add decoder for Ep3 trial download quests

src/Quest.cc

@@ -165,8 +165,7 @@ string find_seed_and_decrypt_download_quest_data_section(
   string result;
   uint64_t result_seed = parallel_range<uint64_t>([&](uint64_t seed, size_t) {
     try {
-      string ret = decrypt_download_quest_data_section<IsBigEndian>(
+      string ret = decrypt_download_quest_data_section<IsBigEndian>(data_section, size, seed);
-          data_section, size, seed);
       lock_guard<mutex> g(result_lock);
       result = std::move(ret);
       return true;
@@ -522,7 +521,23 @@ string Quest::decode_gci_file(
       return compressed_data;
     }
 
-  } else if (header.game_id[2] == 'S') { // Episode 3
+  } else if (header.is_ep3()) {
+    if (header.is_trial()) {
+      if (known_seed >= 0) {
+        return decrypt_download_quest_data_section<true>(
+            r.getv(header.data_size), header.data_size, known_seed);
+      } else {
+        if (find_seed_num_threads < 0) {
+          throw runtime_error("file is encrypted");
+        }
+        if (find_seed_num_threads == 0) {
+          find_seed_num_threads = thread::hardware_concurrency();
+        }
+        return find_seed_and_decrypt_download_quest_data_section<true>(
+            r.getv(header.data_size), header.data_size, find_seed_num_threads);
+      }
+
+    } else {
       // The first 0x10 bytes in the data segment appear to be unused. In most
       // files I've seen, the last half of it (8 bytes) are duplicates of the
       // first 8 bytes of the unscrambled, compressed data, though this is the
@@ -552,6 +567,7 @@ string Quest::decode_gci_file(
             decompressed_size, sizeof(Episode3::MapDefinition)));
       }
       return data;
+    }
 
   } else {
     throw runtime_error("unknown game name in GCI header");

src/SaveFileFormats.cc

@@ -87,7 +87,7 @@ void PSOGCIFileHeader::check() const {
   if (this->developer_id[0] != '8' || this->developer_id[1] != 'P') {
     throw runtime_error("GCI file is not for a Sega game");
   }
-  if (this->game_id[0] != 'G') {
+  if ((this->game_id[0] != 'G') && (this->game_id[0] != 'D')) {
     throw runtime_error("GCI file is not for a GameCube game");
   }
   if (this->game_id[1] != 'P') {
@@ -106,6 +106,10 @@ bool PSOGCIFileHeader::is_ep3() const {
   return (this->game_id[2] == 'S');
 }
 
+bool PSOGCIFileHeader::is_trial() const {
+  return (this->game_id[0] == 'D');
+}
+
 uint32_t compute_psogc_timestamp(
     uint16_t year,
     uint8_t month,

src/SaveFileFormats.hh

@@ -86,6 +86,7 @@ struct PSOGCIFileHeader {
 
   bool is_ep12() const;
   bool is_ep3() const;
+  bool is_trial() const;
 } __attribute__((packed));
 
 struct PSOGCSystemFile {