diff options
| -rw-r--r-- | applause.c | 84 |
1 files changed, 74 insertions, 10 deletions
@@ -1,8 +1,12 @@ +#define _XOPEN_SOURCE + #include <stdio.h> #include <stdlib.h> #include <signal.h> -//#include <semaphore.h> +#include <sys/types.h> +#include <sys/ipc.h> +#include <sys/sem.h> #include <lua.h> #include <lauxlib.h> @@ -16,13 +20,46 @@ #define LUA_MODULE "applause.lua" -static jack_port_t *output_port; -static jack_client_t *client = NULL; +static jack_port_t *output_port; +static jack_client_t *client = NULL; #define BUFFER_SIZE (44100*60) /* 1m samples */ -static jack_ringbuffer_t *buffer = NULL; +static jack_ringbuffer_t *buffer = NULL; +static int buffer_sem; +static sig_atomic_t buffer_xrun = 0; + +static int +svsem_init(size_t value) +{ + int id; + + id = semget(IPC_PRIVATE, 1, IPC_CREAT); + if (id < 0) + return -1; + + if (semctl(id, 0, SETVAL, (int)value) < 0) + return -1; + + return id; +} + +static inline int +svsem_op(int id, int value) +{ + struct sembuf op = { + .sem_num = 0, + .sem_op = value, + .sem_flg = 0 + }; + + return semop(id, &op, 1); +} -static sig_atomic_t buffer_xrun = 0; +static inline int +svsem_free(int id) +{ + return semctl(id, 0, IPC_RMID); +} /** * The process callback for this JACK application is called in a @@ -45,6 +82,15 @@ jack_process(jack_nframes_t nframes, void *arg) r = jack_ringbuffer_read(buffer, (char *)out, len); /* + * The semaphor value corresponds with the number of + * writable samples in buffer, i.e. the available space. + * This operation should never block and is supposed to + * be real-time safe :-) + */ + if (r > 0) + svsem_op(buffer_sem, r); + + /* * Here we're assuming that memset() is realtime-capable. * It might not be on every UNIX!? */ @@ -117,18 +163,28 @@ init_audio(void) } /* - * Initialize ring buffer of samples + * Initialize ring buffer of samples. + * The semaphore is initialized with the same size + * since it represents the available bytes in the ring + * buffer. */ - buffer = jack_ringbuffer_create(sizeof(jack_default_audio_sample_t)*BUFFER_SIZE); + buffer = jack_ringbuffer_create(sizeof(jack_default_audio_sample_t)* + BUFFER_SIZE); if (!buffer) { fprintf(stderr, "cannot create ringbuffer\n"); return 1; } + buffer_sem = svsem_init(BUFFER_SIZE); + if (buffer_sem < 0) { + fprintf(stderr, "error initializing ring buffer\n"); + return 1; + } + /* Tell the JACK server that we are ready to roll. Our * process() callback will start running now. */ - if (jack_activate (client)) { + if (jack_activate(client)) { fprintf (stderr, "cannot activate client\n"); return 1; } @@ -213,10 +269,16 @@ l_Stream_play(lua_State *L) * the garbage collector */ sample = (jack_default_audio_sample_t)lua_tonumber(L, -1); + /* - * FIXME: Buffer may be full -- perhaps we should wait on a - * semaphore + * We are about to "consume" one free sample in the buffer. + * This can block when the buffer is full. + * After this operation, there is __at least__ one sample free + * in buffer since jack_process() will only read from the + * buffer. */ + svsem_op(buffer_sem, -1); + jack_ringbuffer_write(buffer, (const char *)&sample, sizeof(sample)); @@ -302,5 +364,7 @@ main(int argc, char **argv) free(line); } + svsem_free(buffer_sem); + lua_close(L); } |