1 files changed, 413 insertions, 0 deletions
diff --git a/packages/excalidraw/data/encode.ts b/packages/excalidraw/data/encode.ts
new file mode 100644
index 0000000..15dfdb2
--- /dev/null
+++ b/packages/excalidraw/data/encode.ts
@@ -0,0 +1,413 @@
+import { deflate, inflate } from "pako";
+import { encryptData, decryptData } from "./encryption";
+
+// -----------------------------------------------------------------------------
+// byte (binary) strings
+// -----------------------------------------------------------------------------
+
+// Buffer-compatible implem.
+//
+// Note that in V8, spreading the uint8array (by chunks) into
+// `String.fromCharCode(...uint8array)` tends to be faster for large
+// strings/buffers, in case perf is needed in the future.
+export const toByteString = (data: string | Uint8Array | ArrayBuffer) => {
+  const bytes =
+    typeof data === "string"
+      ? new TextEncoder().encode(data)
+      : data instanceof Uint8Array
+      ? data
+      : new Uint8Array(data);
+  let bstring = "";
+  for (const byte of bytes) {
+    bstring += String.fromCharCode(byte);
+  }
+  return bstring;
+};
+
+const byteStringToArrayBuffer = (byteString: string) => {
+  const buffer = new ArrayBuffer(byteString.length);
+  const bufferView = new Uint8Array(buffer);
+  for (let i = 0, len = byteString.length; i < len; i++) {
+    bufferView[i] = byteString.charCodeAt(i);
+  }
+  return buffer;
+};
+
+const byteStringToString = (byteString: string) => {
+  return new TextDecoder("utf-8").decode(byteStringToArrayBuffer(byteString));
+};
+
+// -----------------------------------------------------------------------------
+// base64
+// -----------------------------------------------------------------------------
+
+/**
+ * @param isByteString set to true if already byte string to prevent bloat
+ *  due to reencoding
+ */
+export const stringToBase64 = (str: string, isByteString = false) => {
+  return isByteString ? window.btoa(str) : window.btoa(toByteString(str));
+};
+
+// async to align with stringToBase64
+export const base64ToString = (base64: string, isByteString = false) => {
+  return isByteString
+    ? window.atob(base64)
+    : byteStringToString(window.atob(base64));
+};
+
+export const base64ToArrayBuffer = (base64: string): ArrayBuffer => {
+  if (typeof Buffer !== "undefined") {
+    // Node.js environment
+    return Buffer.from(base64, "base64").buffer;
+  }
+  // Browser environment
+  return byteStringToArrayBuffer(atob(base64));
+};
+
+// -----------------------------------------------------------------------------
+// base64url
+// -----------------------------------------------------------------------------
+
+export const base64urlToString = (str: string) => {
+  return window.atob(
+    // normalize base64URL to base64
+    str
+      .replace(/-/g, "+")
+      .replace(/_/g, "/")
+      .padEnd(str.length + ((4 - (str.length % 4)) % 4), "="),
+  );
+};
+
+// -----------------------------------------------------------------------------
+// text encoding
+// -----------------------------------------------------------------------------
+
+type EncodedData = {
+  encoded: string;
+  encoding: "bstring";
+  /** whether text is compressed (zlib) */
+  compressed: boolean;
+  /** version for potential migration purposes */
+  version?: string;
+};
+
+/**
+ * Encodes (and potentially compresses via zlib) text to byte string
+ */
+export const encode = ({
+  text,
+  compress,
+}: {
+  text: string;
+  /** defaults to `true`. If compression fails, falls back to bstring alone. */
+  compress?: boolean;
+}): EncodedData => {
+  let deflated!: string;
+  if (compress !== false) {
+    try {
+      deflated = toByteString(deflate(text));
+    } catch (error: any) {
+      console.error("encode: cannot deflate", error);
+    }
+  }
+  return {
+    version: "1",
+    encoding: "bstring",
+    compressed: !!deflated,
+    encoded: deflated || toByteString(text),
+  };
+};
+
+export const decode = (data: EncodedData): string => {
+  let decoded: string;
+
+  switch (data.encoding) {
+    case "bstring":
+      // if compressed, do not double decode the bstring
+      decoded = data.compressed
+        ? data.encoded
+        : byteStringToString(data.encoded);
+      break;
+    default:
+      throw new Error(`decode: unknown encoding "${data.encoding}"`);
+  }
+
+  if (data.compressed) {
+    return inflate(new Uint8Array(byteStringToArrayBuffer(decoded)), {
+      to: "string",
+    });
+  }
+
+  return decoded;
+};
+
+// -----------------------------------------------------------------------------
+// binary encoding
+// -----------------------------------------------------------------------------
+
+type FileEncodingInfo = {
+  /* version 2 is the version we're shipping the initial image support with.
