add slice transform support

src/db.rs

@@ -1237,6 +1237,12 @@ impl ReadOptions {
             ffi::rocksdb_readoptions_set_prefix_same_as_start(self.inner, v as c_uchar)
         }
     }
+
+    pub fn set_total_order_seek(&mut self, v:bool) {
+        unsafe {
+            ffi::rocksdb_readoptions_set_total_order_seek(self.inner, v as c_uchar)
+        }
+    }
 }
 
 impl Default for ReadOptions {

src/db_options.rs

@@ -11,20 +11,20 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-//
 
+use std::ffi::{CStr, CString};
+use std::mem;
+
+use libc::{self, c_int, c_uchar, c_uint, c_void, size_t, uint64_t};
 
-use {BlockBasedOptions, DBCompactionStyle, DBCompressionType, DBRecoveryMode, Options,
-     WriteOptions};
+use ffi;
+use {BlockBasedOptions, DBCompactionStyle, DBCompressionType, DBRecoveryMode,
+	 Options, WriteOptions};
 use compaction_filter::{self, CompactionFilterCallback, CompactionFilterFn, filter_callback};
 use comparator::{self, ComparatorCallback, CompareFn};
-use ffi;
-
-use libc::{self, c_int, c_uchar, c_uint, c_void, size_t, uint64_t};
 use merge_operator::{self, MergeFn, MergeOperatorCallback, full_merge_callback,
                      partial_merge_callback};
-use std::ffi::{CStr, CString};
-use std::mem;
+use slice_transform::SliceTransform;
 
 pub fn new_cache(capacity: size_t) -> *mut ffi::rocksdb_cache_t {
     unsafe { ffi::rocksdb_cache_create_lru(capacity) }
@@ -221,7 +221,10 @@ impl Options {
         }
     }
 
-    pub fn set_merge_operator(&mut self, name: &str, full_merge_fn: MergeFn, partial_merge_fn: Option<MergeFn>) {
+    pub fn set_merge_operator(&mut self, name: &str,
+                              full_merge_fn: MergeFn,
+                              partial_merge_fn: Option<MergeFn>) {
+
         let cb = Box::new(MergeOperatorCallback {
             name: CString::new(name.as_bytes()).unwrap(),
             full_merge_fn: full_merge_fn,
@@ -300,6 +303,14 @@ impl Options {
         }
     }
 
+    pub fn set_prefix_extractor(&mut self, prefix_extractor: SliceTransform) {
+        unsafe {
+            ffi::rocksdb_options_set_prefix_extractor(
+                self.inner, prefix_extractor.inner
+            )
+        }
+    }
+
     #[deprecated(since = "0.5.0", note = "add_comparator has been renamed to set_comparator")]
     pub fn add_comparator(&mut self, name: &str, compare_fn: CompareFn) {
         self.set_comparator(name, compare_fn);

src/lib.rs

@@ -58,12 +58,15 @@ pub mod merge_operator;
 pub mod compaction_filter;
 mod db;
 mod db_options;
+mod slice_transform;
 
 pub use compaction_filter::Decision as CompactionDecision;
 pub use db::{DBCompactionStyle, DBCompressionType, DBIterator, DBRawIterator, DBRecoveryMode,
              DBVector, ReadOptions, Direction, IteratorMode, Snapshot, WriteBatch,
              new_bloom_filter};
 
+pub use slice_transform::SliceTransform;
+
 pub use merge_operator::MergeOperands;
 use std::collections::BTreeMap;
 use std::error;

