istream, outstream使用及常见错误

使用方法：

使用filebuf打开文件，并拷贝给istream/ostream。

如下面的例子中，实现读取并处理deseq文件夹下所有文件，输出到ostream fw.

code:

#include
#include
#include
#include
#include
#include
using namespace std;

void parsefile(istream& fi, ostream& fo){
    string tmp;
    while(fi>>tmp){
        fo<d_name;
            if (fbIn.open(filename,ios::in)){
                istream is(&fbIn);
                parsefile(is,fw);//read from is and write in fw
                fbIn.close();
            }
        }
    }
}

int main(){
    process();
    return 0;
}

其中，parsefile的声明为：void parsefile(istream& fi, ostream& fo)

注意这里函数声明必须要加引用，不然会报错：

错误：

$ g++ -g test.cpp -o b.out
In file included from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ios:39,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/ostream:40,
                 from /usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iostream:40,
                 from test.cpp:1:
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h: In copy constructor 'std::basic_ios >::basic_ios(const std::basic_ios >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/bits/ios_base.h:790: error: 'std::ios_base::ios_base(const std::ios_base&)' is private
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:47: error: within this context
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd: In copy constructor 'std::basic_istream >::basic_istream(const std::basic_istream >&)':
/usr/lib/gcc/x86_64-redhat-linux/4.4.6/../../../../include/c++/4.4.6/iosfwd:53: note: synthesized method 'std::basic_ios >::basic_ios(const std::basic_ios >&)' first required here 
test.cpp: In function 'void process()':
test.cpp:24: note: synthesized method 'std::basic_istream >::basic_istream(const std::basic_istream >&)' first required here 

test.cpp:24: error:   initializing argument 1 of 'void parsefile(std::istream, std::ostream)'

原因是stream类型数据不支持拷贝，所以必须传址。

参考：http://stackoverflow.com/questions/6457591/problem-with-ostream-ofstream-inheritance