first cut: establishes base helper classes and main

platform_switch.h

Index: platform_switch.h
diff --git a/platform_switch.h b/platform_switch.h
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+// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Provides a default implementation of a platform switch.  On CrOS, switch
+// state is represented in an integer exposed via a file in /sys.  Each
+// switch recieves one bit which is checked with a subclass-defined
+// bitmask().
+//
+// A subclass only needs to set its name and bitmask to "just work".
+
+#ifndef CROS_BOOT_MODE_PLATFORM_SWITCH_H_
+#define CROS_BOOT_MODE_PLATFORM_SWITCH_H_
+
+#include "platform_reader.h"
+
+namespace cros_boot_mode {
+
+class PlatformSwitch : public PlatformReader {
+ public:
+  PlatformSwitch();
+  virtual ~PlatformSwitch();
+
+  enum { kDisabled, kEnabled };
+  static const char *kPositionText[];
+
+  virtual const char *c_str() const;
+  virtual const char *default_platform_file_path() const {
+    return "/sys/devices/platform/chromeos_acpi/CHSW";
+  }
+  virtual size_t max_size() const {
+    return sizeof("65535");  // largest allowed switch value
+  }
+  virtual int Process(const char *file_contents, size_t length);
+
+  // To be overriden by the implementation
+  virtual unsigned int bitmask() const = 0;
+  virtual const char *name() const = 0;
+};
+
+}  // namespace cros_boot_mode
+#endif  // CROS_BOOT_MODE_PLATFORM_SWITCH_H_