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bio(3) [redhat man page]

bio(3)								      OpenSSL								    bio(3)

bio - I/O abstraction SYNOPSIS
#include <openssl/bio.h> TBA DESCRIPTION
A BIO is an I/O abstraction, it hides many of the underlying I/O details from an application. If an application uses a BIO for its I/O it can transparently handle SSL connections, unencrypted network connections and file I/O. There are two type of BIO, a source/sink BIO and a filter BIO. As its name implies a source/sink BIO is a source and/or sink of data, examples include a socket BIO and a file BIO. A filter BIO takes data from one BIO and passes it through to another, or the application. The data may be left unmodified (for example a message digest BIO) or translated (for example an encryption BIO). The effect of a filter BIO may change according to the I/O operation it is performing: for example an encryption BIO will encrypt data if it is being written to and decrypt data if it is being read from. BIOs can be joined together to form a chain (a single BIO is a chain with one component). A chain normally consist of one source/sink BIO and one or more filter BIOs. Data read from or written to the first BIO then traverses the chain to the end (normally a source/sink BIO). SEE ALSO
BIO_ctrl(3), BIO_f_base64(3), BIO_f_buffer(3), BIO_f_cipher(3), BIO_f_md(3), BIO_f_null(3), BIO_f_ssl(3), BIO_find_type(3), BIO_new(3), BIO_new_bio_pair(3), BIO_push(3), BIO_read(3), BIO_s_accept(3), BIO_s_bio(3), BIO_s_connect(3), BIO_s_fd(3), BIO_s_file(3), BIO_s_mem(3), BIO_s_null(3), BIO_s_socket(3), BIO_set_callback(3), BIO_should_retry(3) 0.9.7a 2001-04-12 bio(3)

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BIO_push(3SSL)                                                        OpenSSL                                                       BIO_push(3SSL)

BIO_push, BIO_pop - add and remove BIOs from a chain. SYNOPSIS
#include <openssl/bio.h> BIO * BIO_push(BIO *b,BIO *append); BIO * BIO_pop(BIO *b); DESCRIPTION
The BIO_push() function appends the BIO append to b, it returns b. BIO_pop() removes the BIO b from a chain and returns the next BIO in the chain, or NULL if there is no next BIO. The removed BIO then becomes a single BIO with no association with the original chain, it can thus be freed or attached to a different chain. NOTES
The names of these functions are perhaps a little misleading. BIO_push() joins two BIO chains whereas BIO_pop() deletes a single BIO from a chain, the deleted BIO does not need to be at the end of a chain. The process of calling BIO_push() and BIO_pop() on a BIO may have additional consequences (a control call is made to the affected BIOs) any effects will be noted in the descriptions of individual BIOs. EXAMPLES
For these examples suppose md1 and md2 are digest BIOs, b64 is a base64 BIO and f is a file BIO. If the call: BIO_push(b64, f); is made then the new chain will be b64-chain. After making the calls BIO_push(md2, b64); BIO_push(md1, md2); the new chain is md1-md2-b64-f. Data written to md1 will be digested by md1 and md2, base64 encoded and written to f. It should be noted that reading causes data to pass in the reverse direction, that is data is read from f, base64 decoded and digested by md1 and md2. If the call: BIO_pop(md2); The call will return b64 and the new chain will be md1-b64-f data can be written to md1 as before. RETURN VALUES
BIO_push() returns the end of the chain, b. BIO_pop() returns the next BIO in the chain, or NULL if there is no next BIO. SEE ALSO
TBA 1.0.1e 2013-02-11 BIO_push(3SSL)

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