Function copy_file_data_read_write_impl

src/operations.cpp:733–773

copy_file read/write loop implementation

//! copy_file read/write loop implementation
int copy_file_data_read_write_impl(int infile, int outfile, char* buf, std::size_t buf_size)
{
#if defined(BOOST_FILESYSTEM_HAS_POSIX_FADVISE)
    ::posix_fadvise(infile, 0, 0, POSIX_FADV_SEQUENTIAL);
#endif

    // Don't use file size to limit the amount of data to copy since some filesystems, like procfs or sysfs,
    // provide files with generated content and indicate that their size is zero or 4096. Just copy as much data
    // as we can read from the input file.
    while (true)
    {
        ssize_t sz_read = ::read(infile, buf, buf_size);
        if (sz_read == 0)
            break;
        if (BOOST_UNLIKELY(sz_read < 0))
        {
            int err = errno;
            if (err == EINTR)
                continue;
            return err;
        }

        // Allow for partial writes - see Advanced Unix Programming (2nd Ed.),
        // Marc Rochkind, Addison-Wesley, 2004, page 94
        for (ssize_t sz_wrote = 0; sz_wrote < sz_read;)
        {
            ssize_t sz = ::write(outfile, buf + sz_wrote, static_cast< std::size_t >(sz_read - sz_wrote));
            if (BOOST_UNLIKELY(sz < 0))
            {
                int err = errno;
                if (err == EINTR)
                    continue;
                return err;
            }

            sz_wrote += sz;
        }
    }

    return 0;
}

//! copy_file implementation that uses read/write loop (fallback using a stack buffer)
int copy_file_data_read_write_stack_buf(int infile, int outfile)