From d7c39cc7190019796c3cbad5b3f1781b4755c894 Mon Sep 17 00:00:00 2001
From: DH <dh.rpcs3@gmail.com>
Date: Fri, 14 Mar 2025 14:54:18 +0300
Subject: [PATCH] FIle: add write_at

---
 rpcs3/Utilities/File.cpp | 47 ++++++++++++++++++++++++++++++++++++++++
 rpcs3/Utilities/File.h   | 33 ++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/rpcs3/Utilities/File.cpp b/rpcs3/Utilities/File.cpp
index c5fecc9d1..45c4b1256 100644
--- a/rpcs3/Utilities/File.cpp
+++ b/rpcs3/Utilities/File.cpp
@@ -539,6 +539,34 @@ namespace fs
 			return nwritten_sum;
 		}
 
+		u64 write_at(u64 offset, const void* buffer, u64 count) override
+		{
+			u64 nwritten_sum = 0;
+
+			for (const char* data = static_cast<const char*>(buffer); count;)
+			{
+				const DWORD size = static_cast<DWORD>(std::min<u64>(count, DWORD{umax} & -4096));
+
+				DWORD nwritten = 0;
+				OVERLAPPED ovl{};
+				ovl.Offset = DWORD(offset);
+				ovl.OffsetHigh = DWORD(offset >> 32);
+				ensure(WriteFile(m_handle, data, size, &nwritten, &ovl)); // "file::write"
+				ensure(nwritten == size);
+				nwritten_sum += nwritten;
+
+				if (nwritten < size)
+				{
+					break;
+				}
+
+				count -= size;
+				data += size;
+			}
+
+			return nwritten_sum;
+		}
+
 		u64 seek(s64 offset, seek_mode whence) override
 		{
 			if (whence > seek_end)
@@ -710,6 +738,25 @@ namespace fs
 			return result;
 		}
 
+		u64 write_at(u64 offset, const void* buffer, u64 count) override
+		{
+			u64 result = 0;
+
+			// For safety; see read()
+			while (auto r = ::pwrite(m_fd, buffer, count, offset))
+			{
+				ensure(r > 0); // "file::write"
+				count -= r;
+				offset += r;
+				result += r;
+				buffer = static_cast<const u8*>(buffer) + r;
+				if (!count)
+					break;
+			}
+
+			return result;
+		}
+
 		u64 seek(s64 offset, seek_mode whence) override
 		{
 			if (whence > seek_end)
diff --git a/rpcs3/Utilities/File.h b/rpcs3/Utilities/File.h
index a5a4c53d7..8c1b0b585 100644
--- a/rpcs3/Utilities/File.h
+++ b/rpcs3/Utilities/File.h
@@ -109,6 +109,10 @@ namespace fs
 		virtual u64 read(void* buffer, u64 size) = 0;
 		virtual u64 read_at(u64 offset, void* buffer, u64 size) = 0;
 		virtual u64 write(const void* buffer, u64 size) = 0;
+		virtual u64 write_at([[maybe_unused]] u64 offset, [[maybe_unused]] const void* buffer, [[maybe_unused]] u64 size)
+		{
+			return 0;
+		}
 		virtual u64 seek(s64 offset, seek_mode whence) = 0;
 		virtual u64 size() = 0;
 		virtual native_handle get_handle();
@@ -343,6 +347,12 @@ namespace fs
 			return m_file->write(buffer, count);
 		}
 
+		u64 write_at(u64 offset, const void* buffer, u64 count, std::source_location src_loc = std::source_location::current()) const
+		{
+			if (!m_file) xnull(src_loc);
+			return m_file->write_at(offset, buffer, count);
+		}
+
 		// Change current position, returns resulting position
 		u64 seek(s64 offset, seek_mode whence = seek_set, std::source_location src_loc = std::source_location::current()) const
 		{
@@ -611,6 +621,29 @@ namespace fs
 		}
 	};
 
+	class virtual_dir final : public fs::dir_base
+	{
+		std::vector<fs::dir_entry> m_entries;
+		std::size_t m_offset = 0;
+	
+	public:
+		virtual_dir(std::vector<fs::dir_entry> entries)
+			: m_entries(std::move(entries)) {}
+		
+		bool read(fs::dir_entry &entry) override
+		{
+			if (m_offset < m_entries.size())
+			{
+				entry = m_entries[m_offset++];
+				return true;
+			}
+		
+			return false;
+		}
+		
+		void rewind() override { m_offset = 0; }
+	};
+
 	// Get executable path
 	std::string get_executable_path();