[英]std::stringstream hex conversion error
I tried to do hex conversions using std::stringstream
as the following: 我尝试使用std::stringstream
进行十六进制转换,如下所示:
std::stringstream s;
s << std::hex;
int i;
s << "100";
s >> i; // 256
s << "10"; // doesn't work
s >> i;
But it fails on subsequent conversions as the comment points out. 但是,正如评论指出的那样,它在随后的转换中失败了。 Do I need to reset the stringstream
? 我需要重置stringstream
吗? Why does it fail? 为什么会失败?
You are performing formatted input and after extracting i out of the string-stream the eofbit is set. 您正在执行格式化输入,并在从字符串流中提取i后,设置了eofbit。 Hence you have to clear the state or all following formatted input/output will fail. 因此,您必须清除状态或所有后续格式化的输入/输出将失败。
#include <sstream>
#include <iostream>
int main()
{
std::stringstream s;
s << std::hex;
int i;
s << "100";
s >> i; // 256
std::cout << i << '\n';
s.clear(); // clear the eofbit
s << "10";
s >> i; // 16
std::cout << i << '\n';
return 0;
}
If you check stream state after s << "10"
, you will see the operation failed. 如果在s << "10"
之后检查流状态,您将看到操作失败。 I don't know exactly why, but you can fix this problem by resetting the stream: 我不确切知道为什么,但您可以通过重置流来解决此问题:
#include <iostream>
#include <sstream>
int main()
{
std::stringstream s;
s << std::hex;
int i;
s << "100";
s >> i; // 256
std::cout << i << '\n';
s.str("");
s.clear(); // might not be necessary if you check stream state above before and after extraction
s << "10"; // doesn't work
s >> i;
std::cout << i << '\n';
}
Live demo here . 现场演示 。
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