What is the recommended way of using libssh2 to implement the “read data from whichever channel has it first” primitive? E.g. I have a simple two-tab terminal program, where each tab corresponds to a LIBSSH2 channel. I want to wait until ANY of the 2 channels gets data and then print it.
The single-channel examples use libssh2_channel_read() in a non-blocking way like this:
while(not done) {
1. Try reading with libssh2_channel_read()
2. If returned LIBSSH2_ERROR_EAGAIN, wait with select()
}
The trivial way of extending this to two-channel case would be:
while(not done) {
1. Try reading channel 1
2. Try reading channel 2
3. If BOTH channels returned LIBSSH2_ERROR_EAGAIN, wait with select()
}
This leads to a rare bug when a packet with some data for channel 1 arrives just before reading channel 2. Then both calls return LIBSSH2_ERROR_EAGAIN, but as the attempt to read channel 2 actually recv()’d the data for channel 1, select() will now hang.
The workaround I am currently employing involves keeping raw data counters for the socket and using them to determine if any new data was consumed by libssh2, but I get the feeling of making a really complex workaround for a fairly simple problem. Am I missing something? Is there some kind of libssh2_session_read_any_channel()?
