// Streams the diff from |last| to |current| into |changes|, using a top-down approach.
// Top-down is parallel and efficiently returns the complete diff, but compared to left-right it's slow to start streaming changes.
func orderedSequenceDiffTopDown(last orderedSequence, current orderedSequence, changes chan<- ValueChanged, stopChan <-chan struct{}) bool {
var lastHeight, currentHeight int
functions.All(
func() { lastHeight = newCursorAt(last, emptyKey, false, false).depth() },
func() { currentHeight = newCursorAt(current, emptyKey, false, false).depth() },
)
return orderedSequenceDiffInternalNodes(last, current, changes, stopChan, lastHeight, currentHeight)
}
// TODO - something other than the literal edit-distance, which is way too much cpu work for this case - https://github.com/attic-labs/noms/issues/2027
func orderedSequenceDiffInternalNodes(last orderedSequence, current orderedSequence, changes chan<- ValueChanged, stopChan <-chan struct{}, lastHeight, currentHeight int) bool {
if lastHeight > currentHeight {
lastChild := last.(orderedMetaSequence).getCompositeChildSequence(0, uint64(last.seqLen())).(orderedSequence)
return orderedSequenceDiffInternalNodes(lastChild, current, changes, stopChan, lastHeight-1, currentHeight)
}
if currentHeight > lastHeight {
currentChild := current.(orderedMetaSequence).getCompositeChildSequence(0, uint64(current.seqLen())).(orderedSequence)
return orderedSequenceDiffInternalNodes(last, currentChild, changes, stopChan, lastHeight, currentHeight-1)
}
if !isMetaSequence(last) && !isMetaSequence(current) {
return orderedSequenceDiffLeftRight(last, current, changes, stopChan)
}
compareFn := last.getCompareFn(current)
initialSplices := calcSplices(uint64(last.seqLen()), uint64(current.seqLen()), DEFAULT_MAX_SPLICE_MATRIX_SIZE,
func(i uint64, j uint64) bool { return compareFn(int(i), int(j)) })
for _, splice := range initialSplices {
var lastChild, currentChild orderedSequence
functions.All(
func() {
lastChild = last.(orderedMetaSequence).getCompositeChildSequence(splice.SpAt, splice.SpRemoved).(orderedSequence)
},
func() {
currentChild = current.(orderedMetaSequence).getCompositeChildSequence(splice.SpFrom, splice.SpAdded).(orderedSequence)
},
)
if ok := orderedSequenceDiffInternalNodes(lastChild, currentChild, changes, stopChan, lastHeight-1, currentHeight-1); !ok {
return false
}
}
return true
}