I'm trying to get rid of ap_get_client_block(), but I don't understand a few things. ap_get_client_block() asks for readbytes from the upstream filter. What happens if the filter returns less bytes (while there is still more data coming?) What happens if the filter returns more bytes than requested (e.g. because it uncompressed some data). After all the incoming filters all propogate a request for N bytes read to the core_in filter, which returns that exact number if it can. Now as the data flows up the filter chain its length may change. Does it mean that if the filter didn't return the exact amount asked for it's broken? Is that the case when it returns less data than requested? Or when it returns more data?
I'm trying to deal with the case where a user call wants N bytes and I've to give that exact number in a single call. I'm not sure whether I should buffer things if I've got too much data or on the opposite ask for more bbs if I don't have enough data. Are there any modules I can look at to learn from?
The doc for ap_get_brigade doesn't say anything about ap_get_brigade satisfying 'readbytes' argument.
/** * Get the current bucket brigade from the next filter on the filter * stack. The filter returns an apr_status_t value. If the bottom-most * filter doesn't read from the network, then ::AP_NOBODY_READ is returned. * The bucket brigade will be empty when there is nothing left to get. * @param filter The next filter in the chain * @param bucket The current bucket brigade. The original brigade passed * to ap_get_brigade() must be empty. * @param mode The way in which the data should be read * @param block How the operations should be performed * ::APR_BLOCK_READ, ::APR_NONBLOCK_READ * @param readbytes How many bytes to read from the next filter. */ AP_DECLARE(apr_status_t) ap_get_brigade(ap_filter_t *filter, apr_bucket_brigade *bucket, ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes);
What bothers me most is the case where a filter may return more data than it has been asked for in the AP_MODE_READBYTES mode. ap_get_client_block() doesn't deal with buffering such data and drops it on the floor. So it either has to be fixed to do the buffering or the filter spec (ap_get_brigade) needs to clearly state that no more than requested amount of data should be returned in the AP_MODE_READBYTES. And ap_get_client_block needs to assert if it gets more.
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