C语言实现进制转换函数的实例详解

其中用到了text_to_cstring(arg1),类型转换的相关函数定义在 src/backend/utils/adt/varlena.c

/*
 * text_to_cstring
 *
 * Create a palloc'd,null-terminated C string from a text value.
 *
 * We support being passed a compressed or toasted text value.
 * This is a bit bogus since such values shouldn't really be referred to as
 * "text *",but it seems useful for robustness. If we didn't handle that
 * case here,we'd need another routine that did,anyway.
 */
char *
text_to_cstring(const text *t)
{
 /* must cast away the const,unfortunately */
 text  *tunpacked = pg_detoast_datum_packed((struct varlena *) t);
 int  len = VARSIZE_ANY_EXHDR(tunpacked);
 char  *result;

 result = (char *) palloc(len + 1);
 memcpy(result,VARDATA_ANY(tunpacked),len);
 result[len] = '';

 if (tunpacked != t)
 pfree(tunpacked);

 return result;
}

结果：

postgres=# select x_to_dec('111',2);
 x_to_dec 
----------
    7
(1 row)

postgres=# select x_to_dec('aA',16);
 x_to_dec 
----------
   170
(1 row)

postgres=# select x_to_dec('aA',1);
ERROR: Out of range! The second parameter,16.
 

以上就是进制转换的实例，如有疑问请留言或者到本站社区交流讨论，感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！

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