Implement missing miner functions on FreeBSD

cryptonote::miner::get_system_times(): Fetch the system's total and
idle time using sysctl kern.cp_time.

cryptonote::miner::get_process_time(): Use the same implementation as
Linux and OSX, the times(3) function conforms to POSIX.1 and is
available on FreeBSD.

cryptonote::miner::on_battery_power(): Try to fetch the battery status
using sysctl hw.acpi.acline. If that fails (if ACPI is not enabled on
the system), then try querying /dev/apm.

src/cryptonote_basic/miner.cpp

@@ -53,6 +53,19 @@
   #include <TargetConditionals.h>
 #endif
 
+#ifdef __FreeBSD__
+#include <devstat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <machine/apm_bios.h>
+#include <stdio.h>
+#include <sys/resource.h>
+#include <sys/sysctl.h>
+#include <sys/times.h>
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
 #undef MONERO_DEFAULT_LOG_CATEGORY
 #define MONERO_DEFAULT_LOG_CATEGORY "miner"
 
@@ -783,6 +796,33 @@ namespace cryptonote
       
       return true;
 
+    #elif defined(__FreeBSD__)
+
+      struct statinfo s;
+      size_t n = sizeof(s.cp_time);
+      if( sysctlbyname("kern.cp_time", s.cp_time, &n, NULL, 0) == -1 )
+      {
+        LOG_ERROR("sysctlbyname(\"kern.cp_time\"): " << strerror(errno));
+        return false;
+      }
+      if( n != sizeof(s.cp_time) )
+      {
+        LOG_ERROR("sysctlbyname(\"kern.cp_time\") output is unexpectedly "
+          << n << " bytes instead of the expected " << sizeof(s.cp_time)
+          << " bytes.");
+        return false;
+      }
+
+      idle_time = s.cp_time[CP_IDLE];
+      total_time =
+        s.cp_time[CP_USER] +
+        s.cp_time[CP_NICE] +
+        s.cp_time[CP_SYS] +
+        s.cp_time[CP_INTR] +
+        s.cp_time[CP_IDLE];
+
+      return true;
+
     #endif
 
     return false; // unsupported system
@@ -805,7 +845,7 @@ namespace cryptonote
         return true;
       }
 
-    #elif (defined(__linux__) && defined(_SC_CLK_TCK)) || defined(__APPLE__)
+    #elif (defined(__linux__) && defined(_SC_CLK_TCK)) || defined(__APPLE__) || defined(__FreeBSD__)
 
       struct tms tms;
       if ( times(&tms) != (clock_t)-1 )
@@ -927,6 +967,70 @@ namespace cryptonote
       }
       return on_battery;
 
+    #elif defined(__FreeBSD__)
+      int ac;
+      size_t n = sizeof(ac);
+      if( sysctlbyname("hw.acpi.acline", &ac, &n, NULL, 0) == -1 )
+      {
+        if( errno != ENOENT )
+        {
+          LOG_ERROR("Cannot query battery status: "
+            << "sysctlbyname(\"hw.acpi.acline\"): " << strerror(errno));
+          return boost::logic::tribool(boost::logic::indeterminate);
+        }
+
+        // If sysctl fails with ENOENT, then try querying /dev/apm.
+
+        static const char* dev_apm = "/dev/apm";
+        const int fd = open(dev_apm, O_RDONLY);
+        if( fd == -1 ) {
+          LOG_ERROR("Cannot query battery status: "
+            << "open(): " << dev_apm << ": " << strerror(errno));
+          return boost::logic::tribool(boost::logic::indeterminate);
+        }
+
+        apm_info info;
+        if( ioctl(fd, APMIO_GETINFO, &info) == -1 ) {
+          close(fd);
+          LOG_ERROR("Cannot query battery status: "
+            << "ioctl(" << dev_apm << ", APMIO_GETINFO): " << strerror(errno));
+          return boost::logic::tribool(boost::logic::indeterminate);
+        }
+
+        close(fd);
+
+        // See apm(8).
+        switch( info.ai_acline )
+        {
+        case 0: // off-line
+        case 2: // backup power
+          return boost::logic::tribool(true);
+        case 1: // on-line
+          return boost::logic::tribool(false);
+        }
+        switch( info.ai_batt_stat )
+        {
+        case 0: // high
+        case 1: // low
+        case 2: // critical
+          return boost::logic::tribool(true);
+        case 3: // charging
+          return boost::logic::tribool(false);
+        }
+
+        LOG_ERROR("Cannot query battery status: "
+          << "sysctl hw.acpi.acline is not available and /dev/apm returns "
+          << "unexpected ac-line status (" << info.ai_acline << ") and "
+          << "battery status (" << info.ai_batt_stat << ").");
+        return boost::logic::tribool(boost::logic::indeterminate);
+      }
+      if( n != sizeof(ac) )
+      {
+        LOG_ERROR("sysctlbyname(\"hw.acpi.acline\") output is unexpectedly "
+          << n << " bytes instead of the expected " << sizeof(ac) << " bytes.");
+        return boost::logic::tribool(boost::logic::indeterminate);
+      }
+      return boost::logic::tribool(ac == 0);
     #endif
     
     LOG_ERROR("couldn't query power status");