Re: 142 (v1): Enhanced Pack/Unpack

[Tom Christiansen]

Here was my old demo/proposal, such as it was.

--tom

    $buff = "\0" x rusage->sizeof();
    syscall(&SYS_getrusage, &RUSAGE_SELF, $buff)      && die "getrusage: $!";

    $ru = rusage->new_from_buffer($buff);
# or
    $ru = rusage->new();
    $ru->unpack($buff);
# or 
    @fields = rusage->unpack($buff);
# or 
    @fields = unpack(rusage->typedef, $buff);
# or 
    $ru = rusage->read(*FH);
# or
    read(FH, $buff, $rusage->sizeof);
    $ru = rusage->new_from_buffer($buff);
# or
    read(FH, $buff, $rusage->sizeof);
    @fields = unpack(rusage->typedef, $buff);

Class methods:

    $obj = CSTRUCT->new();          # construct empty
    $obj = CSTRUCT->unpack($buff);  # construct from packed buffer

    $obj = CSTRUCT->new(            # construct from pairs
        FIELD1 => "value", 
        FIELD2 => "value", 
    );

    $obj = CSTRUCT->read(*FH);      # construct from next bytes on stream
    CSTRUCT->seek(*FH,10);              # goto record 10 on stream of CSTRUCTs

    $recsize   = CSTRUCT->sizeof(); # bytes in packed record
    $pack_mask = CSTRUCT->typedef(); # format for pack/unpack

Object methods:

    $x = $obj->field;           # get
    $obj->field($value);        # set

    $obj->unpack($buff);        
    print $obj->pack;   

    $obj->write(*FH);           # write packed $obj to stream
    $obj->read(*FH);            # read packed object from stream
    $obj->seek(*FH,10);         # goto record 10 on stream of (ref $obj)

    print $obj->as_string;
    print $obj->as_hash;

Example using wtmp log file:

1) Show record of user id #178

    use utmp;  # would have been #include <utmp.h>

    open(WTMP, "/usr/adm/wtmp");

    utmp->seek(*WTMP, 178);
    $him = utmp->read(*WTMP);

    printf "uid %d logged on from %s on %s.\n",
        $him->ut_uid, $him->ut_host, scalar local $him->ut_date;

2) Paul's updating records in place
    
    use employee;
    open(FH, "+< /tmp/empdata");
    $obj = employee->new();
    while ($obj = $obj->read(*FH)) {
        $obj->salary($obj->salary * 1.06); # *= 1.06
        seek(FH, 0, 1);
        $obj->write(*FH);
    }