+    version 1 was a PR version that a lot of people were using anyway.
+    Thus, if there are issues we can check whether they're not using the
+    unoffic version */
+  version: 1 | 2;
+  compression: "pako@1" | null;
+  encryption: "AES-GCM" | null;
+};
+
+// -----------------------------------------------------------------------------
+const CONCAT_BUFFERS_VERSION = 1;
+/** how many bytes we use to encode how many bytes the next chunk has.
+ * Corresponds to DataView setter methods (setUint32, setUint16, etc).
+ *
+ * NOTE ! values must not be changed, which would be backwards incompatible !
+ */
+const VERSION_DATAVIEW_BYTES = 4;
+const NEXT_CHUNK_SIZE_DATAVIEW_BYTES = 4;
+// -----------------------------------------------------------------------------
+
+const DATA_VIEW_BITS_MAP = { 1: 8, 2: 16, 4: 32 } as const;
+
+// getter
+function dataView(buffer: Uint8Array, bytes: 1 | 2 | 4, offset: number): number;
+// setter
+function dataView(
+  buffer: Uint8Array,
+  bytes: 1 | 2 | 4,
+  offset: number,
+  value: number,
+): Uint8Array;
+/**
+ * abstraction over DataView that serves as a typed getter/setter in case
+ * you're using constants for the byte size and want to ensure there's no
+ * discrepenancy in the encoding across refactors.
+ *
+ * DataView serves for an endian-agnostic handling of numbers in ArrayBuffers.
+ */
+function dataView(
+  buffer: Uint8Array,
+  bytes: 1 | 2 | 4,
+  offset: number,
+  value?: number,
+): Uint8Array | number {
+  if (value != null) {
+    if (value > Math.pow(2, DATA_VIEW_BITS_MAP[bytes]) - 1) {
+      throw new Error(
+        `attempting to set value higher than the allocated bytes (value: ${value}, bytes: ${bytes})`,
+      );
+    }
+    const method = `setUint${DATA_VIEW_BITS_MAP[bytes]}` as const;
+    new DataView(buffer.buffer)[method](offset, value);
+    return buffer;
+  }
+  const method = `getUint${DATA_VIEW_BITS_MAP[bytes]}` as const;
+  return new DataView(buffer.buffer)[method](offset);
+}
+
+// -----------------------------------------------------------------------------
+
+/**
+ * Resulting concatenated buffer has this format:
+ *
+ * [
+ *   VERSION chunk (4 bytes)
+ *   LENGTH chunk 1 (4 bytes)
+ *   DATA chunk 1 (up to 2^32 bits)
+ *   LENGTH chunk 2 (4 bytes)
+ *   DATA chunk 2 (up to 2^32 bits)
+ *   ...
+ * ]
+ *
+ * @param buffers each buffer (chunk) must be at most 2^32 bits large (~4GB)
+ */
+const concatBuffers = (...buffers: Uint8Array[]) => {
+  const bufferView = new Uint8Array(
+    VERSION_DATAVIEW_BYTES +
+      NEXT_CHUNK_SIZE_DATAVIEW_BYTES * buffers.length +
+      buffers.reduce((acc, buffer) => acc + buffer.byteLength, 0),
+  );
+
+  let cursor = 0;
+
+  // as the first chunk we'll encode the version for backwards compatibility
+  dataView(bufferView, VERSION_DATAVIEW_BYTES, cursor, CONCAT_BUFFERS_VERSION);
+  cursor += VERSION_DATAVIEW_BYTES;
+
+  for (const buffer of buffers) {
+    dataView(
+      bufferView,
+      NEXT_CHUNK_SIZE_DATAVIEW_BYTES,
+      cursor,
+      buffer.byteLength,
+    );
+    cursor += NEXT_CHUNK_SIZE_DATAVIEW_BYTES;
+
+    bufferView.set(buffer, cursor);
+    cursor += buffer.byteLength;
+  }
+
+  return bufferView;
+};
+
+/** can only be used on buffers created via `concatBuffers()` */
+const splitBuffers = (concatenatedBuffer: Uint8Array) => {
+  const buffers = [];
+
+  let cursor = 0;
+
+  // first chunk is the version
+  const version = dataView(
+    concatenatedBuffer,
+    NEXT_CHUNK_SIZE_DATAVIEW_BYTES,
+    cursor,
+  );
+  // If version is outside of the supported versions, throw an error.
