std::basic_stringbuf<CharT,Traits,Allocator>:: seekpos

如果可能，将 std::basic_streambuf::gptr 和/或 std::basic_streambuf::pptr 重新定位到 sp 指示的位置。

有效地执行 seekoff ( off_type ( sp ) , std:: ios_base :: beg , which ) 。

参数

返回值

sp 表示成功，或 pos_type ( off_type ( - 1 ) ) 表示失败。

注释

seekpos() 由 std::basic_streambuf::pubseekpos() 调用，而后者又由单参数版本的 std::basic_istream::seekg() 和 std::basic_ostream::seekp() 调用。

示例

#include <sstream>
#include <iostream>
struct mybuf : std::stringbuf
{
    mybuf(const std::string& str) : std::stringbuf(str) {}
    pos_type seekpos(pos_type sp, std::ios_base::openmode which)
    {
        std::cout << "Before seekpos(" << sp << "), size of the get area is "
                  << egptr() - eback() << " with "
                  << egptr() - gptr() << " read positions available.\n";
        pos_type rc = std::stringbuf::seekpos(sp, which);
        std::cout << "seekpos() returns " << rc << ".\nAfter the call, "
                  << "size of the get area is "
                  << egptr() - eback() << " with "
                  << egptr() - gptr() << " read positions available.\n";
        return rc;
    }
};
int main()
{
    mybuf buf("12345");
    std::iostream stream(&buf);
    stream.seekg(2);
}

Before seekpos(2), size of the get area is 5 with 5 read positions available.
seekpos() returns 2.
After the call, size of the get area is 5 with 3 read positions available.

缺陷报告

以下行为变更缺陷报告被追溯应用于先前发布的C++标准。

参见