struct bio_st
{
BIO_METHOD *method;
/* bio, mode, argp, argi, argl, ret */
long (*callback)(struct bio_st *,int,const char *,int, long,long);
char *cb_arg; /* first argument for the callback */
int init;
int shutdown;
int flags; /* extra storage */
int retry_reason;
int num;
void *ptr;
struct bio_st *next_bio; /* used by filter BIOs */
struct bio_st *prev_bio; /* used by filter BIOs */
int references;
unsigned long num_read;
unsigned long num_write;
CRYPTO_EX_DATA ex_data;
};