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,
153 /** RTS pin behaviour. */
155 /** Special value to indicate setting should be left alone. */
161 /** RTS used for flow control. */
162 SP_RTS_FLOW_CONTROL = 2,
165 /** CTS pin behaviour. */
167 /** Special value to indicate setting should be left alone. */
171 /** CTS used for flow control. */
172 SP_CTS_FLOW_CONTROL = 1,
175 /** DTR pin behaviour. */
177 /** Special value to indicate setting should be left alone. */
183 /** DTR used for flow control. */
184 SP_DTR_FLOW_CONTROL = 2,
187 /** DSR pin behaviour. */
189 /** Special value to indicate setting should be left alone. */
193 /** DSR used for flow control. */
194 SP_DSR_FLOW_CONTROL = 1,
197 /** XON/XOFF flow control behaviour. */
199 /** Special value to indicate setting should be left alone. */
200 SP_XONXOFF_INVALID = -1,
201 /** XON/XOFF disabled. */
202 SP_XONXOFF_DISABLED = 0,
203 /** XON/XOFF enabled for input only. */
205 /** XON/XOFF enabled for output only. */
207 /** XON/XOFF enabled for input and output. */
208 SP_XONXOFF_INOUT = 3,
211 /** Standard flow control combinations. */
212 enum sp_flowcontrol {
213 /** No flow control. */
214 SP_FLOWCONTROL_NONE = 0,
215 /** Software flow control using XON/XOFF characters. */
216 SP_FLOWCONTROL_XONXOFF = 1,
217 /** Hardware flow control using RTS/CTS signals. */
218 SP_FLOWCONTROL_RTSCTS = 2,
219 /** Hardware flow control using DTR/DSR signals. */
220 SP_FLOWCONTROL_DTRDSR = 3,
223 /** Input signals. */
225 /** Clear to send. */
227 /** Data set ready. */
229 /** Data carrier detect. */
231 /** Ring indicator. */
235 /** A serial port. */
238 /** Configuration for a serial port. */
239 struct sp_port_config;
242 @defgroup Enumeration Port enumeration
247 * Obtain a pointer to a new sp_port structure representing the named port.
249 * The user should allocate a variable of type "struct sp_port *" and pass a
250 * pointer to this to receive the result.
252 * The result should be freed after use by calling sp_free_port().
254 * If any error is returned, the variable pointed to by port_ptr will be set
255 * to NULL. Otherwise, it will be set to point to the newly allocated port.
257 * @return SP_OK upon success, a negative error code otherwise.
259 enum sp_return sp_get_port_by_name(const char *portname, struct sp_port **port_ptr);
262 * Free a port structure obtained from sp_get_port_by_name() or sp_copy_port().
264 void sp_free_port(struct sp_port *port);
267 * List the serial ports available on the system.
269 * The result obtained is an array of pointers to sp_port structures,
270 * terminated by a NULL. The user should allocate a variable of type
271 * "struct sp_port **" and pass a pointer to this to receive the result.
273 * The result should be freed after use by calling sp_free_port_list().
274 * If a port from the list is to be used after freeing the list, it must be
275 * copied first using sp_copy_port().
277 * If any error is returned, the variable pointed to by list_ptr will be set
278 * to NULL. Otherwise, it will be set to point to the newly allocated array.
280 * @return SP_OK upon success, a negative error code otherwise.
282 enum sp_return sp_list_ports(struct sp_port ***list_ptr);
285 * Make a new copy of a sp_port structure.
287 * The user should allocate a variable of type "struct sp_port *" and pass a
288 * pointer to this to receive the result.
290 * The copy should be freed after use by calling sp_free_port().
292 * If any error is returned, the variable pointed to by copy_ptr will be set
293 * to NULL. Otherwise, it will be set to point to the newly allocated copy.
295 * @return SP_OK upon success, a negative error code otherwise.
297 enum sp_return sp_copy_port(const struct sp_port *port, struct sp_port **copy_ptr);
300 * Free a port list obtained from sp_list_ports().
302 * This will also free all the sp_port structures referred to from the list;
303 * any that are to be retained must be copied first using sp_copy_port().
305 void sp_free_port_list(struct sp_port **ports);
309 * @defgroup Ports Opening, closing and querying ports
314 * Open the specified serial port.
316 * @param port Pointer to port structure.
317 * @param flags Flags to use when opening the serial port.
319 * @return SP_OK upon success, a negative error code otherwise.
