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changing to compute visited_count while computing size
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@igor-aptos
igor-aptos committed Nov 13, 2024
1 parent f6c8829 commit 2db92e9
Showing 1 changed file with 35 additions and 66 deletions.
101 changes: 35 additions & 66 deletions aptos-move/framework/move-stdlib/src/natives/bcs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -146,12 +146,11 @@ fn native_constant_serialized_size(
let ty = ty_args.pop().unwrap();
let ty_layout = context.type_to_type_layout(&ty)?;

context.charge(
BCS_CONSTANT_SERIALIZED_SIZE_PER_TYPE_NODE
* NumTypeNodes::new(type_visit_count_for_constant_serialized_size(&ty_layout)),
)?;
let (visited_count, serialized_size_result) = constant_serialized_size(&ty_layout);
context
.charge(BCS_CONSTANT_SERIALIZED_SIZE_PER_TYPE_NODE * NumTypeNodes::new(visited_count))?;

let result = match constant_serialized_size(&ty_layout) {
let result = match serialized_size_result {
Ok(value) => create_option_u64(value.map(|v| v as u64)),
Err(_) => {
context.charge(BCS_SERIALIZED_SIZE_FAILURE)?;
Expand All @@ -166,57 +165,12 @@ fn native_constant_serialized_size(
Ok(smallvec![result])
}

/// Count upper limit on the number of types constant_serialized_size would visit,
/// which is then used for gas charging, before performing the operation.
/// This is different done type.num_nodes(), as some types are not traversed (i.e. vector),
/// and for structs types and number of fields matter as well.
///
/// Unclear if type_visit_count would be the same for other usages
/// (for example, whether vector types need to be traversed),
/// so name it very specifically, and on future usages see how it generalizes.
fn type_visit_count_for_constant_serialized_size(ty_layout: &MoveTypeLayout) -> u64 {
match ty_layout {
MoveTypeLayout::Bool
| MoveTypeLayout::U8
| MoveTypeLayout::U16
| MoveTypeLayout::U32
| MoveTypeLayout::U128
| MoveTypeLayout::U256
| MoveTypeLayout::U64
| MoveTypeLayout::Address
| MoveTypeLayout::Signer => 1,
// non-recursed:
MoveTypeLayout::Struct(
MoveStructLayout::RuntimeVariants(_) | MoveStructLayout::WithVariants(_),
)
| MoveTypeLayout::Vector(_) => 1,
// recursed:
MoveTypeLayout::Struct(MoveStructLayout::Runtime(fields)) => {
let mut total = 1; // Count the current visit, and aggregate all children
for field in fields {
total += type_visit_count_for_constant_serialized_size(field);
}
total
},
MoveTypeLayout::Struct(MoveStructLayout::WithFields(fields))
| MoveTypeLayout::Struct(MoveStructLayout::WithTypes { fields, .. }) => {
let mut total = 1; // Count the current visit, and aggregate all children
for field in fields {
total += type_visit_count_for_constant_serialized_size(&field.layout);
}
total
},
// Count the current visit, and inner visits
MoveTypeLayout::Native(_, inner) => {
1 + type_visit_count_for_constant_serialized_size(inner)
},
}
}

/// If given type has a constant serialized size (irrespective of the instance), it returns the serialized
/// size in bytes any value would have.
/// Otherwise it returns None.
fn constant_serialized_size(ty_layout: &MoveTypeLayout) -> PartialVMResult<Option<usize>> {
/// First element of the returned tuple represents number of visited nodes, used to charge gas.
fn constant_serialized_size(ty_layout: &MoveTypeLayout) -> (u64, PartialVMResult<Option<usize>>) {
let mut visited_count = 1;
let bcs_size_result = match ty_layout {
MoveTypeLayout::Bool => bcs::serialized_size(&false).map(Some),
MoveTypeLayout::U8 => bcs::serialized_size(&0u8).map(Some),
Expand All @@ -237,10 +191,12 @@ fn constant_serialized_size(ty_layout: &MoveTypeLayout) -> PartialVMResult<Optio
MoveTypeLayout::Struct(MoveStructLayout::Runtime(fields)) => {
let mut total = Some(0);
for field in fields {
let cur = constant_serialized_size(field)?;
let (cur_visited_count, cur) = constant_serialized_size(field);
visited_count += cur_visited_count;
match cur {
Some(cur_value) => total = total.map(|v| v + cur_value),
None => {
Err(e) => return (visited_count, Err(e)),
Ok(Some(cur_value)) => total = total.map(|v| v + cur_value),
Ok(None) => {
total = None;
break;
},
Expand All @@ -250,20 +206,33 @@ fn constant_serialized_size(ty_layout: &MoveTypeLayout) -> PartialVMResult<Optio
},
MoveTypeLayout::Struct(MoveStructLayout::WithFields(_))
| MoveTypeLayout::Struct(MoveStructLayout::WithTypes { .. }) => {
return Err(
PartialVMError::new(StatusCode::VALUE_SERIALIZATION_ERROR).with_message(
"Only runtime types expected, but found WithFields/WithTypes".to_string(),
return (
visited_count,
Err(
PartialVMError::new(StatusCode::VALUE_SERIALIZATION_ERROR).with_message(
"Only runtime types expected, but found WithFields/WithTypes".to_string(),
),
),
)
},
MoveTypeLayout::Native(_, inner) => Ok(constant_serialized_size(inner)?),
MoveTypeLayout::Native(_, inner) => {
let (cur_visited_count, cur) = constant_serialized_size(inner);
visited_count += cur_visited_count;
match cur {
Err(e) => return (visited_count, Err(e)),
Ok(v) => Ok(v),
}
},
};
bcs_size_result.map_err(|e| {
PartialVMError::new(StatusCode::VALUE_SERIALIZATION_ERROR).with_message(format!(
"failed to compute serialized size of a value: {:?}",
e
))
})
(
visited_count,
bcs_size_result.map_err(|e| {
PartialVMError::new(StatusCode::VALUE_SERIALIZATION_ERROR).with_message(format!(
"failed to compute serialized size of a value: {:?}",
e
))
}),
)
}

/***************************************************************************************************
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