1Buffer(3) User Contributed Perl Documentation Buffer(3)
2
6 Data::Buffer - Read/write buffer class
7
9 use Data::Buffer;
10 my $buffer = Data::Buffer->new;
11 ## Add a 32-bit integer.
13 $buffer->put_int32(10932930);
14 ## Get it back.
16 my $int = $buffer->get_int32;
17
19 Data::Buffer implements a low-level binary buffer in which you can get
20 and put integers, strings, and other data. Internally the
21 implementation is based on "pack" and "unpack", such that Data::Buffer
22 is really a layer on top of those built-in functions.
23 All of the get_* and put_* methods respect the internal offset state in
25 the buffer object. This means that you should read data out of the
26 buffer in the same order that you put it in. For example:
27 $buf->put_int16(24);
29 $buf->put_int32(1233455);
30 $buf->put_int16(99);
31 $buf->get_int16; # 24
33 $buf->get_int32; # 1233455
34 $buf->get_int16; # 99
35 Of course, this assumes that you know the order of the data items in
37 the buffer. If your setup is such that your sending and receiving
38 processes won't necessarily know what's inside the buffers they
39 receive, take a look at the TEMPLATE USAGE section.
40
42 Data::Buffer->new
43 Creates a new buffer object and returns it. The buffer is initially
44 empty.
45 This method takes no arguments.
47 Data::Buffer->new_with_init(@strs)
49 Creates a new buffer object and appends to it each of the octet strings
50 in @strs.
51 Returns the new buffer object.
53 $buffer->get_int8
55 Returns the next 8-bit integer from the buffer (which is really just
56 the ASCII code for the next character/byte in the buffer).
57 $buffer->put_int8
59 Appends an 8-bit integer to the buffer (which is really just the
60 character corresponding to that integer, in ASCII).
61 $buffer->get_int16
63 Returns the next 16-bit integer from the buffer.
64 $buffer->put_int16($integer)
66 Appends a 16-bit integer to the buffer.
67 $buffer->get_int32
69 Returns the next 32-bit integer from the buffer.
70 $buffer->put_int32($integer)
72 Appends a 32-bit integer to the buffer.
73 $buffer->get_char
75 More appropriately called get_byte, perhaps, this returns the next byte
76 from the buffer.
77 $buffer->put_char($bytes)
79 Appends a byte (or a sequence of bytes) to the buffer. There is no
80 restriction on the length of the byte string $bytes; if it makes you
81 uncomfortable to call put_char to put multiple bytes, you can instead
82 call this method as put_chars. It's the same thing.
83 $buffer->get_bytes($n)
85 Grabs $n bytes from the buffer, where $n is a positive integer.
86 Increments the internal offset state by $n.
87 $buffer->put_bytes($bytes [, $n ])
89 Appends a sequence of bytes to the buffer; if $n is unspecified,
90 appends the entire length of $bytes. Otherwise appends only the first
91 $n bytes of $bytes.
92 $buffer->get_str
94 Returns the next "string" from the buffer. A string here is represented
95 as the length of the string (a 32-bit integer) followed by the string
96 itself.
97 $buffer->put_str($string)
99 Appends a string (32-bit integer length and the string itself) to the
100 buffer.
101 $buffer->extract($n)
103 Extracts the next $n bytes from the buffer $buffer, increments the
104 offset state in $buffer, and returns a new buffer object containing the
105 extracted bytes.
106
108 Generally when you use Data::Buffer it's to communicate with another
109 process (perhaps a C program) that bundles up its data into binary
110 buffers. In those cases, it's very likely that the data will be in some
111 well-known order in the buffer: in other words, it might be documented
112 that a certain C program creates a buffer containing:
113 · an int8
115 · a string
117 · an int32
119 In this case, you would presumably know about the order of the data in
121 the buffer, and you could extract it accordingly:
122 $buffer->get_int8;
124 $buffer->get_str;
125 $buffer->get_int32;
126 In other cases, however, there may not be a well-defined order of data
128 items in the buffer. This might be the case if you're inventing your
129 own protocol, and you want your binary buffers to "know" about their
130 contents. In this case, you'll want to use the templating features of
131 Data::Buffer.
132 When you use the put_ methods to place data in a buffer, Data::Buffer
134 keeps track of the types of data that you're inserting in a template
135 description of the buffer. This template contains all of the
136 information necessary for a process to receive a buffer and extract the
137 data in the buffer without knowledge of the order of the items.
138 To use this feature, simply use the insert_template method after you've
140 filled your buffer to completion. For example:
141 my $buffer = Data::Buffer->new;
143 $buffer->put_str("foo");
144 $buffer->put_int32(9999);
145 $buffer->insert_template;
146 ## Ship off the buffer to another process.
148 The receiving process should then invoke the get_all method on the
150 buffer to extract all of the data:
151 my $buffer = Data::Buffer->new;
153 $buffer->append( $received_buffer_data );
154 my @data = $buffer->get_all;
155 @data will now contain two elements: "foo" and 9999.
157
159 $buffer->append($bytes)
160 Appends raw data $bytes to the end of the in-memory buffer. Generally
161 you don't need to use this method unless you're initializing an empty
162 buffer, because when you need to add data to a buffer you should
163 generally use one of the put_* methods.
164 $buffer->empty
166 Empties out the buffer object.
167 $buffer->bytes([ $offset [, $length [, $replacement ]]])
169 Behaves exactly like the substr built-in function, except on the buffer
170 $buffer. Given no arguments, bytes returns the entire buffer; given one
171 argument $offset, returns everything from that position to the end of
172 the string; given $offset and $length, returns the segment of the
173 buffer starting at $offset and consisting of $length bytes; and given
174 all three arguments, replaces that segment with $replacement.
175 This is a very low-level method, and you generally won't need to use
177 it.
178 Also be warned that you should not intermix use of this method with use
180 of the get_* and put_* methods; the latter classes of methods maintain
181 internal state of the buffer offset where arguments will be gotten from
182 and put, respectively. The bytes method gives no thought to this
183 internal offset state.
184 $buffer->length
186 Returns the length of the buffer object.
187 $buffer->offset
189 Returns the internal offset state.
190 If you insist on intermixing calls to bytes with calls to the get_* and
192 put_* methods, you'll probably want to use this method to get some
193 status on that internal offset.
194 $buffer->set_offset($offset)
196 Sets the internal offset state to $offset.
197 $buffer->reset_offset
199 Sets the internal offset state to 0.
200 $buffer->dump(@args)
202 Returns a hex dump of the buffer. The dump is of the entire buffer
203 $buffer; in other words, dump doesn't respect the internal offset
204 pointer.
205 @args is passed directly through to the bytes method, which means that
207 you can supply arguments to emulate support of the internal offset:
208 my $dump = $buffer->dump($buffer->offset);
210 $buffer->insert_padding
212 A helper method: pads out the buffer so that the length of the
213 transferred packet will be evenly divisible by 8, which is a
214 requirement of the SSH protocol.
215
217 Benjamin Trott, ben@rhumba.pair.com
218 Except where otherwise noted, Data::Buffer is Copyright 2001 Benjamin
220 Trott. All rights reserved. Data::Buffer is free software; you may
221 redistribute it and/or modify it under the same terms as Perl itself.
222perl v5.30.1 2020-01-29 Buffer(3)