When finished, the caller can use `buffer_reset` to deallocate
resources.
+Using temporary files
+---------------------
+
+Temporary files provide a place to store data that should not outlive
+the calling program. A program
+
+ - initializes a `struct line_buffer` to LINE_BUFFER_INIT
+ - requests a temporary file with `buffer_tmpfile_init`
+ - acquires an output handle by calling `buffer_tmpfile_rewind`
+ - uses standard I/O functions like `fprintf` and `fwrite` to fill
+ the temporary file
+ - declares writing is over with `buffer_tmpfile_prepare_to_read`
+ - can re-read what was written with `buffer_read_line`,
+ `buffer_read_string`, and so on
+ - can reuse the temporary file by calling `buffer_tmpfile_rewind`
+ again
+ - removes the temporary file with `buffer_deinit`, perhaps to
+ reuse the line_buffer for some other file.
+
+When finished, the calling program can use `buffer_reset` to deallocate
+resources.
+
Functions
---------
`buffer_skip_bytes`::
Discards `len` bytes from the input stream (stopping early
- if necessary because of an error or eof).
+ if necessary because of an error or eof). Return value is
+ the number of bytes successfully read.
`buffer_reset`::
Deallocates non-static buffers.