|BIO_READ(3)||Library Functions Manual||BIO_READ(3)|
BIO_puts — BIO I/O
void *buf, int len);
char *buf, int size);
const void *buf, int len);
const char *buf);
BIO_read() attempts to read
len bytes from BIO b and places
the data in buf.
BIO_gets() performs the BIOs
"gets" operation and places the data in buf.
Usually this operation will attempt to read a line of data from the BIO of
maximum length len - 1. There
are exceptions to this however, for example
BIO_gets() on a digest BIO will calculate and return
the digest and other BIOs may not support
at all. The returned string is always NUL-terminated.
BIO_write() attempts to write
len bytes from buf to BIO
BIO_puts() attempts to write a null
terminated string buf to BIO
One technique sometimes used with blocking sockets is to use a
system call (such as select(2),
poll(2) or equivalent) to determine when
data is available and then call read(2) to
read the data. The equivalent with BIOs (that is call
select(2) on the underlying I/O structure
and then call
BIO_read() to read the data) should
not be used because a single call to
BIO_read() can cause several reads (and writes in
the case of SSL BIOs) on the underlying I/O structure and may block as a
result. Instead select(2) (or equivalent)
should be combined with non-blocking I/O so successive reads will request a
retry instead of blocking.
See BIO_should_retry(3) for details of how to determine the cause of a retry and other I/O issues.
BIO_gets() function is not
supported by a BIO then it is possible to work around this by adding a
buffering BIO BIO_f_buffer(3) to
All these functions return either the amount of data successfully
read or written (if the return value is positive) or that no data was
successfully read or written if the result is 0 or -1. If the return value
is -2, then the operation is not implemented in the specific BIO type. The
trailing NUL is not included in the length returned by
A 0 or -1 return is not necessarily an indication of an error. In particular when the source/sink is non-blocking or of a certain type it may merely be an indication that no data is currently available and that the application should retry the operation later.
BIO_puts() first appeared in SSLeay 0.6.0 and have
been available since OpenBSD 2.4.
|March 27, 2018||OpenBSD-current|