confused about ngx_write_file

[hook]

Hi 
    I'm writing some module with using ngx_write_file.  I found file's
offset is incorrect, in this case:
    ```
    u_char  av = 0x01 | 0x04;
    // file cur offset -> 4096;
    ngx_write_file(file, &av, 1, 4)
    ```
    file->offset would be 4097, but real offset is 4096.

    I'm confused with the codes :
192 ssize_t
193 ngx_write_file(ngx_file_t *file, u_char *buf, size_t size, off_t
offset)
194 {
........
221
222         file->offset += n;
223         written += n;
224
225         if ((size_t) n == size) {
226             return written;
227         }
228
229         offset += n;
230         size -= n;
231     }

     should it be:
222         written += n;
223         offset += n;
224
225         if (offset > file->offset) {
226             file->offset = offset;
227         }
228
229         if ((size_t) n == size) {
230             return written;
231         }
232
233         size -= n;
234     }


Thanks!

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,277386,277386#msg-277386