clipboard-worker

Base64 codec for clipboard payloads, run off the main thread.

lib/clipboard-worker-bridge.js posts {id, action, payload, mimeType} and receives {id, success, result, mimeType, byteLength} or {id, success: false, error}. ENCODE_BINARY_TO_B64 takes an ArrayBuffer, ENCODE_TEXT_TO_B64 a string, both answering with the base64 text; DECODE_FROM_B64 takes base64 and answers with a string for text/plain, else with a transferred ArrayBuffer. byteLength is the decoded size, which the bridge reports and compares against limits.

A multipart download arrives as DECODE_BEGIN, one DECODE_CHUNK per message and DECODE_END, which alone answers; DECODE_ABORT drops an unfinished one. Only that keeps the payload off the main thread entirely: joining the chunks there first builds the whole base64 string, and then copies it again into the message that carries it here.

Every reply carrying bytes also carries hash, the change-detection digest of those bytes, computed here because this is where they are already being walked; the main thread would otherwise run the same per-byte loop over a payload of any size. HASH_BYTES covers the one caller holding bytes that did not come through a codec, and REENCODE_PNG normalizes an image to PNG on an OffscreenCanvas rather than on the page's own.

Variables

CHUNK_SIZE

const CHUNK_SIZE: 32768 = 0x8000;

Defined in: clipboard-worker.js:34

Bytes per String.fromCharCode.apply call, keeping its argument list bounded.

HASH_SEED

const HASH_SEED: 5381 = 5381;

Defined in: clipboard-worker.js:37

Seed of the djb2 digest the clipboard compares payloads by.

streams

const streams: Map<any, any>;

Defined in: clipboard-worker.js:143

Multipart downloads in progress, by request id.

Functions

hashBytes()

function hashBytes(h, bytes): number;

Defined in: clipboard-worker.js:45

djb2 over bytes, continuing from h so a digest can span several chunks.

Parameters

Returns

number

stringToBase64()

function stringToBase64(text): string;

Defined in: clipboard-worker.js:54

Parameters

Returns

string

Base64 of the UTF-8 encoding of text.

base64ToString()

function base64ToString(base64): object;

Defined in: clipboard-worker.js:68

Parameters

Returns

object

The decoded UTF-8 text and its byte size.

text

text: string;

byteLength

byteLength: number;

base64ToBytes()

function base64ToBytes(base64): Uint8Array<ArrayBufferLike>;

Defined in: clipboard-worker.js:82

Parameters

Returns

Uint8Array<ArrayBufferLike>

bytesToBase64()

function bytesToBase64(bytes): string;

Defined in: clipboard-worker.js:96

Parameters

Returns

string

feedStream()

function feedStream(stream, text): void;

Defined in: clipboard-worker.js:112

Decodes as much of text as forms whole base64 quartets, appending the bytes to stream and keeping the rest for the next chunk. A sender is free to split its base64 anywhere, so a chunk boundary need not fall on one.

Parameters

Returns

void

drainStream()

function drainStream(stream): Uint8Array<any>;

Defined in: clipboard-worker.js:124

The stream's bytes as one buffer, remainder included.

Parameters

Returns

Uint8Array<any>

reencodeToPng()

function reencodeToPng(id, blob): Promise<void>;

Defined in: clipboard-worker.js:152

Normalizes an image to PNG on an OffscreenCanvas, which is the same decode and encode the page would otherwise run on its own canvas and block on for as long as the image is large.

Parameters

Returns

Promise<void>