2 * This file is part of the libserialport project.
4 * Copyright (C) 2013 Martin Ling <martin-libserialport@earth.li>
6 * This program is free software: you can redistribute it and/or modify
7 * it under the terms of the GNU Lesser General Public License as
8 * published by the Free Software Foundation, either version 3 of the
9 * License, or (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
21 * @mainpage libserialport API
26 * libserialport is a minimal library written in C that is intended to take
27 * care of the OS-specific details when writing software that uses serial ports.
29 * By writing your serial code to use libserialport, you enable it to work
30 * transparently on any platform supported by the library.
32 * The operations that are supported are:
34 * - @ref Enumeration (obtaining a list of serial ports on the system)
36 * - @ref Configuration (baud rate, parity, etc.)
37 * - @ref Signals (modem control lines, breaks, etc.)
41 * libserialport is an open source project released under the LGPL3+ license.
46 * The API is simple, and designed to be a minimal wrapper around the serial
47 * port support in each OS.
49 * Most functions take a pointer to a struct sp_port, which represents a serial
50 * port. These structures are always allocated and freed by the library, using
51 * the functions in the @ref Enumeration "Enumeration" section.
53 * Most functions have return type @ref sp_return and can return only four
54 * possible error values:
56 * - @ref SP_ERR_ARG means that a function was called with invalid
57 * arguments. This implies a bug in the caller. The arguments passed would
58 * be invalid regardless of the underlying OS or serial device involved.
60 * - @ref SP_ERR_FAIL means that the OS reported a failure. The error code or
61 * message provided by the OS can be obtained by calling sp_last_error_code()
62 * or sp_last_error_message().
64 * - @ref SP_ERR_SUPP indicates that there is no support for the requested
65 * operation in the current OS, driver or device. No error message is
66 * available from the OS in this case. There is either no way to request
67 * the operation in the first place, or libserialport does not know how to
68 * do so in the current version.
70 * - @ref SP_ERR_MEM indicates that a memory allocation failed.
72 * All of these error values are negative.
74 * Calls that succeed return @ref SP_OK, which is equal to zero. Some functions
75 * declared @ref sp_return can also return a positive value for a successful
76 * numeric result, e.g. sp_read() and sp_write().
79 #ifndef LIBSERIALPORT_LIBSERIALPORT_H
80 #define LIBSERIALPORT_LIBSERIALPORT_H
91 /* Package version macros (e.g. for conditional compilation). */
92 #define SP_PACKAGE_VERSION_MAJOR @SP_PACKAGE_VERSION_MAJOR@
93 #define SP_PACKAGE_VERSION_MINOR @SP_PACKAGE_VERSION_MINOR@
94 #define SP_PACKAGE_VERSION_MICRO @SP_PACKAGE_VERSION_MICRO@
95 #define SP_PACKAGE_VERSION_STRING "@SP_PACKAGE_VERSION@"
97 /* Library/libtool version macros (e.g. for conditional compilation). */
98 #define SP_LIB_VERSION_CURRENT @SP_LIB_VERSION_CURRENT@
99 #define SP_LIB_VERSION_REVISION @SP_LIB_VERSION_REVISION@
100 #define SP_LIB_VERSION_AGE @SP_LIB_VERSION_AGE@
101 #define SP_LIB_VERSION_STRING "@SP_LIB_VERSION@"
103 /** Return values. */
105 /** Operation completed successfully. */
107 /** Invalid arguments were passed to the function. */
109 /** A system error occured while executing the operation. */
111 /** A memory allocation failed while executing the operation. */
113 /** The requested operation is not supported by this system or device. */
117 /** Port access modes. */
119 /** Open port for read access. */
121 /** Open port for write access. */
123 /** Open port in non-blocking mode. */
124 SP_MODE_NONBLOCK = 4,
127 /** Buffer selection. */
131 /** Output buffer. */
137 /** Parity settings. */
139 /** Special value to indicate setting should be left alone. */
140 SP_PARITY_INVALID = -1,
149 /** RTS pin behaviour. */
151 /** Special value to indicate setting should be left alone. */
157 /** RTS used for flow control. */
158 SP_RTS_FLOW_CONTROL = 2,
161 /** CTS pin behaviour. */
163 /** Special value to indicate setting should be left alone. */
167 /** CTS used for flow control. */
