Bug 1838598 - Nyx: Adjust replay format. r=truber

Differential Revision: https://phabricator.services.mozilla.com/D181057

tools/fuzzing/nyx/Nyx.cpp

@@ -67,31 +67,18 @@ void Nyx::start(void) {
     std::ifstream is;
     is.open(testFile, std::ios::binary);
 
-    uint64_t chksum, num_ops, num_data, op_offset, data_offset;
-
-    // If only C++ supported streaming operators on binary files...
-    is.read(reinterpret_cast<char*>(&chksum), sizeof(uint64_t));
-    is.read(reinterpret_cast<char*>(&num_ops), sizeof(uint64_t));
-    is.read(reinterpret_cast<char*>(&num_data), sizeof(uint64_t));
-    is.read(reinterpret_cast<char*>(&op_offset), sizeof(uint64_t));
-    is.read(reinterpret_cast<char*>(&data_offset), sizeof(uint64_t));
-
-    if (!is.good()) {
-      MOZ_FUZZING_NYX_PRINT("[Replay Mode] Error reading input file.\n");
-      _exit(1);
-    }
-
-    is.seekg(data_offset);
-
     // The data chunks we receive through Nyx are stored in the data
     // section of the testfile as chunks prefixed with a 16-bit data
-    // length. We read all chunks and store them away to simulate how
-    // we originally received the data via Nyx.
+    // length that we mask down to 11-bit. We read all chunks and
+    // store them away to simulate how we originally received the data
+    // via Nyx.
 
     while (is.good()) {
       uint16_t pktsize;
       is.read(reinterpret_cast<char*>(&pktsize), sizeof(uint16_t));
 
+      pktsize &= 0x7ff;
+
       if (!is.good()) {
         break;
       }