AU: Update Downloader to support our image formats.

src/platform/update_engine/utils.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/utils.h"
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <dirent.h>
 #include <errno.h>
@@ skipping 279 matching lines @@
     return false;
   return 0 == str.compare(str.size() - suffix.size(), suffix.size(), suffix);
 }
 
 bool StringHasPrefix(const std::string& str, const std::string& prefix) {
   if (prefix.size() > str.size())
     return false;
   return 0 == str.compare(0, prefix.size(), prefix);
 }
 
-const std::string BootDevice() {
+const string BootDevice() {
   string proc_cmdline;
   if (!ReadFileToString("/proc/cmdline", &proc_cmdline))
     return "";
   // look for "root=" in the command line
   string::size_type pos = 0;
   if (!StringHasPrefix(proc_cmdline, "root=")) {
     pos = proc_cmdline.find(" root=") + 1;
   }
   if (pos == string::npos) {
     // can't find root=
     return "";
   }
   // at this point, pos is the point in the string where "root=" starts
   string ret;
   pos += strlen("root=");  // advance to the device name itself
   while (pos < proc_cmdline.size()) {
     char c = proc_cmdline[pos];
     if (c == ' ')
       break;
     ret += c;
     pos++;
   }
   return ret;
   // TODO(adlr): use findfs to figure out UUID= or LABEL= filesystems
 }
 
+const string BootKernelDevice(const std::string& boot_device) {
+  // Currntly this assumes the last digit of the boot device is
+  // 3, 5, or 7, and changes it to 2, 4, or 6, respectively, to
+  // get the kernel device.
+  string ret = boot_device;
+  if (ret.empty())
+    return ret;
+  char last_char = ret[ret.size() - 1];
+  if (last_char == '3' || last_char == '5' || last_char == '7') {
+    ret[ret.size() - 1] = last_char - 1;
+    return ret;
+  }
+  return "";
+}
+
 bool MountFilesystem(const string& device,
                      const string& mountpoint,
                      unsigned long mountflags) {
   int rc = mount(device.c_str(), mountpoint.c_str(), "ext3", mountflags, NULL);
   if (rc < 0) {
     string msg = ErrnoNumberAsString(errno);
     LOG(ERROR) << "Unable to mount destination device: " << msg << ". "
                << device << " on " << mountpoint;
     return false;
   }
@@ skipping 10 matching lines @@
     return "Unknown error.";
   return error->message;
 }
 
 const char* const kStatefulPartition = "/mnt/stateful_partition";
 
 }  // namespace utils
 
 }  // namespace chromeos_update_engine