reintroduce getRegistryEntry (bug 237754). patch by dave532@uklinux.net, r=ben.

browser/components/shell/public/nsIWindowsShellService.idl

@@ -59,5 +59,27 @@ interface nsIWindowsShellService : nsIShellService
      * @return The number of unread (new) mail messages for the current user.
      */
     readonly attribute unsigned long unreadMailCount;
+
+
+    /**
+     * Valid starting keys for the Windows Registry.
+     */
+    const long HKCR = 0; // HKEY_CLASSES_ROOT
+    const long HKCC = 1; // HKEY_CURRENT_CONFIG
+    const long HKCU = 2; // HKEY_CURRENT_USER
+    const long HKLM = 3; // HKEY_LOCAL_MACHINE
+    const long HKU  = 4; // HKEY_USERS
+
+    /** 
+     * Retrieves a Windows Registry entry value.
+     * 
+     * @param aHKeyConstant The starting key, using the constants defined above.
+     * @param aSubKeyName   The sub key to locate
+     * @param aValueName    The value to locate in the sub key. The empty string
+     *                      returns the default value of the sub key.
+     * @return The value of the specified sub key/value, truncated to 4096 bytes.
+     */
+    string getRegistryEntry(in long aHKeyConstant, in string aSubKeyName, in string aValueName);
+
 };
 

browser/components/shell/src/nsWindowsShellService.cpp

@@ -794,3 +794,50 @@ nsWindowsShellService::GetMailAccountKey(HKEY* aResult)
   return PR_FALSE;
 }
 
+NS_IMETHODIMP
+nsWindowsShellService::GetRegistryEntry(PRInt32 aHKEYConstant,
+                                        const char *aSubKeyName,
+                                        const char *aValueName,
+                                        char **aResult)
+{
+  HKEY hKey, fullKey;
+
+  *aResult = 0;
+  // Calculate HKEY_* base key
+  switch (aHKEYConstant) {
+  case HKCR:
+    hKey = HKEY_CLASSES_ROOT;
+    break;
+  case HKCC:
+    hKey = HKEY_CURRENT_CONFIG;
+    break;
+  case HKCU:
+    hKey = HKEY_CURRENT_USER;
+    break;
+  case HKLM:
+    hKey = HKEY_LOCAL_MACHINE;
+    break;
+  case HKU:
+    hKey = HKEY_USERS;
+    break;
+  default:
+    return NS_ERROR_INVALID_ARG;
+  }
+  
+  // Open Key
+  LONG rv = ::RegOpenKeyEx(hKey, aSubKeyName, 0, KEY_READ, &fullKey);
+
+  if (rv == ERROR_SUCCESS) {
+    char buffer[4096] = { 0 };
+    DWORD len = sizeof buffer;
+    rv = ::RegQueryValueEx(fullKey, aValueName, NULL, NULL,
+                           (LPBYTE)buffer, &len);
+
+    if (rv == ERROR_SUCCESS)
+      *aResult = PL_strdup(buffer);
+  }
+
+  ::RegCloseKey(fullKey);
+
+  return *aResult ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+}