增加一个streampos对象
我正在尝试做这样的事情：
for (std::streampos Position = 0; Position < 123; Position++)
{
// Use Position to access something...
}
但是，std::streampos 似乎没有 operator++ 重载。
尝试使用 Position = (Position + 1) 会导致以下错误：
ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
是否有任何解决方法，或者我是否必须依赖 long unsigned int 足够大对于文件？
I'm trying to do something like this:
for (std::streampos Position = 0; Position < 123; Position++)
{
// Use Position to access something...
}
However, it appears that std::streampos does not have operator++ overloaded.
Trying to use Position = (Position + 1) results in the following error:
ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second:
Is there any workaround for this, or do I have to rely on long unsigned int being big enough for files?
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尝试
std::streamoff，它表示偏移量在一个流中。它支持前置和后置递增/递减运算符。编辑Maxpm的评论：您可以应用
streamoff到任何地方，无论是ios::beg还是任意streampos。将其应用于 ios::beg ，它的行为就像普通的streampos 。将其应用到streampos上，您就得到了streampos+streamoff。Try a
std::streamoff, which represents an offset in a stream. It supports both pre- and post increment/decrement operators.Edit to Maxpm's comment: You can apply the
streamoffto anywhere, be itios::begor an arbitarystreampos. Apply it toios::begand it behaves like a normalstreampos. Apply it to astreamposand you gotstreampos+streamoff.使用
+=：+不起作用，因为operator +实际上是为streampos和steamoff 定义的，而不是int。这意味着存在两个同样好的隐式转换：您的
1可以转换为streamoff（这可能是unsigned long的 typedef ）。或者将streampos隐式转换为streamoff，然后添加1。Use
+=:+doesn’t work becauseoperator +is actually defined forstreamposandsteamoff, notint.This means that two implicit conversions exist that are equally good: either your
1could be converted tostreamoff(which is probably a typedef forunsigned long). Or thestreamposis implicitly converted tostreamoffwhich then has1added.std::streampos不是数字类型，尽管它支持转换与数字类型之间的转换。如果你想对
位置，您需要使用
std::streamoff（并指定 from调用seek时的参数）。
另外，不要忘记，你不能在其中寻求任意位置
一个文件，除非它是以二进制模式打开的，并且带有“C”
语言环境。
std::streamposis not a numeric type, although it supports conversionto and from numeric types. If you want to do arithmetic on the
position, you need to use
std::streamoff(and specify the fromargument when calling seek).
Also, don't forget that you can't seek to an arbitrary position in
a file unless it has been opened in binary mode, and imbued with the "C"
locale.
我在研究如何从
std::streampos对象中减去时遇到了这个链接：https://bugs.debian.org/cgi-bin/bugreport。 cgi?bug=187599
建议的解决方案是使用定义的运算符重载
operator+()或operator-()，它们非常适用于 我。聚苯乙烯
使用
operator+()可能比使用operator-()更好，以避免与符号更改相关的任何问题I came across this link while looking into how I can subtract from a
std::streamposobject:https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=187599
The suggested solution is using the defined operator overload
operator+()oroperator-()which work pretty well for me.P.S.
It may be better to use
operator+()thanoperator-()to avoid any problems related to sign change