✏ 编辑: BIO_find_type.3

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.\" ========================================================================
.\"
.IX Title "BIO_find_type 3"
.TH BIO_find_type 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
BIO_find_type, BIO_next, BIO_method_type \- BIO chain traversal
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
\&
\& BIO *  BIO_find_type(BIO *b,int bio_type);
\& BIO *  BIO_next(BIO *b);
\&
\& #define BIO_method_type(b)             ((b)\->method\->type)
\&
\& #define BIO_TYPE_NONE          0
\& #define BIO_TYPE_MEM           (1|0x0400)
\& #define BIO_TYPE_FILE          (2|0x0400)
\&
\& #define BIO_TYPE_FD            (4|0x0400|0x0100)
\& #define BIO_TYPE_SOCKET                (5|0x0400|0x0100)
\& #define BIO_TYPE_NULL          (6|0x0400)
\& #define BIO_TYPE_SSL           (7|0x0200)
\& #define BIO_TYPE_MD            (8|0x0200)
\& #define BIO_TYPE_BUFFER                (9|0x0200)
\& #define BIO_TYPE_CIPHER                (10|0x0200)
\& #define BIO_TYPE_BASE64                (11|0x0200)
\& #define BIO_TYPE_CONNECT       (12|0x0400|0x0100)
\& #define BIO_TYPE_ACCEPT                (13|0x0400|0x0100)
\& #define BIO_TYPE_PROXY_CLIENT  (14|0x0200)
\& #define BIO_TYPE_PROXY_SERVER  (15|0x0200)
\& #define BIO_TYPE_NBIO_TEST     (16|0x0200)
\& #define BIO_TYPE_NULL_FILTER   (17|0x0200)
\& #define BIO_TYPE_BER           (18|0x0200)
\& #define BIO_TYPE_BIO           (19|0x0400)
\&
\& #define BIO_TYPE_DESCRIPTOR    0x0100
\& #define BIO_TYPE_FILTER                0x0200
\& #define BIO_TYPE_SOURCE_SINK   0x0400
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fIBIO_find_type()\fR searches for a \s-1BIO\s0 of a given type in a chain, starting
at \s-1BIO \s0\fBb\fR. If \fBtype\fR is a specific type (such as \s-1BIO_TYPE_MEM\s0) then a search
is made for a \s-1BIO\s0 of that type. If \fBtype\fR is a general type (such as
\&\fB\s-1BIO_TYPE_SOURCE_SINK\s0\fR) then the next matching \s-1BIO\s0 of the given general type is
searched for. \fIBIO_find_type()\fR returns the next matching \s-1BIO\s0 or \s-1NULL\s0 if none is
found.
.PP
Note: not all the \fBBIO_TYPE_*\fR types above have corresponding \s-1BIO\s0 implementations.
.PP
\&\fIBIO_next()\fR returns the next \s-1BIO\s0 in a chain. It can be used to traverse all BIOs
in a chain or used in conjunction with \fIBIO_find_type()\fR to find all BIOs of a
certain type.
.PP
\&\fIBIO_method_type()\fR returns the type of a \s-1BIO.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIBIO_find_type()\fR returns a matching \s-1BIO\s0 or \s-1NULL\s0 for no match.
.PP
\&\fIBIO_next()\fR returns the next \s-1BIO\s0 in a chain.
.PP
\&\fIBIO_method_type()\fR returns the type of the \s-1BIO \s0\fBb\fR.
.SH "NOTES"
.IX Header "NOTES"
\&\fIBIO_next()\fR was added to OpenSSL 0.9.6 to provide a 'clean' way to traverse a \s-1BIO\s0
chain or find multiple matches using \fIBIO_find_type()\fR. Previous versions had to
use:
.PP
.Vb 1
\& next = bio\->next_bio;
.Ve
.SH "BUGS"
.IX Header "BUGS"
\&\fIBIO_find_type()\fR in OpenSSL 0.9.5a and earlier could not be safely passed a
\&\s-1NULL\s0 pointer for the \fBb\fR argument.
.SH "EXAMPLE"
.IX Header "EXAMPLE"
Traverse a chain looking for digest BIOs:
.PP
.Vb 2
\& BIO *btmp;
\& btmp = in_bio; /* in_bio is chain to search through */
\&
\& do {
\&        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);
\& } while(btmp);
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1TBA\s0

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