1 files changed, 36 insertions, 4 deletions

diff --git a/src/core/file_sys/vfs_concat.h b/src/core/file_sys/vfs_concat.h
index 717d04bdc..76211d38a 100644
--- a/src/core/file_sys/vfs_concat.h
+++ b/src/core/file_sys/vfs_concat.h
@@ -4,22 +4,25 @@
 
 #pragma once
 
+#include <map>
 #include <memory>
 #include <string_view>
 #include <boost/container/flat_map.hpp>
 #include "core/file_sys/vfs.h"
+#include "core/file_sys/vfs_static.h"
 
 namespace FileSys {
 
-// Wrapper function to allow for more efficient handling of files.size() == 0, 1 cases.
-VirtualFile ConcatenateFiles(std::vector<VirtualFile> files, std::string name = "");
-
 // Class that wraps multiple vfs files and concatenates them, making reads seamless. Currently
 // read-only.
 class ConcatenatedVfsFile : public VfsFile {
     friend VirtualFile ConcatenateFiles(std::vector<VirtualFile> files, std::string name);
 
+    template <u8 filler_byte>
+    friend VirtualFile ConcatenateFiles(std::map<u64, VirtualFile> files, std::string name);
+
     ConcatenatedVfsFile(std::vector<VirtualFile> files, std::string name);
+    ConcatenatedVfsFile(std::map<u64, VirtualFile> files, std::string name);
 
 public:
     ~ConcatenatedVfsFile() override;
@@ -36,8 +39,37 @@ public:
 
 private:
     // Maps starting offset to file -- more efficient.
-    boost::container::flat_map<u64, VirtualFile> files;
+    std::map<u64, VirtualFile> files;
     std::string name;
 };
 
+// Wrapper function to allow for more efficient handling of files.size() == 0, 1 cases.
+VirtualFile ConcatenateFiles(std::vector<VirtualFile> files, std::string name);
+
+// Convenience function that turns a map of offsets to files into a concatenated file, filling gaps
+// with template parameter.
+template <u8 filler_byte>
+VirtualFile ConcatenateFiles(std::map<u64, VirtualFile> files, std::string name) {
+    if (files.empty())
+        return nullptr;
+    if (files.size() == 1)
+        return files.begin()->second;
+
+    const auto last_valid = --files.end();
+    for (auto iter = files.begin(); iter != last_valid;) {
+        const auto old = iter++;
+        if (old->first + old->second->GetSize() != iter->first) {
+            files.emplace(old->first + old->second->GetSize(),
+                          std::make_shared<StaticVfsFile<filler_byte>>(iter->first - old->first -
+                                                                       old->second->GetSize()));
+        }
+    }
+
+    // Ensure the map starts at offset 0 (start of file), otherwise pad to fill.
+    if (files.begin()->first != 0)
+        files.emplace(0, std::make_shared<StaticVfsFile<filler_byte>>(files.begin()->first));
+
+    return std::shared_ptr<VfsFile>(new ConcatenatedVfsFile(std::move(files), std::move(name)));
+}
+
 } // namespace FileSys