Tavin Cole > MySQL-Packet-0.2007054 > MySQL::Packet

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Module Version: 0.2007054   Source  

NAME ^

MySQL::Packet - encode and decode the MySQL binary protocol

VERSION ^

Version 0.2007054

SYNOPSIS ^

Sorry for the absurdly verbose synopsis. I don't have a proper example script for you at the moment.

    use MySQL::Packet qw(:debug);           # dumping packet contents etc.
    use MySQL::Packet qw(:test :decode);    # decoding subs
    use MySQL::Packet qw(:encode);          # encoding subs

    use MySQL::Packet qw(:COM :CLIENT :SERVER);     # constants

    my $packet;
    my $greeting;
    my $result;
    my $field_end;

    my $mysql_socket = whatever_i_do_to_connect();

    while (read $mysql_socket, $_, 1000, length) {
        if (not $packet) {
            my $_packet = {};
            my $rc = mysql_decode_header $_packet;
            if ($rc < 0) {
                die 'bad header';
            }
            elsif ($rc > 0) {
                $packet = $_packet;
                redo;
            }
        }
        elsif (not $greeting) {
            my $rc = mysql_decode_greeting $_packet;
            if ($rc < 0) {
                die 'bad greeting';
            }
            elsif ($rc > 0) {
                mysql_debug_packet $packet;
                $greeting = $packet;
                undef $packet;
                send_client_auth();
                redo;
            }
        }
        elsif (not $result) {
            my $rc = mysql_decode_result $packet;
            if ($rc < 0) {
                die 'bad result';
            }
            elsif ($rc > 0) {
                mysql_debug_packet $packet;
                if ($packet->{error}) {
                    die 'the server hates me';
                }
                elsif ($packet->{end}) {
                    die 'this should never happen';
                }
                else {
                    if ($packet->{field_count}) {
                        $result = $packet;
                        # fields and rows to come
                    }
                    elsif (not $packet->{server_status} & SERVER_MORE_RESULTS_EXISTS) {
                        # that's that..
                        send_some_query();
                    }
                }
                undef $packet;
                redo;
            }
        }
        elsif (not $field_end) {
            my $rc = do {
                (mysql_test_var $packet}) ? (mysql_decode_field $packet)
                                          : (mysql_decode_result $packet)
            };
            if ($rc < 0) {
                die 'bad field packet';
            }
            elsif ($rc > 0) {
                mysql_debug_packet $packet;
                if ($packet->{error}) {
                    die 'the server hates me';
                }
                elsif ($packet->{end}) {
                    $field_end = $packet;
                }
                else {
                    do_something_with_field_metadata($packet);
                }
                undef $packet;
                redo;
            }
        }
        else {
            my $rc = do {
                (mysql_test_var $packet ? (mysql_decode_row $packet)
                                        : (mysql_decode_result $packet)
            };
            if ($rc < 0) {
                die 'bad row packet';
            }
            elsif ($rc > 0) {
                mysql_debug_packet $packet;
                if ($packet->{error}) {
                    die 'the server hates me';
                }
                elsif ($packet->{end}) {
                    undef $result;
                    undef $field_end;
                    unless ($packet->{server_status} & SERVER_MORE_RESULTS_EXISTS) {
                        # that's that..
                        send_some_query();
                    }
                }
                else {
                    my @row = @{ $packet->{row} };
                    do_something_with_row_data(@row);
                }
                undef $packet;
                redo;
            }
        }
    }

    sub send_client_auth {
        my $flags = CLIENT_LONG_PASSWORD | CLIENT_LONG_FLAG | CLIENT_PROTOCOL_41 | CLIENT_TRANSACTIONS | CLIENT_SECURE_CONNECTION;
        $flags |= CLIENT_CONNECT_WITH_DB if $i_want_to;
        my $pw_crypt = mysql_crypt 'my_password', $greeting->{crypt_seed};
        my $packet_body = mysql_encode_client_auth (
            $flags,                                 # $client_flags
            0x01000000,                             # $max_packet_size
            $greeting->{server_lang},               # $charset_no
            'my_username',                          # $username
            $pw_crypt,                              # $pw_crypt
            'my_database',                          # $database
        );
        my $packet_head = mysql_encode_header $packet_body, 1;
        print $mysql_socket $packet_head, $packet_body;
    }

    sub send_some_query {
        my $packet_body = mysql_encode_com_query 'SELECT * FROM foo';
        my $packet_head = mysql_encode_header $packet_body;
        print $mysql_socket $packet_head, $packet_body;
    }

DESCRIPTION ^

This module exports various functions for encoding and decoding binary packets pertinent to the MySQL client/server protocol. It also exports some useful constants. It does NOT wrap an IO::Socket handle for you.

