Add VTHook header

Co-authored-by: komashchenko <komashchenko@users.noreply.github.com>

Author: Wend4r

include/dynlibutils/vthook.hpp

@@ -0,0 +1,105 @@
+//
+// DynLibUtils
+// Copyright (C) 2023-2025 Vladimir Ezhikov (Wend4r) & komashchenko (Phoenix)
+// Licensed under the MIT license. See LICENSE file in the project root for details.
+//
+
+#ifndef DYNLIBUTILS_VTHOOK_HPP
+#define DYNLIBUTILS_VTHOOK_HPP
+#pragma once
+
+#include "memaddr.hpp"
+
+#if __unix__
+#	include <sys/mman.h>
+#	include <unistd.h>
+#endif
+
+#include <cassert>
+
+namespace DynLibUtils {
+
+class MemUnprotector
+{
+public:
+	MemUnprotector(CMemory pAddress, size_t nLength = sizeof(void*))
+	{
+#if _WIN32
+		VirtualProtect(pAddress, nLength, PAGE_EXECUTE_READWRITE, &m_nOldProtection);
+
+		m_pAddress = pAddress;
+		m_nLength = nLength;
+#else
+		long nPageSize = sysconf(_SC_PAGESIZE);
+		CMemory pPageStart = pAddress & ~(nPageSize - 1l);
+		CMemory pPageEnd = (pAddress + nLength + nPageSize - 1l) & ~(nPageSize - 1l);
+		size_t nAligned = pPageEnd - pPageStart;
+
+		mprotect(pPageStart, nAligned, PROT_READ | PROT_WRITE | PROT_EXEC);
+
+		m_pAddress = pPageStart;
+		m_nLength = nAligned;
+		m_nOldProtection = PROT_READ | PROT_WRITE; //TODO: Need to parse /proc/self/maps
+#endif
+	}
+
+	~MemUnprotector()
+	{
+#if _WIN32
+		DWORD origProtect;
+		VirtualProtect(m_pAddress, m_nLength, m_nOldProtection, &origProtect);
+#else
+		mprotect(m_pAddress, m_nLength, m_nOldProtection);
+#endif
+	}
+
+private:
+	size_t m_nLength;
+	unsigned long m_nOldProtection;
+
+	CMemory m_pAddress;
+}; // class MemUnprotector
+
+template <typename T, typename C, typename ...Args>
+class VTHook
+{
+public:
+	VTHook() = default;
+	~VTHook() { Unhook(); }
+
+	bool IsHooked() const { return m_pOriginalFn.IsValid(); }
+
+	void Hook(CMemory pVTable, int index, T(*pFn)(C*, Args...))
+	{
+		assert(!IsHooked());
+
+		m_vmpFn = pVTable.Offset(index * sizeof(void*));
+		m_pOriginalFn = m_vmpFn.Deref();
+
+		MemUnprotector unprotector(m_vmpFn);
+
+		*m_vmpFn.RCast<T(**)(C*, Args...)>() = pFn;
+	}
+
+	void Unhook()
+	{
+		assert(IsHooked());
+
+		MemUnprotector unprotector(m_vmpFn);
+
+		*m_vmpFn.RCast<void**>() = m_pOriginalFn;
+
+		m_vmpFn = nullptr;
+		m_pOriginalFn = nullptr;
+	}
+
+	T Call(C* pThis, Args... args) { return m_pOriginalFn.RCast<T(*)(C*, Args...)>()(pThis, args...); }
+
+private:
+	CMemory m_vmpFn;
+	CMemory m_pOriginalFn;
+}; // class VTHook
+
+} // namespace DynLibUtils
+
+#endif // DYNLIBUTILS_VTHOOK_HPP