321 enum sp_return sp_open(struct sp_port *port, enum sp_mode flags);
324 * Close the specified serial port.
326 * @return SP_OK upon success, a negative error code otherwise.
328 enum sp_return sp_close(struct sp_port *port);
331 * Get the name of a port.
333 * The name returned is whatever is normally used to refer to a port on the
334 * current operating system; e.g. for Windows it will usually be a "COMn"
335 * device name, and for Unix it will be a device path beginning with "/dev/".
337 * @param port Pointer to port structure.
339 * @return The port name, or NULL if an invalid port is passed. The name
340 * string is part of the port structure and may not be used after the
341 * port structure has been freed.
343 char *sp_get_port_name(const struct sp_port *port);
346 * Get the operating system handle for a port.
348 * The type of the handle depends on the operating system. On Unix based
349 * systems, the handle is a file descriptor of type "int". On Windows, the
350 * handle is of type "HANDLE". The user should allocate a variable of the
351 * appropriate type and pass a pointer to this to receive the result.
353 * To obtain a valid handle, the port must first be opened by calling
354 * sp_open() using the same port structure.
356 * After the port is closed or the port structure freed, the handle may
357 * no longer be valid.
359 * @warning This feature is provided so that programs may make use of
360 * OS-specific functionality where desired. Doing so obviously
361 * comes at a cost in portability. It also cannot be guaranteed
362 * that direct usage of the OS handle will not conflict with the
363 * library's own usage of the port. Be careful.
365 * @return SP_OK upon success, a negative error code otherwise.
367 enum sp_return sp_get_port_handle(const struct sp_port *port, void *result_ptr);
371 * @defgroup Configuration Setting port parameters
376 * Allocate a port configuration structure.
378 * The user should allocate a variable of type "struct sp_config *" and pass a
379 * pointer to this to receive the result. The variable will be updated to
380 * point to the new configuration structure. The structure is opaque and must
381 * be accessed via the functions provided.
383 * All parameters in the structure will be initialised to special values which
384 * are ignored by sp_set_config().
386 * The structure should be freed after use by calling sp_free_config().
388 * @param config_ptr Pointer to variable to receive result.
390 * @return SP_OK upon success, a negative error code otherwise.
392 enum sp_return sp_new_config(struct sp_port_config **config_ptr);
395 * Free a port configuration structure.
397 * @param config Pointer to configuration structure.
399 void sp_free_config(struct sp_port_config *config);
402 * Get the current configuration of the specified serial port.
404 * The user should allocate a configuration structure using sp_new_config()
405 * and pass this as the config parameter. The configuration structure will
406 * be updated with the port configuration.
408 * Any parameters that are configured with settings not recognised or
409 * supported by libserialport, will be set to special values that are
410 * ignored by sp_set_config().
412 * @return SP_OK upon success, a negative error code otherwise.
414 enum sp_return sp_get_config(struct sp_port *port, struct sp_port_config *config);
417 * Set the configuration for the specified serial port.
419 * For each parameter in the configuration, there is a special value (usually
420 * -1, but see the documentation for each field). These values will be ignored
421 * and the corresponding setting left unchanged on the port.
423 * @return SP_OK upon success, a negative error code otherwise.
425 enum sp_return sp_set_config(struct sp_port *port, const struct sp_port_config *config);
428 * Set the baud rate for the specified serial port.
430 * @param port Pointer to port structure.
431 * @param baudrate Baud rate in bits per second.
433 * @return SP_OK upon success, a negative error code otherwise.
435 enum sp_return sp_set_baudrate(struct sp_port *port, int baudrate);
438 * Get the baud rate from a port configuration.
440 * The user should allocate a variable of type int and pass a pointer to this
441 * to receive the result.
443 * @param config Pointer to configuration structure.
444 * @param baudrate_ptr Pointer to variable to store result.
446 * @return SP_OK upon success, a negative error code otherwise.
448 enum sp_return sp_get_config_baudrate(const struct sp_port_config *config, int *baudrate_ptr);
451 * Set the baud rate in a port configuration.
453 * @param config Pointer to configuration structure.
454 * @param baudrate Baud rate in bits per second, or -1 to retain current setting.
456 * @return SP_OK upon success, a negative error code otherwise.
458 enum sp_return sp_set_config_baudrate(struct sp_port_config *config, int baudrate);
461 * Set the data bits for the specified serial port.
463 * @param port Pointer to port structure.
464 * @param bits Number of data bits.
