[Common] Make MemoryManagement.cpp more Android friendly

Source/Common/MemoryManagement.cpp

@@ -1,7 +1,12 @@
 #include "stdafx.h"
+#ifdef _WIN32
 #include <windows.h>
+#else
+#include <sys/mman.h>
+#endif
 #include "MemoryManagement.h"
 
+#ifdef _WIN32
 static bool TranslateFromMemProtect(MEM_PROTECTION memProtection, int & OsMemProtection)
 {
     switch (memProtection)
@@ -29,34 +34,64 @@ static bool TranslateToMemProtect(int OsMemProtection, MEM_PROTECTION & memProte
     }
     return true;
 }
+#endif
 
 void* AllocateAddressSpace(size_t size)
 {
+#ifdef _WIN32
     return VirtualAlloc(NULL, size, MEM_RESERVE | MEM_TOP_DOWN, PAGE_NOACCESS);
+#else
+    void * ptr = mmap((void*)0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
+    msync(ptr, size, MS_SYNC|MS_INVALIDATE);
+    return ptr;
+#endif
 }
 
 bool FreeAddressSpace(void* addr, size_t size)
 {
+#ifdef _WIN32
     return VirtualFree(addr, 0, MEM_RELEASE) != 0;
+#else
+    msync(addr, size, MS_SYNC);
+    munmap(addr, size);
+#endif
 }
 
 void* CommitMemory(void* addr, size_t size, MEM_PROTECTION memProtection)
 {
+#ifdef _WIN32
     int OsMemProtection;
     if (!TranslateFromMemProtect(memProtection, OsMemProtection))
     {
         return NULL;
     }
     return VirtualAlloc(addr, size, MEM_COMMIT, OsMemProtection);
+#else
+    void * ptr = mmap(addr, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED|MAP_ANON, -1, 0);
+    msync(addr, size, MS_SYNC|MS_INVALIDATE);
+    return ptr;
+#endif
 }
 
 bool DecommitMemory(void* addr, size_t size)
 {
+#ifdef _WIN32
     return VirtualFree((void*)addr, size, MEM_DECOMMIT) != 0;
+#else
+    // instead of unmapping the address, we're just gonna trick 
+    // the TLB to mark this as a new mapped area which, due to 
+    // demand paging, will not be committed until used.
+ 
+    mmap(addr, size, PROT_NONE, MAP_FIXED|MAP_PRIVATE|MAP_ANON, -1, 0);
+    msync(addr, size, MS_SYNC|MS_INVALIDATE);
+	
+	return true;
+#endif
 }
 
 bool ProtectMemory(void* addr, size_t size, MEM_PROTECTION memProtection, MEM_PROTECTION * OldProtect)
 {
+#ifdef _WIN32
     int OsMemProtection;
     if (!TranslateFromMemProtect(memProtection, OsMemProtection))
     {
@@ -73,4 +108,7 @@ bool ProtectMemory(void* addr, size_t size, MEM_PROTECTION memProtection, MEM_PR
         }
     }
     return res != 0;
+#else
+	return false;
+#endif
 }