osfmk/man/mapped_tvalspec.html

   1 <h2>mapped_tvalspec</h2>
   2 <hr>
   3 <p>
   4 <strong>Structure</strong> - Specifies the format the kernel uses to maintain a mapped clock's time.
   5 <h3>SYNOPSIS</h3>
   6 <pre>
   7 <strong>struct mapped_tvalspec</strong>
   8 <strong>{</strong>
   9        <strong>tvalspec_t</strong>          <var>mtv_time</var><strong>;</strong>
  10        <strong>unsigned int</strong>        <var>mtv_csec</var><strong>;</strong>
  11 <strong>};</strong>
  12
  13 <strong>typedef struct mapped_tvalspec mapped_tvalspec_t;</strong>
  14 </pre>
  15 <h3>FIELDS</h3>
  16 <dl>
  17 <dt> <var>mtv_time</var>
  18 <dd>
  19 Clock time.
  20 <p>
  21 <dt> <var>mtv_csec</var>
  22 <dd>
  23 A field used to synchronize with the kernel's setting of the time.
  24 </dl>
  25 <h3>DESCRIPTION</h3>
  26 <p>
  27 The <strong>mapped_tvalspec</strong> structure defines the format of the
  28 current-time structure
  29 maintained by the kernel and visible through a mapped clock
  30 (<strong>clock_map_time</strong>).  The data in this structure is updated at the
  31 clock's current resolution and contains the same <strong>tvalspec</strong> value that
  32 would be returned by <strong>clock_get_time</strong>.
  33 <h3>NOTES</h3>
  34 <p>
  35 Because of the race between the referencing of the multiple fields
  36 in the clock
  37 value and the kernel's setting them, they should be referenced as follows:
  38 <p>
  39 <pre>
  40    <strong>tvalspec_t* ts;</strong>
  41    <strong>do</strong>
  42    <strong>{</strong>
  43               <strong>ts-> tv_sec = mtime -> mtv_time.tv_sec;</strong>
  44               <strong>ts  -> tv_nsec = mtime -> mtv_time.tv_nsec;</strong>
  45    <strong>} while (ts  -> tv_sec != mtime -> mtv_csec);</strong>
  46 </pre>
  47 <h3>RELATED INFORMATION</h3>
  48 <p>
  49 Functions:
  50 <a href="clock_map_time.html"><strong>clock_map_time</strong></a>,
  51 <a href="clock_get_time.html"><strong>clock_get_time</strong></a>.
  52 <p>
  53 Data Structures:
  54 <a href="tvalspec.html"><strong>tvalspec</strong></a>.