+
+error:
+ free(buf);
+ return NULL;
+}
+
+static void destroy_buffer(struct buffer_info *buf)
+{
+ int result;
+
+ result = ustcomm_close_app(&buf->conn);
+ if(result == -1) {
+ WARN("problem calling ustcomm_close_app");
+ }
+
+ result = shmdt(buf->mem);
+ if(result == -1) {
+ PERROR("shmdt");
+ }
+
+ result = shmdt(buf->bufstruct_mem);
+ if(result == -1) {
+ PERROR("shmdt");
+ }
+
+ result = close(buf->file_fd);
+ if(result == -1) {
+ PERROR("close");
+ }
+
+ free(buf);
+}
+
+int unwrite_last_subbuffer(struct buffer_info *buf)
+{
+ int result;
+
+ result = ftruncate(buf->file_fd, buf->previous_offset);
+ if(result == -1) {
+ PERROR("ftruncate");
+ return -1;
+ }
+
+ result = lseek(buf->file_fd, buf->previous_offset, SEEK_SET);
+ if(result == (int)(off_t)-1) {
+ PERROR("lseek");
+ return -1;
+ }
+
+ return 0;
+}
+
+int write_current_subbuffer(struct buffer_info *buf)
+{
+ int result;
+
+ void *subbuf_mem = buf->mem + (buf->consumed_old & (buf->n_subbufs * buf->subbuf_size-1));
+
+ size_t cur_sb_size = subbuffer_data_size(subbuf_mem);
+
+ off_t cur_offset = lseek(buf->file_fd, 0, SEEK_CUR);
+ if(cur_offset == (off_t)-1) {
+ PERROR("lseek");
+ return -1;
+ }
+
+ buf->previous_offset = cur_offset;
+ DBG("previous_offset: %ld", cur_offset);
+
+ result = patient_write(buf->file_fd, subbuf_mem, cur_sb_size);
+ if(result == -1) {
+ PERROR("write");
+ /* FIXME: maybe drop this trace */
+ return -1;
+ }
+
+ return 0;