MWMessagePack.php

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<?php
class MWMessagePack {
    public static $bigendian = null;

    public static function pack( $value ) {
        if ( self::$bigendian === null ) {
            self::$bigendian = pack( 'S', 1 ) === pack( 'n', 1 );
        }

        switch ( gettype( $value ) ) {
        case 'NULL':
            return "\xC0";

        case 'boolean':
            return $value ? "\xC3" : "\xC2";

        case 'double':
        case 'float':
            return self::$bigendian
                ? "\xCB" . pack( 'd', $value )
                : "\xCB" . strrev( pack( 'd', $value ) );

        case 'string':
            $length = strlen( $value );
            if ( $length < 32 ) {
                return pack( 'Ca*', 0xA0 | $length, $value );
            } elseif ( $length <= 0xFFFF ) {
                return pack( 'Cna*', 0xDA, $length, $value );
            } elseif ( $length <= 0xFFFFFFFF ) {
                return pack( 'CNa*', 0xDB, $length, $value );
            }
            throw new InvalidArgumentException( __METHOD__
                . ": string too long (length: $length; max: 4294967295)" );

        case 'integer':
            if ( $value >= 0 ) {
                if ( $value <= 0x7F ) {
                    // positive fixnum
                    return chr( $value );
                }
                if ( $value <= 0xFF ) {
                    // uint8
                    return pack( 'CC', 0xCC, $value );
                }
                if ( $value <= 0xFFFF ) {
                    // uint16
                    return pack( 'Cn', 0xCD, $value );
                }
                if ( $value <= 0xFFFFFFFF ) {
                    // uint32
                    return pack( 'CN', 0xCE, $value );
                }
                if ( $value <= 0xFFFFFFFFFFFFFFFF ) {
                    // uint64
                    $hi = ( $value & 0xFFFFFFFF00000000 ) >> 32;
                    $lo = $value & 0xFFFFFFFF;
                    return self::$bigendian
                        ? pack( 'CNN', 0xCF, $lo, $hi )
                        : pack( 'CNN', 0xCF, $hi, $lo );
                }
            } else {
                if ( $value >= -32 ) {
                    // negative fixnum
                    return pack( 'c', $value );
                }
                if ( $value >= -0x80 ) {
                    // int8
                    return pack( 'Cc', 0xD0, $value );
                }
                if ( $value >= -0x8000 ) {
                    // int16
                    $p = pack( 's', $value );
                    return self::$bigendian
                        ? pack( 'Ca2', 0xD1, $p )
                        : pack( 'Ca2', 0xD1, strrev( $p ) );
                }
                if ( $value >= -0x80000000 ) {
                    // int32
                    $p = pack( 'l', $value );
                    return self::$bigendian
                        ? pack( 'Ca4', 0xD2, $p )
                        : pack( 'Ca4', 0xD2, strrev( $p ) );
                }
                if ( $value >= -0x8000000000000000 ) {
                    // int64
                    // pack() does not support 64-bit ints either so pack into two 32-bits
                    $p1 = pack( 'l', $value & 0xFFFFFFFF );
                    $p2 = pack( 'l', ( $value >> 32 ) & 0xFFFFFFFF );
                    return self::$bigendian
                        ? pack( 'Ca4a4', 0xD3, $p1, $p2 )
                        : pack( 'Ca4a4', 0xD3, strrev( $p2 ), strrev( $p1 ) );
                }
            }
            throw new InvalidArgumentException( __METHOD__ . ": invalid integer '$value'" );

        case 'array':
            $buffer = '';
            $length = count( $value );
            if ( $length > 0xFFFFFFFF ) {
                throw new InvalidArgumentException( __METHOD__
                    . ": array too long (length: $length, max: 4294967295)" );
            }

            $index = 0;
            foreach ( $value as $k => $v ) {
                if ( $index !== $k || $index === $length ) {
                    break;
                } else {
                    $index++;
                }
            }
            $associative = $index !== $length;

            if ( $associative ) {
                if ( $length < 16 ) {
                    $buffer .= pack( 'C', 0x80 | $length );
                } elseif ( $length <= 0xFFFF ) {
                    $buffer .= pack( 'Cn', 0xDE, $length );
                } else {
                    $buffer .= pack( 'CN', 0xDF, $length );
                }
                foreach ( $value as $k => $v ) {
                    $buffer .= self::pack( $k );
                    $buffer .= self::pack( $v );
                }
            } else {
                if ( $length < 16 ) {
                    $buffer .= pack( 'C', 0x90 | $length );
                } elseif ( $length <= 0xFFFF ) {
                    $buffer .= pack( 'Cn', 0xDC, $length );
                } else {
                    $buffer .= pack( 'CN', 0xDD, $length );
                }
                foreach ( $value as $v ) {
                    $buffer .= self::pack( $v );
                }
            }
            return $buffer;

        default:
            throw new InvalidArgumentException( __METHOD__ . ': unsupported type ' . gettype( $value ) );
        }
    }
}