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<dl class="section see"><dt>See also</dt><dd><a class="el" href="json_8h.html" title="JavaScript Object Notation (JSON) utilities.">ah_json/include/ah/json.h</a></dd></dl>
<div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno"> 1</span><span class="comment">// SPDX-License-Identifier: EPL-2.0</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno"> 2</span> </div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno"> 9</span><span class="comment">// An example of how to construct a JSON representation using C99 standard</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno"> 10</span><span class="comment">// library functions and our ah_json_str_escape() function.</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno"> 11</span> </div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno"> 12</span><span class="preprocessor">#include <<a class="code" href="err_8h.html" title="Error management.">ah/err.h</a>></span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno"> 13</span><span class="preprocessor">#include <<a class="code" href="json_8h.html" title="JavaScript Object Notation (JSON) utilities.">ah/json.h</a>></span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno"> 14</span><span class="preprocessor">#include <limits.h></span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno"> 15</span><span class="preprocessor">#include <stddef.h></span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno"> 16</span><span class="preprocessor">#include <stdio.h></span></div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno"> 17</span><span class="preprocessor">#include <stdlib.h></span></div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span><span class="preprocessor">#include <string.h></span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno"> 19</span> </div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span><span class="keywordtype">int</span> main(<span class="keywordtype">void</span>)</div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span>{</div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno"> 22</span> <a class="code hl_typedef" href="defs_8h.html#a746483e29fbbad8cb71e1b3875763ae2" title="Signed integer type used to hold an error code.">ah_err_t</a> err;</div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno"> 23</span> <span class="keywordtype">char</span> err_buf[128u];</div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno"> 24</span> <span class="keyword">const</span> <span class="keywordtype">char</span>* err_ctx;</div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno"> 25</span> </div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span> <span class="keyword">const</span> <span class="keywordtype">char</span>* sensor_id = <span class="stringliteral">"aa-xx-142b"</span>;</div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno"> 27</span> <span class="keywordtype">float</span> kelvin = 296.55f;</div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno"> 28</span> </div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno"> 29</span> <span class="comment">// Here, we assume that `sensor_id` may contain characters that must be</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno"> 30</span> <span class="comment">// escaped before they can be part of a JSON message. If we had known that</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno"> 31</span> <span class="comment">// `sensor_id` will never contain control characters, backslashes or double</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno"> 32</span> <span class="comment">// quotes, we could have skipped escaping it.</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span> </div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span> <span class="keywordtype">char</span> sensor_id_buf[32u];</div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span> <span class="keywordtype">size_t</span> sensor_id_buf_length = <span class="keyword">sizeof</span>(sensor_id_buf);</div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span> err = <a id="a0" name="a0"></a><a class="code hl_function" href="json_8h.html#a4ea19991f7a0ffd9bf4b089ee1892236" title="Substitutes any UTF-8 code point below 32, " and \ with its corresponding JSON escape sequence and wr...">ah_json_str_escape</a>(sensor_id, strlen(sensor_id), sensor_id_buf, &sensor_id_buf_length);</div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span> <span class="keywordflow">if</span> (err != <a id="a1" name="a1"></a><a class="code hl_define" href="err_8h.html#af1346324d9368d43e1e103d395368306" title="No error.">AH_ENONE</a>) {</div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span> err_ctx = <span class="stringliteral">"ah_json_str_escape()"</span>;</div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span> <span class="keywordflow">goto</span> handle_err;</div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span> }</div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span> <span class="keywordflow">if</span> (sensor_id_buf_length > INT_MAX) {</div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span> err = <a id="a2" name="a2"></a><a class="code hl_define" href="err_8h.html#a8f0da4abff1f0f31740022d6939fb28d" title="Arithmetic argument outside accepted domain.">AH_EDOM</a>;</div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span> err_ctx = <span class="stringliteral">"ah_json_str_escape()"</span>;</div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span> <span class="keywordflow">goto</span> handle_err;</div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"> 45</span> }</div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno"> 46</span> </div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno"> 47</span> <span class="comment">// We are not ready to produce the actual JSON object.</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno"> 48</span> </div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno"> 49</span> <span class="keywordtype">char</span> out_buf[128u];</div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span> <span class="keywordtype">int</span> size = snprintf(out_buf, <span class="keyword">sizeof</span>(out_buf), <span class="stringliteral">"{\"sensor-id\":\"%.*s\",\"kelvin\":%f}"</span>,</div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span> (<span class="keywordtype">int</span>) sensor_id_buf_length, sensor_id_buf, kelvin);</div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno"> 52</span> </div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno"> 53</span> <span class="keywordflow">if</span> (size < 0) {</div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno"> 54</span> perror(NULL);</div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span> exit(EXIT_FAILURE);</div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span> }</div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span> </div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span> <span class="keywordflow">if</span> (((<span class="keywordtype">size_t</span>) size) > <span class="keyword">sizeof</span>(out_buf)) {</div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span> fputs(<span class="stringliteral">"out_buf overflowed\n"</span>, stderr);</div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span> exit(EXIT_FAILURE);</div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span> }</div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span> </div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span> <span class="comment">// `out_buf` now contains a JSON object of size `res`. You may, for example,</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span> <span class="comment">// choose to send the contents of `out_buf` over the Internet or some other</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span> <span class="comment">// network. We print it just to make it visible if you run this program.</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span> </div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span> printf(<span class="stringliteral">"%.*s\n"</span>, size, out_buf); <span class="comment">// Prints `{"sensor_name":"aa-xx-142b","kelvin":296.55}`.</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span> </div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno"> 69</span> exit(EXIT_SUCCESS);</div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno"> 70</span> </div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno"> 71</span>handle_err:</div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno"> 72</span> <a id="a3" name="a3"></a><a class="code hl_function" href="err_8h.html#abd464ae90e215314e9fca67df382dadd" title="Writes human-readable representation of err to buf.">ah_strerror_r</a>(err, err_buf, <span class="keyword">sizeof</span>(err_buf));</div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span> fprintf(stderr, <span class="stringliteral">"%s failed: %s\n"</span>, err_ctx, err_buf);</div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno"> 74</span> exit(EXIT_FAILURE);</div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno"> 75</span>}</div>
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