From 25cc02431b61097b2adfc2fbc493b648b0300c3b Mon Sep 17 00:00:00 2001
From: Mason Reed <mason@vector35.com>
Date: Mon, 10 Mar 2025 11:05:40 -0400
Subject: [SharedCache] Refactor Shared Cache

In absence of a better name, this commit refactors the shared cache code.
---
 view/sharedcache/core/MappedFile.h | 86 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 view/sharedcache/core/MappedFile.h

(limited to 'view/sharedcache/core/MappedFile.h')

diff --git a/view/sharedcache/core/MappedFile.h b/view/sharedcache/core/MappedFile.h
new file mode 100644
index 00000000..ced79f52
--- /dev/null
+++ b/view/sharedcache/core/MappedFile.h
@@ -0,0 +1,86 @@
+#pragma once
+
+#include <string>
+#include <cstdint>
+#include <cstdio>
+#include <optional>
+
+// Call this when initializing the plugin so that the process file descriptor limit is raised.
+uint64_t AdjustFileDescriptorLimit();
+
+enum MapStatus : int
+{
+	Success,
+	// TODO: Split this error out into more contextual errors.
+	Error,
+};
+
+struct MappedFile
+{
+	uint8_t* _mmap = nullptr;
+	size_t len = 0;
+
+#ifdef _MSC_VER
+	HANDLE hFile = INVALID_HANDLE_VALUE;
+#else
+	FILE* fd = nullptr;
+#endif
+
+	MappedFile() = default;
+
+	~MappedFile();
+
+	MappedFile(const MappedFile&) = delete;
+
+	MappedFile& operator=(const MappedFile&) = delete;
+
+	MappedFile(MappedFile&& other) noexcept : _mmap(other._mmap), len(other.len)
+	{
+#ifdef _MSC_VER
+		hFile = other.hFile;
+		// Don't close the hFile in the move.
+		other.hFile = nullptr;
+#else
+		fd = other.fd;
+		// Don't close the fd in the move.
+		other.fd = nullptr;
+#endif
+		other._mmap = nullptr;
+	}
+
+	// I hate C++
+	MappedFile& operator=(MappedFile&& other) noexcept
+	{
+		if (this != &other)
+		{
+			Unmap();
+#ifdef _MSC_VER
+			if (hFile != nullptr)
+			{
+				CloseHandle(hFile);
+			}
+			hFile = other.hFile;
+			// Don't close the hFile in the move.
+			other.hFile = nullptr;
+#else
+			if (fd != nullptr)
+			{
+				fclose(fd);
+			}
+			fd = other.fd;
+			// Don't close the fd in the move.
+			other.fd = nullptr;
+#endif
+			len = other.len;
+			_mmap = other._mmap;
+			other._mmap = nullptr;
+		}
+		return *this;
+	}
+
+	static std::optional<MappedFile> OpenFile(const std::string& path);
+
+	MapStatus Map();
+
+	MapStatus Unmap();
+};
-- 
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