168 SP_CTS_FLOW_CONTROL = 1,
171 /** DTR pin behaviour. */
173 /** Special value to indicate setting should be left alone. */
179 /** DTR used for flow control. */
180 SP_DTR_FLOW_CONTROL = 2,
183 /** DSR pin behaviour. */
185 /** Special value to indicate setting should be left alone. */
189 /** DSR used for flow control. */
190 SP_DSR_FLOW_CONTROL = 1,
193 /** XON/XOFF flow control behaviour. */
195 /** Special value to indicate setting should be left alone. */
196 SP_XONXOFF_INVALID = -1,
197 /** XON/XOFF disabled. */
198 SP_XONXOFF_DISABLED = 0,
199 /** XON/XOFF enabled for input only. */
201 /** XON/XOFF enabled for output only. */
203 /** XON/XOFF enabled for input and output. */
204 SP_XONXOFF_INOUT = 3,
207 /** Standard flow control combinations. */
208 enum sp_flowcontrol {
209 /** No flow control. */
210 SP_FLOWCONTROL_NONE = 0,
211 /** Software flow control using XON/XOFF characters. */
212 SP_FLOWCONTROL_XONXOFF = 1,
213 /** Hardware flow control using RTS/CTS signals. */
214 SP_FLOWCONTROL_RTSCTS = 2,
215 /** Hardware flow control using DTR/DSR signals. */
216 SP_FLOWCONTROL_DTRDSR = 3,
219 /** Input signals. */
221 /** Clear to send. */
223 /** Data set ready. */
225 /** Data carrier detect. */
227 /** Ring indicator. */
231 /** A serial port. */
234 /** Configuration for a serial port. */
235 struct sp_port_config;
238 @defgroup Enumeration Port enumeration
243 * Obtain a pointer to a new sp_port structure representing the named port.
245 * The user should allocate a variable of type "struct sp_port *" and pass a
246 * pointer to this to receive the result.
248 * The result should be freed after use by calling sp_free_port().
250 * If any error is returned, the variable pointed to by port_ptr will be set
251 * to NULL. Otherwise, it will be set to point to the newly allocated port.
253 * @return SP_OK upon success, a negative error code otherwise.
255 enum sp_return sp_get_port_by_name(const char *portname, struct sp_port **port_ptr);
258 * Free a port structure obtained from sp_get_port_by_name() or sp_copy_port().
260 void sp_free_port(struct sp_port *port);
263 * List the serial ports available on the system.
265 * The result obtained is an array of pointers to sp_port structures,
266 * terminated by a NULL. The user should allocate a variable of type
267 * "struct sp_port **" and pass a pointer to this to receive the result.
269 * The result should be freed after use by calling sp_free_port_list().
270 * If a port from the list is to be used after freeing the list, it must be
271 * copied first using sp_copy_port().
273 * If any error is returned, the variable pointed to by list_ptr will be set
274 * to NULL. Otherwise, it will be set to point to the newly allocated array.
276 * @return SP_OK upon success, a negative error code otherwise.
278 enum sp_return sp_list_ports(struct sp_port ***list_ptr);
281 * Make a new copy of a sp_port structure.
283 * The user should allocate a variable of type "struct sp_port *" and pass a
284 * pointer to this to receive the result.
286 * The copy should be freed after use by calling sp_free_port().
288 * If any error is returned, the variable pointed to by copy_ptr will be set
289 * to NULL. Otherwise, it will be set to point to the newly allocated copy.
291 * @return SP_OK upon success, a negative error code otherwise.
293 enum sp_return sp_copy_port(const struct sp_port *port, struct sp_port **copy_ptr);
296 * Free a port list obtained from sp_list_ports().
298 * This will also free all the sp_port structures referred to from the list;
299 * any that are to be retained must be copied first using sp_copy_port().
301 void sp_free_port_list(struct sp_port **ports);
305 * @defgroup Ports Opening, closing and querying ports
310 * Open the specified serial port.
312 * @param port Pointer to port structure.
313 * @param flags Flags to use when opening the serial port.
315 * @return SP_OK upon success, a negative error code otherwise.
317 enum sp_return sp_open(struct sp_port *port, enum sp_mode flags);
320 * Close the specified serial port.
322 * @return SP_OK upon success, a negative error code otherwise.
324 enum sp_return sp_close(struct sp_port *port);
327 * Get the name of a port.
