+int pa_stream_begin_write(
+ pa_stream *s,
+ void **data,
+ size_t *nbytes) {
+
+ pa_assert(s);
+ pa_assert(PA_REFCNT_VALUE(s) >= 1);
+
+ PA_CHECK_VALIDITY(s->context, !pa_detect_fork(), PA_ERR_FORKED);
+ PA_CHECK_VALIDITY(s->context, s->state == PA_STREAM_READY, PA_ERR_BADSTATE);
+ PA_CHECK_VALIDITY(s->context, s->direction == PA_STREAM_PLAYBACK || s->direction == PA_STREAM_UPLOAD, PA_ERR_BADSTATE);
+ PA_CHECK_VALIDITY(s->context, data, PA_ERR_INVALID);
+ PA_CHECK_VALIDITY(s->context, nbytes && *nbytes != 0, PA_ERR_INVALID);
+
+ if (*nbytes != (size_t) -1) {
+ size_t m, fs;
+
+ m = pa_mempool_block_size_max(s->context->mempool);
+ fs = pa_frame_size(&s->sample_spec);
+
+ m = (m / fs) * fs;
+ if (*nbytes > m)
+ *nbytes = m;
+ }
+
+ if (!s->write_memblock) {
+ s->write_memblock = pa_memblock_new(s->context->mempool, *nbytes);
+ s->write_data = pa_memblock_acquire(s->write_memblock);
+ }
+
+ *data = s->write_data;
+ *nbytes = pa_memblock_get_length(s->write_memblock);
+
+ return 0;
+}
+
+int pa_stream_cancel_write(
+ pa_stream *s) {
+
+ pa_assert(s);
+ pa_assert(PA_REFCNT_VALUE(s) >= 1);
+
+ PA_CHECK_VALIDITY(s->context, !pa_detect_fork(), PA_ERR_FORKED);
+ PA_CHECK_VALIDITY(s->context, s->state == PA_STREAM_READY, PA_ERR_BADSTATE);
+ PA_CHECK_VALIDITY(s->context, s->direction == PA_STREAM_PLAYBACK || s->direction == PA_STREAM_UPLOAD, PA_ERR_BADSTATE);
+ PA_CHECK_VALIDITY(s->context, s->write_memblock, PA_ERR_BADSTATE);
+
+ pa_assert(s->write_data);
+
+ pa_memblock_release(s->write_memblock);
+ pa_memblock_unref(s->write_memblock);
+ s->write_memblock = NULL;
+ s->write_data = NULL;
+
+ return 0;
+}
+