DESCRIPTION

The library can be included in any program that wishes to make use of these features. It forms the heart of three Morse code tutor applications that accompany the package in which it is distributed.

See the cw(7) man page for information on Morse code timings, and the dot and dash representations for the various Morse characters.

TONE QUEUE

As well as being used by the library functions that sound Morse code characters and provide a keyer sidetone, the primitive tone queue functions are publicly available to caller programs.

CONTROLLING AN EXTERNAL DEVICE

libcw calls the external keying function only when the keying state changes. A call is likely each time a tone is taken off the tone queue.

SENDING CW CHARACTERS AND STRINGS

Characters and strings are converted into representations, and then the correct tones for the dots and dashes in these representations are queued on the tone queue, for action by the background queue emptying process.

RECEIVING CW CHARACTERS AND REPRESENTATIONS

Errors in receiving may be detected by means of the flags passed back on receive character functions.

IAMBIC KEYER

STRAIGHT KEY

RETURN CODES

FUNCTIONS

int cw_generator_new(int audio_system, const char *device)
Brief: Create new generator

Allocate memory for new generator data structure, set up default values of some of the generator's properties. The function does not start the generator (generator does not produce a sound), you have to use cw_generator_start() for this.

Notice that the function doesn't return a generator variable. There is at most one generator variable at any given time. You can't have two generators. In some future version of the library the function will return pointer to newly allocated generator, and then you could have as many of them as you want, but not yet.

audio_system can be one of following: NULL, console, OSS, ALSA, PulseAudio, soundcard. See "enum cw_audio_systems" in libcw.h for exact names of symbolic constants.

Parameter: audio_system - audio system to be used by the generator
Parameter: device - name of audio device to be used; if NULL then library will use default device.

void cw_generator_delete(void)
Brief: Deallocate generator

Deallocate/destroy generator data structure created with call to cw_generator_new(). You can't start nor use the generator after the call to this function.

int cw_generator_start(void)
Brief: Start a generator

Start producing tones using generator created with cw_generator_new(). The source of tones is a tone queue associated with the generator. If the tone queue is empty, the generator will wait for new tones to be queued.

Returns: CW_FAILURE on errors
Returns: CW_SUCCESS on success

void cw_generator_stop(void)
Brief: Shut down a generator

Silence tone generated by generator (level of generated sine wave is set to zero, with falling slope), and shut the generator down.

The shutdown does not erase generator's configuration.

If you want to have this generator running again, you have to call cw_generator_start().

int cw_set_send_speed(int new_value)
Brief: Set sending speed of generator

See libcw.h/CW_SPEED_{INITIAL|MIN|MAX} for initial/minimal/maximal value of send speed.

errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of send speed to be assigned to generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_set_frequency(int new_value)
Brief: Set frequency of generator

Set frequency of sound wave generated by generator. The frequency must be within limits marked by CW_FREQUENCY_MIN and CW_FREQUENCY_MAX.

See libcw.h/CW_FREQUENCY_{INITIAL|MIN|MAX} for initial/minimal/maximal value of frequency.

errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of frequency to be assigned to generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_set_volume(int new_value)
Brief: Set volume of generator

Set volume of sound wave generated by generator. The volume must be within limits marked by CW_VOLUME_MIN and CW_VOLUME_MAX.

Note that volume settings are not fully possible for the console speaker. In this case, volume settings greater than zero indicate console speaker sound is on, and setting volume to zero will turn off console speaker sound.

See libcw.h/CW_VOLUME_{INITIAL|MIN|MAX} for initial/minimal/maximal value of volume. errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of volume to be assigned to generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_set_gap(int new_value)
Brief: Set sending gap of generator

See libcw.h/CW_GAP_{INITIAL|MIN|MAX} for initial/minimal/maximal value of gap. errno is set to EINVAL if new_value is out of range.

Notice that this function also sets the same gap value for library's receiver.

Parameter: new_value - new value of gap to be assigned to generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_set_weighting(int new_value)
Brief: Set sending weighting for generator

See libcw.h/CW_WEIGHTING_{INITIAL|MIN|MAX} for initial/minimal/maximal value of weighting. errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of weighting to be assigned for generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_get_send_speed(void)
Brief: Get sending speed from generator

Returns: current value of the generator's send speed

int cw_get_frequency(void)
Brief: Get frequency from generator

Function returns "frequency" parameter of generator, even if the generator is stopped, or volume of generated sound is zero.

Returns: current value of generator's frequency

int cw_get_volume(void)
Brief: Get sound volume from generator

Function returns "volume" parameter of generator, even if the generator is stopped.

Returns: current value of generator's sound volume

int cw_get_gap(void)
Brief: Get sending gap from generator

Returns: current value of generator's sending gap

int cw_get_weighting(void)
Brief: Get sending weighting from generator

Returns: current value of generator's sending weighting

void cw_get_send_parameters(int *dot_usecs, int *dash_usecs,
int *end_of_element_usecs,
int *end_of_character_usecs, int *end_of_word_usecs,
int *additional_usecs, int *adjustment_usecs)
Brief: Get timing parameters for sending

Return the low-level timing parameters calculated from the speed, gap, tolerance, and weighting set. Parameter values are returned in microseconds.

Use NULL for the pointer argument to any parameter value not required.

