phpMan > man > Data::Buffer(3pm)

NAME
    Data::Buffer - Read/write buffer class

SYNOPSIS
        use Data::Buffer;
        my $buffer = Data::Buffer->new;

        ## Add a 32-bit integer.
        $buffer->put_int32(10932930);

        ## Get it back.
        my $int = $buffer->get_int32;

DESCRIPTION
    *Data::Buffer* implements a low-level binary buffer in which you can get and put integers,
    strings, and other data. Internally the implementation is based on "pack" and "unpack", such
    that *Data::Buffer* is really a layer on top of those built-in functions.

    All of the *get_** and *put_** methods respect the internal offset state in the buffer object.
    This means that you should read data out of the buffer in the same order that you put it in. For
    example:

        $buf->put_int16(24);
        $buf->put_int32(1233455);
        $buf->put_int16(99);

        $buf->get_int16;   # 24
        $buf->get_int32;   # 1233455
        $buf->get_int16;   # 99

    Of course, this assumes that you *know* the order of the data items in the buffer. If your setup
    is such that your sending and receiving processes won't necessarily know what's inside the
    buffers they receive, take a look at the *TEMPLATE USAGE* section.

USAGE
  Data::Buffer->new
    Creates a new buffer object and returns it. The buffer is initially empty.

    This method takes no arguments.

  Data::Buffer->new_with_init(@strs)
    Creates a new buffer object and appends to it each of the octet strings in *@strs*.

    Returns the new buffer object.

  $buffer->get_int8
    Returns the next 8-bit integer from the buffer (which is really just the ASCII code for the next
    character/byte in the buffer).

  $buffer->put_int8
    Appends an 8-bit integer to the buffer (which is really just the character corresponding to that
    integer, in ASCII).

  $buffer->get_int16
    Returns the next 16-bit integer from the buffer.

  $buffer->put_int16($integer)
    Appends a 16-bit integer to the buffer.

  $buffer->get_int32
    Returns the next 32-bit integer from the buffer.

  $buffer->put_int32($integer)
    Appends a 32-bit integer to the buffer.

  $buffer->get_char
    More appropriately called *get_byte*, perhaps, this returns the next byte from the buffer.

  $buffer->put_char($bytes)
    Appends a byte (or a sequence of bytes) to the buffer. There is no restriction on the length of
    the byte string *$bytes*; if it makes you uncomfortable to call *put_char* to put multiple
    bytes, you can instead call this method as *put_chars*. It's the same thing.

  $buffer->get_bytes($n)
    Grabs *$n* bytes from the buffer, where *$n* is a positive integer. Increments the internal
    offset state by *$n*.

  $buffer->put_bytes($bytes [, $n ])
    Appends a sequence of bytes to the buffer; if *$n* is unspecified, appends the entire length of
    *$bytes*. Otherwise appends only the first *$n* bytes of *$bytes*.

  $buffer->get_str
    Returns the next "string" from the buffer. A string here is represented as the length of the
    string (a 32-bit integer) followed by the string itself.

  $buffer->put_str($string)
    Appends a string (32-bit integer length and the string itself) to the buffer.

  $buffer->extract($n)
    Extracts the next *$n* bytes from the buffer *$buffer*, increments the offset state in
    *$buffer*, and returns a new buffer object containing the extracted bytes.

TEMPLATE USAGE
    Generally when you use *Data::Buffer* it's to communicate with another process (perhaps a C
    program) that bundles up its data into binary buffers. In those cases, it's very likely that the
    data will be in some well-known order in the buffer: in other words, it might be documented that
    a certain C program creates a buffer containing:

    *   an int8

    *   a string

    *   an int32

    In this case, you would presumably know about the order of the data in the buffer, and you could
    extract it accordingly:

        $buffer->get_int8;
        $buffer->get_str;
        $buffer->get_int32;

    In other cases, however, there may not be a well-defined order of data items in the buffer. This
    might be the case if you're inventing your own protocol, and you want your binary buffers to
    "know" about their contents. In this case, you'll want to use the templating features of
    *Data::Buffer*.

    When you use the *put_* methods to place data in a buffer, *Data::Buffer* keeps track of the
    types of data that you're inserting in a template description of the buffer. This template
    contains all of the information necessary for a process to receive a buffer and extract the data
    in the buffer without knowledge of the order of the items.

    To use this feature, simply use the *insert_template* method after you've filled your buffer to
    completion. For example:

        my $buffer = Data::Buffer->new;
        $buffer->put_str("foo");
        $buffer->put_int32(9999);
        $buffer->insert_template;

        ## Ship off the buffer to another process.

    The receiving process should then invoke the *get_all* method on the buffer to extract all of
    the data:

        my $buffer = Data::Buffer->new;
        $buffer->append( $received_buffer_data );
        my @data = $buffer->get_all;

    @data will now contain two elements: "foo" and 9999.

LOW-LEVEL METHODS
  $buffer->append($bytes)
    Appends raw data *$bytes* to the end of the in-memory buffer. Generally you don't need to use
    this method unless you're initializing an empty buffer, because when you need to add data to a
    buffer you should generally use one of the *put_** methods.

  $buffer->empty
    Empties out the buffer object.

  $buffer->bytes([ $offset [, $length [, $replacement ]]])
    Behaves exactly like the *substr* built-in function, except on the buffer *$buffer*. Given no
    arguments, *bytes* returns the entire buffer; given one argument *$offset*, returns everything
    from that position to the end of the string; given *$offset* and *$length*, returns the segment
    of the buffer starting at *$offset* and consisting of *$length* bytes; and given all three
    arguments, replaces that segment with *$replacement*.

    This is a very low-level method, and you generally won't need to use it.

    Also be warned that you should not intermix use of this method with use of the *get_** and
    *put_** methods; the latter classes of methods maintain internal state of the buffer offset
    where arguments will be gotten from and put, respectively. The *bytes* method gives no thought
    to this internal offset state.

  $buffer->length
    Returns the length of the buffer object.

  $buffer->offset
    Returns the internal offset state.

    If you insist on intermixing calls to *bytes* with calls to the *get_** and *put_** methods,
    you'll probably want to use this method to get some status on that internal offset.

  $buffer->set_offset($offset)
    Sets the internal offset state to *$offset*.

  $buffer->reset_offset
    Sets the internal offset state to 0.

  $buffer->dump(@args)
    Returns a hex dump of the buffer. The dump is of the *entire* buffer *$buffer*; in other words,
    *dump* doesn't respect the internal offset pointer.

    *@args* is passed directly through to the *bytes* method, which means that you can supply
    arguments to emulate support of the internal offset:

        my $dump = $buffer->dump($buffer->offset);

  $buffer->insert_padding
    A helper method: pads out the buffer so that the length of the transferred packet will be evenly
    divisible by 8, which is a requirement of the SSH protocol.

AUTHOR & COPYRIGHTS
    Benjamin Trott, ben AT rhumba.com

    Except where otherwise noted, Data::Buffer is Copyright 2001 Benjamin Trott. All rights
    reserved. Data::Buffer is free software; you may redistribute it and/or modify it under the same
    terms as Perl itself.