🚧 Add reader for .solidpkg files

src/installPatch.ts

@@ -1,6 +1,10 @@
 import getSolidpkg from './getSolidpkg';
+import readSolidpkg from './readSolidpkg';
 
 (async () => {
   const buffer = await getSolidpkg('assets_swtor_de_de', -1, 0);
   console.log(buffer.length, buffer);
+
+  const output = readSolidpkg(buffer);
+  console.log(output);
 })();

src/readSolidpkg.ts

@@ -0,0 +1,83 @@
+const MAGIC_END_OF_CENTRAL_DIR = 0x06054b50;
+const MAGIC_CENTRAL_DIR = 0x02014b50;
+const COMPRESSION_DEFLATE = 8;
+
+export default function readSolidpkg(buffer: Buffer) {
+  const dv = new DataView(buffer.buffer);
+
+  //--------------- READ END OF CENTRAL DIR ---------------
+
+  //Go to end of file
+  let pos = buffer.length - 22; //end of central dir is at least 22 bytes long
+
+  //Find end of central dir
+  while (pos >= 0 && dv.getUint32(pos, true) !== MAGIC_END_OF_CENTRAL_DIR) {
+    pos -= 1;
+  }
+  if (pos < 0) {
+    throw new Error('Could not find end of central dir.');
+  }
+
+  //skip 6 bytes
+  pos += 6;
+
+  /** Total number of entries in the central directory */
+  const numEntries = dv.getUint16(pos, true); pos += 2;
+  /** Size of the central directory */
+  const centralDirSize = dv.getUint32(pos, true); pos += 4;
+  /** Offset of start of central directory with respect to the starting disk number */
+  const centralDirOffset = dv.getUint32(pos, true); pos += 4;
+
+  if (numEntries !== 1) {
+    throw new Error(`Expected numEntries == 1 in end of central dir but it was "${numEntries}"`);
+  }
+  if (centralDirSize < 46 * numEntries) {
+    throw new Error('centralDirSize was smaller than expected in end of central dir.');
+  }
+  if (pos - centralDirSize < 0) {
+    throw new Error(`Central dir points before file start (0x${(pos - centralDirSize).toString(16)})`);
+  }
+
+  //--------------- READ CENTRAL DIR ---------------
+
+  //Go to start of central dir
+  pos -= -20 - centralDirSize;
+
+  {
+    const magicNum = dv.getUint32(pos, true); pos += 4;
+    if (magicNum !== MAGIC_CENTRAL_DIR) {
+      throw new Error(`Expected central dir signature but found "0x${magicNum.toString(16)}"`);
+    }
+  }
+
+  pos += 4; //skip version
+
+  /** The bitflag stores whether the file is encrypted or not. Most files are encrypted but there are
+   * some exceptions: assets_swtor_test_main_248to249.solidpkg, assets_swtor_test_en_us_270to271.solidpkg, and
+   * retailclient_publictest_246to247.solidpkg are not encrypted.
+   */
+  const bitFlag = dv.getUint16(pos, true); pos += 2;
+
+  /** Type of compression, 8 = DEFLATE. Files are always compressed. */
+  const compression = dv.getUint16(pos, true); pos += 2;
+  if (compression !== COMPRESSION_DEFLATE) {
+    throw new Error(`File is not using DEFLATE compression but "${compression}"`);
+  }
+
+  const lastMod1 = dv.getUint16(pos, true); pos += 2;
+  const lastMod2 = dv.getUint16(pos, true); pos += 2;
+  const fileCrc = dv.getUint32(pos, true); pos += 4;
+  const comprSize = dv.getUint32(pos, true); pos += 4;
+  const uncomprSize = dv.getUint32(pos, true); pos += 4;
+  const fileNameLength = dv.getUint16(pos, true); pos += 2;
+  const extraFieldLength = dv.getUint16(pos, true); pos += 2;
+  const fileCommentLength = dv.getUint16(pos, true); pos += 2;
+  pos += 8; //skip disk num start and file attributes
+  const relOffset = dv.getUint32(pos, true); pos += 4;
+  pos += fileNameLength; //skip file name
+  //TODO: read password from extra field
+
+  //...
+
+  return { lastMod1, lastMod2, fileCrc, comprSize, uncomprSize, fileNameLength, extraFieldLength, fileCommentLength, relOffset };
+}