src/slice_transform.rs

@@ -0,0 +1,149 @@
+// Copyright 2018 Tyler Neely
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::ffi::CString;
+use std::mem;
+use std::ptr;
+use std::slice;
+
+use libc::{self, c_char, c_void, size_t};
+
+use ffi;
+
+/// A SliceTranform is a generic pluggable way of transforming one string
+/// to another. Its primary use-case is in configuring rocksdb
+/// to store prefix blooms by setting prefix_extractor in
+/// ColumnFamilyOptions.
+pub struct SliceTransform {
+    pub inner: *mut ffi::rocksdb_slicetransform_t,
+}
+
+// NB we intentionally don't implement a Drop that passes
+// through to rocksdb_slicetransform_destroy because
+// this is currently only used (to my knowledge)
+// by people passing it as a prefix extractor when
+// opening a DB. 
+
+impl SliceTransform {
+    pub fn create(
+        name: &str,
+        transform_fn: TransformFn,
+        in_domain_fn: Option<InDomainFn>,
+    ) -> SliceTransform{
+        let cb = Box::new(TransformCallback {
+            name: CString::new(name.as_bytes()).unwrap(),
+            transform_fn: transform_fn,
+            in_domain_fn: in_domain_fn,
+        });
+
+        let st = unsafe {
+             ffi::rocksdb_slicetransform_create(
+                mem::transmute(cb),
+                Some(slice_transform_destructor_callback),
+                Some(transform_callback),
+
+                // this is ugly, but I can't get the compiler
+                // not to barf with "expected fn pointer, found fn item"
+                // without this. sorry.
+                if let Some(_) = in_domain_fn {
+                    Some(in_domain_callback)
+                } else {
+                    None
+                },
+
+                // this None points to the deprecated InRange callback
+                None,
+                Some(slice_transform_name_callback),
+            )
+        };
+
+        SliceTransform {
+            inner: st
+        }
+    }
+
+    pub fn create_fixed_prefix(len: size_t) -> SliceTransform {
+        SliceTransform {
+            inner: unsafe {
+                ffi::rocksdb_slicetransform_create_fixed_prefix(len)
+            },
+        }
+    }
+
+    pub fn create_noop() -> SliceTransform {
+        SliceTransform {
+            inner: unsafe {
+                ffi::rocksdb_slicetransform_create_noop()
+            },
+        }
+    }
+}
+
+pub type TransformFn = fn(&[u8]) -> Vec<u8>;
+pub type InDomainFn = fn(&[u8]) -> bool;
+
+pub struct TransformCallback {
+	pub name: CString,
+	pub transform_fn: TransformFn,
+	pub in_domain_fn: Option<InDomainFn>,
+}
+
+pub unsafe extern "C" fn slice_transform_destructor_callback(
+    raw_cb: *mut c_void
+) {
+	let transform: Box<TransformCallback> = mem::transmute(raw_cb);
+	drop(transform);
+}
+
+pub unsafe extern "C" fn slice_transform_name_callback(
+    raw_cb: *mut c_void
+) -> *const c_char {
+	let cb = &mut *(raw_cb as *mut TransformCallback);
+	cb.name.as_ptr()
+}
+
+pub unsafe extern "C" fn transform_callback(
+	raw_cb: *mut c_void,
+	raw_key: *const c_char,
+	key_len: size_t,
+	dst_length: *mut size_t,
+) -> *mut c_char {
+	let cb = &mut *(raw_cb as *mut TransformCallback);
+	let key = slice::from_raw_parts(raw_key as *const u8, key_len as usize);
+	let mut result = (cb.transform_fn)(key);
+    result.shrink_to_fit();
+
+    // copy the result into a C++ destroyable buffer
+    let buf = libc::malloc(result.len() as size_t);
+    assert!(!buf.is_null());
+    ptr::copy(result.as_ptr() as *mut c_void, &mut *buf, result.len());
+
+    *dst_length = result.len() as size_t;
+    buf as *mut c_char
+}
+
+pub unsafe extern "C" fn in_domain_callback(
+    raw_cb: *mut c_void,
+	raw_key: *const c_char,
+	key_len: size_t,
+) -> u8 {
+	let cb = &mut *(raw_cb as *mut TransformCallback);
+	let key = slice::from_raw_parts(raw_key as *const u8, key_len as usize);
+
+    if (cb.in_domain_fn.unwrap())(key) {
+        1
+    } else {
+        0
+    }
+}

tests/test_slice_transform.rs

@@ -0,0 +1,48 @@
+extern crate rocksdb;
+
+use rocksdb::{DB, Options, SliceTransform};
+
+#[test]
+pub fn test_slice_transform() {
+
+    let path = "_rust_rocksdb_slicetransform_test";
+    let a1: Box<[u8]> = key(b"aaa1");
+    let a2: Box<[u8]> = key(b"aaa2");
+    let b1: Box<[u8]> = key(b"bbb1");
+    let b2: Box<[u8]> = key(b"bbb2");
+
+    fn first_three(k: &[u8]) -> Vec<u8> {
+        k.iter().take(3).cloned().collect()
+    }
+
+    let prefix_extractor = SliceTransform::create("first_three", first_three, None);
+
+    let mut opts = Options::default();
+    opts.create_if_missing(true);
+    opts.set_prefix_extractor(prefix_extractor);
+
+    let db = DB::open(&opts, path).unwrap();
+
+    assert!(db.put(&*a1, &*a1).is_ok());
+    assert!(db.put(&*a2, &*a2).is_ok());
+    assert!(db.put(&*b1, &*b1).is_ok());
+    assert!(db.put(&*b2, &*b2).is_ok());
+
+    fn cba(input: &Box<[u8]>) -> Box<[u8]> {
+        input.iter().cloned().collect::<Vec<_>>().into_boxed_slice()
+    }
+
+    fn key(k: &[u8]) -> Box<[u8]> { k.to_vec().into_boxed_slice() }
+
+    {
+        let expected = vec![(cba(&a1), cba(&a1)), (cba(&a2), cba(&a2))];
+        let a_iterator = db.prefix_iterator(b"aaa");
+        assert_eq!(a_iterator.collect::<Vec<_>>(), expected)
+    }
+
+    {
+        let expected = vec![(cba(&b1), cba(&b1)), (cba(&b2), cba(&b2))];
+        let b_iterator = db.prefix_iterator(b"bbb");
+        assert_eq!(b_iterator.collect::<Vec<_>>(), expected)
+    }
+}