# std::basic_streambuf<CharT,Traits>::setg

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< cpp‎ | io‎ | basic streambuf

protected: void setg( char_type* gbeg, char_type* gcurr, char_type* gend ); |  |

Sets the values of the pointers defining the get area.

After the call, eback() == gbeg, gptr() == gcurr and egptr() == gend are all true.

If any of `[`gbeg`,` gend`)`, `[`gbeg`,` gcurr`)` and `[`gcurr`,` gend`)` is not a valid range, the behavior is undefined.

### Parameters

gbeg | - | pointer to the new beginning of the get area
gcurr | - | pointer to the new current character (get pointer) in the get area
gend | - | pointer to the new end of the get area

### Example

Run this code

    #include <iostream>
    #include <sstream>

    class null_filter_buf : public std::streambuf
    {
        std::streambuf* src;
        char ch; // single-byte buffer
    protected:
        int underflow()
        {
            traits_type::int_type i;
            while ((i = src->sbumpc()) == '\0')
                ; // skip zeroes
            if (!traits_type::eq_int_type(i, traits_type::eof()))
            {
                ch = traits_type::to_char_type(i);
                setg(&ch, &ch, &ch+1); // make one read position available
            }
            return i;
        }
    public:
        null_filter_buf(std::streambuf* buf) : src(buf)
        {
            setg(&ch, &ch + 1, &ch + 1); // buffer is initially full
        }
    };

    void filtered_read(std::istream& in)
    {
        std::streambuf* orig = in.rdbuf();
        null_filter_buf buf(orig);
        in.rdbuf(&buf);
        for (char c; in.get(c);)
            std::cout << c;
        in.rdbuf(orig);
    }

    int main()
    {
        char a[] = "This i\0s \0an e\0\0\0xample";
        std::istringstream in(std::string(std::begin(a), std::end(a)));
        filtered_read(in);
    }

Output:

    This is an example

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 4023 | C++98 | `setg` did not require the input sequence to be a valid range | requires

### See also

setp | repositions the beginning, next, and end pointers of the output sequence (protected member function)

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