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| <h4 class="subsection">12.13.2 Conversion Specifier Options</h4> |
| |
| <p>If you define a meaning for ‘<samp><span class="samp">%A</span></samp>’, what if the template contains |
| ‘<samp><span class="samp">%+23A</span></samp>’ or ‘<samp><span class="samp">%-#A</span></samp>’? To implement a sensible meaning for these, |
| the handler when called needs to be able to get the options specified in |
| the template. |
| |
| <p>Both the <var>handler-function</var> and <var>arginfo-function</var> accept an |
| argument that points to a <code>struct printf_info</code>, which contains |
| information about the options appearing in an instance of the conversion |
| specifier. This data type is declared in the header file |
| <samp><span class="file">printf.h</span></samp>. |
| <a name="index-printf_002eh-1066"></a> |
| <!-- printf.h --> |
| <!-- GNU --> |
| |
| <div class="defun"> |
| — Type: <b>struct printf_info</b><var><a name="index-struct-printf_005finfo-1067"></a></var><br> |
| <blockquote><p>This structure is used to pass information about the options appearing |
| in an instance of a conversion specifier in a <code>printf</code> template |
| string to the handler and arginfo functions for that specifier. It |
| contains the following members: |
| |
| <dl> |
| <dt><code>int prec</code><dd>This is the precision specified. The value is <code>-1</code> if no precision |
| was specified. If the precision was given as ‘<samp><span class="samp">*</span></samp>’, the |
| <code>printf_info</code> structure passed to the handler function contains the |
| actual value retrieved from the argument list. But the structure passed |
| to the arginfo function contains a value of <code>INT_MIN</code>, since the |
| actual value is not known. |
| |
| <br><dt><code>int width</code><dd>This is the minimum field width specified. The value is <code>0</code> if no |
| width was specified. If the field width was given as ‘<samp><span class="samp">*</span></samp>’, the |
| <code>printf_info</code> structure passed to the handler function contains the |
| actual value retrieved from the argument list. But the structure passed |
| to the arginfo function contains a value of <code>INT_MIN</code>, since the |
| actual value is not known. |
| |
| <br><dt><code>wchar_t spec</code><dd>This is the conversion specifier character specified. It's stored in |
| the structure so that you can register the same handler function for |
| multiple characters, but still have a way to tell them apart when the |
| handler function is called. |
| |
| <br><dt><code>unsigned int is_long_double</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">L</span></samp>’, ‘<samp><span class="samp">ll</span></samp>’, or ‘<samp><span class="samp">q</span></samp>’ |
| type modifier was specified. For integer conversions, this indicates |
| <code>long long int</code>, as opposed to <code>long double</code> for floating |
| point conversions. |
| |
| <br><dt><code>unsigned int is_char</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">hh</span></samp>’ type modifier was specified. |
| |
| <br><dt><code>unsigned int is_short</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">h</span></samp>’ type modifier was specified. |
| |
| <br><dt><code>unsigned int is_long</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">l</span></samp>’ type modifier was specified. |
| |
| <br><dt><code>unsigned int alt</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">#</span></samp>’ flag was specified. |
| |
| <br><dt><code>unsigned int space</code><dd>This is a boolean that is true if the ‘<samp> </samp>’ flag was specified. |
| |
| <br><dt><code>unsigned int left</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">-</span></samp>’ flag was specified. |
| |
| <br><dt><code>unsigned int showsign</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">+</span></samp>’ flag was specified. |
| |
| <br><dt><code>unsigned int group</code><dd>This is a boolean that is true if the ‘<samp><span class="samp">'</span></samp>’ flag was specified. |
| |
| <br><dt><code>unsigned int extra</code><dd>This flag has a special meaning depending on the context. It could |
| be used freely by the user-defined handlers but when called from |
| the <code>printf</code> function this variable always contains the value |
| <code>0</code>. |
| |
| <br><dt><code>unsigned int wide</code><dd>This flag is set if the stream is wide oriented. |
| |
| <br><dt><code>wchar_t pad</code><dd>This is the character to use for padding the output to the minimum field |
| width. The value is <code>'0'</code> if the ‘<samp><span class="samp">0</span></samp>’ flag was specified, and |
| <code>' '</code> otherwise. |
| </dl> |
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