buffer_flush - feed buffer to write function

       buffer_flush feeds a string d[0], d[1], ..., d[dlen-1] to the write operation by calling

         op(fd,d,dlen)

       If op successfully handles one or more bytes at the beginning of the string, it must return the number of
       bytes  handled; if this number is smaller than dlen, buffer_flush will call op again with the rest of the
       string. If op does not handle any bytes, and does not encounter an error, it must return 0, or return  -1
       with errno set to EINTR; in either case, buffer_flush will immediately call op again. If op encounters an
       error,  it  must return -1 with errno set to something other than EINTR; buffer_flush will pass the error
       to the caller.

       On success, buffer_flush returns 0. On error, buffer_flush returns -1, setting errno appropriately.

       buffer_flush - feed buffer to write function

buffer_init(3)

                                                                                                 buffer_flush(3)

#include<libowfat/buffer.h>

       int buffer_flush(buffer* b);