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Fix off-by-one. #243

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Merged
ordian merged 2 commits into from
Oct 21, 2019
Merged

Fix off-by-one. #243

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dda38b0
Fix off-by-one.
tomusdrw Oct 21, 2019
32b559e
Fix.
tomusdrw Oct 21, 2019
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5 changes: 3 additions & 2 deletions primitive-types/impls/serde/Cargo.toml
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
[package]
name = "impl-serde"
version = "0.2.1"
version = "0.2.2"
authors = ["Parity Technologies <[email protected]>"]
license = "Apache-2.0/MIT"
homepage = "https://github.com/paritytech/parity-common"
Expand All @@ -11,8 +11,9 @@ serde = "1.0"

[dev-dependencies]
criterion = "0.3.0"
uint = "0.8.1"
serde_derive = "1.0"
serde_json = "1.0.40"
uint = "0.8.1"

[[bench]]
name = "impl_serde"
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41 changes: 40 additions & 1 deletion primitive-types/impls/serde/src/serialize.rs
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Expand Up @@ -105,7 +105,7 @@ pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<u8>, D::Error> where

let bytes_len = v.len() - 2;
let mut modulus = bytes_len % 2;
let mut bytes = vec![0u8; bytes_len / 2];
let mut bytes = vec![0u8; (bytes_len + 1) / 2];
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@niklasad1 niklasad1 Oct 21, 2019 •
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why bother with this complex logic?
Isn't better to use Vec::new() / Vec::with_capacity() and Vec::push?

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@tomusdrw tomusdrw Oct 21, 2019

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Well, it's a performance optimization (hopefuly measureable), which is justified, since this code might be on a hot path.
Also this logic is not that complex imho, seems it was just untested properly.

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@dvdplm dvdplm Oct 21, 2019

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I for one kind of agree with Niklas here: it's a bit odd and I'm surprised to learn it's faster to init a vec with vec![0u8; 123] than Vec::with_capacity(123).

(No action needed here, I'm just curious)

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@niklasad1 niklasad1 Oct 21, 2019

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I'm about to add benches for Bytes to be continued :P

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@tomusdrw tomusdrw Oct 21, 2019

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Wow, thanks for making me realize this is actually a vec. I was pretty sure that we just allocate an array here (but obviously we don't cause it's not a constant size)
I'm really curious about the performance indeed, as just using push instead of direct access seems way less error prone, and with_capacity should ensure that there are no re-allocations.

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@dvdplm dvdplm Oct 21, 2019

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I really hope there's no difference in performance! :)

let mut buf = 0;
let mut pos = 0;
for (idx, byte) in v.bytes().enumerate().skip(2) {
Expand Down Expand Up @@ -217,3 +217,42 @@ pub fn deserialize_check_len<'a, 'de, D>(deserializer: D, len: ExpectedLen<'a>)

deserializer.deserialize_str(Visitor { len })
}

#[cfg(test)]
mod tests {
extern crate serde_derive;

use self::serde_derive::Deserialize;

#[derive(Deserialize)]
struct Bytes(#[serde(with="super")] Vec<u8>);

#[test]
fn should_not_fail_on_short_string() {
let a: Bytes = serde_json::from_str("\"0x\"").unwrap();
let b: Bytes = serde_json::from_str("\"0x1\"").unwrap();
let c: Bytes = serde_json::from_str("\"0x12\"").unwrap();
let d: Bytes = serde_json::from_str("\"0x123\"").unwrap();
let e: Bytes = serde_json::from_str("\"0x1234\"").unwrap();
let f: Bytes = serde_json::from_str("\"0x12345\"").unwrap();

assert!(a.0.is_empty());
assert_eq!(b.0, vec![1]);
assert_eq!(c.0, vec![0x12]);
assert_eq!(d.0, vec![0x1, 0x23]);
assert_eq!(e.0, vec![0x12, 0x34]);
assert_eq!(f.0, vec![0x1, 0x23, 0x45]);
}


#[test]
fn should_not_fail_on_other_strings() {
let a: Bytes = serde_json::from_str("\"0x7f864e18e3dd8b58386310d2fe0919eef27c6e558564b7f67f22d99d20f587\"").unwrap();
let b: Bytes = serde_json::from_str("\"0x7f864e18e3dd8b58386310d2fe0919eef27c6e558564b7f67f22d99d20f587b\"").unwrap();
let c: Bytes = serde_json::from_str("\"0x7f864e18e3dd8b58386310d2fe0919eef27c6e558564b7f67f22d99d20f587b4\"").unwrap();

assert_eq!(a.0.len(), 31);
assert_eq!(b.0.len(), 32);
assert_eq!(c.0.len(), 32);
}
}