[#2330] Uptime should not make redundant system calls

Rewrite of uptime facts and supporting utility methods. Works on unix,
BSD, windows. No longer makes redundant system calls.

Uses Facter::Util::Uptime utility methods:

* Implemented uptime_seconds_unix using /proc/uptime or who -b on unix,
  sysctl on BSD.

  Added unit tests for the behaviors of get_uptime_seconds_unix: read
  from proc/uptime, read uptime from "sysctl -b kern.boottime", read
  uptime from "who -b", and return nil if nothing else works.

* Implemented uptime_seconds_win using the Win32 API.

Facts implemented:

* uptime_{seconds,hours,days}

    Returns the respective integer value.

* uptime

    Returns human readable uptime statistic that preserves original
    behavior.

    Examples:

      3 days
      1 day
      5:08 hours
      0:35 hours

5 files changed, 84 insertions, 37 deletions

diff --git a/lib/facter/uptime.rb b/lib/facter/uptime.rb
index 3a3bc86..56a959b 100644
--- a/lib/facter/uptime.rb
+++ b/lib/facter/uptime.rb
@@ -1,20 +1,23 @@
 require 'facter/util/uptime'
 
 Facter.add(:uptime) do
-    confine :operatingsystem => %w{Solaris Linux Fedora RedHat CentOS SuSE SLES Debian Ubuntu Gentoo AIX}
-    setcode do
-        Facter::Util::Uptime.get_uptime_simple
-    end
-end
+  setcode do
+    seconds = Facter.fact(:uptime_seconds).value
 
-if FileTest.exists?("/proc/uptime")
-    uptime = Facter::Util::Uptime.get_uptime
+    unless seconds
+      "unknown"
+    else
+      days    = seconds / (60 * 60 * 24)
+      hours   = seconds / (60 * 60) % 24
+      minutes = seconds / 60 % 60
 
-    %w{days hours seconds}.each do |label|
-        Facter.add("uptime_" + label) do
-            setcode do
-                Facter::Util::Uptime.get_uptime_period(uptime, label)
-            end 
-        end 
-    end 
+      case days
+      when 0 then "#{hours}:#{"%02d" % minutes} hours"
+      when 1 then '1 day'
+      else "#{days} days"
+      end
+    end
+
+  end
 end
+
diff --git a/lib/facter/uptime_days.rb b/lib/facter/uptime_days.rb
new file mode 100644
index 0000000..add305c
--- /dev/null
+++ b/lib/facter/uptime_days.rb
@@ -0,0 +1,7 @@
+Facter.add(:uptime_days) do
+  setcode do
+    hours = Facter.value(:uptime_hours)
+    hours && hours / 24 # hours in day
+  end
+end
+
diff --git a/lib/facter/uptime_hours.rb b/lib/facter/uptime_hours.rb
new file mode 100644
index 0000000..ce691d2
--- /dev/null
+++ b/lib/facter/uptime_hours.rb
@@ -0,0 +1,7 @@
+Facter.add(:uptime_hours) do
+  setcode do
+    seconds = Facter.value(:uptime_seconds)
+    seconds && seconds / (60 * 60) # seconds in hour
+  end
+end
+
diff --git a/lib/facter/uptime_seconds.rb b/lib/facter/uptime_seconds.rb
new file mode 100644
index 0000000..14bb573
--- /dev/null
+++ b/lib/facter/uptime_seconds.rb
@@ -0,0 +1,10 @@
+require 'facter/util/uptime'
+
+Facter.add(:uptime_seconds) do
+  setcode { Facter::Util::Uptime.get_uptime_seconds_unix }
+end
+
+Facter.add(:uptime_seconds) do
+  confine :kernel => :windows
+  setcode { Facter::Util::Uptime.get_uptime_seconds_win }
+end
diff --git a/lib/facter/util/uptime.rb b/lib/facter/util/uptime.rb
index c1e339b..f8a17db 100644
--- a/lib/facter/util/uptime.rb
+++ b/lib/facter/util/uptime.rb
@@ -1,32 +1,52 @@
+require 'time'
+
 # A module to gather uptime facts
 #
 module Facter::Util::Uptime
-    def self.get_uptime_simple
-        time = Facter::Util::Resolution.exec('uptime')
-        if time =~ /up\s*(\d+\s\w+)/
-            $1
-        elsif time =~ /up\s*(\d+:\d+)/
-            $1 + " hours"
-        else
-            "unknown"
+    def self.get_uptime_seconds_unix
+        uptime_proc_uptime or uptime_sysctl or uptime_who_dash_b
+    end
+
+    def self.get_uptime_seconds_win
+        require 'Win32API'
+        getTickCount = Win32API.new("kernel32", "GetTickCount", nil, 'L')
+        compute_uptime(Time.at(getTickCount.call() / 1000.0))
+    end
+
+    private
+
+    def self.uptime_proc_uptime
+        if File.exists? uptime_file
+            r = File.read uptime_file
+            r.split(" ").first.to_i
+        end
+    end
+
+    def self.uptime_sysctl
+        if (output = `#{uptime_sysctl_cmd}`) and $?.success?
+            compute_uptime(Time.at(output.unpack('L').first))
+        end
+    end
+
+    def self.uptime_who_dash_b
+        if (output = `#{uptime_who_cmd}`) and $?.success?
+            compute_uptime(Time.parse(output))
         end
     end
 
-    def self.get_uptime
-        r = IO.popen("/bin/cat /proc/uptime")
-        uptime, idletime = r.readline.split(" ")        
-        r.close
-        uptime_seconds = uptime.to_i
+    def self.compute_uptime(time)
+        (Time.now - time).to_i
+    end
+
+    def self.uptime_file
+        "/proc/uptime"
+    end
+
+    def self.uptime_sysctl_cmd
+        'sysctl -b kern.boottime 2>/dev/null'
     end
 
-    def self.get_uptime_period(seconds, label)
-        case label
-        when 'days'
-            value = seconds / 86400
-        when 'hours'
-            value = seconds / 3600
-        when 'seconds'
-            seconds
-        end     
+    def self.uptime_who_cmd
+        'who -b 2>/dev/null'
     end
-end   
+end