BIO

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 BIO_read and BIO_gets.

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

Filter BIOs

• BIO_f_base64
• BIO_f_buffer
• BIO_f_cipher
• BIO_f_md
• BIO_f_ssl

Source/sink BIOs

• BIO_s_accept
• BIO_s_bio
• BIO_s_connect
• BIO_s_fd
• BIO_s_file
• BIO_s_mem
• BIO_s_null
• BIO_s_socket