ssize_t ngx_write_chain_to_file(ngx_file_t *file, ngx_chain_t *cl, off_t offset, ngx_pool_t *pool) { ssize_t total, n; ngx_iovec_t vec; struct iovec iovs[NGX_IOVS_PREALLOCATE]; /* use pwrite() if there is the only buf in a chain */ if (cl->next == NULL) { return ngx_write_file(file, cl->buf->pos, (size_t) (cl->buf->last - cl->buf->pos), offset); } total = 0; vec.iovs = iovs; vec.nalloc = NGX_IOVS_PREALLOCATE; do { /* create the iovec and coalesce the neighbouring bufs */ cl = ngx_chain_to_iovec(&vec, cl); /* use pwrite() if there is the only iovec buffer */ if (vec.count == 1) { n = ngx_write_file(file, (u_char *) iovs[0].iov_base, iovs[0].iov_len, offset); if (n == NGX_ERROR) { return n; } return total + n; } n = ngx_writev_file(file, &vec, offset); if (n == NGX_ERROR) { return n; } offset += n; total += n; } while (cl); return total; }
ssize_t ngx_write_chain_to_file(ngx_file_t *file, ngx_chain_t *cl, off_t offset, ngx_pool_t *pool) { u_char *prev; size_t size; ssize_t total, n; ngx_array_t vec; struct iovec *iov, iovs[NGX_IOVS]; /* use pwrite() if there is the only buf in a chain */ if (cl->next == NULL) { return ngx_write_file(file, cl->buf->pos, (size_t) (cl->buf->last - cl->buf->pos), offset); } total = 0; vec.elts = iovs; vec.size = sizeof(struct iovec); vec.nalloc = NGX_IOVS; vec.pool = pool; do { prev = NULL; iov = NULL; size = 0; vec.nelts = 0; /* create the iovec and coalesce the neighbouring bufs */ while (cl && vec.nelts < IOV_MAX) { if (prev == cl->buf->pos) { iov->iov_len += cl->buf->last - cl->buf->pos; } else { iov = ngx_array_push(&vec); if (iov == NULL) { return NGX_ERROR; } iov->iov_base = (void *) cl->buf->pos; iov->iov_len = cl->buf->last - cl->buf->pos; } size += cl->buf->last - cl->buf->pos; prev = cl->buf->last; cl = cl->next; } /* use pwrite() if there is the only iovec buffer */ if (vec.nelts == 1) { iov = vec.elts; n = ngx_write_file(file, (u_char *) iov[0].iov_base, iov[0].iov_len, offset); if (n == NGX_ERROR) { return n; } return total + n; } n = ngx_writev_file(file, &vec, size, offset); if (n == NGX_ERROR) { return n; } offset += n; total += n; } while (cl); return total; }