329 * The name returned is whatever is normally used to refer to a port on the
330 * current operating system; e.g. for Windows it will usually be a "COMn"
331 * device name, and for Unix it will be a device path beginning with "/dev/".
333 * @param port Pointer to port structure.
335 * @return The port name, or NULL if an invalid port is passed. The name
336 * string is part of the port structure and may not be used after the
337 * port structure has been freed.
339 char *sp_get_port_name(const struct sp_port *port);
342 * Get the operating system handle for a port.
344 * The type of the handle depends on the operating system. On Unix based
345 * systems, the handle is a file descriptor of type "int". On Windows, the
346 * handle is of type "HANDLE". The user should allocate a variable of the
347 * appropriate type and pass a pointer to this to receive the result.
349 * To obtain a valid handle, the port must first be opened by calling
350 * sp_open() using the same port structure.
352 * After the port is closed or the port structure freed, the handle may
353 * no longer be valid.
355 * @warning This feature is provided so that programs may make use of
356 * OS-specific functionality where desired. Doing so obviously
357 * comes at a cost in portability. It also cannot be guaranteed
358 * that direct usage of the OS handle will not conflict with the
359 * library's own usage of the port. Be careful.
361 * @return SP_OK upon success, a negative error code otherwise.
363 enum sp_return sp_get_port_handle(const struct sp_port *port, void *result_ptr);
367 * @defgroup Configuration Setting port parameters
372 * Allocate a port configuration structure.
374 * The user should allocate a variable of type "struct sp_config *" and pass a
375 * pointer to this to receive the result. The variable will be updated to
376 * point to the new configuration structure. The structure is opaque and must
377 * be accessed via the functions provided.
379 * All parameters in the structure will be initialised to special values which
380 * are ignored by sp_set_config().
382 * The structure should be freed after use by calling sp_free_config().
384 * @param config_ptr Pointer to variable to receive result.
386 * @return SP_OK upon success, a negative error code otherwise.
388 enum sp_return sp_new_config(struct sp_port_config **config_ptr);
391 * Free a port configuration structure.
393 * @param config Pointer to configuration structure.
395 void sp_free_config(struct sp_port_config *config);
398 * Get the current configuration of the specified serial port.
400 * The user should allocate a configuration structure using sp_new_config()
401 * and pass this as the config parameter. The configuration structure will
402 * be updated with the port configuration.
404 * Any parameters that are configured with settings not recognised or
405 * supported by libserialport, will be set to special values that are
406 * ignored by sp_set_config().
408 * @return SP_OK upon success, a negative error code otherwise.
410 enum sp_return sp_get_config(struct sp_port *port, struct sp_port_config *config);
413 * Set the configuration for the specified serial port.
415 * For each parameter in the configuration, there is a special value (usually
416 * -1, but see the documentation for each field). These values will be ignored
417 * and the corresponding setting left unchanged on the port.
419 * @return SP_OK upon success, a negative error code otherwise.
421 enum sp_return sp_set_config(struct sp_port *port, const struct sp_port_config *config);
424 * Set the baud rate for the specified serial port.
426 * @param port Pointer to port structure.
427 * @param baudrate Baud rate in bits per second.
429 * @return SP_OK upon success, a negative error code otherwise.
431 enum sp_return sp_set_baudrate(struct sp_port *port, int baudrate);
434 * Get the baud rate from a port configuration.
436 * The user should allocate a variable of type int and pass a pointer to this
437 * to receive the result.
439 * @param config Pointer to configuration structure.
440 * @param baudrate_ptr Pointer to variable to store result.
442 * @return SP_OK upon success, a negative error code otherwise.
444 enum sp_return sp_get_config_baudrate(const struct sp_port_config *config, int *baudrate_ptr);
447 * Set the baud rate in a port configuration.
449 * @param config Pointer to configuration structure.
450 * @param baudrate Baud rate in bits per second, or -1 to retain current setting.
452 * @return SP_OK upon success, a negative error code otherwise.
454 enum sp_return sp_set_config_baudrate(struct sp_port_config *config, int baudrate);
457 * Set the data bits for the specified serial port.
459 * @param port Pointer to port structure.
460 * @param bits Number of data bits.
462 * @return SP_OK upon success, a negative error code otherwise.
464 enum sp_return sp_set_bits(struct sp_port *port, int bits);
467 * Get the data bits from a port configuration.
469 * The user should allocate a variable of type int and pass a pointer to this
470 * to receive the result.