+  // This usually means the buffer wasn't encoded using this API, so we'd only
+  // waste compute.
+  if (version > CONCAT_BUFFERS_VERSION) {
+    throw new Error(`invalid version ${version}`);
+  }
+
+  cursor += VERSION_DATAVIEW_BYTES;
+
+  while (true) {
+    const chunkSize = dataView(
+      concatenatedBuffer,
+      NEXT_CHUNK_SIZE_DATAVIEW_BYTES,
+      cursor,
+    );
+    cursor += NEXT_CHUNK_SIZE_DATAVIEW_BYTES;
+
+    buffers.push(concatenatedBuffer.slice(cursor, cursor + chunkSize));
+    cursor += chunkSize;
+    if (cursor >= concatenatedBuffer.byteLength) {
+      break;
+    }
+  }
+
+  return buffers;
+};
+
+// helpers for (de)compressing data with JSON metadata including encryption
+// -----------------------------------------------------------------------------
+
+/** @private */
+const _encryptAndCompress = async (
+  data: Uint8Array | string,
+  encryptionKey: string,
+) => {
+  const { encryptedBuffer, iv } = await encryptData(
+    encryptionKey,
+    deflate(data),
+  );
+
+  return { iv, buffer: new Uint8Array(encryptedBuffer) };
+};
+
+/**
+ * The returned buffer has following format:
+ * `[]` refers to a buffers wrapper (see `concatBuffers`)
+ *
+ * [
+ *   encodingMetadataBuffer,
+ *   iv,
+ *   [
+ *      contentsMetadataBuffer
+ *      contentsBuffer
+ *   ]
+ * ]
+ */
+export const compressData = async <T extends Record<string, any> = never>(
+  dataBuffer: Uint8Array,
+  options: {
+    encryptionKey: string;
+  } & ([T] extends [never]
+    ? {
+        metadata?: T;
+      }
+    : {
+        metadata: T;
+      }),
+): Promise<Uint8Array> => {
+  const fileInfo: FileEncodingInfo = {
+    version: 2,
+    compression: "pako@1",
+    encryption: "AES-GCM",
+  };
+
+  const encodingMetadataBuffer = new TextEncoder().encode(
+    JSON.stringify(fileInfo),
+  );
+
+  const contentsMetadataBuffer = new TextEncoder().encode(
+    JSON.stringify(options.metadata || null),
+  );
+
+  const { iv, buffer } = await _encryptAndCompress(
+    concatBuffers(contentsMetadataBuffer, dataBuffer),
+    options.encryptionKey,
+  );
+
+  return concatBuffers(encodingMetadataBuffer, iv, buffer);
+};
+
+/** @private */
+const _decryptAndDecompress = async (
+  iv: Uint8Array,
+  decryptedBuffer: Uint8Array,
+  decryptionKey: string,
+  isCompressed: boolean,
+) => {
+  decryptedBuffer = new Uint8Array(
+    await decryptData(iv, decryptedBuffer, decryptionKey),
+  );
+
+  if (isCompressed) {
+    return inflate(decryptedBuffer);
+  }
+
+  return decryptedBuffer;
+};
+
+export const decompressData = async <T extends Record<string, any>>(
+  bufferView: Uint8Array,
+  options: { decryptionKey: string },
+) => {
+  // first chunk is encoding metadata (ignored for now)
+  const [encodingMetadataBuffer, iv, buffer] = splitBuffers(bufferView);
+
+  const encodingMetadata: FileEncodingInfo = JSON.parse(
+    new TextDecoder().decode(encodingMetadataBuffer),
+  );
+
+  try {
+    const [contentsMetadataBuffer, contentsBuffer] = splitBuffers(
+      await _decryptAndDecompress(
+        iv,
+        buffer,
+        options.decryptionKey,
+        !!encodingMetadata.compression,
+      ),
+    );
+
+    const metadata = JSON.parse(
+      new TextDecoder().decode(contentsMetadataBuffer),
+    ) as T;
+
+    return {
+      /** metadata source is always JSON so we can decode it here */
+      metadata,
+      /** data can be anything so the caller must decode it */
+      data: contentsBuffer,
+    };
+  } catch (error: any) {
+    console.error(
+      `Error during decompressing and decrypting the file.`,
+      encodingMetadata,
+    );
+    throw error;
+  }
+};
+
+// -----------------------------------------------------------------------------