This is ALPHA code. It currently groks only the new v4.1+ protocol. It currently handles only authentication, the COM_QUERY and COM_QUIT commands, and the associated server responses. In other words, just enough to send plain SQL and get the results.

For what it does, it seems to be quite stable, by my own yardstick.

This module should eventually grow to support statement prepare and execute, the pre-v4.1 protocol, compression, and so on.

EXPORTABLE CONSTANTS ^

Commands (Tag :COM)

    COM_SLEEP
    COM_QUIT
    COM_INIT_DB
    COM_QUERY
    COM_FIELD_LIST
    COM_CREATE_DB
    COM_DROP_DB
    COM_REFRESH
    COM_SHUTDOWN
    COM_STATISTICS
    COM_PROCESS_INFO
    COM_CONNECT
    COM_PROCESS_KILL
    COM_DEBUG
    COM_PING
    COM_TIME
    COM_DELAYED_INSERT
    COM_CHANGE_USER
    COM_BINLOG_DUMP
    COM_TABLE_DUMP
    COM_CONNECT_OUT
    COM_REGISTER_SLAVE
    COM_STMT_PREPARE
    COM_STMT_EXECUTE
    COM_STMT_SEND_LONG_DATA
    COM_STMT_CLOSE
    COM_STMT_RESET
    COM_SET_OPTION
    COM_STMT_FETCH

Client Flags / Server Capabilities (Tag :CLIENT)

    CLIENT_LONG_PASSWORD
    CLIENT_FOUND_ROWS
    CLIENT_LONG_FLAG
    CLIENT_CONNECT_WITH_DB
    CLIENT_NO_SCHEMA
    CLIENT_COMPRESS
    CLIENT_ODBC
    CLIENT_LOCAL_FILES
    CLIENT_IGNORE_SPACE
    CLIENT_PROTOCOL_41
    CLIENT_INTERACTIVE
    CLIENT_SSL
    CLIENT_IGNORE_SIGPIPE
    CLIENT_TRANSACTIONS
    CLIENT_RESERVED
    CLIENT_SECURE_CONNECTION
    CLIENT_MULTI_STATEMENTS
    CLIENT_MULTI_RESULTS

Server Status Flags (Tag :SERVER)

    SERVER_STATUS_IN_TRANS
    SERVER_STATUS_AUTOCOMMIT
    SERVER_MORE_RESULTS_EXISTS
    SERVER_QUERY_NO_GOOD_INDEX_USED
    SERVER_QUERY_NO_INDEX_USED
    SERVER_STATUS_CURSOR_EXISTS
    SERVER_STATUS_LAST_ROW_SENT
    SERVER_STATUS_DB_DROPPED
    SERVER_STATUS_NO_BACKSLASH_ESCAPES

EXPORTABLE FUNCTIONS ^

Debugging (Tag :debug)

mysql_debug_packet \%packet
mysql_debug_packet \%packet, $file_handle

Dumps a textual representation of the packet to STDERR or the given handle.

Packet Type Tests (Tag :test)

These functions operate on $_ if no data argument is given. They must be used only after "mysql_decode_header" has succeeded.

$bool = mysql_test_var \%packet;
$bool = mysql_test_var \%packet, $data

Returns true if the data encodes a variable-length binary number or string.

$bool = mysql_test_end \%packet
$bool = mysql_test_end \%packet, $data

Returns true if the data is an end packet (often called EOF packet).

$bool = mysql_test_error \%packet
$bool = mysql_test_error \%packet, $data

Returns true if the data is an error packet.

Decoding Packets (Tag :decode)

These functions take either a hash reference (to be populated with packet information), or a scalar (to receive a number or string). The optional second argument is always the data to decode. If omitted, $_ is used instead, and bytes are consumed from the beginning of $_ as it is processed.

All except "mysql_decode_skip" return the number of bytes consumed, -1 if the data is invalid, or 0 if processing cannot continue until there is more data available. If the return is -1 there is no way to continue, and an unknown number of bytes may have been consumed.

$rc = mysql_decode_header \%packet
$rc = mysql_decode_header \%packet, $data

Populates %packet with header information. This always has to be done before any other decoding subs, or any testing subs, are used.

    packet_size         => size of packet body
    packet_serial       => packet serial number from 0 to 255
$rc = mysql_decode_skip \%packet
$rc = mysql_decode_skip \%packet, $data

If the number of available bytes is equal to or greater than the packet size, consumes that many bytes and returns them. Otherwise, returns undef.