472 * @param config Pointer to configuration structure.
473 * @param bits_ptr Pointer to variable to store result.
475 * @return SP_OK upon success, a negative error code otherwise.
477 enum sp_return sp_get_config_bits(const struct sp_port_config *config, int *bits_ptr);
480 * Set the data bits in a port configuration.
482 * @param config Pointer to configuration structure.
483 * @param bits Number of data bits, or -1 to retain current setting.
485 * @return SP_OK upon success, a negative error code otherwise.
487 enum sp_return sp_set_config_bits(struct sp_port_config *config, int bits);
490 * Set the parity setting for the specified serial port.
492 * @param port Pointer to port structure.
493 * @param parity Parity setting.
495 * @return SP_OK upon success, a negative error code otherwise.
497 enum sp_return sp_set_parity(struct sp_port *port, enum sp_parity parity);
500 * Get the parity setting from a port configuration.
502 * The user should allocate a variable of type enum sp_parity and pass a pointer to this
503 * to receive the result.
505 * @param config Pointer to configuration structure.
506 * @param parity_ptr Pointer to variable to store result.
508 * @return SP_OK upon success, a negative error code otherwise.
510 enum sp_return sp_get_config_parity(const struct sp_port_config *config, enum sp_parity *parity_ptr);
513 * Set the parity setting in a port configuration.
515 * @param config Pointer to configuration structure.
516 * @param parity Parity setting, or -1 to retain current setting.
518 * @return SP_OK upon success, a negative error code otherwise.
520 enum sp_return sp_set_config_parity(struct sp_port_config *config, enum sp_parity parity);
523 * Set the stop bits for the specified serial port.
525 * @param port Pointer to port structure.
526 * @param stopbits Number of stop bits.
528 * @return SP_OK upon success, a negative error code otherwise.
530 enum sp_return sp_set_stopbits(struct sp_port *port, int stopbits);
533 * Get the stop bits from a port configuration.
535 * The user should allocate a variable of type int and pass a pointer to this
536 * to receive the result.
538 * @param config Pointer to configuration structure.
539 * @param stopbits_ptr Pointer to variable to store result.
541 * @return SP_OK upon success, a negative error code otherwise.
543 enum sp_return sp_get_config_stopbits(const struct sp_port_config *config, int *stopbits_ptr);
546 * Set the stop bits in a port configuration.
548 * @param config Pointer to configuration structure.
549 * @param stopbits Number of stop bits, or -1 to retain current setting.
551 * @return SP_OK upon success, a negative error code otherwise.
553 enum sp_return sp_set_config_stopbits(struct sp_port_config *config, int stopbits);
556 * Set the RTS pin behaviour for the specified serial port.
558 * @param port Pointer to port structure.
559 * @param rts RTS pin mode.
561 * @return SP_OK upon success, a negative error code otherwise.
563 enum sp_return sp_set_rts(struct sp_port *port, enum sp_rts rts);
566 * Get the RTS pin behaviour from a port configuration.
568 * The user should allocate a variable of type enum sp_rts and pass a pointer to this
569 * to receive the result.
571 * @param config Pointer to configuration structure.
572 * @param rts_ptr Pointer to variable to store result.
574 * @return SP_OK upon success, a negative error code otherwise.
576 enum sp_return sp_get_config_rts(const struct sp_port_config *config, enum sp_rts *rts_ptr);
579 * Set the RTS pin behaviour in a port configuration.
581 * @param config Pointer to configuration structure.
582 * @param rts RTS pin mode, or -1 to retain current setting.
584 * @return SP_OK upon success, a negative error code otherwise.
586 enum sp_return sp_set_config_rts(struct sp_port_config *config, enum sp_rts rts);
589 * Set the CTS pin behaviour for the specified serial port.
591 * @param port Pointer to port structure.
592 * @param cts CTS pin mode.
594 * @return SP_OK upon success, a negative error code otherwise.
596 enum sp_return sp_set_cts(struct sp_port *port, enum sp_cts cts);
599 * Get the CTS pin behaviour from a port configuration.
601 * The user should allocate a variable of type enum sp_cts and pass a pointer to this
602 * to receive the result.
604 * @param config Pointer to configuration structure.
605 * @param cts_ptr Pointer to variable to store result.
607 * @return SP_OK upon success, a negative error code otherwise.
