Print first n entries

storage_engine/src/binary_coding.rs

@@ -0,0 +1,78 @@
+use bincode;
+use bincode::{Decode, Encode};
+use bincode::config::{BigEndian, Configuration, Fixint};
+use std::mem::size_of;
+
+const BIN_CONFIG: Configuration<BigEndian, Fixint> = bincode::config::standard().with_big_endian().with_fixed_int_encoding();
+
+pub fn encode<T: Encode>(t: &T) -> Result<Vec<u8>, bincode::error::EncodeError> {
+    bincode::encode_to_vec(t, BIN_CONFIG)
+}
+
+pub fn decode<T: Decode>(bytes: &[u8]) -> Result<(T, usize), bincode::error::DecodeError> {
+    bincode::decode_from_slice(bytes, BIN_CONFIG)
+}
+
+pub fn encode_vector<T: Encode>(ts: &[T]) -> Result<Vec<u8>, bincode::error::EncodeError> {
+    let size: usize = ts.len();
+    let mut result = encode(&size)?;
+    for t in ts {
+        result.append(&mut encode(&t)?);
+    }
+    Ok(result)
+}
+
+pub fn decode_vector<T: Decode>(bytes: &[u8]) -> Result<Vec<T>, bincode::error::DecodeError> {
+    let mut offset = size_of::<usize>();
+    let result_len: usize = decode(&bytes[..offset])?.0;
+    let mut result: Vec<T> = Vec::with_capacity(result_len);
+    for _ in 0..result_len {
+        let (x, bytes_consumed) = decode::<T>(&bytes[offset..])?;
+        offset += bytes_consumed;
+        result.push(x);
+    }
+    Ok(result)
+}
+
+// We don't care about encoding the length here (since it will be used for a row with known column
+// size)
+pub fn encode_sequence<T: Encode>(ts: &[T]) -> Result<Vec<u8>, bincode::error::EncodeError> {
+    let mut result = vec![];
+    for t in ts {
+        result.append(&mut encode(&t)?);
+
+    }
+    Ok(result)
+}
+
+pub fn decode_sequence<T: Decode>(len: usize, bytes: &[u8]) -> Result<Vec<T>, bincode::error::DecodeError> {
+    let mut result: Vec<T> = Vec::with_capacity(len);
+    let mut offset = 0;
+    for _ in 0..len {
+        let (x, bytes_consumed) = decode::<T>(&bytes[offset..])?;
+        offset += bytes_consumed;
+        result.push(x);
+    }
+    Ok(result)
+}
+
+
+fn example_encoding_decoding() {
+    let xs: Vec<u32> = vec![123, 250, 256, 123, 123, 123];
+    let xs: Vec<u32> = vec![];
+    let xs: Vec<u32> = vec![123];
+    let xs: Vec<u32> = vec![123, 250];
+
+    let xs: Vec<String> = vec!["foo".to_string(), "bar".to_string()];
+
+
+    println!("original {:?}", xs);
+    let exs = encode_vector(&xs[..]).unwrap();
+    println!("encoded {:?}", exs);
+
+    // WARNING: Don't forget to specify the type here
+    // let dxs = decode_vector::<u32>(&exs[..]).unwrap();
+    let dxs = decode_vector::<String>(&exs[..]).unwrap();
+    println!("decoded {:?}", dxs);
+}
+