Use fuzzer data on both encoder and decoder (fixes #7)

fuzzing/fuzz_target.cc

@@ -12,6 +12,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     strm.bits_per_sample = (Data[0] & 0x1f) | 1;
     strm.block_size = 8 << (Data[1] & 3);
     strm.rsi = 2;
+
     strm.flags = AEC_DATA_PREPROCESS;
     if (Data[1] & 0x80)
         strm.flags |= AEC_DATA_MSB;
@@ -21,14 +22,21 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
         strm.bits_per_sample > 16 &&
         Data[1] & 0x10)
         strm.flags |= AEC_DATA_3BYTE;
+
+    // Decode data
+    strm.next_in = (unsigned char *)(Data + 2);
+    strm.avail_in = Size - 2;
+    strm.next_out = dest;
+    strm.avail_out = (Size - 2) * 4;
+    aec_buffer_encode(&strm);
+
+    // Encode data
     strm.next_in = (unsigned char *)(Data + 2);
     strm.avail_in = Size - 2;
     strm.next_out = dest;
     strm.avail_out = (Size - 2) * 4;
-    if (Data[1] & 0x20)
-        aec_buffer_encode(&strm);
-    else
-        aec_buffer_decode(&strm);
+    aec_buffer_decode(&strm);
+
     free(dest);
     return 0;
 }