add ROM::SaveToFile

src/app/rom.cc

@@ -570,6 +570,7 @@ absl::StatusOr<Bytes> ROM::SNES3bppTo8bppSheet(Bytes sheet, int size) {
 }
 
 absl::Status ROM::LoadFromFile(const absl::string_view& filename) {
+  filename_ = filename;
   std::ifstream file(filename.data(), std::ios::binary);
   if (!file.is_open()) {
     return absl::InternalError(
@@ -607,6 +608,18 @@ absl::Status ROM::LoadFromBytes(Bytes data) {
   return absl::OkStatus();
 }
 
+absl::Status ROM::SaveToFile() {
+  std::fstream file(filename_.data(), std::ios::binary | std::ios::out);
+  if (!file.is_open()) {
+    return absl::InternalError(
+        absl::StrCat("Could not open ROM file: ", filename_));
+  }
+  for (auto i = 0; i < size_; ++i) {
+    file << rom_data_[i];
+  }
+  return absl::OkStatus();
+}
+
 // 0-112 -> compressed 3bpp bgr -> (decompressed each) 0x600 chars
 // 113-114 -> compressed 2bpp -> (decompressed each) 0x800 chars
 // 115-126 -> uncompressed 3bpp sprites -> (each) 0x600 chars

src/app/rom.h

@@ -83,6 +83,8 @@ class ROM {
   absl::Status LoadFromPointer(uchar* data, size_t length);
   absl::Status LoadFromBytes(Bytes data);
 
+  absl::Status SaveToFile();
+
   auto GetSize() const { return size_; }
   auto GetTitle() const { return title; }
   auto GetGraphicsBin() const { return graphics_bin_; }
@@ -112,6 +114,7 @@ class ROM {
 
  private:
   long size_ = 0;
+  std::string filename_;
   uchar title[21] = "ROM Not Loaded";
   bool is_loaded_ = false;