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;
pub struct MergeOperatorCallback {
pub name: CString,
pub merge_fn: fn(&[u8], Option<&[u8]>, &mut MergeOperands) -> Vec<u8>,
}
pub extern "C" fn destructor_callback(raw_cb: *mut c_void) {
let _: Box<MergeOperatorCallback> = unsafe { mem::transmute(raw_cb) };
}
pub extern "C" fn name_callback(raw_cb: *mut c_void) -> *const c_char {
unsafe {
let cb: &mut MergeOperatorCallback =
&mut *(raw_cb as *mut MergeOperatorCallback);
let ptr = cb.name.as_ptr();
ptr as *const c_char
}
}
pub extern "C" fn full_merge_callback(raw_cb: *mut c_void,
raw_key: *const c_char,
key_len: size_t,
existing_value: *const c_char,
existing_value_len: size_t,
operands_list: *const *const c_char,
operands_list_len: *const size_t,
num_operands: c_int,
success: *mut u8,
new_value_length: *mut size_t)
-> *const c_char {
unsafe {
let cb: &mut MergeOperatorCallback =
&mut *(raw_cb as *mut MergeOperatorCallback);
let operands = &mut MergeOperands::new(operands_list,
operands_list_len,
num_operands);
let key: &[u8] = slice::from_raw_parts(raw_key as *const u8,
key_len as usize);
let oldval: &[u8] = slice::from_raw_parts(existing_value as *const u8,
existing_value_len as usize);
let mut result = (cb.merge_fn)(key, Some(oldval), operands);
result.shrink_to_fit();
let buf = libc::malloc(result.len() as size_t);
assert!(!buf.is_null());
*new_value_length = result.len() as size_t;
*success = 1 as u8;
ptr::copy(result.as_ptr() as *mut c_void, &mut *buf, result.len());
buf as *const c_char
}
}
pub extern "C" fn partial_merge_callback(raw_cb: *mut c_void,
raw_key: *const c_char,
key_len: size_t,
operands_list: *const *const c_char,
operands_list_len: *const size_t,
num_operands: c_int,
success: *mut u8,
new_value_length: *mut size_t)
-> *const c_char {
unsafe {
let cb: &mut MergeOperatorCallback =
&mut *(raw_cb as *mut MergeOperatorCallback);
let operands = &mut MergeOperands::new(operands_list,
operands_list_len,
num_operands);
let key: &[u8] = slice::from_raw_parts(raw_key as *const u8,
key_len as usize);
let mut result = (cb.merge_fn)(key, None, operands);
result.shrink_to_fit();
let buf = libc::malloc(result.len() as size_t);
assert!(!buf.is_null());
*new_value_length = 1 as size_t;
*success = 1 as u8;
ptr::copy(result.as_ptr() as *mut c_void, &mut *buf, result.len());
buf as *const c_char
}
}
pub struct MergeOperands {
operands_list: *const *const c_char,
operands_list_len: *const size_t,
num_operands: usize,
cursor: usize,
}
impl MergeOperands {
fn new(operands_list: *const *const c_char,
operands_list_len: *const size_t,
num_operands: c_int)
-> MergeOperands {
assert!(num_operands >= 0);
MergeOperands {
operands_list: operands_list,
operands_list_len: operands_list_len,
num_operands: num_operands as usize,
cursor: 0,
}
}
}
impl<'a> Iterator for &'a mut MergeOperands {
type Item = &'a [u8];
fn next(&mut self) -> Option<&'a [u8]> {
match self.cursor == self.num_operands {
true => None,
false => unsafe {
let base = self.operands_list as usize;
let base_len = self.operands_list_len as usize;
let spacing = mem::size_of::<*const *const u8>();
let spacing_len = mem::size_of::<*const size_t>();
let len_ptr =
(base_len + (spacing_len * self.cursor)) as *const size_t;
let len = *len_ptr as usize;
let ptr = base + (spacing * self.cursor);
self.cursor += 1;
Some(mem::transmute(slice::from_raw_parts(*(ptr as *const *const u8)
as *const u8, len)))
},
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let remaining = self.num_operands - self.cursor;
(remaining, Some(remaining))
}
}
#[allow(unused_variables)]
#[allow(dead_code)]
fn test_provided_merge(new_key: &[u8],
existing_val: Option<&[u8]>,
operands: &mut MergeOperands)
-> Vec<u8> {
let nops = operands.size_hint().0;
let mut result: Vec<u8> = Vec::with_capacity(nops);
match existing_val {
Some(v) => {
for e in v {
result.push(*e);
}
}
None => (),
}
for op in operands {
for e in op {
result.push(*e);
}
}
result
}
#[allow(dead_code)]
#[test]
fn mergetest() {
use rocksdb_options::Options;
use rocksdb::{DB, DBVector, Writable};
let path = "_rust_rocksdb_mergetest";
let mut opts = Options::new();
opts.create_if_missing(true);
opts.add_merge_operator("test operator", test_provided_merge);
{
let db = DB::open(&opts, path).unwrap();
let p = db.put(b"k1", b"a");
assert!(p.is_ok());
let _ = db.merge(b"k1", b"b");
let _ = db.merge(b"k1", b"c");
let _ = db.merge(b"k1", b"d");
let _ = db.merge(b"k1", b"efg");
let m = db.merge(b"k1", b"h");
assert!(m.is_ok());
match db.get(b"k1") {
Ok(Some(value)) => {
match value.to_utf8() {
Some(v) => println!("retrieved utf8 value: {}", v),
None => println!("did not read valid utf-8 out of the db"),
}
}
Err(e) => println!("error reading value"),
_ => panic!("value not present"),
}
assert!(m.is_ok());
let r: Result<Option<DBVector>, String> = db.get(b"k1");
assert!(r.unwrap().unwrap().to_utf8().unwrap() == "abcdefgh");
assert!(db.delete(b"k1").is_ok());
assert!(db.get(b"k1").unwrap().is_none());
}
assert!(DB::destroy(&opts, path).is_ok());
}