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Revision as of 21:39, 31 October 2014 by Philippe lhardy (talk | contribs) (Combining Filters and Source Sink BIOs)

A BIO is an I/O stream abstraction; essentially OpenSSL's answer to the C library's FILE *. OpenSSL comes with a number of useful BIO types predefined, or you can create your own.

BIOs come in two flavors: source/sink, or filter. BIOs can be chained together. Each chain always has exactly one source/sink, but can have any number (zero or more) of filters.

Reading from a BIO can be done with Manual:BIO_read(3) and BIO_gets.

Writing to a BIO can be done with BIO_write, BIO_puts, BIO_printf, and BIO_vprintf.

Filter BIOs

Source/sink BIOs

implementation of those bio are within bio/bss_xxx.c bss stading for Bio Source Sink

Combining Filters and Source Sink BIOs

new_head = BIO_push(BIO * local_head, BIO * tail)

will connect tail at end of local_head chain.

WARNING BIO_push will never fail, but can create invalid chains.

In standard usage end of a chain is a source sink, and all other elements are filters.