Parameter: dot_usecs
Parameter: dash_usecs
Parameter: end_of_element_usecs
Parameter: end_of_character_usecs
Parameter: end_of_word_usecs
Parameter: additional_usecs
Parameter: adjustment_usecs

int cw_send_dot(void)
Brief: Low-level primitive for sending a dot mark

Low-level primitive function able to play/send single dot mark. The function appends to a tone queue a normal inter-mark gap after the dot mark.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_dash(void)
Brief: Low-level primitive for sending a dash mark

Low-level primitive function able to play/send single dash mark. The function appends to a tone queue a normal inter-mark gap after the dash mark.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_character_space(void)

The function plays space timed to exclude the expected prior dot/dash inter-mark gap. FIXME: fix this description.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_word_space(void)

The function sends space timed to exclude both the expected prior dot/dash inter-mark gap and the prior end of character space. FIXME: fix this description.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_representation(const char *representation)
Brief: Check, then send the given string as dots and dashes.

The representation passed in is assumed to be a complete Morse character; that is, all post-character delays will be added when the character is sent.

On success, the routine returns CW_SUCCESS. On failure, it returns CW_FAILURE, with errno set to EINVAL if any character of the representation is invalid, EBUSY if the sound card, console speaker, or keying system is busy, or EAGAIN if the tone queue is full, or if there is insufficient space to queue the tones or the representation.

Parameter: representation - representation to send

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_representation_partial(const char *representation)
Brief: Check, then send the given string as dots and dashes

The representation passed in is assumed to be only part of a larger Morse representation; that is, no post-character delays will be added when the character is sent.

On success, the routine returns CW_SUCCESS. On failure, it returns CW_FAILURE, with errno set to EINVAL if any character of the representation is invalid, EBUSY if the sound card, console speaker, or keying system is busy, or EAGAIN if the tone queue is full, or if there is insufficient space to queue the tones for the representation.

int cw_send_character(char c)
Brief: Look up and send a given ASCII character as Morse

The end of character delay is appended to the Morse sent.

On success the routine returns CW_SUCCESS. On failure the function returns CW_FAILURE and sets errno.

errno is set to ENOENT if the given character c is not a valid Morse character. errno is set to EBUSY if current audio sink or keying system is busy. errno is set to EAGAIN if the generator's tone queue is full, or if there is insufficient space to queue the tones for the character.

This routine returns as soon as the character has been successfully queued for sending; that is, almost immediately. The actual sending happens in background processing. See cw_wait_for_tone() and cw_wait_for_tone_queue() for ways to check the progress of sending.

Parameter: c - character to send

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_character_partial(char c)
Brief: Look up and send a given ASCII character as Morse code

"partial" means that the "end of character" delay is not appended to the Morse code sent by the function, to support the formation of combination characters.

On success the function returns CW_SUCCESS. On failure the function returns CW_FAILURE and sets errno.

errno is set to ENOENT if the given character c is not a valid Morse character. errno is set to EBUSY if the audio sink or keying system is busy. errno is set to EAGAIN if the tone queue is full, or if there is insufficient space to queue the tones for the character.

This routine queues its arguments for background processing. See cw_wait_for_tone() and cw_wait_for_tone_queue() for ways to check the progress of sending.

Parameter: c - character to send

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_send_string(const char *string)
Brief: Send a given ASCII string in Morse code

errno is set to ENOENT if any character in the string is not a valid Morse character.

errno is set to EBUSY if audio sink or keying system is busy.

errno is set to EAGAIN if the tone queue is full or if the tone queue runs out of space part way through queueing the string. However, an indeterminate number of the characters from the string will have already been queued.

For safety, clients can ensure the tone queue is empty before queueing a string, or use cw_send_character() if they need finer control.

This routine queues its arguments for background processing, the actual sending happens in background processing. See cw_wait_for_tone() and cw_wait_for_tone_queue() for ways to check the progress of sending.

Parameter: string - string to send

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

void cw_reset_send_receive_parameters(void)
Brief: Reset send/receive parameters

Reset the library speed, frequency, volume, gap, tolerance, weighting, adaptive receive, and noise spike threshold to their initial default values: send/receive speed 12 WPM, volume 70 %, frequency 800 Hz, gap 0 dots, tolerance 50 %, and weighting 50 %.

const char *cw_get_console_device(void)
Brief: Return char string with console device path

Returned pointer is owned by library.

Returns: char string with current console device path

const char *cw_get_soundcard_device(void)
Brief: Return char string with soundcard device name/path

Returned pointer is owned by library.

Returns: char string with current soundcard device name or device path

const char *cw_generator_get_audio_system_label(void)
Brief: Get a readable label of current audio system

The function returns one of following strings: None, Null, Console, OSS, ALSA, PulseAudio, Soundcard

Returns: audio system's label

int cw_register_tone_queue_low_callback(void (*callback_func)(void*), void *callback_arg, int level)
Brief: Register callback for low queue state

Register a function to be called automatically by the dequeue routine whenever the tone queue falls to a given level. To be more precise: the callback is called by queue manager if, after dequeueing a tone, the manager notices that tone queue length has become equal or less than level.

callback_arg may be used to give a value passed back on callback calls. A NULL function pointer suppresses callbacks. On success, the routine returns CW_SUCCESS.

If level is invalid, the routine returns CW_FAILURE with errno set to EINVAL. Any callback supplied will be called in signal handler context.

Parameter: callback_func - callback function to be registered
Parameter: callback_arg - argument for callback_func to pass return value
Parameter: level - low level of queue triggering callback call

Returns: CW_SUCCESS on successful registration
Returns: CW_FAILURE on failure

bool cw_is_tone_busy(void)
Brief: Check if tone sender is busy

Indicate if the tone sender is busy.

