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Fix compatibility de/serialization of Policies #878
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…ion' into backward_compatible_deserialization
Co-authored-by: Andrea Cerone <[email protected]>
General comment on serialization and deserialization: You can still derive most of it. The main idea is that you can define your own structure PoliciesV1 and PoliciesV2, only for serialization/deserialization purposes, for which This is what I have got locally: pub struct Policies {
/// A bitmask that indicates what policies are set.
bits: PoliciesBits,
/// The array of policy values.
values: [Word; POLICIES_NUMBER],
}
#[derive(serde::Serialize, serde::Deserialize)]
#[serde(rename = "Policies")]
pub struct PoliciesV1 {
bits: PoliciesBits,
values: [Word; 4],
}
#[derive(serde::Serialize, serde::Deserialize)]
#[serde(rename = "Policies")]
pub struct PoliciesV2 {
bits: PoliciesBits,
values: Vec<Word>,
}
// This serde is manually implemented because of the `values` field format.
// Serialization of the `values` field :
// 1. Always write the 4 elements for the first 4 policies even if they are not set for
// backward compatibility.
// 2. For the remaining, write the value only if the policy is set.
impl serde::Serialize for Policies {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
let Policies { bits, values } = self;
if self.bits.intersection(PoliciesBits::all())
== self.bits.intersection(
PoliciesBits::Maturity
.union(PoliciesBits::MaxFee)
.union(PoliciesBits::Tip)
.union(PoliciesBits::WitnessLimit),
)
{
PoliciesV1 {
bits: *bits,
values: values[..4].try_into().map_err(|_| {
serde::ser::Error::custom("The first 4 values should be present")
})?,
}
.serialize(serializer)
} else {
PoliciesV2 {
bits: *bits,
values: values.to_vec(),
}
.serialize(serializer)
}
}
}
impl<'de> serde::Deserialize<'de> for Policies {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
let policies_v2 = PoliciesV2::deserialize(deserializer)?;
if policies_v2.bits.intersection(PoliciesBits::all())
== policies_v2.bits.intersection(
PoliciesBits::Maturity
.union(PoliciesBits::MaxFee)
.union(PoliciesBits::Tip)
.union(PoliciesBits::WitnessLimit),
)
{
let mut values: [Word; POLICIES_NUMBER] = [0; POLICIES_NUMBER];
values[..4].copy_from_slice(&policies_v2.values[..4]);
Ok(Policies {
bits: policies_v2.bits,
values,
})
} else {
let mut values: [Word; POLICIES_NUMBER] = [0; POLICIES_NUMBER];
values[..POLICIES_NUMBER]
.copy_from_slice(&policies_v2.values[..POLICIES_NUMBER]);
Ok(Policies {
bits: policies_v2.bits,
values,
})
}
}
} |
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LGTM. I have proposed a change but it can be implemented on top of your PR
Issue
We want to be able to execute transactions that were created with transactions builders using versions before 0.59.0 in the next VM versions.
The problem is that with the new policy (#871) the array of policies values is now of length 5 and before it was length 4. On 0.59.0 the serde de/serialization is taking 5 "Words" to decode the policies values array which cause transactions from 0.58.0 to not be able to be deserialized correctly.
Fix
We want in this PR to change the serde de/serialization so that we ensure that previous format is still supported and new policies too.
We first de/serialize the
PoliciesBits
this allow us to know if we have only policies set in the first 4 (old) policies then we just the backward compatibility mode otherwise we use a new mode with a flexible length.Previous serde derive expanded (to compare with new implementation)
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