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trie: improve comment

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This commit is contained in:
Gary Rong 2023-12-12 16:10:43 +08:00
parent eb8f7ac0de
commit bbc0c64074
1 changed files with 15 additions and 13 deletions
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28
trie/iterator.go
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@ -145,7 +145,7 @@ type nodeIterator struct {
err error // Failure set in case of an internal error in the iterator err error // Failure set in case of an internal error in the iterator
resolver NodeResolver // optional node resolver for avoiding disk hits resolver NodeResolver // optional node resolver for avoiding disk hits
pool []*nodeIteratorState // local pool for iteratorstates pool []*nodeIteratorState // local pool for iterator states
} }
// errIteratorEnd is stored in nodeIterator.err when iteration is done. // errIteratorEnd is stored in nodeIterator.err when iteration is done.
@ -550,13 +550,14 @@ func (it *nodeIterator) pop() {
it.path = it.path[:last.pathlen] it.path = it.path[:last.pathlen]
it.stack[len(it.stack)-1] = nil it.stack[len(it.stack)-1] = nil
it.stack = it.stack[:len(it.stack)-1] it.stack = it.stack[:len(it.stack)-1]
// last is now unused
it.putInPool(last) it.putInPool(last) // last is now unused
} }
// reachedPath normalizes a path by truncating a terminator if present, and returns true if it is // reachedPath normalizes a path by truncating a terminator if present, and
// greater than or equal to the target. Using this, the path of a value node embedded a full node // returns true if it is greater than or equal to the target. Using this,
// will compare less than the full node's children. // the path of a value node embedded a full node will compare less than the
// full node's children.
func reachedPath(path, target []byte) bool { func reachedPath(path, target []byte) bool {
if hasTerm(path) { if hasTerm(path) {
path = path[:len(path)-1] path = path[:len(path)-1]
@ -564,12 +565,13 @@ func reachedPath(path, target []byte) bool {
return bytes.Compare(path, target) >= 0 return bytes.Compare(path, target) >= 0
} }
// A value embedded in a full node occupies the last slot (16) of the array of children. In order to // A value embedded in a full node occupies the last slot (16) of the array of
// produce a pre-order traversal when iterating children, we jump to this last slot first, then go // children. In order to produce a pre-order traversal when iterating children,
// back iterate the child nodes (and skip the last slot at the end): // we jump to this last slot first, then go back iterate the child nodes (and
// skip the last slot at the end):
// prevChildIndex returns the index of a child in a full node which precedes the given index when // prevChildIndex returns the index of a child in a full node which precedes
// performing a pre-order traversal. // the given index when performing a pre-order traversal.
func prevChildIndex(index int) int { func prevChildIndex(index int) int {
switch index { switch index {
case 0: // We jumped back to iterate the children, from the value slot case 0: // We jumped back to iterate the children, from the value slot
@ -583,8 +585,8 @@ func prevChildIndex(index int) int {
} }
} }
// nextChildIndex returns the index of a child in a full node which follows the given index when // nextChildIndex returns the index of a child in a full node which follows
// performing a pre-order traversal. // the given index when performing a pre-order traversal.
func nextChildIndex(index int) int { func nextChildIndex(index int) int {
switch index { switch index {
case -1: // Jump from the placeholder index to the embedded value slot case -1: // Jump from the placeholder index to the embedded value slot