Returns: true if there are still entries in the tone queue
Returns: false if the queue is empty

int cw_wait_for_tone(void)
Brief: Wait for the current tone to complete

The routine returns CW_SUCCESS on success. If called with SIGALRM blocked, the routine returns CW_FAILURE, with errno set to EDEADLK, to avoid indefinite waits.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_wait_for_tone_queue(void)
Brief: Wait for the tone queue to drain

The routine returns CW_SUCCESS on success. If called with SIGALRM blocked, the routine returns false, with errno set to EDEADLK, to avoid indefinite waits.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_wait_for_tone_queue_critical(int level)
Brief: Wait for the tone queue to drain until only as many tones as given in level remain queued

This routine is for use by programs that want to optimize themselves to avoid the cleanup that happens when the tone queue drains completely; such programs have a short time in which to add more tones to the queue.

The routine returns CW_SUCCESS on success. If called with SIGALRM blocked, the routine returns false, with errno set to EDEADLK, to avoid indefinite waits.

Parameter: level - low level in queue, at which to return

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

bool cw_is_tone_queue_full(void)
Brief: Indicate if the tone queue is full

Returns: true if tone queue is full
Returns: false if tone queue is not full

int cw_get_tone_queue_capacity(void)
Brief: Return the number of entries the tone queue can accommodate

int cw_get_tone_queue_length(void)
Brief: Return the number of entries currently pending in the tone queue

void cw_flush_tone_queue(void)
Brief: Cancel all pending queued tones, and return to silence.

If there is a tone in progress, the function will wait until this last one has completed, then silence the tones.

This function may be called with SIGALRM blocked, in which case it will empty the queue as best it can, then return without waiting for the final tone to complete. In this case, it may not be possible to guarantee silence after the call.

void cw_reset_tone_queue(void)
Cancel all pending queued tones, reset any queue low callback registered, and return to silence. This function is suitable for calling from an application exit handler.

int cw_queue_tone(int usecs, int frequency)
Brief: Primitive access to simple tone generation

This routine queues a tone of given duration and frequency. The routine returns CW_SUCCESS on success. If usec or frequency are invalid, it returns CW_FAILURE with errno set to EINVAL. If the sound card, console speaker, or keying function are busy, it returns CW_FAILURE with errno set to EBUSY. If the tone queue is full, it returns false with errno set to EAGAIN.

Parameter: usecs - duration of queued tone, in microseconds
Parameter: frequency - frequency of queued tone

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_set_receive_speed(int new_value)
Brief: Set receiving speed of receiver

See documentation of cw_set_send_speed() for more information.

See libcw.h/CW_SPEED_{INITIAL|MIN|MAX} for initial/minimal/maximal value of receive speed. errno is set to EINVAL if new_value is out of range. errno is set to EPERM if adaptive receive speed tracking is enabled.

Parameter: new_value - new value of receive speed to be assigned to receiver

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_get_receive_speed(void)
Brief: Get receiving speed from receiver

Returns: current value of the receiver's receive speed

int cw_set_tolerance(int new_value)
Brief: Set tolerance for receiver

See libcw.h/CW_TOLERANCE_{INITIAL|MIN|MAX} for initial/minimal/maximal value of tolerance. errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of tolerance to be assigned to receiver

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_get_tolerance(void)
Brief: Get tolerance from receiver

Returns: current value of receiver's tolerance

void cw_get_receive_parameters(int *dot_usecs, int *dash_usecs,
int *dot_min_usecs, int *dot_max_usecs,
int *dash_min_usecs, int *dash_max_usecs,
int *end_of_element_min_usecs,
int *end_of_element_max_usecs,
int *end_of_element_ideal_usecs,
int *end_of_character_min_usecs,
int *end_of_character_max_usecs,
int *end_of_character_ideal_usecs,
int *adaptive_threshold)
Brief: Get timing parameters for receiving, and adaptive threshold

Return the low-level timing parameters calculated from the speed, gap, tolerance, and weighting set. Parameter values are returned in microseconds.

Use NULL for the pointer argument to any parameter value not required.

Parameter: dot_usecs
Parameter: dash_usecs
Parameter: dot_min_usecs
Parameter: dot_max_usecs
Parameter: dash_min_usecs
Parameter: dash_max_usecs
Parameter: end_of_element_min_usecs
Parameter: end_of_element_max_usecs
Parameter: end_of_element_ideal_usecs
Parameter: end_of_character_min_usecs
Parameter: end_of_character_max_usecs
Parameter: end_of_character_ideal_usecs
Parameter: adaptive_threshold

int cw_set_noise_spike_threshold(int new_value)
Brief: Set noise spike threshold for receiver

Set the period shorter than which, on receive, received marks are ignored. This allows the "receive mark" functions to apply noise canceling for very short apparent marks. For useful results the value should never exceed the dot length of a dot at maximum speed: 20000 microseconds (the dot length at 60WPM). Setting a noise threshold of zero turns off receive mark noise canceling.

The default noise spike threshold is 10000 microseconds.

errno is set to EINVAL if new_value is out of range.

Parameter: new_value - new value of noise spike threshold to be assigned to receiver

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_get_noise_spike_threshold(void)
Brief: Get noise spike threshold from receiver

See documentation of cw_set_noise_spike_threshold() for more information

Returns: current value of receiver's threshold

void cw_get_receive_statistics(double *dot_sd, double *dash_sd,
double *element_end_sd, double *character_end_sd)
Brief: Calculate and return receiver's timing statistics

These statistics may be used to obtain a measure of the accuracy of received CW. The values dot_sd and dot_sd contain the standard deviation of dot and dash lengths from the ideal values, and element_end_sd and element_end_sd the deviations for inter element and inter character spacing. Statistics are held for all timings in a 256 element circular buffer. If any statistic cannot be calculated, because no records for it exist, the returned value is 0.0. Use NULL for the pointer argument to any statistic not required.

