BIO_FIND_TYPE(3)           Library Functions Manual           BIO_FIND_TYPE(3)

NAME
     BIO_find_type, BIO_next, BIO_method_type, BIO_method_name - BIO chain
     traversal

SYNOPSIS
     #include <openssl/bio.h>

     BIO *
     BIO_find_type(BIO *bio, int type);

     BIO *
     BIO_next(BIO *bio);

     int
     BIO_method_type(const BIO *bio);

     const char *
     BIO_method_name(const BIO *bio);

     #define BIO_TYPE_NONE         0
     #define BIO_TYPE_START        128

DESCRIPTION
     BIO_find_type() searches for a BIO matching the given type in the chain
     starting at bio.  If the least significant byte of the type argument is
     non-zero, only exact matches of the type are accepted.  Otherwise, a
     match only requires that any of the bits set in the type argument is also
     set in the candidate BIO.

     Types with a least significant byte in the range from 0 to
     BIO_TYPE_START, inclusive, are reserved for BIO types built into the
     library.  Types with a least significant byte greater than BIO_TYPE_START
     are available for user-defined BIO types; see BIO_get_new_index(3) for
     details.

     BIO_next() returns the next BIO in the chain after bio.  This function
     can be used to traverse all BIOs in a chain or in conjunction with
     BIO_find_type() to find all BIOs of a certain type.

     BIO_method_type() returns the type of the given bio.

     BIO_method_name() returns an ASCII string representing the type of the
     bio.

     The following are the built-in source/sink BIO types that operate on file
     descriptors.  They all have both of the bits BIO_TYPE_SOURCE_SINK and
     BIO_TYPE_DESCRIPTOR but not the bit BIO_TYPE_FILTER set in their type
     constant.

     type constant           name string        BIO_METHOD
     BIO_TYPE_ACCEPT         socket accept      BIO_s_accept(3)
     BIO_TYPE_CONNECT        socket connect     BIO_s_connect(3)
     BIO_TYPE_DGRAM          datagram socket    BIO_s_datagram(3)
     BIO_TYPE_FD             file descriptor    BIO_s_fd(3)
     BIO_TYPE_SOCKET         socket             BIO_s_socket(3)

     The following are the built-in source/sink BIO types that do not directly
     operate on file descriptors.  They all have the bit BIO_TYPE_SOURCE_SINK
     but not the bits BIO_TYPE_DESCRIPTOR and BIO_TYPE_FILTER set in their
     type constant.

     type constant           name string        BIO_METHOD
     BIO_TYPE_BIO            BIO pair           BIO_s_bio(3)
     BIO_TYPE_FILE           FILE pointer       BIO_s_file(3)
     BIO_TYPE_MEM            memory buffer      BIO_s_mem(3)
     BIO_TYPE_NULL           NULL               BIO_s_null(3)

     The following are the built-in filter BIO types.  They all have the bit
     BIO_TYPE_FILTER but not the bits BIO_TYPE_SOURCE_SINK and
     BIO_TYPE_DESCRIPTOR set in their type constant.

     type constant           name string        BIO_METHOD
     BIO_TYPE_BASE64         base64 encoding    BIO_f_base64(3)
     BIO_TYPE_BUFFER         buffer             BIO_f_buffer(3)
     BIO_TYPE_CIPHER         cipher             BIO_f_cipher(3)
     BIO_TYPE_MD             message digest     BIO_f_md(3)
     BIO_TYPE_NULL_FILTER    NULL filter        BIO_f_null(3)
     BIO_TYPE_SSL            ssl                BIO_f_ssl(3)

     The constants BIO_TYPE_BER, BIO_TYPE_PROXY_CLIENT, and
     BIO_TYPE_PROXY_SERVER do not correspond to any BIO types implemented by
     the library and are not intended to be used for application-defined
     types, either.  The constants BIO_TYPE_COMP, BIO_TYPE_LINEBUFFER, and
     BIO_TYPE_NBIO_TEST corresponds to a deprecated BIO types that are
     intentionally undocumented.

     If a variable in an application program is intended to store a BIO type
     but temporarily does not refer to any BIO or refers to a BIO of an
     unknown type, setting the variable to BIO_TYPE_NONE is recommended.

RETURN VALUES
     BIO_find_type() returns the next matching BIO or NULL if bio is a NULL
     pointer or if no matching BIO is found.

     BIO_next() returns the next BIO or NULL if bio is a NULL pointer or
     points to the last BIO in a chain.

     BIO_method_type() returns one of the BIO_TYPE_* constants.

     BIO_method_name() returns an internal pointer to a string.

EXAMPLES
     Traverse a chain looking for digest BIOs:

       BIO *btmp;

       btmp = in_bio;  /* in_bio is the chain to search through */
       while (btmp != NULL) {
               btmp = BIO_find_type(btmp, BIO_TYPE_MD);
               if (btmp == NULL)
                       break;  /* Not found */

               /* btmp is a digest BIO, do something with it ... */
               ...

               btmp = BIO_next(btmp);
       }

SEE ALSO
     BIO_meth_new(3), BIO_new(3)

HISTORY
     BIO_method_type() and BIO_method_name() first appeared in SSLeay 0.6.0.
     BIO_find_type() first appeared in SSLeay 0.6.6.  These functions have
     been available since OpenBSD 2.4.

     BIO_next() first appeared in OpenSSL 0.9.6 and has been available since
     OpenBSD 2.9.

Linux 6.8.2-arch2-1              July 26, 2023             Linux 6.8.2-arch2-1