diff --git a/src/exdll.c b/src/exdll.c
new file mode 100644
index 00000000..4a800f1c
--- /dev/null
+++ b/src/exdll.c
@@ -0,0 +1,286 @@
+#include "exdll.h"
+
+unsigned int g_stringsize;
+stack_t **g_stacktop;
+LPTSTR g_variables;
+
+// utility functions (not required but often useful)
+
+int NSISCALL popstring(LPTSTR str)
+{
+  stack_t *th;
+  if (!g_stacktop || !*g_stacktop) return 1;
+  th=(*g_stacktop);
+  if (str) lstrcpy(str,th->text);
+  *g_stacktop = th->next;
+  GlobalFree((HGLOBAL)th);
+  return 0;
+}
+
+int NSISCALL popstringn(LPTSTR str, int maxlen)
+{
+  stack_t *th;
+  if (!g_stacktop || !*g_stacktop) return 1;
+  th=(*g_stacktop);
+  if (str) lstrcpyn(str,th->text,maxlen?maxlen:g_stringsize);
+  *g_stacktop = th->next;
+  GlobalFree((HGLOBAL)th);
+  return 0;
+}
+
+void NSISCALL pushstring(LPCTSTR str)
+{
+  stack_t *th;
+  if (!g_stacktop) return;
+  th=(stack_t*)GlobalAlloc(GPTR,(sizeof(stack_t)+(g_stringsize)*sizeof(*str)));
+  lstrcpyn(th->text,str,g_stringsize);
+  th->next=*g_stacktop;
+  *g_stacktop=th;
+}
+
+LPTSTR NSISCALL getuservariable(const int varnum)
+{
+  if (!isvalidnsisvarindex(varnum)) return NULL;
+  return g_variables+varnum*g_stringsize;
+}
+
+void NSISCALL setuservariable(const int varnum, LPCTSTR var)
+{
+  if (var && isvalidnsisvarindex(varnum))
+    lstrcpy(g_variables + varnum*g_stringsize, var);
+}
+
+#ifdef UNICODE
+int NSISCALL PopStringA(LPSTR ansiStr)
+{
+   LPWSTR wideStr = (LPWSTR) GlobalAlloc(GPTR, g_stringsize*sizeof(WCHAR));
+   int rval = popstring(wideStr);
+   WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, g_stringsize, NULL, NULL);
+   GlobalFree((HGLOBAL)wideStr);
+   return rval;
+}
+
+int NSISCALL PopStringNA(LPSTR ansiStr, int maxlen)
+{
+   int realLen = maxlen ? maxlen : g_stringsize;
+   LPWSTR wideStr = (LPWSTR) GlobalAlloc(GPTR, realLen*sizeof(WCHAR));
+   int rval = popstringn(wideStr, realLen);
+   WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, realLen, NULL, NULL);
+   GlobalFree((HGLOBAL)wideStr);
+   return rval;
+}
+
+void NSISCALL PushStringA(LPCSTR ansiStr)
+{
+   LPWSTR wideStr = (LPWSTR) GlobalAlloc(GPTR, g_stringsize*sizeof(WCHAR));
+   MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, g_stringsize);
+   pushstring(wideStr);
+   GlobalFree((HGLOBAL)wideStr);
+   return;
+}
+
+void NSISCALL GetUserVariableW(const int varnum, LPWSTR wideStr)
+{
+   lstrcpyW(wideStr, getuservariable(varnum));
+}
+
+void NSISCALL GetUserVariableA(const int varnum, LPSTR ansiStr)
+{
+   LPWSTR wideStr = getuservariable(varnum);
+   WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, g_stringsize, NULL, NULL);
+}
+
+void NSISCALL SetUserVariableA(const int varnum, LPCSTR ansiStr)
+{
+   if (ansiStr && isvalidnsisvarindex(varnum))
+   {
+      LPWSTR wideStr = g_variables + varnum * g_stringsize;
+      MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, g_stringsize);
+   }
+}
+
+#else
+// ANSI defs
+int NSISCALL PopStringW(LPWSTR wideStr)
+{
+   LPSTR ansiStr = (LPSTR) GlobalAlloc(GPTR, g_stringsize);
+   int rval = popstring(ansiStr);
+   MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, g_stringsize);
+   GlobalFree((HGLOBAL)ansiStr);
+   return rval;
+}
+
+int NSISCALL PopStringNW(LPWSTR wideStr, int maxlen)
+{
+   int realLen = maxlen ? maxlen : g_stringsize;
+   LPSTR ansiStr = (LPSTR) GlobalAlloc(GPTR, realLen);
+   int rval = popstringn(ansiStr, realLen);
+   MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, realLen);
