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1 .\" $OpenBSD: BIO_f_buffer.3,v 1.6 2016/12/06 12:24:33 schwarze Exp $
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52 .Dd $Mdocdate: December 6 2016 $
53 .Dt BIO_F_BUFFER 3
54 .Os
55 .Sh NAME
56 .Nm BIO_f_buffer ,
57 .Nm BIO_get_buffer_num_lines ,
58 .Nm BIO_set_read_buffer_size ,
59 .Nm BIO_set_write_buffer_size ,
60 .Nm BIO_set_buffer_size ,
61 .Nm BIO_set_buffer_read_data
62 .Nd buffering BIO
63 .Sh SYNOPSIS
64 .In openssl/bio.h
65 .Ft BIO_METHOD *
66 .Fo BIO_f_buffer
67 .Fa void
68 .Fc
69 .Ft long
70 .Fo BIO_get_buffer_num_lines
71 .Fa "BIO *b"
72 .Fc
73 .Ft long
74 .Fo BIO_set_read_buffer_size
75 .Fa "BIO *b"
76 .Fa "long size"
77 .Fc
78 .Ft long
79 .Fo BIO_set_write_buffer_size
80 .Fa "BIO *b"
81 .Fa "long size"
82 .Fc
83 .Ft long
84 .Fo BIO_set_buffer_size
85 .Fa "BIO *b"
86 .Fa "long size"
87 .Fc
88 .Fo BIO_set_buffer_read_data
89 .Fa "BIO *b"
90 .Fa "void *buf"
91 .Fa "long num"
92 .Fc
93 .Sh DESCRIPTION
94 .Fn BIO_f_buffer
95 returns the buffering BIO method.
96 .Pp
97 Data written to a buffering BIO is buffered and periodically written
98 to the next BIO in the chain.
99 Data read from a buffering BIO comes from an internal buffer
100 which is filled from the next BIO in the chain.
101 Both
102 .Xr BIO_gets 3
103 and
104 .Xr BIO_puts 3
105 are supported.
106 .Pp
107 Calling
108 .Xr BIO_reset 3
109 on a buffering BIO clears any buffered data.
110 .Pp
111 .Fn BIO_get_buffer_num_lines
112 returns the number of lines currently buffered.
113 .Pp
114 .Fn BIO_set_read_buffer_size ,
115 .Fn BIO_set_write_buffer_size ,
116 and
117 .Fn BIO_set_buffer_size
118 set the read, write or both read and write buffer sizes to
119 .Fa size .
120 The initial buffer size is
121 .Dv DEFAULT_BUFFER_SIZE ,
122 currently 4096.
123 Any attempt to reduce the buffer size below
124 .Dv DEFAULT_BUFFER_SIZE
125 is ignored.
126 Any buffered data is cleared when the buffer is resized.
127 .Pp
128 .Fn BIO_set_buffer_read_data
129 clears the read buffer and fills it with
130 .Fa num
131 bytes of
132 .Fa buf .
133 If
134 .Fa num
135 is larger than the current buffer size the buffer is expanded.
136 .Pp
137 Except
138 .Fn BIO_f_buffer ,
139 these functions are implemented as macros.
140 .Pp
141 Buffering BIOs implement
142 .Xr BIO_gets 3
143 by using
144 .Xr BIO_read 3
145 operations on the next BIO in the chain.
146 By prepending a buffering BIO to a chain
147 it is therefore possible to provide the functionality of
148 .Xr BIO_gets 3
149 if the following BIOs do not support it (for example SSL BIOs).
150 .Pp
151 Data is only written to the next BIO in the chain
152 when the write buffer fills or when
153 .Xr BIO_flush 3
154 is called.
155 It is therefore important to call
156 .Xr BIO_flush 3
157 whenever any pending data should be written
158 such as when removing a buffering BIO using
159 .Xr BIO_pop 3 .
160 .Xr BIO_flush 3
161 may need to be retried if the ultimate source/sink BIO is non-blocking.
162 .Sh RETURN VALUES
163 .Fn BIO_f_buffer
164 returns the buffering BIO method.
165 .Pp
166 .Fn BIO_get_buffer_num_lines
167 returns the number of lines buffered (may be 0).
168 .Pp
169 .Fn BIO_set_read_buffer_size ,
170 .Fn BIO_set_write_buffer_size ,
171 and
172 .Fn BIO_set_buffer_size
173 return 1 if the buffer was successfully resized or 0 for failure.
174 .Pp
175 .Fn BIO_set_buffer_read_data
176 returns 1 if the data was set correctly or 0 if there was an error.
177 .Sh SEE ALSO
178 .Xr BIO_ctrl 3 ,
179 .Xr BIO_flush 3 ,
180 .Xr BIO_new 3 ,
181 .Xr BIO_pop 3 ,
182 .Xr BIO_reset 3