extindex 
Immutable persisted index (on disk) that can be built in one pass using a sorted iterator, or uses extsort
to externally sort the iterator first, and then build the index. The index allow random lookups and sorted scans.
An indexed entry consists of a key and a value. The key needs to implement Eq and Ord, and both the key and values
need to implement a Encodable trait for serialization to and from disk.
Example
extern crate extindex;
extern crate tempdir;
use std::io::{Read, Write};
use extindex::{Builder, Encodable, Entry, Reader};
#[derive(Ord, PartialOrd, Eq, PartialEq, Debug)]
struct TestString(String);
impl Encodable<TestString> for TestString {
fn encode_size(item: &TestString) -> usize {
item.0.as_bytes().len()
}
fn encode(item: &TestString, write: &mut Write) -> Result<(), std::io::Error> {
write.write(item.0.as_bytes()).map(|_| ())
}
fn decode(data: &mut Read, size: usize) -> Result<TestString, std::io::Error> {
let mut bytes = vec![0u8; size];
data.read_exact(&mut bytes)?;
Ok(TestString(String::from_utf8_lossy(&bytes).to_string()))
}
}
fn main() {
let tempdir = tempdir::TempDir::new("extindex").unwrap();
let index_file = tempdir.path().join("index.idx");
let builder = Builder::new(index_file.clone());
let entries = vec![
Entry::new(TestString("mykey".to_string()), TestString("my value".to_string()))
];
builder.build(entries.into_iter()).unwrap();
let reader = Reader::<TestString, TestString>::open(&index_file).unwrap();
assert!(reader.find(&TestString("mykey".to_string())).unwrap().is_some());
assert!(reader.find(&TestString("notfound".to_string())).unwrap().is_none());
}
TODO
