From 6b407a3486c654ab507f9ca3616a9f24a6bd0242 Mon Sep 17 00:00:00 2001
From: Karl Hobley <karl@kaed.uk>
Date: Tue, 25 Jul 2017 10:10:31 +0100
Subject: [PATCH] Implement support for DirectIO

As per: https://github.com/facebook/rocksdb/commit/972f96b3fbae1a4675043bdf4279c9072ad69645
---
 librocksdb-sys/src/lib.rs |  3 ++-
 src/db_options.rs         | 54 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/librocksdb-sys/src/lib.rs b/librocksdb-sys/src/lib.rs
index fb1ce6c..6e86a38 100644
--- a/librocksdb-sys/src/lib.rs
+++ b/librocksdb-sys/src/lib.rs
@@ -633,7 +633,8 @@ extern "C" {
     pub fn rocksdb_options_set_purge_redundant_kvs_while_flush(opt: *mut rocksdb_options_t,
                                                                v: c_uchar);
 
-    pub fn rocksdb_options_set_allow_os_buffer(opt: *mut rocksdb_options_t, v: c_uchar);
+    pub fn rocksdb_options_set_use_direct_reads(opt: *mut rocksdb_options_t, v: c_uchar);
+    pub fn rocksdb_options_set_use_direct_writes(opt: *mut rocksdb_options_t, v: c_uchar);
 
     pub fn rocksdb_options_set_allow_mmap_reads(opt: *mut rocksdb_options_t, v: c_uchar);
 
diff --git a/src/db_options.rs b/src/db_options.rs
index 5c5ede9..8952d97 100644
--- a/src/db_options.rs
+++ b/src/db_options.rs
@@ -351,6 +351,54 @@ impl Options {
         unsafe { ffi::rocksdb_options_set_disable_data_sync(self.inner, disable as c_int) }
     }
 
+    /// Enable direct I/O mode for reading
+    /// they may or may not improve performance depending on the use case
+    ///
+    /// Files will be opened in "direct I/O" mode
+    /// which means that data read from the disk will not be cached or
+    /// buffered. The hardware buffer of the devices may however still
+    /// be used. Memory mapped files are not impacted by these parameters.
+    ///
+    /// Default: false
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rocksdb::Options;
+    ///
+    /// let mut opts = Options::default();
+    /// opts.set_use_direct_reads(true);
+    /// ```
+    pub fn set_use_direct_reads(&mut self, enabled: bool) {
+        unsafe {
+            ffi::rocksdb_options_set_use_direct_reads(self.inner, enabled as c_uchar);
+        }
+    }
+
+    /// Enable direct I/O mode for writing
+    /// they may or may not improve performance depending on the use case
+    ///
+    /// Files will be opened in "direct I/O" mode
+    /// which means that data written to the disk will not be cached or
+    /// buffered. The hardware buffer of the devices may however still
+    /// be used. Memory mapped files are not impacted by these parameters.
+    ///
+    /// Default: false
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rocksdb::Options;
+    ///
+    /// let mut opts = Options::default();
+    /// opts.set_use_direct_writes(true);
+    /// ```
+    pub fn set_use_direct_writes(&mut self, enabled: bool) {
+        unsafe {
+            ffi::rocksdb_options_set_use_direct_writes(self.inner, enabled as c_uchar);
+        }
+    }
+
     /// Hints to the OS that it should not buffer disk I/O. Enabling this
     /// parameter may improve performance but increases pressure on the
     /// system cache.
@@ -378,10 +426,10 @@ impl Options {
     /// let mut opts = Options::default();
     /// opts.set_allow_os_buffer(false);
     /// ```
+    #[deprecated(since="0.7.0", note="replaced with set_use_direct_reads/set_use_direct_writes methods")]
     pub fn set_allow_os_buffer(&mut self, is_allow: bool) {
-        unsafe {
-            ffi::rocksdb_options_set_allow_os_buffer(self.inner, is_allow as c_uchar);
-        }
+        self.set_use_direct_reads(!is_allow);
+        self.set_use_direct_writes(!is_allow);
     }
 
     /// Sets the number of shards used for table cache.