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avoid copying excess consideration items when decoding contract orders #42

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Feb 29, 2024
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avoid copying excess consideration items when decoding contract orders #42

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56 changes: 22 additions & 34 deletions src/core/lib/ConsiderationDecoder.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -1100,41 +1100,52 @@ contract ConsiderationDecoder {
// Cache the original consideration array length
let originalConsiderationLength := mload(mPtrLengthOriginal)

// Allocate memory for the array.
// Ensure returned array length does not exceed original length.
invalidReceivedItems := gt(length, originalConsiderationLength)

// Derive the length of the new array in memory, capped by the
// original consideration array length.
let newLength := min(length, originalConsiderationLength)

// Allocate memory for the array. Note that memory does not need
// to be allocated for new elements without a corresponding
// original item as the new array will be invalid if its length
// exceeds the original array length.
mstore(
FreeMemoryPointerSlot,
add(
mPtrLength,
add(
OneWord,
mul(length, ConsiderationItem_size_with_length)
mul(newLength, ConsiderationItem_size_with_length)
)
)
)

// Write the length of the array to the start of free memory.
mstore(mPtrLength, length)
mstore(mPtrLength, newLength)

// Use offset from length to minimize stack depth.
let headOffsetFromLength := OneWord
let headSizeWithLength := shl(OneWordShift, add(1, length))
let mPtrTailNext := add(mPtrLength, headSizeWithLength)
let mPtrTailNext := add(
mPtrLength,
shl(OneWordShift, add(1, newLength))
)
let mPtrTailOriginalNext := add(
mPtrLengthOriginal,
shl(OneWordShift, add(1, originalConsiderationLength))
)

let headSizeToCompareWithLength := shl(
OneWordShift,
add(1, min(length, originalConsiderationLength))
add(1, newLength)
)

// Iterate over each new element with a corresponding original
// item. For each new received item, check that:
// - The new & original items match according to compareItems.
// - The new consideration item amount <= the original amount.
// - The items have the same recipient if original != null.
invalidReceivedItems := gt(length, originalConsiderationLength)
for { } lt(
headOffsetFromLength,
headSizeToCompareWithLength
Expand All @@ -1156,6 +1167,7 @@ contract ConsiderationDecoder {
OneWord
)

// Retrieve both the new and original item amounts.
let newAmount := mload(
add(mPtrTailNext, Common_amount_offset)
)
Expand Down Expand Up @@ -1206,33 +1218,9 @@ contract ConsiderationDecoder {
headOffsetFromLength := add(headOffsetFromLength, OneWord)
}

// Iterate over new elements with no corresponding original item
for { } lt(headOffsetFromLength, headSizeWithLength) { } {
// Write the memory pointer to the accompanying head offset.
mstore(add(mPtrLength, headOffsetFromLength), mPtrTailNext)

// Copy itemType, token, identifier, amount and recipient.
returndatacopy(
mPtrTailNext,
rdPtrHeadReceivedItems,
ReceivedItem_size
)

// Copy amount to consideration item's recipient offset.
returndatacopy(
add(mPtrTailNext, ConsiderationItem_recipient_offset),
add(rdPtrHeadReceivedItems, Common_amount_offset),
OneWord
)

// Update read pointer, next tail pointer, and head offset.
rdPtrHeadReceivedItems := add(
rdPtrHeadReceivedItems,
ReceivedItem_size
)
mPtrTailNext := add(mPtrTailNext, ConsiderationItem_size)
headOffsetFromLength := add(headOffsetFromLength, OneWord)
}
// Note: skip copying new elements without a corresponding
// original item as the new array will be invalid if its length
// exceeds the original array length.
}

/**
Expand Down
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