466 * @return SP_OK upon success, a negative error code otherwise.
468 enum sp_return sp_set_bits(struct sp_port *port, int bits);
471 * Get the data bits from a port configuration.
473 * The user should allocate a variable of type int and pass a pointer to this
474 * to receive the result.
476 * @param config Pointer to configuration structure.
477 * @param bits_ptr Pointer to variable to store result.
479 * @return SP_OK upon success, a negative error code otherwise.
481 enum sp_return sp_get_config_bits(const struct sp_port_config *config, int *bits_ptr);
484 * Set the data bits in a port configuration.
486 * @param config Pointer to configuration structure.
487 * @param bits Number of data bits, or -1 to retain current setting.
489 * @return SP_OK upon success, a negative error code otherwise.
491 enum sp_return sp_set_config_bits(struct sp_port_config *config, int bits);
494 * Set the parity setting for the specified serial port.
496 * @param port Pointer to port structure.
497 * @param parity Parity setting.
499 * @return SP_OK upon success, a negative error code otherwise.
501 enum sp_return sp_set_parity(struct sp_port *port, enum sp_parity parity);
504 * Get the parity setting from a port configuration.
506 * The user should allocate a variable of type enum sp_parity and pass a pointer to this
507 * to receive the result.
509 * @param config Pointer to configuration structure.
510 * @param parity_ptr Pointer to variable to store result.
512 * @return SP_OK upon success, a negative error code otherwise.
514 enum sp_return sp_get_config_parity(const struct sp_port_config *config, enum sp_parity *parity_ptr);
517 * Set the parity setting in a port configuration.
519 * @param config Pointer to configuration structure.
520 * @param parity Parity setting, or -1 to retain current setting.
522 * @return SP_OK upon success, a negative error code otherwise.
524 enum sp_return sp_set_config_parity(struct sp_port_config *config, enum sp_parity parity);
527 * Set the stop bits for the specified serial port.
529 * @param port Pointer to port structure.
530 * @param stopbits Number of stop bits.
532 * @return SP_OK upon success, a negative error code otherwise.
534 enum sp_return sp_set_stopbits(struct sp_port *port, int stopbits);
537 * Get the stop bits from a port configuration.
539 * The user should allocate a variable of type int and pass a pointer to this
540 * to receive the result.
542 * @param config Pointer to configuration structure.
543 * @param stopbits_ptr Pointer to variable to store result.
545 * @return SP_OK upon success, a negative error code otherwise.
547 enum sp_return sp_get_config_stopbits(const struct sp_port_config *config, int *stopbits_ptr);
550 * Set the stop bits in a port configuration.
552 * @param config Pointer to configuration structure.
553 * @param stopbits Number of stop bits, or -1 to retain current setting.
555 * @return SP_OK upon success, a negative error code otherwise.
557 enum sp_return sp_set_config_stopbits(struct sp_port_config *config, int stopbits);
560 * Set the RTS pin behaviour for the specified serial port.
562 * @param port Pointer to port structure.
563 * @param rts RTS pin mode.
565 * @return SP_OK upon success, a negative error code otherwise.
567 enum sp_return sp_set_rts(struct sp_port *port, enum sp_rts rts);
570 * Get the RTS pin behaviour from a port configuration.
572 * The user should allocate a variable of type enum sp_rts and pass a pointer to this
573 * to receive the result.
575 * @param config Pointer to configuration structure.
576 * @param rts_ptr Pointer to variable to store result.
578 * @return SP_OK upon success, a negative error code otherwise.
580 enum sp_return sp_get_config_rts(const struct sp_port_config *config, enum sp_rts *rts_ptr);
583 * Set the RTS pin behaviour in a port configuration.
585 * @param config Pointer to configuration structure.
586 * @param rts RTS pin mode, or -1 to retain current setting.
588 * @return SP_OK upon success, a negative error code otherwise.
590 enum sp_return sp_set_config_rts(struct sp_port_config *config, enum sp_rts rts);
593 * Set the CTS pin behaviour for the specified serial port.
595 * @param port Pointer to port structure.
596 * @param cts CTS pin mode.
598 * @return SP_OK upon success, a negative error code otherwise.
600 enum sp_return sp_set_cts(struct sp_port *port, enum sp_cts cts);
603 * Get the CTS pin behaviour from a port configuration.
605 * The user should allocate a variable of type enum sp_cts and pass a pointer to this
606 * to receive the result.
608 * @param config Pointer to configuration structure.
