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Add optimized SSZ decoding for fixed-len items (#865)

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* Add custom SSZ decode for Validator

* Move efficient decode into macro

* Don't allocate SSZ offset to heap

* Use smallvec in SszDecoder

* Fix test compile error
This commit is contained in:
Paul Hauner
2020-03-04 11:45:01 +11:00
committed by GitHub
parent 58fb144276
commit 871163aecc
6 changed files with 79 additions and 32 deletions
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22
eth2/utils/ssz/src/encode.rs
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@@ -115,7 +115,7 @@ impl<'a> SszEncoder<'a> {
item.ssz_append(&mut self.buf);
} else {
self.buf
.append(&mut encode_length(self.offset + self.variable_bytes.len()));
.extend_from_slice(&encode_length(self.offset + self.variable_bytes.len()));
item.ssz_append(&mut self.variable_bytes);
}
@@ -132,17 +132,17 @@ impl<'a> SszEncoder<'a> {
}
}
/// Encode `index` as a little-endian byte vec of `BYTES_PER_LENGTH_OFFSET` length.
/// Encode `index` as a little-endian byte array of `BYTES_PER_LENGTH_OFFSET` length.
///
/// If `len` is larger than `2 ^ BYTES_PER_LENGTH_OFFSET`, a `debug_assert` is raised.
pub fn encode_union_index(index: usize) -> Vec<u8> {
pub fn encode_union_index(index: usize) -> [u8; BYTES_PER_LENGTH_OFFSET] {
encode_length(index)
}
/// Encode `len` as a little-endian byte vec of `BYTES_PER_LENGTH_OFFSET` length.
/// Encode `len` as a little-endian byte array of `BYTES_PER_LENGTH_OFFSET` length.
///
/// If `len` is larger than `2 ^ BYTES_PER_LENGTH_OFFSET`, a `debug_assert` is raised.
pub fn encode_length(len: usize) -> Vec<u8> {
pub fn encode_length(len: usize) -> [u8; BYTES_PER_LENGTH_OFFSET] {
// Note: it is possible for `len` to be larger than what can be encoded in
// `BYTES_PER_LENGTH_OFFSET` bytes, triggering this debug assertion.
//
@@ -166,7 +166,9 @@ pub fn encode_length(len: usize) -> Vec<u8> {
// If you have a different opinion, feel free to start an issue and tag @paulhauner.
debug_assert!(len <= MAX_LENGTH_VALUE);
len.to_le_bytes()[0..BYTES_PER_LENGTH_OFFSET].to_vec()
let mut bytes = [0; BYTES_PER_LENGTH_OFFSET];
bytes.copy_from_slice(&len.to_le_bytes()[0..BYTES_PER_LENGTH_OFFSET]);
bytes
}
#[cfg(test)]
@@ -175,13 +177,13 @@ mod tests {
#[test]
fn test_encode_length() {
assert_eq!(encode_length(0), vec![0; 4]);
assert_eq!(encode_length(0), [0; 4]);
assert_eq!(encode_length(1), vec![1, 0, 0, 0]);
assert_eq!(encode_length(1), [1, 0, 0, 0]);
assert_eq!(
encode_length(MAX_LENGTH_VALUE),
vec![255; BYTES_PER_LENGTH_OFFSET]
[255; BYTES_PER_LENGTH_OFFSET]
);
}
@@ -195,6 +197,6 @@ mod tests {
#[test]
#[cfg(not(debug_assertions))]
fn test_encode_length_above_max_not_debug_does_not_panic() {
assert_eq!(encode_length(MAX_LENGTH_VALUE + 1), vec![0; 4]);
assert_eq!(&encode_length(MAX_LENGTH_VALUE + 1)[..], &[0; 4]);
}
}