/* delimited, authenticated, encrypted connection */
enum {
       Maxmsg  = 4096,         /* messages > Maxmsg bytes are truncated */
};

typedef struct SConn SConn;
struct SConn {
       void    *chan;
       int     secretlen;
       int     (*secret)(SConn*, uchar*, int);
       int     (*read)(SConn*, uchar*, int); /* <0 if error; errmess in buffer */
       int     (*write)(SConn*, uchar*, int);
       void    (*free)(SConn*);        /* also closes file descriptor */
};

SConn *newSConn(int);                   /* arg is open file descriptor */

/*
* secret(s,b,dir) sets secret for digest, encrypt, using the secretlen
*              bytes in b to form keys         for the two directions;
*        set dir=0 in client, dir=1 in server
*/

/* error convention: write !message in-band */
void    writerr(SConn*, char*);

/*
* returns -1 upon error, with error message in buf
* call with buf of size Maxmsg+1
*/
int     readstr(SConn*, char*);

void    *emalloc(ulong);                /* dies on failure; clears memory */
void    *erealloc(void*, ulong);
char    *estrdup(char*);