Parameter: dot_sd
Parameter: dash_sd
Parameter: element_end_sd
Parameter: character_end_sd

void cw_reset_receive_statistics(void)
Brief: Clear the receive statistics buffer

Clear the receive statistics buffer by removing all records from it and returning it to its initial default state.

void cw_enable_adaptive_receive(void)
Brief: Enable adaptive receive speed tracking

If adaptive speed tracking is enabled, the receive functions will attempt to automatically adjust the receive speed setting to match the speed of the incoming Morse code. If it is disabled, the receive functions will use fixed speed settings, and reject incoming Morse which is not at the expected speed.

Adaptive speed tracking uses a moving average length of the past N marks as its baseline for tracking speeds. The default state is adaptive speed tracking disabled.

void cw_disable_adaptive_receive(void)
Brief: Disable adaptive receive speed tracking

See documentation of cw_enable_adaptive_receive() for more information

bool cw_get_adaptive_receive_state(void)
Brief: Get adaptive receive speed tracking flag

The function returns state of "adaptive receive enabled" flag. See documentation of cw_enable_adaptive_receive() for more information

Returns: true if adaptive speed tracking is enabled
Returns: false otherwise

int cw_start_receive_tone(const struct timeval *timestamp)
Brief: Signal beginning of receive mark

Called on the start of a receive mark. If the timestamp is NULL, the current timestamp is used as beginning of mark.

The function should be called by client application when pressing a key down (closing a circuit) has been detected by client application.

On error the function returns CW_FAILURE, with errno set to ERANGE if the call is directly after another cw_start_receive_tone() call or if an existing received character has not been cleared from the buffer, or EINVAL if the timestamp passed in is invalid.

Parameter: timestamp - time stamp of "key down" event

Returns: CW_SUCCESS on success
Returns: CW_FAILURE otherwise (with errno set)

int cw_end_receive_tone(const struct timeval *timestamp)
Brief: Signal end of mark

The function should be called by client application when releasing a key (opening a circuit) has been detected by client application.

If the timestamp is NULL, the current time is used as timestamp of end of mark.

On success, the routine adds a dot or dash to the receiver's representation buffer, and returns CW_SUCCESS.

On failure, it returns CW_FAIURE, with errno set to: ERANGE if the call was not preceded by a cw_start_receive_tone() call, EINVAL if the timestamp passed in is not valid, ENOENT if the mark length was out of bounds for the permissible dot and dash lengths and fixed speed receiving is selected, ENOMEM if the receiver's representation buffer is full, EAGAIN if the mark was shorter than the threshold for noise and was therefore ignored.

Parameter: timestamp - time stamp of "key up" event

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_receive_buffer_dot(const struct timeval *timestamp)
Brief: Add a dot to the receiver's representation buffer

Documentation for both cw_receive_buffer_dot() and cw_receive_buffer_dash():

Since we can't add a mark to the buffer without any accompanying timing information, the functions accepts timestamp of the "end of mark" event. If the timestamp is NULL, the current timestamp is used.

These routines are for client code that has already determined whether a dot or dash was received by a method other than calling the routines cw_start_receive_tone() and cw_end_receive_tone().

On success, the relevant mark is added to the receiver's representation buffer.

On failure, the routines return CW_FAILURE, with errno set to ERANGE if preceded by a cw_start_receive_tone() call with no matching cw_end_receive_tone() or if an error condition currently exists within the receiver's buffer, or ENOMEM if the receiver's representation buffer is full.

Parameter: timestamp - timestamp of "end of dot" event

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_receive_buffer_dash(const struct timeval *timestamp)
Brief: Add a dash to the receiver's representation buffer

See documentation of cw_receive_buffer_dot() for more information.

Parameter: timestamp - timestamp of "end of dash" event

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_receive_representation(const struct timeval *timestamp,
/* out */ char *representation,
/* out */ bool *is_end_of_word,
/* out */ bool *is_error)
Brief: Get the current buffered representation from the receiver's representation buffer

On success the function fills in representation with the contents of the current representation buffer and returns CW_SUCCESS.

On failure, it returns CW_FAILURE and sets errno to: ERANGE if not preceded by a cw_end_receive_tone() call, a prior successful cw_receive_representation call, or a prior cw_receive_buffer_dot or cw_receive_buffer_dash, EINVAL if the timestamp passed in is invalid, EAGAIN if the call is made too early to determine whether a complete representation has yet been placed in the buffer (that is, less than the end-of-character gap period elapsed since the last cw_end_receive_tone() or cw_receive_buffer_dot/dash call). This is not a *hard* error, just an information that the caller should try to get the representation later.

is_end_of_word indicates that the space after the last mark received is longer that the end-of-character gap, so it must be qualified as end-of-word gap.

is_error indicates that the representation was terminated by an error condition.

TODO: the function should be called cw_receiver_poll_representation().

The function is called periodically (poll()-like function) by client code in hope that at some attempt receiver will be ready to pass representation. The attempt succeeds only if data stream is in "space" state. To mark end of the space, client code has to provide a timestamp (or pass NULL timestamp, the function will get time stamp at function call). The receiver needs to know the "end of space" event - thus the timestamp parameter.

Parameter: timestamp - timestamp of event that ends "end-of-character" gap or "end-of-word" gap
Parameter: representation - buffer for representation (output parameter)
Parameter: is_end_of_word - buffer for "is end of word" state (output parameter)
Parameter: is_error - buffer for "error" state (output parameter)

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_receive_character(const struct timeval *timestamp,
/* out */ char *c,
/* out */ bool *is_end_of_word,
/* out */ bool *is_error)
Brief: Get a current character

Function returns the character currently stored in receiver's representation buffer.

On success the function returns CW_SUCCESS, and fills c with the contents of the current representation buffer, translated into a character.

