blocks|key|1609381|text|似乎ostr.str("")调用做到了这一点。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1609382|entityMap^0|2|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

Seems to be that the <code>ostr.str("")</code> call does the trick.

blocks|key|1394531|text|为了清楚起见，使用两个不同名称的流，让优化编译器找出它可以重用旧的流。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1394532|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You don't. Use two differently named streams for clarity and let the optimizing compiler figure out that it can reuse the old one.

blocks|key|1609481|text|在过去，我使用了一系列的clear和str：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1609482|//+clear,+because+eof+or+other+bits+may+be+still+set.+
s.clear();
s.str("");|code-block|syntax|javascript|1609483|它已经完成了输入和输出字符串流的工作。或者，您可以手动清除，然后在开始处查找适当的序列：|1609484|s.clear();
s.seekp(0);+//+for+outputs:+seek+put+ptr+to+start
s.seekg(0);+//+for+inputs:+seek+get+ptr+to+start|1609485|这将防止str通过覆盖当前输出缓冲区中的任何内容来进行某些重新分配。结果如下所示：|offset|length|style|CODE|1609486|std::ostringstream+s;
s+<<+"hello";
s.seekp(0);
s+<<+"b";
assert(s.str()+==+"bello");|1609487|如果你想使用c函数的字符串，你可以使用std::ends，把一个终止null放在下面：|1609488|std::ostringstream+s;
s+<<+"hello";
s.seekp(0);
s+<<+"b"+<<+std::ends;
assert(s.str().size()+==+5+&&+std::strlen(s.str().data())+==+1);|1609489|std::ends是废弃的std::strstream的遗留物，它能够直接写入堆栈上分配的字符数组。您必须手动插入一个终止null。然而，我认为std::ends并没有被弃用，因为在上面的例子中它仍然很有用。|1609490|entityMap^0|0|0|0|0|4|3|0|0|J|9|0|0|0|9|D|E|20|9|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@$M|15|N|16|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|18|8|@$M|19|N|1A|O|P]]|9|@]|A|$]]|$1|U|3|V|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1C|8|@$M|1D|N|1E|O|P]|$M|1F|N|1G|O|P]|$M|1H|N|1I|O|P]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|Z|$]]

I've used a sequence of clear and str in the past:

<pre><code>// clear, because eof or other bits may be still set. 
s.clear();
s.str("");
</code></pre>

Which has done the thing for both input and output stringstreams. Alternatively, you can manually clear, then seek the appropriate sequence to the begin:

<pre><code>s.clear();
s.seekp(0); // for outputs: seek put ptr to start
s.seekg(0); // for inputs: seek get ptr to start
</code></pre>

That will prevent some reallocations done by <code>str</code> by overwriting whatever is in the output buffer currently instead. Results are like this:

<pre><code>std::ostringstream s;
s &lt;&lt; "hello";
s.seekp(0);
s &lt;&lt; "b";
assert(s.str() == "bello");
</code></pre>

If you want to use the string for c-functions, you can use <code>std::ends</code>, putting a terminating null like this:

<pre><code>std::ostringstream s;
s &lt;&lt; "hello";
s.seekp(0);
s &lt;&lt; "b" &lt;&lt; std::ends;
assert(s.str().size() == 5 &amp;&amp; std::strlen(s.str().data()) == 1);
</code></pre>

<code>std::ends</code> is a relict of the deprecated <code>std::strstream</code>, which was able to write directly to a char array you allocated on the stack. You had to insert a terminating null manually. However, <code>std::ends</code> is not deprecated, i think because it's still useful as in the above cases.

blocks|key|1609525|text|如果您要清除缓冲区，使其在第一次使用之前被清除，则需要首先使用MSVC向缓冲区添加一些内容。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1609526|struct+Foo+{
++++std::ostringstream+d_str;
++++Foo()+{+
++++++++d_str+<<+std::ends;+++//+Add+this
++++}
++++void+StrFunc(const+char+*);
++++template<class+T>
++++inline+void+StrIt(const+T+&value)+{
++++++++d_str.clear();
++++++++d_str.seekp(0);++//+Or+else+you'll+get+an+error+with+this+seek
++++++++d_str+<<+value+<<+std::ends;
++++++++StrFunc(d_str.str().c_str());++//+And+your+string+will+be+empty
++++}
};|code-block|syntax|javascript|1609527|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you're going to clear the buffer in a way that will cause it to be cleared before it's first use, you'll need to add something to the buffer first w/ MSVC.

<pre><code>struct Foo {
 std::ostringstream d_str;
 Foo() { 
 d_str &lt;&lt; std::ends; // Add this
 }
 void StrFunc(const char *);
 template&lt;class T&gt;
 inline void StrIt(const T &amp;value) {
 d_str.clear();
 d_str.seekp(0); // Or else you'll get an error with this seek
 d_str &lt;&lt; value &lt;&lt; std::ends;
 StrFunc(d_str.str().c_str()); // And your string will be empty
 }
};
</code></pre>

I'd like to clear out and reuse an ostringstream (and the underlying buffer) so that my app doesn't have to do as many allocations. How do I reset the object to its initial state?

How to reuse an ostringstream?

我想要清理和重用一个ostringstream (和底层缓冲区)，这样我的应用程序就不需要做太多的分配。如何将对象重置为其初始状态？

问如何重用一个ostringstream？
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