detect specific_version without using a patch

src/FunctionCompiler.cc

@@ -4,6 +4,7 @@
 #include <string.h>
 
 #include <phosg/Filesystem.hh>
+#include <phosg/Hash.hh>
 #include <phosg/Time.hh>
 #include <stdexcept>
 
@@ -347,3 +348,34 @@ DOLFileIndex::DOLFileIndex(const string& directory, bool compress)
     }
   }
 }
+
+uint32_t specific_version_for_gc_header_checksum(uint32_t header_checksum) {
+  static unordered_map<uint32_t, uint32_t> checksum_to_specific_version;
+  if (checksum_to_specific_version.empty()) {
+    struct {
+      char system_code = 'G';
+      char game_code1 = 'P';
+      char game_code2;
+      char region_code;
+      char developer_code1 = '8';
+      char developer_code2 = 'P';
+      uint8_t disc_number = 0;
+      uint8_t version_code;
+    } __attribute__((packed)) data;
+    for (const char* game_code2 = "OS"; *game_code2; game_code2++) {
+      data.game_code2 = *game_code2;
+      for (const char* region_code = "JEP"; *region_code; region_code++) {
+        data.region_code = *region_code;
+        for (uint8_t version_code = 0; version_code < 8; version_code++) {
+          data.version_code = version_code;
+          uint32_t checksum = crc32(&data, sizeof(data));
+          uint32_t specific_version = 0x33000030 | (*game_code2 << 16) | (*region_code << 8) | version_code;
+          if (!checksum_to_specific_version.emplace(checksum, specific_version).second) {
+            throw logic_error("multiple specific_versions have same header checksum");
+          }
+        }
+      }
+    }
+  }
+  return checksum_to_specific_version.at(header_checksum);
+}

src/FunctionCompiler.hh

@@ -88,3 +88,5 @@ struct DOLFileIndex {
     return this->name_to_file.empty() && this->item_id_to_file.empty();
   }
 };
+
+uint32_t specific_version_for_gc_header_checksum(uint32_t header_checksum);

src/SendCommands.cc

@@ -333,12 +333,18 @@ void prepare_client_for_patches(shared_ptr<ServerState> s, shared_ptr<Client> c,
   };
 
   if (!(c->flags & Client::Flag::SEND_FUNCTION_CALL_NO_CACHE_PATCH)) {
-    send_function_call(c, s->function_code_index->name_to_function.at("CacheClearFix-Phase1"), {}, "", 0, 0, 0x7F2734EC);
-    c->function_call_response_queue.emplace_back([s, wc = weak_ptr<Client>(c), send_version_detect](uint32_t, uint32_t) -> void {
+    send_function_call(c, s->function_code_index->name_to_function.at("CacheClearFix-Phase1"), {}, "", 0x80000000, 8, 0x7F2734EC);
+    c->function_call_response_queue.emplace_back([s, wc = weak_ptr<Client>(c), send_version_detect](uint32_t, uint32_t header_checksum) -> void {
       auto c = wc.lock();
       if (!c) {
         return;
       }
+      try {
+        c->specific_version = specific_version_for_gc_header_checksum(header_checksum);
+        c->log.info("Version detected as %08" PRIX32 " from header checksum %08" PRIX32, c->specific_version, header_checksum);
+      } catch (const out_of_range&) {
+        c->log.info("Could not detect specific version from header checksum %08" PRIX32, header_checksum);
+      }
       send_function_call(c, s->function_code_index->name_to_function.at("CacheClearFix-Phase2"));
       c->function_call_response_queue.emplace_back([s, wc = weak_ptr<Client>(c), send_version_detect](uint32_t, uint32_t) -> void {
         auto c = wc.lock();