On failure the function returns CW_FAILURE, with errno set to:

ERANGE if not preceded by a cw_end_receive_tone() call, a prior successful cw_receive_character() call, or a cw_receive_buffer_dot() or cw_receive_buffer_dash() call, EINVAL if the timestamp passed in is invalid, or EAGAIN if the call is made too early to determine whether a complete character has yet been placed in the buffer (that is, less than the end-of-character gap period elapsed since the last cw_end_receive_tone() or cw_receive_buffer_dot/dash call). ENOENT if character stored in receiver cannot be recognized as valid

is_end_of_word indicates that the space after the last mark received is longer that the end-of-character gap, so it must be qualified as end-of-word gap.

is_error indicates that the character was terminated by an error condition.

Parameter: timestamp - timestamp of event that ends end-of-character gap or end-of-word gap
Parameter: c - buffer for character (output parameter)
Parameter: is_end_of_word - buffer for "is end of word" state (output parameter)
Parameter: is_error - buffer for "error" state (output parameter)

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

void cw_clear_receive_buffer(void)
Brief: Clear receiver's representation buffer

Clears the receiver's representation buffer, resets receiver's internal state. This prepares the receiver to receive marks and spaces again.

This routine must be called after successful, or terminating, cw_receive_representation() or cw_receive_character() calls, to clear the states and prepare the buffer to receive more marks and spaces.

int cw_get_receive_buffer_capacity(void)
Brief: Get the number of elements (dots/dashes) the receiver's buffer can accommodate

The maximum number of elements written out by cw_receive_representation() is the capacity + 1, the extra character being used for the terminating NUL.

Returns: number of elements that can be stored in receiver's representation buffer

int cw_get_receive_buffer_length(void)
Brief: Get the number of elements (dots/dashes) currently pending in the cw_receiver's representation buffer

Returns: number of elements in receiver's representation buffer

void cw_reset_receive(void)
Brief: Clear receive data

Clear the receiver's representation buffer, statistics, and any retained receiver's state. This function is suitable for calling from an application exit handler.

void cw_register_keying_callback(void (*callback_func)(void*, int), void *callback_arg)
Brief: Register external callback function for keying

Register a callback_func function that should be called when a state of a key changes from "key open" to "key closed", or vice-versa.

The first argument passed to the registered callback function is the supplied callback_arg, if any. The second argument passed to registered callback function is the key state: CW_KEY_STATE_CLOSED (one/true) for "key closed", and CW_KEY_STATE_OPEN (zero/false) for "key open".

Calling this routine with a NULL function address disables keying callbacks. Any callback supplied will be called in signal handler context (??).

Parameter: callback_func - callback function to be called on key state changes
Parameter: callback_arg - first argument to callback_func

void cw_enable_iambic_curtis_mode_b(void)
Brief: Enable iambic Curtis mode B

Normally, the iambic keying functions will emulate Curtis 8044 Keyer mode A. In this mode, when both paddles are pressed together, the last dot or dash being sent on release is completed, and nothing else is sent. In mode B, when both paddles are pressed together, the last dot or dash being sent on release is completed, then an opposite element is also sent. Some operators prefer mode B, but timing is more critical in this mode. The default mode is Curtis mode A.

void cw_disable_iambic_curtis_mode_b(void)
See documentation of cw_enable_iambic_curtis_mode_b() for more information

int cw_get_iambic_curtis_mode_b_state(void)
See documentation of cw_enable_iambic_curtis_mode_b() for more information

int cw_notify_keyer_paddle_event(int dot_paddle_state, int dash_paddle_state)
Brief: Inform about changed state of iambic keyer's paddles

Function informs the library that the iambic keyer paddles have changed state. The new paddle states are recorded, and if either transition from false to true, paddle latches, for iambic functions, are also set.

On success, the routine returns CW_SUCCESS. On failure, it returns CW_FAILURE, with errno set to EBUSY if the tone queue or straight key are using the sound card, console speaker, or keying system.

If appropriate, this routine starts the keyer functions sending the relevant element. Element send and timing occurs in the background, so this routine returns almost immediately. See cw_keyer_element_wait() and cw_keyer_wait() for details about how to check the current status of iambic keyer background processing.

Parameter: dot_paddle_state
Parameter: dash_paddle_state

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_notify_keyer_dot_paddle_event(int dot_paddle_state)
Brief: Change state of dot paddle

Alter the state of just one of the two iambic keyer paddles. The other paddle state of the paddle pair remains unchanged.

See cw_notify_keyer_paddle_event() for details of iambic keyer background processing, and how to check its status.

Parameter: dot_paddle_state

int cw_notify_keyer_dash_paddle_event(int dash_paddle_state)
See documentation of cw_notify_keyer_dot_paddle_event() for more information

void cw_get_keyer_paddles(int *dot_paddle_state, int *dash_paddle_state)
Brief: Get the current saved states of the two paddles

Parameter: dot_paddle_state
Parameter: dash_paddle_state

void cw_get_keyer_paddle_latches(int *dot_paddle_latch_state, int *dash_paddle_latch_state)
Brief: Get the current states of paddle latches

Function returns the current saved states of the two paddle latches. A paddle latches is set to true when the paddle state becomes true, and is cleared if the paddle state is false when the element finishes sending.

Parameter: dot_paddle_latch_state
Parameter: dash_paddle_latch_state

bool cw_is_keyer_busy(void)
Brief: Check if a keyer is busy

Returns: true if keyer is busy
Returns: false if keyer is not busy

int cw_wait_for_keyer_element(void)
Brief: Wait for end of element from the keyer

Waits until the end of the current element, dot or dash, from the keyer.

