+
+#define REG_ROOT "SOFTWARE\\GNU\\Emacs"
+
+/* Retrieve an environment variable from the Emacs subkeys of the registry.
+ Return NULL if the variable was not found, or it was empty.
+ This code is based on w32_get_resource (w32.c). */
+char *
+w32_get_resource (predefined, key, type)
+ HKEY predefined;
+ char *key;
+ LPDWORD type;
+{
+ HKEY hrootkey = NULL;
+ char *result = NULL;
+ DWORD cbData;
+
+ if (RegOpenKeyEx (predefined, REG_ROOT, 0, KEY_READ, &hrootkey) == ERROR_SUCCESS)
+ {
+ if (RegQueryValueEx (hrootkey, key, NULL, NULL, NULL, &cbData) == ERROR_SUCCESS)
+ {
+ result = (char *) xmalloc (cbData);
+
+ if ((RegQueryValueEx (hrootkey, key, NULL, type, result, &cbData) != ERROR_SUCCESS) ||
+ (*result == 0))
+ {
+ free (result);
+ result = NULL;
+ }
+ }
+
+ RegCloseKey (hrootkey);
+ }
+
+ return result;
+}
+
+/*
+ getenv wrapper for Windows
+
+ This is needed to duplicate Emacs's behavior, which is to look for enviroment
+ variables in the registry if they don't appear in the environment.
+*/
+char *
+w32_getenv (envvar)
+ char *envvar;
+{
+ char *value;
+ DWORD dwType;
+
+ if (value = getenv (envvar))
+ /* Found in the environment. */
+ return value;
+
+ if (! (value = w32_get_resource (HKEY_CURRENT_USER, envvar, &dwType)) &&
+ ! (value = w32_get_resource (HKEY_LOCAL_MACHINE, envvar, &dwType)))
+ /* Not found in the registry. */
+ return NULL;
+
+ if (dwType == REG_SZ)
+ /* Registry; no need to expand. */
+ return value;
+
+ if (dwType == REG_EXPAND_SZ)
+ {
+ DWORD size;
+
+ if (size = ExpandEnvironmentStrings (value, NULL, 0))
+ {
+ char *buffer = (char *) xmalloc (size);
+ if (ExpandEnvironmentStrings (value, buffer, size))
+ {
+ /* Found and expanded. */
+ free (value);
+ return buffer;
+ }
+
+ /* Error expanding. */
+ free (buffer);
+ }
+ }
+
+ /* Not the right type, or not correctly expanded. */
+ free (value);
+ return NULL;
+}
+