$rc = mysql_decode_varnum $number
$rc = mysql_decode_varnum $number, $data

Consumes a variable-length binary number and stores it in $number. Note that $number is NOT passed as a reference.

$rc = mysql_decode_varstr $string
$rc = mysql_decode_varstr $string, $data

Consumes a variable-length string and stores it in $string. Note that $string is NOT passed as a reference.

$rc = mysql_decode_greeting \%packet
$rc = mysql_decode_greeting \%packet, $data

Consumes the greeting packet (also called handshake initialization packet) sent by the server upon connection, and populates %packet. After this the client authentication may be encoded and sent.

    protocol_version    => equal to 10 for modern MySQL servers
    server_version      => e.g. "5.0.26-log"
    thread_id           => unique to each active client connection
    crypt_seed          => some random bytes for challenge/response auth
    server_capa         => flags the client may specify during auth
    server_lang         => server's charset number
    server_status       => server status flags
$rc = mysql_decode_result \%packet
$rc = mysql_decode_result \%packet, $data

Consumes a result packet and populates %packet. Handles OK packets, error packets, end packets, and result-set header packets.

    Error Packet:

    error       => 1
    errno       => MySQL's errno
    message     => description of error
    sqlstate    => some sort of official 5-digit code

    End Packet:

    end             => 1
    warning_count   => a number
    server_status   => bitwise flags

    OK Packet:

    field_count     => 0
    affected_rows   => a number
    last_insert_id  => a number
    server_status   => bitwise flags
    warning_count   => a number
    message         => some text

    Result Header Packet:

    field_count     => a number greater than zero
$rc = mysql_decode_field \%packet
$rc = mysql_decode_field \%packet, $data

Consumes a field packet and populates %packet.

    catalog         => catalog name
    db              => database name
    table           => table name after aliasing
    org_table       => original table name
    name            => field name after aliasing
    org_name        => original field name
    charset_no      => field character set number
    display_length  => suggested field display width
    field_type      => a number from 0 to 255
    flags           => bitwise flags
    scale           => number of digits after decimal point
$rc = mysql_decode_row \%packet
$rc = mysql_decode_row \%packet, $data

Consumes a row packet and populates %packet.

    row => ref to array of (stringified) values

Encoding Packets (Tag :encode)

These functions all return the encoded binary data.

$header_data = mysql_encode_header $packet_data
$header_data = mysql_encode_header $packet_data, $packet_serial

Returns the header for the already encoded packet. The serial number defaults to 0 which is fine except for the authentication packet, for which it must be 1.

$data = mysql_encode_varnum $number

Returns the variable-length binary encoding for $number.

$data = mysql_encode_varnum $string

Returns the variable-length binary encoding for $string.

$data = mysql_encode_client_auth @args

Returns the payload for an authentication packet where @args = ($flags, $max_packet_size, $charset_no, $username, $crypt_pw, $database). The $database is optional.

$data = mysql_encode_com_quit

Encodes the QUIT command. Takes no arguments.

$data = mysql_encode_com_query @sql

Encodes the QUERY command, using the concatenation of the arguments as the SQL string.

Password Cryption (Tag :crypt)

$crypt_pw = mysql_crypt $password, $crypt_seed

Implements MySQL's crypt algorithm to crypt a plaintext $password using the $crypt_seed from the greeting packet. Returns a binary string suitable for passing to "mysql_encode_client_auth". Requires either Digest::SHA or Digest::SHA1.

BUGS ^

Most client commands are unimplemented. Does not handle the pre-v4.1 protocol and could mess up in unpredictable ways (even fatal exceptions) if you try. It's possible to get a fatal exception calling a decode function on the wrong data, since Perl's unpack can barf fatally (this got me by surprise after the code was written, so all the unpack calls need to be audited now).

And so forth.

SEE ALSO ^

The MySQL client/server protocol at http://dev.mysql.com/doc/internals/en/client-server-protocol.html.

ACKNOWLEDGEMENTS ^

Thanks to those on #poe for their help with packaging and CPAN.

Thanks to Rob for giving me a good reason to write this!

LICENSE ^

Copyright (c) 2007 Tavin Cole <tavin at cpan.org>.

MySQL::Packet is free software and is licensed under the same terms as Perl itself.

It's interesting to read this licensing notice: http://dev.mysql.com/doc/internals/en/licensing-notice.html

MySQL AB seems to think that any software which communicates with a MySQL server must be GPL'd, because the protocol is GPL. However, they have been quoted in interviews saying that isn't true after all, and that in any case they don't really care.

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