allocbuf
if ((bp = allocbuf(&buffer, fd, COPY_BUFLEN)) == NULL) {
if ((bp = allocbuf(&buffer, ofd, COPY_BUFLEN)) == NULL) {
BUF *allocbuf(BUF *, int, int);
allocbuf(bp, 0);
allocbuf(bp, 0);
allocbuf(bp, size);
void allocbuf (struct buf *bp, int size);
allocbuf(bp, size);
allocbuf(bp, nsize);
allocbuf(bp, nsize);
allocbuf(bp, size);