{"id":828,"date":"2014-04-07T20:15:22","date_gmt":"2014-04-07T12:15:22","guid":{"rendered":"http:\/\/newbiecoder.0ginr.com\/blog\/?p=828"},"modified":"2014-04-07T20:20:07","modified_gmt":"2014-04-07T12:20:07","slug":"vxxxxf-%e7%b3%bb%e5%88%97%e5%87%bd%e6%95%b0%e4%bc%9a%e4%bf%ae%e6%94%b9-args","status":"publish","type":"post","link":"https:\/\/newbiecoder.0ginr.com\/blog\/?p=828","title":{"rendered":"vxxxxf \u7cfb\u5217\u51fd\u6570\u4f1a\u4fee\u6539 args"},"content":{"rendered":"<p>\u4e4b\u524d\u78b0\u5230\u8fc7\u4e00\u6b21\uff0c\u7ed3\u679c de \u5b8c bug \u8f6c\u5934\u5c31\u5fd8\u4e86\u3002<br \/>\n\u4e8e\u662f\u4eca\u5929\u5c31\u53c8\u82b1\u4e86\u534a\u5929\u6765 de \u8fd9\u4e2a bug\u3002<\/p>\n<p>vxxxxf \u5305\u62ec vsnprintf \u7b49\u7b49\u7b49\u7b49\u3002<\/p>\n<p>C99 \/ C++11 \u6709\u4e00\u4e2a\u65b0\u7684\u5b8f va_copy\uff0c\u53ef\u4ee5\u5236\u9020\u4e00\u4e2a args \u7684\u526f\u672c\uff0c\u7136\u540e\u6bcf\u6b21\u8c03\u7528 vxxxxf \u4e4b\u524d\u4f20\u526f\u672c\u8fdb\u53bb\u5c31\u597d\u3002<br \/>\nref: <a href=\"http:\/\/en.cppreference.com\/w\/cpp\/utility\/variadic\/va_copy\" title=\"http:\/\/en.cppreference.com\/w\/cpp\/utility\/variadic\/va_copy\">http:\/\/en.cppreference.com\/w\/cpp\/utility\/variadic\/va_copy<\/a><\/p>\n<p>\u4e00\u4e2a\u4f8b\u5b50\uff08\u628a vsnprintf \u901a\u8fc7\u8fd4\u56de\u503c\u8fd4\u56de\u9519\u8bef\u6539\u6210\u4e86\u901a\u8fc7\u5f02\u5e38\u6307\u793a\u9519\u8bef\uff09\uff1a<br \/>\n<pre><code class=\"preserve-code-formatting\">size_t string_printf(\n    char *buffer,\n    size_t buffer_size,\n    const char *format,\n    va_list args\n    )\n{\n    \n    \/\/\n    \/\/ args \u7b2c\u4e00\u6b21\u7528\u4e8e vsnprintf \u8ba1\u7b97\u6240\u9700\u8981\u7684\u5b57\u7b26\u6570\uff0c\u7531\u4e8e vsnprintf\n    \/\/ \u53ef\u80fd\u4f1a\u4fee\u6539 args\uff08\u5b9e\u9645\u4e0a\u786e\u5b9e\u4fee\u6539\u4e86\uff09\uff0c\u6240\u4ee5\u8981\u641e\u4e00\u4e2a\u526f\u672c\u7ed9\u7b2c\u4e00\u6b21\n    \/\/ \u7684 vsnprintf \u505a\u53c2\u6570\u3002\n    \/\/\n\n    va_list args_copy;\n\n    va_copy(args_copy, args);\n\n    BOOST_SCOPE_EXIT(&amp;args_copy)\n    {\n        va_end(args_copy);\n    }\n    BOOST_SCOPE_EXIT_END;\n\n    int cch_needed = vsnprintf(nullptr, 0, format, args_copy);\n\n    if (cch_needed &lt; 0)\n    {\n        throw std::runtime_error(&quot;vsnprintf failed.&quot;);\n    }\n    else if (static_cast&lt;size_t&gt;(cch_needed) &gt; buffer_size - 1)\n    {\n        throw std::overflow_error(&quot;Buffer is too small.&quot;);\n    }\n\n    cch_needed = vsnprintf(buffer, buffer_size, format, args);\n\n    if (cch_needed &lt; 0 || static_cast&lt;size_t&gt;(cch_needed) &gt; buffer_size - 1)\n    {\n        throw std::runtime_error(&quot;Unexpected exception.&quot;);\n    }\n\n    return cch_needed;\n}<\/code><\/pre><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e4b\u524d\u78b0\u5230\u8fc7\u4e00\u6b21\uff0c\u7ed3\u679c de \u5b8c bug \u8f6c\u5934\u5c31\u5fd8\u4e86\u3002 \u4e8e\u662f\u4eca\u5929\u5c31\u53c8\u82b1\u4e86\u534a\u5929\u6765 de \u8fd9\u4e2a bug\u3002 vxxxx [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-828","post","type-post","status-publish","format-standard","hentry","category-1"],"_links":{"self":[{"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/828","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=828"}],"version-history":[{"count":2,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/828\/revisions"}],"predecessor-version":[{"id":830,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/828\/revisions\/830"}],"wp:attachment":[{"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=828"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=828"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/newbiecoder.0ginr.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=828"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}