typedef char* KEY;

// gives a channel id
// path has to exist
// -1 on error
int ctok(char *path);

/// Channel creation
// first caller will create channel
// cid can be CHAN_PRIVATE, which will always be a unique cid 
// Function returns -1 on error
// Receiver will get private key, sender will get public key of sender
// The receiver call will never block but sender might block until  receiver
// calls the get function
CHANNEL chnget_sender(int cid);
CHANNEL chnget_receiver(int cid);

/// Closes a channel
// All subsequent reads or writes on this channel will fail
// (even those on the matching process)
void chan_close(CHANNEL c);

/// Send and receive on channel, note that only the sender side can send,
/// and vice versa
// Output on chan; will block until receiver receives data
int chan_out(CHANNEL c, char *buf, int size);
// Input from chan; will block until data is received
// options can be 0 which will fail if data is larger than size
// or CHAN_TRUNC that will truncate if message is larger
// size is always updated with size of message received
// -1 on error
int chan_in(CHANNEL, char *buf, int *size, int options);

// will block on multiple output channels, only one can succeed
// -1 on error
// will return channel number that unblocked the call (starting from 0)
int chanalt_out(const CHANNEL ca[], int chan_nos, char *buf, int size);
int chanalt_outl(char *buf, int size,int chan_nos, const CHANNEL c1,...);
// will block on multiple input channels, only one can succeed
// -1 on error
// options and size like chan_in
// will return channel number that unblocked the call (starting from 0)
int chanalt_in(const CHANNEL ca[], int chan_nos, char *buf, int *size, int options);
int chanalt_inl(char *buf, int* size, int options, int chan_nos, const CHANNEL c1,...);

// to be called to generate a new set of private and 
// public key
void generate(KEY *private,KEY *public);

// called with a key will encode or decode your buffer
void code(char *buf,int size,KEY key);