+/* Wrappers to calling from function called "f" of fopen(), fclose(), fgets()
+ * and fwrite() and calling exit_err() with appropriate error messages.
+ */
+extern FILE * try_fopen(char * path, char * mode, char * f);
+extern void try_fclose(FILE * file, char * f);
+extern void try_fwrite(void * ptr, size_t size, size_t nmemb, FILE * stream,
+ char * f);
+
+
+
+/* Wrapper to calling fgets() from function called "f". The return code of
+ * fgets() is returned unless it is NULL *and* ferror() indicates that an error
+ * occured; otherwise end of file is assumed and NULL is returned properly.
+ */
+extern char * try_fgets(char * line, int size, FILE * file, char * f);
+
+
+
+/* Wrapper to successive call of fclose() from function called "f" on "file",
+ * then unlink() on file at "p2" if it exists, then rename() on "p1" to "p2".
+ * Used for handling atomic saving of files via temp files.
+ */
+extern void try_fclose_unlink_rename(FILE * file, char * p1, char * p2,
+ char * f);
+
+
+
+/* Wrapper: Call textfile_sizes() from function called "f" to get max line
+ * length of "file", exit via exit_err() with trouble_msg()-generated error
+ * message on failure.
+ */
+extern uint16_t get_linemax(FILE * file, char * f);
+
+
+
+/* Learn from "file" the largest line length (pointed to by "linemax_p"; length
+ * includes newline chars) and (pointed to by "n_lines_p" if it is not set to
+ * NULL) the number of lines (= number of newline chars).
+ *
+ * Returns 0 on success, 1 on error of fseek() (called to return to initial file
+ * reading position).
+ */
+extern uint8_t textfile_sizes(FILE * file, uint16_t * linemax_p,
+ uint16_t * n_lines_p);
+
+
+
+/* These routines for reading values "x" from / writing values to "file" ensure
+ * a defined endianness and consistent error codes: return 0 on success and 1 on
+ * fgetc()/fputc() failure.
+ */
+extern uint8_t read_uint8(FILE * file, uint8_t * x);
+extern uint8_t read_uint16_bigendian(FILE * file, uint16_t * x);
+extern uint8_t read_uint32_bigendian(FILE * file, uint32_t * x);
+extern uint8_t write_uint8(uint8_t x, FILE * file);
+extern uint8_t write_uint16_bigendian(uint16_t x, FILE * file);
+extern uint8_t write_uint32_bigendian(uint32_t x, FILE * file);