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| 18 | </style><a href="index.html">Index </a>· | |
| 19 | <a href="systemd.directives.html">Directives </a>· | |
| 20 | <a href="../python-systemd/index.html">Python </a>· | |
| 21 | <a href="../libudev/index.html">libudev </a>· | |
| e3bff60a | 22 | <a href="../libudev/index.html">gudev </a><span style="float:right">systemd 220</span><hr><div class="refentry"><a name="sd-id128"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd-id128, sd_id128_t, SD_ID128_MAKE, SD_ID128_CONST_STR, SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL, sd_id128_equal — APIs for processing 128-bit IDs</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-id128.h></pre></div><div class="cmdsynopsis"><p><code class="command">pkg-config --cflags --libs libsystemd</code> </p></div></div><div class="refsect1"><a name="idm140538944672128"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="filename">sd-id128.h</code> provides APIs to process and |
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23 | generate 128-bit ID values. The 128-bit ID values processed and |
| 24 | generated by these APIs are a generalization of OSF UUIDs as | |
| 25 | defined by <a class="ulink" href="https://tools.ietf.org/html/rfc4122" target="_top">RFC | |
| 26 | 4122</a> but use a simpler string format. These functions | |
| 27 | impose no structure on the used IDs, much unlike OSF UUIDs or | |
| 28 | Microsoft GUIDs, but are fully compatible with those types of IDs. | |
| 29 | </p><p>See | |
| 30 | <a href="sd_id128_to_string.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_to_string</span>(3)</span></a>, | |
| 31 | <a href="sd_id128_randomize.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_randomize</span>(3)</span></a> | |
| 32 | and | |
| 33 | <a href="sd_id128_get_machine.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_machine</span>(3)</span></a> | |
| 34 | for more information about the implemented functions.</p><p>A 128-bit ID is implemented as the following | |
| 35 | union type:</p><pre class="programlisting">typedef union sd_id128 { | |
| 36 | uint8_t bytes[16]; | |
| 37 | uint64_t qwords[2]; | |
| 38 | } sd_id128_t;</pre><p>This union type allows accessing the 128-bit ID as 16 | |
| 39 | separate bytes or two 64-bit words. It is generally safer to | |
| 40 | access the ID components by their 8-bit array to avoid endianness | |
| 41 | issues. This union is intended to be passed call-by-value (as | |
| 42 | opposed to call-by-reference) and may be directly manipulated by | |
| 43 | clients.</p><p>A couple of macros are defined to denote and decode 128-bit | |
| 44 | IDs:</p><p><code class="function">SD_ID128_MAKE()</code> may be used to denote a | |
| 45 | constant 128-bit ID in source code. A commonly used idiom is to | |
| 46 | assign a name to a 128-bit ID using this macro:</p><pre class="programlisting">#define SD_MESSAGE_COREDUMP SD_ID128_MAKE(fc,2e,22,bc,6e,e6,47,b6,b9,07,29,ab,34,a2,50,b1)</pre><p><code class="function">SD_ID128_CONST_STR()</code> may be used to | |
| 47 | convert constant 128-bit IDs into constant strings for output. The | |
| 48 | following example code will output the string | |
| 49 | "fc2e22bc6ee647b6b90729ab34a250b1":</p><pre class="programlisting">int main(int argc, char *argv[]) { | |
| 50 | puts(SD_ID128_CONST_STR(SD_MESSAGE_COREDUMP)); | |
| 663996b3 | 51 | }</pre><p><code class="function">SD_ID128_FORMAT_STR</code> and |
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52 | <code class="function">SD_ID128_FORMAT_VAL()</code> may be used to format a |
| 53 | 128-bit ID in a | |
| 54 | <a href="http://man7.org/linux/man-pages/man3/printf.3.html"><span class="citerefentry"><span class="refentrytitle">printf</span>(3)</span></a> | |
| 55 | format string, as shown in the following example:</p><pre class="programlisting">int main(int argc, char *argv[]) { | |
| 56 | sd_id128_t id; | |
| 57 | id = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07); | |
| 58 | printf("The ID encoded in this C file is " SD_ID128_FORMAT_STR ".\n", SD_ID128_FORMAT_VAL(id)); | |
| 59 | return 0; | |
| 14228c0d | 60 | }</pre><p>Use <code class="function">sd_id128_equal()</code> to compare two 128-bit IDs:</p><pre class="programlisting">int main(int argc, char *argv[]) { |
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61 | sd_id128_t a, b, c; |
| 62 | a = SD_ID128_MAKE(ee,89,be,71,bd,6e,43,d6,91,e6,c5,5d,eb,03,02,07); | |
| 63 | b = SD_ID128_MAKE(f2,28,88,9c,5f,09,44,15,9d,d7,04,77,58,cb,e7,3e); | |
| 64 | c = a; | |
| 65 | assert(sd_id128_equal(a, c)); | |
| 66 | assert(!sd_id128_equal(a, b)); | |
| 67 | return 0; | |
| 68 | }</pre><p>Note that new, randomized IDs may be generated with | |
| 69 | <a href="journalctl.html"><span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span></a>'s | |
| e3bff60a | 70 | <code class="option">--new-id</code> option.</p></div><div class="refsect1"><a name="idm140538937363120"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p><a name="pkgconfig-text"></a>These APIs are implemented as a shared |
| 60f067b4 | 71 | library, which can be compiled and linked to with the |
| 5eef597e | 72 | <code class="constant">libsystemd</code> <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a> |
| e3bff60a | 73 | file.</p></div><div class="refsect1"><a name="idm140538940038128"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p> |
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74 | <a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>, |
| 75 | <a href="sd_id128_to_string.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_to_string</span>(3)</span></a>, | |
| 76 | <a href="sd_id128_randomize.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_randomize</span>(3)</span></a>, | |
| 77 | <a href="sd_id128_get_machine.html"><span class="citerefentry"><span class="refentrytitle">sd_id128_get_machine</span>(3)</span></a>, | |
| 78 | <a href="http://man7.org/linux/man-pages/man3/printf.3.html"><span class="citerefentry"><span class="refentrytitle">printf</span>(3)</span></a>, | |
| 79 | <a href="journalctl.html"><span class="citerefentry"><span class="refentrytitle">journalctl</span>(1)</span></a>, | |
| 80 | <a href="sd-journal.html"><span class="citerefentry"><span class="refentrytitle">sd-journal</span>(7)</span></a>, | |
| 81 | <a href="http://linux.die.net/man/1/pkg-config"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>, | |
| 82 | <a href="machine-id.html"><span class="citerefentry"><span class="refentrytitle">machine-id</span>(5)</span></a> | |
| 83 | </p></div></div></body></html> |