+   GlobalFree((HGLOBAL)ansiStr);
+   return rval;
+}
+
+void NSISCALL PushStringW(LPWSTR wideStr)
+{
+   LPSTR ansiStr = (LPSTR) GlobalAlloc(GPTR, g_stringsize);
+   WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, g_stringsize, NULL, NULL);
+   pushstring(ansiStr);
+   GlobalFree((HGLOBAL)ansiStr);
+}
+
+void NSISCALL GetUserVariableW(const int varnum, LPWSTR wideStr)
+{
+   LPSTR ansiStr = getuservariable(varnum);
+   MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, g_stringsize);
+}
+
+void NSISCALL GetUserVariableA(const int varnum, LPSTR ansiStr)
+{
+   lstrcpyA(ansiStr, getuservariable(varnum));
+}
+
+void NSISCALL SetUserVariableW(const int varnum, LPCWSTR wideStr)
+{
+   if (wideStr && isvalidnsisvarindex(varnum))
+   {
+      LPSTR ansiStr = g_variables + varnum * g_stringsize;
+      WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, g_stringsize, NULL, NULL);
+   }
+}
+#endif
+
+// playing with integers
+
+INT_PTR NSISCALL nsishelper_str_to_ptr(LPCTSTR s)
+{
+  INT_PTR v=0;
+  if (*s == _T('0') && (s[1] == _T('x') || s[1] == _T('X')))
+  {
+    s++;
+    for (;;)
+    {
+      int c=*(++s);
+      if (c >= _T('0') && c <= _T('9')) c-=_T('0');
+      else if (c >= _T('a') && c <= _T('f')) c-=_T('a')-10;
+      else if (c >= _T('A') && c <= _T('F')) c-=_T('A')-10;
+      else break;
+      v<<=4;
+      v+=c;
+    }
+  }
+  else if (*s == _T('0') && s[1] <= _T('7') && s[1] >= _T('0'))
+  {
+    for (;;)
+    {
+      int c=*(++s);
+      if (c >= _T('0') && c <= _T('7')) c-=_T('0');
+      else break;
+      v<<=3;
+      v+=c;
+    }
+  }
+  else
+  {
+    int sign=0;
+    if (*s == _T('-')) sign++; else s--;
+    for (;;)
+    {
+      int c=*(++s) - _T('0');
+      if (c < 0 || c > 9) break;
+      v*=10;
+      v+=c;
+    }
+    if (sign) v = -v;
+  }
+
+  return v;
+}
+
+unsigned int NSISCALL myatou(LPCTSTR s)
+{
+  unsigned int v=0;
+
+  for (;;)
+  {
+    unsigned int c=*s++;
+    if (c >= _T('0') && c <= _T('9')) c-=_T('0');
+    else break;
+    v*=10;
+    v+=c;
+  }
+  return v;
+}
+
+int NSISCALL myatoi_or(LPCTSTR s)
+{
+  int v=0;
+  if (*s == _T('0') && (s[1] == _T('x') || s[1] == _T('X')))
+  {
+    s++;
+    for (;;)
+    {
+      int c=*(++s);
+      if (c >= _T('0') && c <= _T('9')) c-=_T('0');
+      else if (c >= _T('a') && c <= _T('f')) c-=_T('a')-10;
+      else if (c >= _T('A') && c <= _T('F')) c-=_T('A')-10;
+      else break;
+      v<<=4;
+      v+=c;
+    }
+  }
+  else if (*s == _T('0') && s[1] <= _T('7') && s[1] >= _T('0'))
+  {
+    for (;;)
+    {
+      int c=*(++s);
+      if (c >= _T('0') && c <= _T('7')) c-=_T('0');
+      else break;
+      v<<=3;
+      v+=c;
+    }
+  }
+  else
+  {
+    int sign=0;
+    if (*s == _T('-')) sign++; else s--;
+    for (;;)
+    {
+      int c=*(++s) - _T('0');
+      if (c < 0 || c > 9) break;
+      v*=10;
+      v+=c;
+    }
+    if (sign) v = -v;
+  }
+
+  // Support for simple ORed expressions
+  if (*s == _T('|'))
+  {
+      v |= myatoi_or(s+1);
+  }
+
+  return v;
+}
+
+INT_PTR NSISCALL popintptr()
+{
+  TCHAR buf[128];
+  if (popstringn(buf,COUNTOF(buf)))
+    return 0;
+  return nsishelper_str_to_ptr(buf);
+}
+
+int NSISCALL popint_or()
+{
+  TCHAR buf[128];
+  if (popstringn(buf,COUNTOF(buf)))
+    return 0;
+  return myatoi_or(buf);
+}
+
+void NSISCALL pushintptr(INT_PTR value)
+{
+  TCHAR buffer[30];
+  wsprintf(buffer, sizeof(void*) > 4 ? _T("%Id") : _T("%d"), value);
+  pushstring(buffer);
+}