HardwareAdapter/controller/ringbuffer.c

void _ringBufferIncReader(struct ringBuffer *buf) {
  buf->reader += buf->blockSize;
  if (buf->reader >= buf->buffer + buf->blocks * buf->blockSize) {
    buf->reader = buf->buffer;
  }
}

void _ringBufferIncWriter(struct ringBuffer *buf) {
  buf->writer += buf->blockSize;
  if (buf->writer == buf->buffer + buf->blocks * buf->blockSize) {
    buf->writer = buf->buffer;
  }

  if (buf->writer == buf->reader) {
    // we incremented the writer and now it is equal to reader
    // this means, the writer is overtaking the reader
    // so push the reader forward, even if we are
    // loosing data but this is how ring buffers work, eh?
    _ringBufferIncReader(buf);
  }
}

void ringBufferCreate(int blocks, size_t blockSize, struct ringBuffer *out) {
  out->buffer = malloc(blocks * blockSize);
  out->blocks = blocks;
  out->blockSize = blockSize;
  out->reader = out->buffer;
  out->writer = out->buffer;
#ifdef RINGBUFFER_THREAD_SAFE
  pthread_mutex_init(&out->mutex, NULL);
#endif
}

void ringBufferDestroy(struct ringBuffer *buf) {
  free(buf->buffer);
#ifdef RINGBUFFER_THREAD_SAFE
  pthread_mutex_destroy(&buf->mutex);
#endif
}

int ringBufferRead(struct ringBuffer *buf, void *out) {
#ifdef RINGBUFFER_THREAD_SAFE
  pthread_mutex_lock(&buf->mutex);
#endif
  if (buf->reader != buf->writer) {
    // we have data to read
    memcpy(out, buf->reader, buf->blockSize);
    _ringBufferIncReader(buf);
#ifdef RINGBUFFER_THREAD_SAFE
    pthread_mutex_unlock(&buf->mutex);
#endif
    return 0;
  } else {
    // nothing to read
#ifdef RINGBUFFER_THREAD_SAFE
    pthread_mutex_unlock(&buf->mutex);
#endif
    return 1;
  }
}

void ringBufferWrite(struct ringBuffer *buf, void *in) {
#ifdef RINGBUFFER_THREAD_SAFE
  pthread_mutex_lock(&buf->mutex);
#endif
  memcpy(buf->writer, in, buf->blockSize);
  _ringBufferIncWriter(buf);
#ifdef RINGBUFFER_THREAD_SAFE
  pthread_mutex_unlock(&buf->mutex);
#endif
}