609 enum sp_return sp_get_config_cts(const struct sp_port_config *config, enum sp_cts *cts_ptr);
612 * Set the CTS pin behaviour in a port configuration.
614 * @param config Pointer to configuration structure.
615 * @param cts CTS pin mode, or -1 to retain current setting.
617 * @return SP_OK upon success, a negative error code otherwise.
619 enum sp_return sp_set_config_cts(struct sp_port_config *config, enum sp_cts cts);
622 * Set the DTR pin behaviour for the specified serial port.
624 * @param port Pointer to port structure.
625 * @param dtr DTR pin mode.
627 * @return SP_OK upon success, a negative error code otherwise.
629 enum sp_return sp_set_dtr(struct sp_port *port, enum sp_dtr dtr);
632 * Get the DTR pin behaviour from a port configuration.
634 * The user should allocate a variable of type enum sp_dtr and pass a pointer to this
635 * to receive the result.
637 * @param config Pointer to configuration structure.
638 * @param dtr_ptr Pointer to variable to store result.
640 * @return SP_OK upon success, a negative error code otherwise.
642 enum sp_return sp_get_config_dtr(const struct sp_port_config *config, enum sp_dtr *dtr_ptr);
645 * Set the DTR pin behaviour in a port configuration.
647 * @param config Pointer to configuration structure.
648 * @param dtr DTR pin mode, or -1 to retain current setting.
650 * @return SP_OK upon success, a negative error code otherwise.
652 enum sp_return sp_set_config_dtr(struct sp_port_config *config, enum sp_dtr dtr);
655 * Set the DSR pin behaviour for the specified serial port.
657 * @param port Pointer to port structure.
658 * @param dsr DSR pin mode.
660 * @return SP_OK upon success, a negative error code otherwise.
662 enum sp_return sp_set_dsr(struct sp_port *port, enum sp_dsr dsr);
665 * Get the DSR pin behaviour from a port configuration.
667 * The user should allocate a variable of type enum sp_dsr and pass a pointer to this
668 * to receive the result.
670 * @param config Pointer to configuration structure.
671 * @param dsr_ptr Pointer to variable to store result.
673 * @return SP_OK upon success, a negative error code otherwise.
675 enum sp_return sp_get_config_dsr(const struct sp_port_config *config, enum sp_dsr *dsr_ptr);
678 * Set the DSR pin behaviour in a port configuration.
680 * @param config Pointer to configuration structure.
681 * @param dsr DSR pin mode, or -1 to retain current setting.
683 * @return SP_OK upon success, a negative error code otherwise.
685 enum sp_return sp_set_config_dsr(struct sp_port_config *config, enum sp_dsr dsr);
688 * Set the XON/XOFF configuration for the specified serial port.
690 * @param port Pointer to port structure.
691 * @param xon_xoff XON/XOFF mode.
693 * @return SP_OK upon success, a negative error code otherwise.
695 enum sp_return sp_set_xon_xoff(struct sp_port *port, enum sp_xonxoff xon_xoff);
698 * Get the XON/XOFF configuration from a port configuration.
700 * The user should allocate a variable of type enum sp_xonxoff and pass a pointer to this
701 * to receive the result.
703 * @param config Pointer to configuration structure.
704 * @param xon_xoff_ptr Pointer to variable to store result.
706 * @return SP_OK upon success, a negative error code otherwise.
708 enum sp_return sp_get_config_xon_xoff(const struct sp_port_config *config, enum sp_xonxoff *xon_xoff_ptr);
711 * Set the XON/XOFF configuration in a port configuration.
713 * @param config Pointer to configuration structure.
714 * @param xon_xoff XON/XOFF mode, or -1 to retain current setting.
716 * @return SP_OK upon success, a negative error code otherwise.
718 enum sp_return sp_set_config_xon_xoff(struct sp_port_config *config, enum sp_xonxoff xon_xoff);
721 * Set the flow control type in a port configuration.
723 * This function is a wrapper that sets the RTS, CTS, DTR, DSR and
724 * XON/XOFF settings as necessary for the specified flow control
725 * type. For more fine-grained control of these settings, use their
726 * individual configuration functions.
728 * @param config Pointer to configuration structure.
729 * @param flowcontrol Flow control setting to use.
731 * @return SP_OK upon success, a negative error code otherwise.
733 enum sp_return sp_set_config_flowcontrol(struct sp_port_config *config, enum sp_flowcontrol flowcontrol);
736 * Set the flow control type for the specified serial port.
