common: Add VirtualBuffer class, to abstract memory virtualization.

src/common/virtual_buffer.cpp

@@ -0,0 +1,52 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#if defined __APPLE__ || defined __FreeBSD__ || defined __OpenBSD__
+#include <sys/sysctl.h>
+#elif defined __HAIKU__
+#include <OS.h>
+#else
+#include <sys/sysinfo.h>
+#endif
+#endif
+
+#include "common/assert.h"
+#include "common/virtual_buffer.h"
+
+namespace Common {
+
+void* AllocateMemoryPages(std::size_t size) {
+#ifdef _WIN32
+    void* base{VirtualAlloc(nullptr, size, MEM_COMMIT, PAGE_READWRITE)};
+#else
+    void* base{mmap(nullptr, size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0)};
+
+    if (base == MAP_FAILED) {
+        base = nullptr;
+    }
+#endif
+
+    ASSERT(base);
+
+    return base;
+}
+
+void FreeMemoryPages(void* base, std::size_t size) {
+    if (!base) {
+        return;
+    }
+#ifdef _WIN32
+    ASSERT(VirtualFree(base, 0, MEM_RELEASE));
+#else
+    ASSERT(munmap(base, size) == 0);
+#endif
+}
+
+} // namespace Common