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chain_getBlock extrinsics encoding #1024

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merged 8 commits into from
Jul 13, 2023
Merged

chain_getBlock extrinsics encoding #1024

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ebd7360
deserialize without decoding
tadeohepperle Jul 10, 2023
eeefa5c
change decoding approach
tadeohepperle Jul 10, 2023
daef05e
Merge branch 'master' into tadeo-hepperle-chain-get-block-extrinsic-d…
tadeohepperle Jul 10, 2023
04f74fd
fix tests
tadeohepperle Jul 11, 2023
1cc8f55
decode without allocating
tadeohepperle Jul 11, 2023
a343001
strip compact prefix
tadeohepperle Jul 11, 2023
d6d502b
cargo fmt
tadeohepperle Jul 11, 2023
743e73a
nit adjustment
tadeohepperle Jul 13, 2023
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7 changes: 4 additions & 3 deletions subxt/src/tx/tx_progress.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@

//! Types representing extrinsics/transactions that have been submitted to a node.

use codec::Decode;
use codec::{Compact, Decode, Encode};
use std::task::Poll;

use crate::{
Expand Down Expand Up @@ -389,10 +389,11 @@ impl<T: Config, C: OnlineClientT<T>> TxInBlock<T, C> {
.iter()
.position(|ext| {
use crate::config::Hasher;
let Ok(ext_without_prefix) = <Vec<u8>>::decode(&mut &ext.0[..]) else {
let Ok(compact) = <Compact<u32>>::decode(&mut &ext.0[..]) else {
return false;
};
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@jsdw jsdw Jul 11, 2023 •
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Just because size_hint is only a "hint" at the size by the docs, I'd prefer that we have a function, something like this:

/// Decode the compact prefix, returning the remainder of the
/// bytes and the decoded value. 
fn strip_compact_prefix(bytes: &[u8]) -> Result<(u64, &[u8]), codec::Error>
    let cursor = &mut &*bytes;
    let val = <Compact<u64>>::decode(cursor)?;
    Ok((val, *cursor))
}

This decodes the value, consuming any bytes used and then we return the value + rest of the bytes (so we are guaranteed to have stripped the right number off the front).

Then in your code you can:

let Ok((compact, rest)) = strip_compact_prefix(&ext.0) else {
    return false;
}
let hash = T::Hasher::hash_of(rest);
hash == self.ext_hash

You could also use .compact_len from the CompactLen trait for more of a guarantee, though since you want the remaining bytes I think the above is probably more straightrforward :)

let hash = T::Hasher::hash_of(&ext_without_prefix);
let extrinsic_start_index = compact.size_hint();
let hash = T::Hasher::hash_of(&&ext.0[extrinsic_start_index..]);
hash == self.ext_hash
})
// If we successfully obtain the block hash we think contains our
Expand Down