# get the next utf-8 character from the input stream
# and encode as UTF8 if possible/necessary
sub nextchar {
    my $self = shift;
    $self->next;

    return unless defined $self->[CURRENT];

    if ($self->[CURRENT] eq "\x0D") {
        $self->next;
        return unless defined($self->[CURRENT]);
        if ($self->[CURRENT] ne "\x0A") {
            $self->buffer("\x0A");
        }
    }

    return unless $self->[ENCODING];
    my $n = ord($self->[CURRENT]);
    # warn(sprintf("ch: 0x%x ($self->[CURRENT])\n", $n));
    if (($] < 5.007002) && ($n > 0x7F)) {
        # utf8 surrogate
        my $current = $self->[CURRENT];
        if    ($n >= 0xFC) {
            # read 5 chars
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
        }
        elsif ($n >= 0xF8) {
            # read 4 chars
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
        }
        elsif ($n >= 0xF0) {
            # read 3 chars
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
        }
        elsif ($n >= 0xE0) {
            # read 2 chars
            $self->next; $current .= $self->[CURRENT];
            $self->next; $current .= $self->[CURRENT];
        }
        elsif ($n >= 0xC0) {
            # read 1 char
            $self->next; $current .= $self->[CURRENT];
        }
        else {
            throw XML::SAX::Exception::Parse(
                Message => sprintf("Invalid character 0x%x", $n),
                ColumnNumber => $self->column,
                LineNumber => $self->line,
                PublicId => $self->public_id,
                SystemId => $self->system_id,
            );
        }
        if ($] >= 5.006001) {
            $self->[CURRENT] = pack("U0A*", $current);
        }
        else {
            $self->[CURRENT] = $current;
        }
    }
}

######################################################

# match anything *not* in the list of characters given
sub match_not {
    my $self = shift;

    my $current = $self->[CURRENT];
    return 0 unless defined $current;

    for my $m (@_) {
        if ($current eq $m) {
            $self->[MATCHED] = '';
            return 0;
        }
    }
    $self->[MATCHED] = $current;
    $self->nextchar;
    return 1;
}

######################################################

# get the next byte or character (character on 5.7.2+
# or byte on 5.5 or 5.6) from a fh, or from the buffer
# if one exists.
sub next {
    my $self = shift;

    # check for chars in buffer first.
    if (length($self->[BUFFER])) {
        return $self->[CURRENT] = substr($self->[BUFFER], 0, 1, ''); # last param truncates buffer
    }


    if (length($self->[INTERNAL_BUFFER])) {
BUFFERED_READ:
        $self->[CURRENT] = substr($self->[INTERNAL_BUFFER], 0, 1, '');
        if ($self->[CURRENT] eq "\x0A") {
            $self->[LINE]++;
            $self->[COLUMN] = 1;
        }
        else { $self->[COLUMN]++ }
        return;
    }

    my $bytesread = read($self->[FH], $self->[INTERNAL_BUFFER], $self->[BUFFER_SIZE]);
    if ($bytesread) {
        # yes, goto. If you have a faster way feel free!
        goto BUFFERED_READ;
    }
    elsif (defined($bytesread)) {
        $self->[EOF]++;
        return $self->[CURRENT] = undef;
    }
    throw XML::SAX::Exception::Parse(
        Message => "Error reading from filehandle: $!",
    );
}

##########################################################

# consume everything not matching chars listed in @_
sub consume_not {
    my $self = shift;

    my $consumed = '';

    while(!$self->[EOF] && $self->match_not(@_)) {
        $consumed .= $self->[MATCHED];
    }
    return length($self->[CONSUMED] = $consumed);
}

########################################################

# Does the current token match a single character?
sub match_char {
    my $self = shift;

    if (defined($self->[CURRENT]) && $self->[CURRENT] eq $_[0]) {
        $self->[MATCHED] = $_[0];
        $self->nextchar;
        return 1;
    }
    $self->[MATCHED] = '';
    return 0;
}

#########################################################

# Does the current token match a single regexp?
sub match_re {
    my $self = shift;

    if ($self->[CURRENT] =~ $_[0]) {
        $self->[MATCHED] = $self->[CURRENT];
        $self->nextchar;
        return 1;
    }
    $self->[MATCHED] = '';
    return 0;
}