609 * @param cts_ptr Pointer to variable to store result.
611 * @return SP_OK upon success, a negative error code otherwise.
613 enum sp_return sp_get_config_cts(const struct sp_port_config *config, enum sp_cts *cts_ptr);
616 * Set the CTS pin behaviour in a port configuration.
618 * @param config Pointer to configuration structure.
619 * @param cts CTS pin mode, or -1 to retain current setting.
621 * @return SP_OK upon success, a negative error code otherwise.
623 enum sp_return sp_set_config_cts(struct sp_port_config *config, enum sp_cts cts);
626 * Set the DTR pin behaviour for the specified serial port.
628 * @param port Pointer to port structure.
629 * @param dtr DTR pin mode.
631 * @return SP_OK upon success, a negative error code otherwise.
633 enum sp_return sp_set_dtr(struct sp_port *port, enum sp_dtr dtr);
636 * Get the DTR pin behaviour from a port configuration.
638 * The user should allocate a variable of type enum sp_dtr and pass a pointer to this
639 * to receive the result.
641 * @param config Pointer to configuration structure.
642 * @param dtr_ptr Pointer to variable to store result.
644 * @return SP_OK upon success, a negative error code otherwise.
646 enum sp_return sp_get_config_dtr(const struct sp_port_config *config, enum sp_dtr *dtr_ptr);
649 * Set the DTR pin behaviour in a port configuration.
651 * @param config Pointer to configuration structure.
652 * @param dtr DTR pin mode, or -1 to retain current setting.
654 * @return SP_OK upon success, a negative error code otherwise.
656 enum sp_return sp_set_config_dtr(struct sp_port_config *config, enum sp_dtr dtr);
659 * Set the DSR pin behaviour for the specified serial port.
661 * @param port Pointer to port structure.
662 * @param dsr DSR pin mode.
664 * @return SP_OK upon success, a negative error code otherwise.
666 enum sp_return sp_set_dsr(struct sp_port *port, enum sp_dsr dsr);
669 * Get the DSR pin behaviour from a port configuration.
671 * The user should allocate a variable of type enum sp_dsr and pass a pointer to this
672 * to receive the result.
674 * @param config Pointer to configuration structure.
675 * @param dsr_ptr Pointer to variable to store result.
677 * @return SP_OK upon success, a negative error code otherwise.
679 enum sp_return sp_get_config_dsr(const struct sp_port_config *config, enum sp_dsr *dsr_ptr);
682 * Set the DSR pin behaviour in a port configuration.
684 * @param config Pointer to configuration structure.
685 * @param dsr DSR pin mode, or -1 to retain current setting.
687 * @return SP_OK upon success, a negative error code otherwise.
689 enum sp_return sp_set_config_dsr(struct sp_port_config *config, enum sp_dsr dsr);
692 * Set the XON/XOFF configuration for the specified serial port.
694 * @param port Pointer to port structure.
695 * @param xon_xoff XON/XOFF mode.
697 * @return SP_OK upon success, a negative error code otherwise.
699 enum sp_return sp_set_xon_xoff(struct sp_port *port, enum sp_xonxoff xon_xoff);
702 * Get the XON/XOFF configuration from a port configuration.
704 * The user should allocate a variable of type enum sp_xonxoff and pass a pointer to this
705 * to receive the result.
707 * @param config Pointer to configuration structure.
708 * @param xon_xoff_ptr Pointer to variable to store result.
710 * @return SP_OK upon success, a negative error code otherwise.
712 enum sp_return sp_get_config_xon_xoff(const struct sp_port_config *config, enum sp_xonxoff *xon_xoff_ptr);
715 * Set the XON/XOFF configuration in a port configuration.
717 * @param config Pointer to configuration structure.
718 * @param xon_xoff XON/XOFF mode, or -1 to retain current setting.
720 * @return SP_OK upon success, a negative error code otherwise.
722 enum sp_return sp_set_config_xon_xoff(struct sp_port_config *config, enum sp_xonxoff xon_xoff);
725 * Set the flow control type in a port configuration.
727 * This function is a wrapper that sets the RTS, CTS, DTR, DSR and
728 * XON/XOFF settings as necessary for the specified flow control
729 * type. For more fine-grained control of these settings, use their
730 * individual configuration functions.
732 * @param config Pointer to configuration structure.
733 * @param flowcontrol Flow control setting to use.
735 * @return SP_OK upon success, a negative error code otherwise.
