Add WASI support

Cargo.toml

@@ -22,18 +22,20 @@ libc = "0.2.104"
 log = {version = "0.4.17", optional = true }
 pyo3 = {version = "0.18.0", features=["extension-module", "abi3-py37"], optional = true }
 
-[dev-dependencies]
+[target.'cfg(not(target_os = "wasi"))'.dev-dependencies]
 ctrlc = "3.2.3"
 fastrand = "1.9.0"
-rand = "0.8"
 lmdb-rkv = "0.14.0"
 sanakirja = "1.3.3"
-tempfile = "3.5.0"
 sled = "0.34.7"
 rocksdb = "0.21.0"
 libc = "0.2.99"
 comfy-table = "6.1.0"
 
+[dev-dependencies]
+rand = "0.8"
+tempfile = "3.5.0"
+
 [target.'cfg(target_os = "linux")'.dev-dependencies]
 io-uring = "0.5.1"
 
@@ -43,6 +45,8 @@ python = ["pyo3"]
 logging = ["log"]
 # Enable cache hit metrics
 cache_metrics = []
+# Enable experimental wasi support (requires nightly and has no file locking!)
+wasi = []
 
 [profile.bench]
 debug = true

src/db.rs

@@ -650,7 +650,7 @@ impl Builder {
     /// Set the amount of memory (in bytes) used for caching data
     pub fn set_cache_size(&mut self, bytes: usize) -> &mut Self {
         // TODO: allow dynamic expansion of the read/write cache
-        self.read_cache_size_bytes = bytes * 9 / 10;
+        self.read_cache_size_bytes = bytes / 10 * 9;
         self.write_cache_size_bytes = bytes / 10;
         self
     }

src/lib.rs

@@ -5,6 +5,13 @@
     clippy::cast_precision_loss,
     clippy::cast_sign_loss
 )]
+// TODO remove these (and the "wasi" Cargo feature) once wasi no longer requires nightly
+#![cfg_attr(feature = "wasi", feature(wasi_ext))]
+#[cfg(all(target_os = "wasi", not(feature = "wasi")))]
+compile_error!(
+    r"To compile to WASI, you must enable the 'wasi' feature for now!
+See redb's Cargo.toml for why; this restriction will be lifted in the future."
+);
 
 pub use db::{
     Builder, Database, MultimapTableDefinition, MultimapTableHandle, TableDefinition, TableHandle,

src/tree_store/page_store/file_lock/mod.rs

@@ -1,6 +1,6 @@
-#[cfg(unix)]
+#[cfg(any(unix, target_os = "wasi"))]
 mod unix;
-#[cfg(unix)]
+#[cfg(any(unix, target_os = "wasi"))]
 pub(super) use unix::LockedFile;
 
 #[cfg(windows)]

src/tree_store/page_store/file_lock/unix.rs

@@ -1,14 +1,33 @@
+// TODO once Rust's libc has flock implemented for WASI, this file needs to be revisited.
+// What needs to be changed is commented below.
+// See also: https://github.com/WebAssembly/wasi-filesystem/issues/2
+
+// Remove this line once wasi-libc has flock
+#![cfg_attr(feature = "wasi", allow(unused_imports))]
+
 use crate::{Error, Result};
 use std::fs::File;
 use std::io;
-use std::os::unix::fs::FileExt;
-use std::os::unix::io::AsRawFd;
+
+#[cfg(unix)]
+use std::os::unix::{fs::FileExt, io::AsRawFd};
+
+#[cfg(target_os = "wasi")]
+use std::os::wasi::{fs::FileExt, io::AsRawFd};
 
 pub(crate) struct LockedFile {
     file: File,
 }
 
 impl LockedFile {
+    // This is a no-op until we get flock in wasi-libc.
+    // Delete this function when we get flock.
+    #[cfg(target_os = "wasi")]
+    pub(crate) fn new(file: File) -> Result<Self> {
+        Ok(Self { file })
+    }
+
+    #[cfg(unix)] // remove this line when wasi-libc gets flock
     pub(crate) fn new(file: File) -> Result<Self> {
         let fd = file.as_raw_fd();
         let result = unsafe { libc::flock(fd, libc::LOCK_EX | libc::LOCK_NB) };
@@ -41,6 +60,7 @@ impl LockedFile {
     }
 }
 
+#[cfg(unix)] // remove this line when wasi-libc gets flock
 impl Drop for LockedFile {
     fn drop(&mut self) {
         unsafe { libc::flock(self.file.as_raw_fd(), libc::LOCK_UN) };