On error the function returns CW_FAILURE, with errno set to EDEADLK if SIGALRM is blocked.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_wait_for_keyer(void)
Brief: Wait for the current keyer cycle to complete

The routine returns CW_SUCCESS on success. On error, it returns CW_FAILURE, with errno set to EDEADLK if SIGALRM is blocked or if either paddle state is true.

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

void cw_reset_keyer(void)
Brief: Reset iambic keyer data

Clear all latches and paddle states of iambic keyer, return to Curtis 8044 Keyer mode A, and return to silence. This function is suitable for calling from an application exit handler.

int cw_notify_straight_key_event(int key_state)
Brief: Inform the library that the straight key has changed state

This routine returns CW_SUCCESS on success. On error, it returns CW_FAILURE, with errno set to EBUSY if the tone queue or iambic keyer are using the sound card, console speaker, or keying control system. If key_state indicates no change of state, the call is ignored.

key_state may be either CW_KEY_STATE_OPEN (false) or CW_KEY_STATE_CLOSED (true).

Parameter: key_state - state of straight key

int cw_get_straight_key_state(void)
Brief: Get saved state of straight key

Returns the current saved state of the straight key.

Returns: CW_KEY_STATE_CLOSED (true) if the key is down
Returns: CW_KEY_STATE_OPEN (false) if the key up

bool cw_is_straight_key_busy(void)
Brief: Check if the straight key is busy

This routine is just a pseudonym for cw_get_straight_key_state(), and exists to fill a hole in the API naming conventions.

Returns: true if the straight key is busy
Returns: false if the straight key is not busy

void cw_reset_straight_key(void)
Brief: Clear the straight key state, and return to silence

This function is suitable for calling from an application exit handler.

bool cw_is_alsa_possible(const char *device)
Brief: Check if it is possible to open ALSA output

Function first tries to load ALSA library, and then does a test opening of ALSA output, but it closes it before returning.

Parameter: device - name of ALSA device to be used; if NULL then library will use default device.

Returns: true if opening ALSA output succeeded;
Returns: false if opening ALSA output failed;

bool cw_is_console_possible(const char *device)
Brief: Check if it is possible to open console output

Function does a test opening and test writing to console device, but it closes it before returning.

The function tests that the given console file exists, and that it will accept the KIOCSOUND ioctl. It unconditionally returns false on platforms that do no support the KIOCSOUND ioctl.

Call to ioctl will fail if calling code doesn't have root privileges.

This is the only place where we ask if KIOCSOUND is defined, so client code must call this function whenever it wants to use console output, as every other function called to perform console operations will happily assume that it is allowed to perform such operations.

Parameter: device - name of console device to be used; if NULL then library will use default device.

Returns: true if opening console output succeeded;
Returns: false if opening console output failed;

int cw_console_write(cw_gen_t *gen, cw_tone_t *tone)
Brief: Pseudo-device for playing sound with console

Function behaving like a device, to which one does a blocking write. It generates sound with parameters (frequency and duration) specified in tone.. After playing X microseconds of tone it returns. It is intended to behave like a blocking write() function.

Parameter: gen - current generator
Parameter: tone - tone to play with generator

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_get_character_count(void)
Brief: Return the number of characters present in character lookup table

Return the number of characters that are known to libcw. The number includes:

Returns: number of characters known to libcw

void cw_list_characters(char *list)
Brief: Get list of characters present in character lookup table

Function provides a string containing all of the characters represented in library's lookup table.

The list includes:

Parameter: list - pointer to space to be filled by function

int cw_get_maximum_representation_length(void)
Brief: Get length of the longest representation

Function returns the string length of the longest representation in the character lookup table.

Returns: a positive number - length of the longest representation

int cw_lookup_character(char c, char *representation)
Brief: Get representation of a given character

The function is depreciated, use cw_character_to_representation() instead.

Return the string representation (shape) of a given Morse code character c.

The routine returns CW_SUCCESS on success, and fills in the string pointer (representation) passed in. On failure, it returns CW_FAILURE and sets errno to ENOENT, indicating that the character c could not be found.

The length of representation buffer must be at least one greater than the length of longest representation held in the character lookup table. The largest value of length is returned by cw_get_maximum_representation_length().

Parameter: c - character to look up
Parameter: representation - pointer to space for representation of character

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

char *cw_character_to_representation(int c)
Brief: Get representation of a given character

On success return representation of a given character. Returned pointer is owned by caller of the function.

On failure function returns NULL and sets errno: ENOENT indicates that the character could not be found. ENOMEM indicates that character has been found, but function failed to strdup() representation.

Parameter: c - character to look up

Returns: pointer to freshly allocated representation on success
Returns: NULL on failure

int cw_check_representation(const char *representation)
Brief: Check if representation of a character is valid

This function is depreciated, use cw_representation_is_valid() instead.

Check that the given string is a valid Morse representation. A valid string is one composed of only "." and "-" characters.

If representation is invalid, function returns CW_FAILURE and sets errno to EINVAL.

Parameter: representation - representation of a character to check

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

bool cw_representation_is_valid(const char *representation)
Brief: Check if representation of a character is valid

Check that the given string is a valid Morse representation. A valid string is one composed of only "." and "-" characters. This means that the function checks only if representation is error-free, and not whether the representation represents existing/defined character.

If representation is invalid, function returns false and sets errno to EINVAL.

Parameter: representation - representation of a character to check

Returns: true on success
Returns: false on failure

int cw_lookup_representation(const char *representation, char *c)
Brief: Get the character represented by a given Morse representation

This function is depreciated, use cw_representation_to_character() instead.

Function checks representation, and if it is valid and represents a known character, function returns CW_SUCCESS. Additionally, if c is non-NULL, function puts the looked up character in c.

c should be allocated by caller. Function assumes that c being NULL pointer is a valid situation, and can return CW_SUCCESS in such situation.

