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Break decode out into own file

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This commit is contained in:
Paul Hauner 2018-09-11 12:17:54 +02:00
parent 2d29c34892
commit 51352c4657
3 changed files with 146 additions and 77 deletions
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135
ssz/src/decode.rs Normal file
View File

@ -0,0 +1,135 @@
use super::{
LENGTH_BYTES,
};
#[derive(Debug)]
pub enum DecodeError {
OutOfBounds,
TooShort,
TooLong,
}
pub trait Decodable: Sized {
fn ssz_decode(bytes: &[u8]) -> Result<Self, DecodeError>;
}
pub fn decode_ssz_list_element<T>(ssz_bytes: &[u8], n: usize)
-> Result<T, DecodeError>
where T: Decodable
{
T::ssz_decode(nth_value(ssz_bytes, n)?)
}
fn nth_value(ssz_bytes: &[u8], n: usize)
-> Result<&[u8], DecodeError>
{
let mut c: usize = 0;
for i in 0..(n + 1) {
let length = decode_length(&ssz_bytes[c..], LENGTH_BYTES)?;
let next = c + LENGTH_BYTES + length;
if i == n {
return Ok(&ssz_bytes[c + LENGTH_BYTES..next]);
} else {
if next >= ssz_bytes.len() {
return Err(DecodeError::OutOfBounds);
} else {
c = next;
}
}
}
Err(DecodeError::OutOfBounds)
}
fn decode_length(bytes: &[u8], length_bytes: usize)
-> Result<usize, DecodeError>
{
if bytes.len() < length_bytes {
return Err(DecodeError::TooShort);
};
let mut len: usize = 0;
for i in 0..length_bytes {
let offset = (length_bytes - i - 1) * 8;
len = ((bytes[i] as usize) << offset) | len;
};
Ok(len)
}
#[cfg(test)]
mod tests {
use super::*;
use super::super::encode_length;
#[test]
fn test_ssz_decode_length() {
let decoded = decode_length(
&vec![0, 0, 0, 1],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 1);
let decoded = decode_length(
&vec![0, 0, 1, 0],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 256);
let decoded = decode_length(
&vec![0, 0, 1, 255],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 511);
let decoded = decode_length(
&vec![255, 255, 255, 255],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 4294967295);
}
#[test]
fn test_encode_decode_length() {
let params: Vec<usize> = vec![
0, 1, 2, 3, 7, 8, 16,
2^8, 2^8 + 1,
2^16, 2^16 + 1,
2^24, 2^24 + 1,
2^32,
];
for i in params {
let decoded = decode_length(
&encode_length(i, LENGTH_BYTES),
LENGTH_BYTES).unwrap();
assert_eq!(i, decoded);
}
}
#[test]
fn test_ssz_nth_value() {
let ssz = vec![0, 0, 0, 1, 0];
let result = nth_value(&ssz, 0).unwrap();
assert_eq!(result, vec![0].as_slice());
let ssz = vec![0, 0, 0, 4, 1, 2, 3, 4];
let result = nth_value(&ssz, 0).unwrap();
assert_eq!(result, vec![1, 2, 3, 4].as_slice());
let ssz = vec![0, 0, 0, 1, 0, 0, 0, 0, 1, 1];
let result = nth_value(&ssz, 1).unwrap();
assert_eq!(result, vec![1].as_slice());
let mut ssz = vec![0, 0, 1, 255];
ssz.append(&mut vec![42; 511]);
let result = nth_value(&ssz, 0).unwrap();
assert_eq!(result, vec![42; 511].as_slice());
}
/*
#[test]
fn test_ssz_decode_u16() {
let x: u16 = 100;
let mut s = SszStream::new();
s.append(&x);
let y: u16 = u16::ssz_decode(s.nth_value(0).unwrap())
.unwrap();
assert_eq!(x, y);
}
*/
}

15
ssz/src/impls.rs
View File

@ -13,18 +13,14 @@ use super::ethereum_types::{ H256, U256 };
macro_rules! impl_decodable_for_uint {
($type: ident, $bit_size: expr) => {
impl Decodable for $type {
type Decoded = $type;
fn ssz_decode<$type>(bytes: &[u8])
-> Result<Self::Decoded, DecodeError>
fn ssz_decode(bytes: &[u8])
-> Result<Self, DecodeError>
{
// TOOD: figure out if than can be done at compile time
// instead of runtime (where I assume it happens).
assert!(0 < $bit_size &&
$bit_size <= 64 &&
$bit_size % 8 == 0);
let bytes_required = $bit_size / 8;
if bytes_required == bytes.len() {
if bytes_required <= bytes.len() {
let mut result = 0;
for i in 0..bytes.len() {
let offset = (bytes.len() - i - 1) * 8;
@ -32,10 +28,7 @@ macro_rules! impl_decodable_for_uint {
};
Ok(result.into())
} else {
match bytes_required > bytes.len() {
true => Err(DecodeError::TooLong),
false => Err(DecodeError::TooShort),
}
Err(DecodeError::TooLong)
}
}
}

73
ssz/src/lib.rs
View File

@ -11,6 +11,13 @@ extern crate bytes;
extern crate ethereum_types;
mod impls;
mod decode;
pub use decode::{
decode_ssz_list_element,
Decodable,
DecodeError
};
pub const LENGTH_BYTES: usize = 4;
@ -18,23 +25,10 @@ pub trait Encodable {
fn ssz_append(&self, s: &mut SszStream);
}
pub trait Decodable {
type Decoded;
fn ssz_decode<T>(bytes: &[u8]) -> Result<Self::Decoded, DecodeError>;
}
pub struct SszStream {
buffer: Vec<u8>
}
#[derive(Debug)]
pub enum DecodeError {
OutOfBounds,
TooShort,
TooLong,
}
impl SszStream {
/// Create a new, empty steam for writing ssz values.
pub fn new() -> Self {
@ -92,20 +86,6 @@ fn encode_length(len: usize, length_bytes: usize) -> Vec<u8> {
header
}
fn decode_length(bytes: &Vec<u8>, length_bytes: usize)
-> Result<usize, DecodeError>
{
if bytes.len() < length_bytes {
return Err(DecodeError::TooShort);
};
let mut len: usize = 0;
for i in 0..length_bytes {
let offset = (length_bytes - i - 1) * 8;
len = ((bytes[i] as usize) << offset) | len;
};
Ok(len)
}
#[cfg(test)]
mod tests {
@ -148,45 +128,6 @@ mod tests {
encode_length(4294967296, 4); // 2^(4*8)
}
#[test]
fn test_decode_length() {
let decoded = decode_length(
&vec![0, 0, 0, 1],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 1);
let decoded = decode_length(
&vec![0, 0, 1, 0],
LENGTH_BYTES);
assert_eq!(decoded.unwrap(), 256);
}
#[test]
fn test_encode_decode_length() {
let params: Vec<usize> = vec![
0,
1,
2,
3,
7,
8,
16,
2^8,
2^8 + 1,
2^16,
2^16 + 1,
2^24,
2^24 + 1,
2^32,
];
for i in params {
let decoded = decode_length(
&encode_length(i, LENGTH_BYTES),
LENGTH_BYTES).unwrap();
assert_eq!(i, decoded);
}
}
#[test]
fn test_serialization() {
pub struct TestStruct {