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perf(shared): class-based BTree iterators #5607

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47 changes: 47 additions & 0 deletions packages/shared/src/btree-set.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -182,6 +182,53 @@ test('add should allow replacing equal entry', () => {
]);
});

suite('class-based iterators', () => {
test('forward iterator produces same results as spread', () => {
const t = new BTreeSet<number>((a, b) => a - b);
for (let i = 0; i < 100; i++) {
t.add(i);
}
const forward = [...t.valuesFrom()];
expect(forward).toEqual(Array.from({length: 100}, (_, i) => i));
});

test('reverse iterator produces same results as spread', () => {
const t = new BTreeSet<number>((a, b) => a - b);
for (let i = 0; i < 100; i++) {
t.add(i);
}
const reversed = [...t.valuesReversed()];
expect(reversed).toEqual(
Array.from({length: 100}, (_, i) => 99 - i),
);
});

test('empty tree iterator returns done immediately', () => {
const t = new BTreeSet<number>((a, b) => a - b);
const fwd = t.values();
expect(fwd.next()).toEqual({done: true, value: undefined});
const rev = t.valuesReversed();
expect(rev.next()).toEqual({done: true, value: undefined});
});

test('single element tree works', () => {
const t = new BTreeSet<number>((a, b) => a - b);
t.add(42);
expect([...t.values()]).toEqual([42]);
expect([...t.valuesReversed()]).toEqual([42]);
});

test('iterator protocol: [Symbol.iterator] returns self', () => {
const t = new BTreeSet<number>((a, b) => a - b);
t.add(1);
t.add(2);
const fwd = t.values();
expect(fwd[Symbol.iterator]()).toBe(fwd);
const rev = t.valuesReversed();
expect(rev[Symbol.iterator]()).toBe(rev);
});
});

suite('fast-check', () => {
test('OrderedSet Property-based Tests (large)', () => {
assert(
Expand Down
152 changes: 101 additions & 51 deletions packages/shared/src/btree-set.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -132,6 +132,105 @@ export class BTreeSet<K> {
}
}

class BTreeForwardIterator<K> implements IterableIterator<K> {
_nodeQueue: BNode<K>[][];
_nodeIndex: number[];
_leaf: BNode<K>;
_i: number;

constructor(
nodeQueue: BNode<K>[][],
nodeIndex: number[],
leaf: BNode<K>,
startI: number,
) {
this._nodeQueue = nodeQueue;
this._nodeIndex = nodeIndex;
this._leaf = leaf;
this._i = startI;
}

next(): IteratorResult<K> {
for (;;) {
if (++this._i < this._leaf.keys.length) {
return {done: false, value: this._leaf.keys[this._i]};
}

let level = -1;
for (;;) {
if (++level >= this._nodeQueue.length) {
return {done: true, value: undefined as unknown as K};
}
if (++this._nodeIndex[level] < this._nodeQueue[level].length) {
break;
}
}
for (; level > 0; level--) {
this._nodeQueue[level - 1] = (
this._nodeQueue[level][this._nodeIndex[level]] as BNodeInternal<K>
).children;
this._nodeIndex[level - 1] = 0;
}
this._leaf = this._nodeQueue[0][this._nodeIndex[0]];
this._i = -1;
}
}

[Symbol.iterator]() {
return this;
}
}

class BTreeReverseIterator<K> implements IterableIterator<K> {
_nodeQueue: BNode<K>[][];
_nodeIndex: number[];
_leaf: BNode<K>;
_i: number;

constructor(
nodeQueue: BNode<K>[][],
nodeIndex: number[],
leaf: BNode<K>,
startI: number,
) {
this._nodeQueue = nodeQueue;
this._nodeIndex = nodeIndex;
this._leaf = leaf;
this._i = startI;
}

next(): IteratorResult<K> {
for (;;) {
if (--this._i >= 0) {
return {done: false, value: this._leaf.keys[this._i]};
}

let level;
// Advance to the next leaf node
for (level = -1; ; ) {
if (++level >= this._nodeQueue.length) {
return {done: true, value: undefined as unknown as K};
}
if (--this._nodeIndex[level] >= 0) {
break;
}
}
for (; level > 0; level--) {
this._nodeQueue[level - 1] = (
this._nodeQueue[level][this._nodeIndex[level]] as BNodeInternal<K>
).children;
this._nodeIndex[level - 1] = this._nodeQueue[level - 1].length - 1;
}
this._leaf = this._nodeQueue[0][this._nodeIndex[0]];
this._i = this._leaf.keys.length;
}
}

[Symbol.iterator]() {
return this;
}
}

function valuesFrom<K>(
root: BNode<K>,
comparator: Comparator<K>,
Expand All @@ -158,31 +257,7 @@ function valuesFrom<K>(
i++;
}

return iterator<K>(() => {
for (;;) {
if (++i < leaf.keys.length) {
return {done: false, value: leaf.keys[i]};
}

let level = -1;
for (;;) {
if (++level >= nodeQueue.length) {
return {done: true, value: undefined};
}
if (++nodeIndex[level] < nodeQueue[level].length) {
break;
}
}
for (; level > 0; level--) {
nodeQueue[level - 1] = (
nodeQueue[level][nodeIndex[level]] as BNodeInternal<K>
).children;
nodeIndex[level - 1] = 0;
}
leaf = nodeQueue[0][nodeIndex[0]];
i = -1;
}
});
return new BTreeForwardIterator(nodeQueue, nodeIndex, leaf, i);
}

function valuesFromReversed<K>(
Expand Down Expand Up @@ -210,32 +285,7 @@ function valuesFromReversed<K>(
i++;
}

return iterator<K>(() => {
for (;;) {
if (--i >= 0) {
return {done: false, value: leaf.keys[i]};
}

let level;
// Advance to the next leaf node
for (level = -1; ; ) {
if (++level >= nodeQueue.length) {
return {done: true, value: undefined};
}
if (--nodeIndex[level] >= 0) {
break;
}
}
for (; level > 0; level--) {
nodeQueue[level - 1] = (
nodeQueue[level][nodeIndex[level]] as BNodeInternal<K>
).children;
nodeIndex[level - 1] = nodeQueue[level - 1].length - 1;
}
leaf = nodeQueue[0][nodeIndex[0]];
i = leaf.keys.length;
}
});
return new BTreeReverseIterator(nodeQueue, nodeIndex, leaf, i);
}

function findPath<K>(
Expand Down