@tldraw/sync-core/dist-esm/lib/chunk.mjs

tldraw infinite canvas SDK (multiplayer sync).

const MAX_CLIENT_SENT_MESSAGE_SIZE_BYTES = 1024 * 1024;
const MAX_BYTES_PER_CHAR = 4;
const MAX_SAFE_MESSAGE_SIZE = MAX_CLIENT_SENT_MESSAGE_SIZE_BYTES / MAX_BYTES_PER_CHAR;
function chunk(msg, maxSafeMessageSize = MAX_SAFE_MESSAGE_SIZE) {
  if (msg.length < maxSafeMessageSize) {
    return [msg];
  } else {
    const chunks = [];
    let chunkNumber = 0;
    let offset = msg.length;
    while (offset > 0) {
      const prefix = `${chunkNumber}_`;
      const chunkSize = Math.max(Math.min(maxSafeMessageSize - prefix.length, offset), 1);
      chunks.unshift(prefix + msg.slice(offset - chunkSize, offset));
      offset -= chunkSize;
      chunkNumber++;
    }
    return chunks;
  }
}
const chunkRe = /^(\d+)_(.*)$/;
class JsonChunkAssembler {
  state = "idle";
  handleMessage(msg) {
    if (msg.startsWith("{")) {
      const error = this.state === "idle" ? void 0 : new Error("Unexpected non-chunk message");
      this.state = "idle";
      return error ? { error } : { data: JSON.parse(msg), stringified: msg };
    } else {
      const match = chunkRe.exec(msg);
      if (!match) {
        this.state = "idle";
        return { error: new Error("Invalid chunk: " + JSON.stringify(msg.slice(0, 20) + "...")) };
      }
      const numChunksRemaining = Number(match[1]);
      const data = match[2];
      if (this.state === "idle") {
        this.state = {
          chunksReceived: [data],
          totalChunks: numChunksRemaining + 1
        };
      } else {
        this.state.chunksReceived.push(data);
        if (numChunksRemaining !== this.state.totalChunks - this.state.chunksReceived.length) {
          this.state = "idle";
          return { error: new Error(`Chunks received in wrong order`) };
        }
      }
      if (this.state.chunksReceived.length === this.state.totalChunks) {
        try {
          const stringified = this.state.chunksReceived.join("");
          const data2 = JSON.parse(stringified);
          return { data: data2, stringified };
        } catch (e) {
          return { error: e };
        } finally {
          this.state = "idle";
        }
      }
      return null;
    }
  }
}
export {
  JsonChunkAssembler,
  chunk
};
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