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rust-rocksdb/src/comparator.rs

83 lines
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// Copyright 2014 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.
//
extern crate libc;
use self::libc::{c_char, c_int, c_void, size_t};
use std::ffi::CString;
use std::mem;
use std::ptr;
use std::slice;
use rocksdb_options::Options;
use rocksdb::DB;
pub struct ComparatorCallback {
pub name: CString,
pub f: fn(&[u8], &[u8]) -> i32,
}
pub extern "C" fn destructor_callback(raw_cb: *mut c_void) {
// turn this back into a local variable so rust will reclaim it
let _: Box<ComparatorCallback> = unsafe { mem::transmute(raw_cb) };
}
pub extern "C" fn name_callback(raw_cb: *mut c_void) -> *const c_char {
unsafe {
let cb: &mut ComparatorCallback =
&mut *(raw_cb as *mut ComparatorCallback);
let ptr = cb.name.as_ptr();
ptr as *const c_char
}
}
pub extern "C" fn compare_callback(raw_cb: *mut c_void,
a_raw: *const c_char,
a_len: size_t,
b_raw: *const c_char,
b_len: size_t)
-> c_int {
unsafe {
let cb: &mut ComparatorCallback =
&mut *(raw_cb as *mut ComparatorCallback);
let a: &[u8] = slice::from_raw_parts(a_raw as *const u8,
a_len as usize);
let b: &[u8] = slice::from_raw_parts(b_raw as *const u8,
b_len as usize);
(cb.f)(a, b)
}
}
fn test_reverse_compare(a: &[u8], b: &[u8]) -> c_int {
if a < b {
1
} else if a > b {
-1
} else {
0
}
}
// #[allow(dead_code)]
// #[test]
// fn compare_works() {
// let path = "_rust_rocksdb_comparetest";
// let mut opts = Options::new();
// opts.create_if_missing(true);
// opts.add_comparator("test comparator", test_reverse_compare);
// {
// let db = DB::open(&opts, path).unwrap();
// // TODO add interesting test
// }
// assert!(DB::destroy(&opts, path).is_ok());
// }