737 enum sp_return sp_set_config_flowcontrol(struct sp_port_config *config, enum sp_flowcontrol flowcontrol);
740 * Set the flow control type for the specified serial port.
742 * This function is a wrapper that sets the RTS, CTS, DTR, DSR and
743 * XON/XOFF settings as necessary for the specified flow control
744 * type. For more fine-grained control of these settings, use their
745 * individual configuration functions.
747 * @param port Pointer to port structure.
748 * @param flowcontrol Flow control setting to use.
750 * @return SP_OK upon success, a negative error code otherwise.
752 enum sp_return sp_set_flowcontrol(struct sp_port *port, enum sp_flowcontrol flowcontrol);
756 * @defgroup Data Reading, writing, and flushing data
761 * Read bytes from the specified serial port.
763 * Note that this function may return after reading less than the specified
764 * number of bytes; it is the user's responsibility to iterate as necessary
767 * @param port Pointer to port structure.
768 * @param buf Buffer in which to store the bytes read.
769 * @param count Maximum number of bytes to read.
771 * @return The number of bytes read on success, or a negative error code.
773 enum sp_return sp_read(struct sp_port *port, void *buf, size_t count);
776 * Write bytes to the specified serial port.
778 * Note that this function may return after writing less than the specified
779 * number of bytes; it is the user's responsibility to iterate as necessary
782 * @param port Pointer to port structure.
783 * @param buf Buffer containing the bytes to write.
784 * @param count Maximum number of bytes to write.
786 * @return The number of bytes written on success, or a negative error code.
788 enum sp_return sp_write(struct sp_port *port, const void *buf, size_t count);
791 * Flush serial port buffers. Data in the selected buffer(s) is discarded.
793 * @param port Pointer to port structure.
794 * @param buffers Which buffer(s) to flush.
796 * @return SP_OK upon success, a negative error code otherwise.
798 enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers);
801 * Wait for buffered data to be transmitted.
803 * @param port Pointer to port structure.
805 * @return SP_OK upon success, a negative error code otherwise.
807 enum sp_return sp_drain(struct sp_port *port);
811 * @defgroup Signals Port signalling operations
816 * Gets the status of the control signals for the specified port.
818 * The user should allocate a variable of type "enum sp_signal" and pass a
819 * pointer to this variable to receive the result. The result is a bitmask
820 * in which individual signals can be checked by bitwise OR with values of
821 * the sp_signal enum.
823 * @param port Pointer to port structure.
824 * @param signals Pointer to variable to receive result.
826 * @return SP_OK upon success, a negative error code otherwise.
828 enum sp_return sp_get_signals(struct sp_port *port, enum sp_signal *signals);
831 * Put the port transmit line into the break state.
833 * @param port Pointer to port structure.
835 * @return SP_OK upon success, a negative error code otherwise.
837 enum sp_return sp_start_break(struct sp_port *port);
840 * Take the port transmit line out of the break state.
842 * @param port Pointer to port structure.
844 * @return SP_OK upon success, a negative error code otherwise.
846 enum sp_return sp_end_break(struct sp_port *port);
850 * @defgroup Errors Obtaining error information
855 * Get the error code for a failed operation.
857 * In order to obtain the correct result, this function should be called
858 * straight after the failure, before executing any other system operations.
860 * @return The system's numeric code for the error that caused the last
863 int sp_last_error_code(void);
866 * Get the error message for a failed operation.
868 * In order to obtain the correct result, this function should be called
869 * straight after the failure, before executing other system operations.
871 * @return The system's message for the error that caused the last
872 * operation to fail. This string may be allocated by the function,
873 * and should be freed after use by calling sp_free_error_message().
875 char *sp_last_error_message(void);
878 * Free an error message returned by sp_last_error_message().
880 void sp_free_error_message(char *message);
883 * Set the handler function for library debugging messages.
885 * Debugging messages are generated by the library during each operation,
886 * to help in diagnosing problems. The handler will be called for each
887 * message. The handler can be set to NULL to ignore all debug messages.
889 * The handler function should accept a format string and variable length
890 * argument list, in the same manner as e.g. printf().
892 * The default handler is sp_default_debug_handler().
894 void sp_set_debug_handler(void (*handler)(const char *format, ...));
897 * Default handler function for library debugging messages.
899 * This function prints debug messages to the standard error stream if the
900 * environment variable LIBSERIALPORT_DEBUG is set. Otherwise, they are
903 void sp_default_debug_handler(const char *format, ...);