# nghttp2_session_set_local_window_size

## Synopsis

#include <nghttp2/nghttp2.h>

int nghttp2_session_set_local_window_size(nghttp2_session *session, uint8_t flags, int32_t stream_id, int32_t window_size)

  Set local window size (local endpoints's window size) to the given window_size for the given stream denoted by stream_id. To change connection level window size, specify 0 to stream_id. To increase window size, this function may submit WINDOW_UPDATE frame to transmission queue.

  The flags is currently ignored and should be `nghttp2_flag.NGHTTP2_FLAG_NONE`.

  This sounds similar to `nghttp2_submit_window_update()`, but there are 2 differences. The first difference is that this function takes the absolute value of window size to set, rather than the delta. To change the window size, this may be easier to use since the application just declares the intended window size, rather than calculating delta. The second difference is that `nghttp2_submit_window_update()` affects the received bytes count which has not acked yet. By the specification of `nghttp2_submit_window_update()`, to strictly increase the local window size, we have to submit delta including all received bytes count, which might not be desirable in some cases. On the other hand, this function does not affect the received bytes count. It just sets the local window size to the given value.

  This function returns 0 if it succeeds, or one of the following negative error codes:

  `nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`

    The stream_id is negative.

  `nghttp2_error.NGHTTP2_ERR_NOMEM`

    Out of memory.