On error, function returns CW_FAILURE. errno is set to EINVAL if any character of the representation is invalid, or ENOENT to indicate that the character represented by representation could not be found.

Parameter: representation - representation of a character to look up
Parameter: c - location where to put looked up character

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

int cw_representation_to_character(const char *representation)
Brief: Return the character represented by a given Morse representation

Function checks representation, and if it is valid and represents a known character, function returns the character (a non-zero value).

On error, function returns zero. errno is set to EINVAL if any character of the representation is invalid, or ENOENT to indicate that the character represented by representation could not be found.

Parameter: representation - representation of a character to look up

Returns: non-zero character on success
Returns: zero on failure

int cw_get_procedural_character_count(void)
Brief: Get number of procedural signals

Returns: the number of characters represented in the procedural signal expansion lookup table

void cw_list_procedural_characters(char *list)
Brief: Get list of characters for which procedural expansion is available

Function returns into list a string containing all of the Morse characters for which procedural expansion is available. The length of list must be at least by one greater than the number of characters represented in the procedural signal expansion lookup table, returned by cw_get_procedural_character_count().

list is managed by caller

Parameter: list - space for returned characters

int cw_get_maximum_procedural_expansion_length(void)
Brief: Get length of the longest procedural expansion

Function returns the string length of the longest expansion in the procedural signal expansion table.

Returns: length

int cw_lookup_procedural_character(char c, char *expansion, int *is_usually_expanded)
Brief: Get the string expansion of a given Morse code procedural signal character

On success the function - fills expansion with the string expansion of a given Morse code procedural signal character c; - sets is_usuall_expanded to true as a display hint for the caller; - returns CW_SUCCESS.

Both expansion and expansion must be allocated and managed by caller. They can be NULL, then the function won't attempt to use them.

The length of expansion must be at least by one greater than the longest expansion held in the procedural signal character lookup table, as returned by cw_get_maximum_procedural_expansion_length().

If procedural signal character c cannot be found, the function sets errno to ENOENT and returns CW_FAILURE.

Parameter: c - character to look up
Parameter: expansion - output, space to fill with expansion of the character
Parameter: is_usually_expanded - visual hint

Returns: CW_FAILURE on failure (errno is set to ENOENT)
Returns: CW_SUCCESS on success

int cw_get_maximum_phonetic_length(void)
Brief: Get maximum length of a phonetic

Returns: the string length of the longest phonetic in the phonetics lookup table

int cw_lookup_phonetic(char c, char *phonetic)
Brief: Get the phonetic of a given character

On success the routine fills in the string pointer passed in with the phonetic of given character c.

The length of phonetic must be at least one greater than the longest phonetic held in the phonetic lookup table, as returned by cw_get_maximum_phonetic_length().

If character cannot be found, the function sets errno to ENOENT.

Parameter: c - character to look up
Parameter: phonetic - output, space for phonetic of a character

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

bool cw_character_is_valid(char c)
Brief: Checks that the given character is validly sendable in Morse

Function sets errno to ENOENT on failure.

Parameter: c - character to check

Returns: CW_SUCCESS if character is valid
Returns: CW_FAILURE if character is invalid

bool cw_string_is_valid(const char *string)
Brief: Validate a string

Check that each character in the given string is valid and can be sent by libcw as a Morse character.

Function sets errno to EINVAL on failure

Parameter: string - string to check

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

void cw_debug_flush(cw_debug_t *debug)
Brief: Write all events from the debug object to a file

Function writes all events stored in the debug object to file associated with the object, and removes the events.

List of events is preceded with "FLUSH START0 line, and followed by "FLUSH END0 line.

Parameter: debug - debug object

void cw_set_debug_flags(uint32_t flags)
Brief: Set a value of internal debug flags variable

Assign specified value to library's internal debug flags variable. Note that this function doesn't *append* given flag to the variable, it erases existing value and assigns new one. Use cw_get_debug_flags() if you want to OR new flag with existing ones.

Parameter: new_value - new value to be assigned to the library

void cw_debug_set_flags(cw_debug_t *debug_object, uint32_t flags)

uint32_t cw_get_debug_flags(void)
Brief: Get current library's debug flags

Function returns value of library's internal debug variable.

Returns: value of library's debug flags variable

uint32_t cw_debug_get_flags(cw_debug_t *debug_object)

bool cw_debug_has_flag(cw_debug_t *debug_object, uint32_t flag)
Brief: Check if given debug flag is set

Function checks if a specified debug flag is set in internal variable of libcw library.

Parameter: flag - flag to be checked.

Returns: true if given flag is set
Returns: false if given flag is not set

int cw_generator_set_tone_slope(cw_gen_t *gen, int slope_shape, int slope_len)
Brief: Set parameters of tones generated by generator

Most of variables related to slope of tones is in tone data type, but there are still some variables that are generator-specific, as they are common for all tones. This function sets two of these variables.

A: If you pass to function conflicting values of slope_shape and slope_len, the function will return CW_FAILURE. These conflicting values are rectangular slope shape and larger than zero slope length. You just can't have rectangular slopes that have non-zero length.

B: If you pass to function '-1' as value of both slope_shape and slope_len, the function won't change any of the related two generator's parameters.

C1: If you pass to function '-1' as value of either slope_shape or slope_len, the function will attempt to set only this generator's parameter that is different than '-1'.

C2: However, if selected slope shape is rectangular, function will set generator's slope length to zero, even if value of slope_len is '-1'.

D: Notice that the function allows non-rectangular slope shape with zero length of the slopes. The slopes will be non-rectangular, but just unusually short.

