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fix(RateChangeQueue): empty queue behavior #272

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fix(RateChangeQueue): empty queue behavior #272

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ca3ae1b
fix #266
wjmelements Jan 28, 2026
068d5f4
can rm this return
wjmelements Jan 28, 2026
acb772a
Merge branch 'main' into fix-266
wjmelements Jan 28, 2026
7d3dbfc
Merge remote-tracking branch 'origin/main' into fix-266
wjmelements Jan 28, 2026
a8051f0
zero out queue when zeroing out rail
wjmelements Jan 28, 2026
cb671ea
fmt
wjmelements Jan 28, 2026
0b90251
document the behavior if invoked when queue is not empty
wjmelements Jan 28, 2026
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1 change: 1 addition & 0 deletions src/FilecoinPayV1.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -1596,6 +1596,7 @@ contract FilecoinPayV1 is ReentrancyGuard {
rail.settledUpTo = 0;
rail.endEpoch = 0;
rail.commissionRateBps = 0;
rail.rateChangeQueue.clearEmpty();
}

function updateOperatorRateUsage(OperatorApproval storage approval, uint256 oldRate, uint256 newRate) internal {
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47 changes: 27 additions & 20 deletions src/RateChangeQueue.sol
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Expand Up @@ -2,6 +2,8 @@
pragma solidity ^0.8.27;

library RateChangeQueue {
error EmptyQueue();

struct RateChange {
// The payment rate to apply
uint256 rate;
Expand All @@ -18,33 +20,38 @@ library RateChangeQueue {
queue.changes.push(RateChange(rate, untilEpoch));
}

function dequeue(Queue storage queue) internal returns (RateChange memory) {
function dequeue(Queue storage queue) internal returns (RateChange memory change) {
RateChange[] storage c = queue.changes;
require(queue.head < c.length, "Queue is empty");
RateChange memory change = c[queue.head];
delete c[queue.head];

if (isEmpty(queue)) {
queue.head = 0;
// The array is already empty, waste no time zeroing it.
assembly {
sstore(c.slot, 0)
}
} else {
queue.head++;
require(queue.head < c.length, EmptyQueue());
unchecked {
change = c[queue.head];
delete c[queue.head++];
}
}

return change;
// Clears the storage of the Queue
// If the queue isEmpty, all queue storage will be cleared
// Otherwise, the queue is functionally emptied but pending RateChange are not cleared from storage
function clearEmpty(Queue storage queue) internal {
queue.head = 0;
RateChange[] storage c = queue.changes;
assembly ("memory-safe") {
sstore(c.slot, 0)
}
}

function peek(Queue storage queue) internal view returns (RateChange memory) {
require(queue.head < queue.changes.length, "Queue is empty");
return queue.changes[queue.head];
function peek(Queue storage queue) internal view returns (RateChange memory change) {
require(queue.head < queue.changes.length, EmptyQueue());
unchecked {
change = queue.changes[queue.head];
}
}

function peekTail(Queue storage queue) internal view returns (RateChange memory) {
require(queue.head < queue.changes.length, "Queue is empty");
return queue.changes[queue.changes.length - 1];
function peekTail(Queue storage queue) internal view returns (RateChange memory change) {
require(queue.head < queue.changes.length, EmptyQueue());
unchecked {
change = queue.changes[queue.changes.length - 1];
}
}

function isEmpty(Queue storage queue) internal view returns (bool) {
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11 changes: 8 additions & 3 deletions test/RateChangeQueue.t.sol
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Expand Up @@ -117,14 +117,19 @@ contract RateChangeQueueTest is Test {
// Queue should now be empty
assertTrue(RateChangeQueue.isEmpty(queue()));
assertEq(RateChangeQueue.size(queue()), 0);

// Empty queue should have reset to head = 0
queue().clearEmpty();
assertEq(queue().head, 0);
assertEq(queue().changes.length, 0);
}

/// forge-config: default.allow_internal_expect_revert = true
function testEmptyQueueDequeue() public {
createEmptyQueue();

// Test dequeue on empty queue
vm.expectRevert("Queue is empty");
vm.expectRevert(abi.encodeWithSelector(RateChangeQueue.EmptyQueue.selector));
RateChangeQueue.dequeue(queue());
}

Expand All @@ -133,7 +138,7 @@ contract RateChangeQueueTest is Test {
createEmptyQueue();

// Test peek on empty queue
vm.expectRevert("Queue is empty");
vm.expectRevert(abi.encodeWithSelector(RateChangeQueue.EmptyQueue.selector));
RateChangeQueue.peek(queue());
}

Expand All @@ -142,7 +147,7 @@ contract RateChangeQueueTest is Test {
createEmptyQueue();

// Test peekTail on empty queue
vm.expectRevert("Queue is empty");
vm.expectRevert(abi.encodeWithSelector(RateChangeQueue.EmptyQueue.selector));
RateChangeQueue.peekTail(queue());
}

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