738 * This function is a wrapper that sets the RTS, CTS, DTR, DSR and
739 * XON/XOFF settings as necessary for the specified flow control
740 * type. For more fine-grained control of these settings, use their
741 * individual configuration functions.
743 * @param port Pointer to port structure.
744 * @param flowcontrol Flow control setting to use.
746 * @return SP_OK upon success, a negative error code otherwise.
748 enum sp_return sp_set_flowcontrol(struct sp_port *port, enum sp_flowcontrol flowcontrol);
752 * @defgroup Data Reading, writing, and flushing data
757 * Read bytes from the specified serial port.
759 * Note that this function may return after reading less than the specified
760 * number of bytes; it is the user's responsibility to iterate as necessary
763 * @param port Pointer to port structure.
764 * @param buf Buffer in which to store the bytes read.
765 * @param count Maximum number of bytes to read.
767 * @return The number of bytes read on success, or a negative error code.
769 enum sp_return sp_read(struct sp_port *port, void *buf, size_t count);
772 * Write bytes to the specified serial port.
774 * Note that this function may return after writing less than the specified
775 * number of bytes; it is the user's responsibility to iterate as necessary
778 * @param port Pointer to port structure.
779 * @param buf Buffer containing the bytes to write.
780 * @param count Maximum number of bytes to write.
782 * @return The number of bytes written on success, or a negative error code.
784 enum sp_return sp_write(struct sp_port *port, const void *buf, size_t count);
787 * Flush serial port buffers. Data in the selected buffer(s) is discarded.
789 * @param port Pointer to port structure.
790 * @param buffers Which buffer(s) to flush.
792 * @return SP_OK upon success, a negative error code otherwise.
794 enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers);
797 * Wait for buffered data to be transmitted.
799 * @param port Pointer to port structure.
801 * @return SP_OK upon success, a negative error code otherwise.
803 enum sp_return sp_drain(struct sp_port *port);
807 * @defgroup Signals Port signalling operations
812 * Gets the status of the control signals for the specified port.
814 * The user should allocate a variable of type "enum sp_signal" and pass a
815 * pointer to this variable to receive the result. The result is a bitmask
816 * in which individual signals can be checked by bitwise OR with values of
817 * the sp_signal enum.
819 * @param port Pointer to port structure.
820 * @param signals Pointer to variable to receive result.
822 * @return SP_OK upon success, a negative error code otherwise.
824 enum sp_return sp_get_signals(struct sp_port *port, enum sp_signal *signals);
827 * Put the port transmit line into the break state.
829 * @param port Pointer to port structure.
831 * @return SP_OK upon success, a negative error code otherwise.
833 enum sp_return sp_start_break(struct sp_port *port);
836 * Take the port transmit line out of the break state.
838 * @param port Pointer to port structure.
840 * @return SP_OK upon success, a negative error code otherwise.
842 enum sp_return sp_end_break(struct sp_port *port);
846 * @defgroup Errors Obtaining error information
851 * Get the error code for a failed operation.
853 * In order to obtain the correct result, this function should be called
854 * straight after the failure, before executing any other system operations.
856 * @return The system's numeric code for the error that caused the last
859 int sp_last_error_code(void);
862 * Get the error message for a failed operation.
864 * In order to obtain the correct result, this function should be called
865 * straight after the failure, before executing other system operations.
867 * @return The system's message for the error that caused the last
868 * operation to fail. This string may be allocated by the function,
869 * and should be freed after use by calling sp_free_error_message().
871 char *sp_last_error_message(void);
874 * Free an error message returned by sp_last_error_message().
876 void sp_free_error_message(char *message);
879 * Set the handler function for library debugging messages.
881 * Debugging messages are generated by the library during each operation,
882 * to help in diagnosing problems. The handler will be called for each
883 * message. The handler can be set to NULL to ignore all debug messages.
885 * The handler function should accept a format string and variable length
886 * argument list, in the same manner as e.g. printf().
888 * The default handler is sp_default_debug_handler().
890 void sp_set_debug_handler(void (*handler)(const char *format, ...));
893 * Default handler function for library debugging messages.
895 * This function prints debug messages to the standard error stream if the
896 * environment variable LIBSERIALPORT_DEBUG is set. Otherwise, they are
899 void sp_default_debug_handler(const char *format, ...);