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.\" ========================================================================
.\"
.IX Title "BIO_f_buffer 3"
.TH BIO_f_buffer 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.
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.nh
.SH "NAME"
BIO_f_buffer \- buffering BIO
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/bio.h>
\&
\& BIO_METHOD * BIO_f_buffer(void);
\&
\& #define BIO_get_buffer_num_lines(b)    BIO_ctrl(b,BIO_C_GET_BUFF_NUM_LINES,0,NULL)
\& #define BIO_set_read_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,0)
\& #define BIO_set_write_buffer_size(b,size) BIO_int_ctrl(b,BIO_C_SET_BUFF_SIZE,size,1)
\& #define BIO_set_buffer_size(b,size)    BIO_ctrl(b,BIO_C_SET_BUFF_SIZE,size,NULL)
\& #define BIO_set_buffer_read_data(b,buf,num) BIO_ctrl(b,BIO_C_SET_BUFF_READ_DATA,num,buf)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fIBIO_f_buffer()\fR returns the buffering \s-1BIO\s0 method.
.PP
Data written to a buffering \s-1BIO\s0 is buffered and periodically written
to the next \s-1BIO\s0 in the chain. Data read from a buffering \s-1BIO\s0 comes from
an internal buffer which is filled from the next \s-1BIO\s0 in the chain.
Both \fIBIO_gets()\fR and \fIBIO_puts()\fR are supported.
.PP
Calling \fIBIO_reset()\fR on a buffering \s-1BIO\s0 clears any buffered data.
.PP
\&\fIBIO_get_buffer_num_lines()\fR returns the number of lines currently buffered.
.PP
\&\fIBIO_set_read_buffer_size()\fR, \fIBIO_set_write_buffer_size()\fR and \fIBIO_set_buffer_size()\fR
set the read, write or both read and write buffer sizes to \fBsize\fR. The initial
buffer size is \s-1DEFAULT_BUFFER_SIZE,\s0 currently 4096. Any attempt to reduce the
buffer size below \s-1DEFAULT_BUFFER_SIZE\s0 is ignored. Any buffered data is cleared
when the buffer is resized.
.PP
\&\fIBIO_set_buffer_read_data()\fR clears the read buffer and fills it with \fBnum\fR
bytes of \fBbuf\fR. If \fBnum\fR is larger than the current buffer size the buffer
is expanded.
.SH "NOTES"
.IX Header "NOTES"
Buffering BIOs implement \fIBIO_gets()\fR by using \fIBIO_read()\fR operations on the
next \s-1BIO\s0 in the chain. By prepending a buffering \s-1BIO\s0 to a chain it is therefore
possible to provide \fIBIO_gets()\fR functionality if the following BIOs do not
support it (for example \s-1SSL\s0 BIOs).
.PP
Data is only written to the next \s-1BIO\s0 in the chain when the write buffer fills
or when \fIBIO_flush()\fR is called. It is therefore important to call \fIBIO_flush()\fR
whenever any pending data should be written such as when removing a buffering
\&\s-1BIO\s0 using \fIBIO_pop()\fR. \fIBIO_flush()\fR may need to be retried if the ultimate
source/sink \s-1BIO\s0 is non blocking.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIBIO_f_buffer()\fR returns the buffering \s-1BIO\s0 method.
.PP
\&\fIBIO_get_buffer_num_lines()\fR returns the number of lines buffered (may be 0).
.PP
\&\fIBIO_set_read_buffer_size()\fR, \fIBIO_set_write_buffer_size()\fR and \fIBIO_set_buffer_size()\fR
return 1 if the buffer was successfully resized or 0 for failure.
.PP
\&\fIBIO_set_buffer_read_data()\fR returns 1 if the data was set correctly or 0 if
there was an error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fIBIO\s0\fR\|(3),
\&\fIBIO_reset\fR\|(3),
\&\fIBIO_flush\fR\|(3),
\&\fIBIO_pop\fR\|(3),
\&\fIBIO_ctrl\fR\|(3),
\&\fIBIO_int_ctrl\fR\|(3)