The function should be called every time one of following parameters change:

FIXME: first argument of this public function is gen, but no function provides access to generator variable.

Parameter: gen - generator for which to set tone slope parameters
Parameter: slope_shape - shape of slope: linear, raised cosine, sine, rectangular
Parameter: slope_len - length of slope [microseconds]

Returns: CW_SUCCESS on success
Returns: CW_FAILURE on failure

bool cw_is_oss_possible(const char *device)
Brief: Check if it is possible to open OSS output

Function does a test opening and test configuration of OSS output, but it closes it before returning.

Parameter: device - name of OSS device to be used; if NULL then library will use default device.

Returns: true if opening OSS output succeeded;
Returns: false if opening OSS output failed;

bool cw_is_pa_possible(const char *device)
Brief: Check if it is possible to open PulseAudio output

Function first tries to load PulseAudio library, and then does a test opening of PulseAudio output, but it closes it before returning.

Parameter: device - sink device, NULL for default PulseAudio device

Returns: true if opening PulseAudio output succeeded;
Returns: false if opening PulseAudio output failed;

void cw_block_callback(int block)
Brief: Block the callback from being called

Function blocks the callback from being called for a critical section of caller code if block is true, and unblocks the callback if block is false.

Function works by blocking SIGALRM; a block should always be matched by an unblock, otherwise the tone queue will suspend forever.

Parameter: block - pass 1 to block SIGALRM, and 0 to unblock it

int cw_register_signal_handler(int signal_number, void (*callback_func)(int))
Brief: Register a signal handler and optional callback function for given signal number

On receipt of that signal, all library features will be reset to their default states. Following the reset, if callback_func is a function pointer, the function is called; if it is SIG_DFL, the library calls exit(); and if it is SIG_IGN, the library returns from the signal handler.

This is a convenience function for clients that need to clean up library on signals, with either exit, continue, or an additional function call; in effect, a wrapper round a restricted form of sigaction.

The signal_number argument indicates which signal to catch.

On problems errno is set to EINVAL if signal_number is invalid or if a handler is already installed for that signal, or to the sigaction error code.

Parameter: signal_number
Parameter: callback_func

Returns: CW_SUCCESS - if the signal handler installs correctly
Returns: CW_FAILURE - on errors or problems

int cw_unregister_signal_handler(int signal_number)
Brief: Unregister a signal handler interception

Function removes a signal handler interception previously registered with cw_register_signal_handler().

Parameter: signal_number

Returns: true if the signal handler uninstalls correctly
Returns: false otherwise (with errno set to EINVAL or to the sigaction error code)

int cw_version(void)
Brief: Return version number of libcw library

Return the version number of the library. Version numbers (major and minor) are returned as an int, composed of major_version << 16 | minor_version.

Returns: library's major and minor version number encoded as single int

void cw_license(void)
Brief: Print libcw's license text to stdout

Function prints information about libcw version, followed by short text presenting libcw's copyright and license notice.

const char *cw_get_audio_system_label(int audio_system)
Brief: Get a readable label of given audio system

The function returns one of following strings: None, Null, Console, OSS, ALSA, PulseAudio, Soundcard

Returned pointer is owned and managed by the library.

TODO: change the declaration to "const char *const cw_get_audio_system_label(...)"?

Parameter: audio_system - ID of audio system

Returns: audio system's label

void cw_get_speed_limits(int *min_speed, int *max_speed)
Brief: Get speed limits

Get (through function's arguments) limits on speed of morse code that can be generated by generator.

See CW_SPEED_MIN and CW_SPEED_MAX in libcw.h for values.

Parameter: min_speed - minimal allowed speed
Parameter: max_speed - maximal allowed speed

void cw_get_frequency_limits(int *min_frequency, int *max_frequency)
Brief: Get frequency limits

Get (through function's arguments) limits on frequency that can be generated by generator.

See CW_FREQUENCY_MIN and CW_FREQUENCY_MAX in libcw.h for values.

Parameter: min_frequency - minimal allowed frequency
Parameter: max_frequency - maximal allowed frequency

void cw_get_volume_limits(int *min_volume, int *max_volume)
Brief: Get volume limits

Get (through function's arguments) limits on volume of sound generated by generator.

See CW_VOLUME_MIN and CW_VOLUME_MAX in libcw.h for values.

Parameter: min_volume - minimal allowed volume
Parameter: max_volume - maximal allowed volume

void cw_get_gap_limits(int *min_gap, int *max_gap)
Brief: Get gap limits

Get (through function's arguments) limits on gap in cw signal generated by generator.

See CW_GAP_MIN and CW_GAP_MAX in libcw.h for values.

Parameter: min_gap - minimal allowed gap
Parameter: max_gap - maximal allowed gap

void cw_get_tolerance_limits(int *min_tolerance, int *max_tolerance)
Brief: Get tolerance limits

Get (through function's arguments) limits on "tolerance" parameter of generator.

See CW_TOLERANCE_MIN and CW_TOLERANCE_MAX in libcw.h for values.

Parameter: min_tolerance - minimal allowed tolerance
Parameter: max_tolerance - maximal allowed tolerance

void cw_get_weighting_limits(int *min_weighting, int *max_weighting)
Brief: Get weighting limits

Get (through function's arguments) limits on "weighting" parameter of generator.

See CW_WEIGHTING_MIN and CW_WEIGHTING_MAX in libcw.h for values.

Parameter: min_weighting - minimal allowed weighting
Parameter: max_weighting - maximal allowed weighting

void cw_complete_reset(void)
Brief: Reset all library features to their default states

Clears the tone queue, receive buffers and retained state information, any current keyer activity, and any straight key activity, returns to silence, and closes soundcard and console devices. This function is suitable for calling from an application exit handler.