALPos, data: WALBytes) -> Result<(), ()>;
+    /// Read data with offset. Return Ok(None) when it reaches EOF.
     fn read(
         &self,
         offset: WALPos,
@@ -158,7 +161,7 @@ impl<F: WALStore> WALFilePool<F> {
     }
 
     // TODO: evict stale handles
-    fn write(&mut self, writes: Vec<(WALPos, WALBytes)>) -> Result<(), ()> {
+    async fn write(&mut self, writes: Vec<(WALPos, WALBytes)>) -> Result<(), ()> {
         // pre-allocate the file space
         let mut fid = writes[0].0 >> self.file_nbit;
         let mut alloc_start = writes[0].0 & (self.file_size - 1);
@@ -175,7 +178,7 @@ impl<F: WALStore> WALFilePool<F> {
                 last_h.allocate(
                     alloc_start,
                     (alloc_end - alloc_start) as usize,
-                )?;
+                ).await?;
                 last_h = *h;
                 alloc_start = 0;
                 alloc_end = alloc_start + w.len() as u64;
@@ -184,10 +187,10 @@ impl<F: WALStore> WALFilePool<F> {
                 alloc_end += w.len() as u64;
             }
         }
-        last_h.allocate(alloc_start, (alloc_end - alloc_start) as usize)?;
+        last_h.allocate(alloc_start, (alloc_end - alloc_start) as usize).await?;
         for (off, w) in writes.into_iter() {
             self.get_file(off >> self.file_nbit, true)?
-                .write(off & (self.file_size - 1), w)?;
+                .write(off & (self.file_size - 1), w).await?;
         }
         Ok(())
     }
@@ -231,10 +234,10 @@ impl<F: WALStore> WALWriter<F> {
     /// 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,
+    pub fn grow<'a, T: AsRef<[WALBytes]>>(
+        &'a mut self,
         records: T,
-    ) -> (Box<[WALRingId]>, Result<(), ()>) {
+    ) -> (Box<[WALRingId]>, impl Future<Output = Result<(), ()>> + 'a) {
         let mut res = Vec::new();
         let mut writes = Vec::new();
         let msize = self.msize as u32;
-- 
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