Skip to content

⚡ Optimize ShareableArray.unshift and addOrSetItem #45

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
google-labs-jules wants to merge 1 commit into
base: master
Choose a base branch
from
Draft

⚡ Optimize ShareableArray.unshift and addOrSetItem #45

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
65 changes: 32 additions & 33 deletions src/array/ShareableArray.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -474,12 +474,12 @@ export class ShareableArray<T> extends TransferableDataStructure {

// Push all items in the index array the required amount of positions to the right (to make room for the items
// that should be added now)
for (let i = this.length - 1; i >= 0; i--) {
this.indexView.setUint32(
ShareableArray.INDEX_TABLE_OFFSET + 4 * (i + items.length),
this.indexView.getUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * i)
);
}
const byteLengthToCopy = this.length * 4;
new Uint8Array(this.indexMem).copyWithin(
ShareableArray.INDEX_TABLE_OFFSET + 4 * items.length,
ShareableArray.INDEX_TABLE_OFFSET,
ShareableArray.INDEX_TABLE_OFFSET + byteLengthToCopy
);

// Store undefined at the first positions (temporarily)
for (let i = 0; i < items.length; i++) {
Expand Down Expand Up @@ -785,10 +785,17 @@ export class ShareableArray<T> extends TransferableDataStructure {
this.doubleIndexStorage();
}

if (index < this.length) {
// There is already an item at this position in the array, we have to remove the value currently present
// there and then update it with the new item we want to add.
this.deleteItem(index);
const isReplacement = index < this.length;

if (isReplacement) {
// There is already an item at this position in the array.
// We have to free the value currently present there.
const dataPos = this.indexView.getUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * index);
if (dataPos !== ShareableArray.UNDEFINED_VALUE_IDENTIFIER) {
const valueLength = this.dataView.getUint32(dataPos + 4);
const currentlyUsedSpace = this.indexView.getUint32(ShareableArray.INDEX_TOTAL_USED_SPACE_OFFSET);
this.indexView.setUint32(ShareableArray.INDEX_TOTAL_USED_SPACE_OFFSET, currentlyUsedSpace - (valueLength + ShareableArray.DATA_OBJECT_OFFSET));
}
}

if (item === undefined) {
Expand Down Expand Up @@ -834,22 +841,8 @@ export class ShareableArray<T> extends TransferableDataStructure {
// Keep track of the exact length in bytes for this value object.
this.dataView.setUint32(this.freeStart + 4, exactValueLength);

// Check if the item we're trying to add is at the end of the array or not
if (index === this.length) {
// Set pointer in index array to the last position.
this.indexView.setUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * index, this.freeStart);
} else {
// Shift all items in the array to the right to make space for the new item
const currentLength = this.length;
for (let i = currentLength; i > index; i--) {
this.indexView.setUint32(
ShareableArray.INDEX_TABLE_OFFSET + 4 * i,
this.indexView.getUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * (i - 1))
);
}
// Set the new item's position in the index array
this.indexView.setUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * index, this.freeStart);
}
// Set the new item's position in the index array
this.indexView.setUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * index, this.freeStart);

// Increase the space used in the data array
const usedSpace = this.indexView.getUint32(ShareableArray.INDEX_TOTAL_USED_SPACE_OFFSET);
Expand All @@ -859,10 +852,11 @@ export class ShareableArray<T> extends TransferableDataStructure {
this.freeStart += exactValueLength + ShareableArray.DATA_OBJECT_OFFSET;
}


// Increase the size of the array
const previousSize = this.indexView.getUint32(ShareableArray.INDEX_SIZE_OFFSET);
this.indexView.setUint32(ShareableArray.INDEX_SIZE_OFFSET, previousSize + 1);
if (!isReplacement) {
// Increase the size of the array
const previousSize = this.indexView.getUint32(ShareableArray.INDEX_SIZE_OFFSET);
this.indexView.setUint32(ShareableArray.INDEX_SIZE_OFFSET, previousSize + 1);
}
}

private readItem(index: number): T | undefined {
Expand Down Expand Up @@ -899,9 +893,14 @@ export class ShareableArray<T> extends TransferableDataStructure {

// Move the items in the index array that follow the removed index forward (such that the hole in the
// index array is removed)
for (let i = index; i < this.length; i++) {
this.indexView.setUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * i, this.indexView.getUint32(ShareableArray.INDEX_TABLE_OFFSET + 4 * (i + 1)));
}
const sourceStart = ShareableArray.INDEX_TABLE_OFFSET + 4 * (index + 1);
const sourceEnd = ShareableArray.INDEX_TABLE_OFFSET + 4 * this.length;

new Uint8Array(this.indexMem).copyWithin(
ShareableArray.INDEX_TABLE_OFFSET + 4 * index,
sourceStart,
sourceEnd
);

if (dataPos !== ShareableArray.UNDEFINED_VALUE_IDENTIFIER) {
const valueLength = this.dataView.getUint32(dataPos + 4);
Expand Down