in reply to Re^3: Geo Package files
in thread Geo Package files

As I've reached the point I've got to, my gut feeling is that it is worth continuing. Perhaps not for this project, but certainly for what I am learning in the process of doing this. Previously, the only use I've made of unpack is to split up an authentication string.

I think knowing more about pack and unpack would be beneficial to me. Thanks to soonix and Marshall my understanding of these two functions in improving. That alone makes continuing worthwhile.

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Re^5: Geo Package files
by Fletch (Bishop) on Mar 05, 2022 at 22:56 UTC

    Certainly a good learning opportunity and from the (cursory) read over the linked docs it looks like those should well serve. Having something “tangible” to use for practical samples is great; I’d just rather (for $work purposes) defer to off the shelf and play with things on the back burner.

    The cake is a lie.
    The cake is a lie.
    The cake is a lie.

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Re^5: Geo Package files
by Marshall (Canon) on Mar 08, 2022 at 03:35 UTC
    I still would like binary dump as I request in here.

    I don't want to get into the idea of "real" vs "fake" OS. Windows is certainly "real". I've worked with several variants of MS O/S's and several variants of Unix, one IBM mainframe OS and several real time O/S's. They are all "real" and have their own jobs.

    Your question is interesting and a little bit different than what I normally deal with. Worst case, I believe that I can write an inline C subroutine that will do what you want (as long as we are both on 64 bit little endian architecture). Although I don't think that is necessary.

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      I still would like binary dump as I request in here.

      Sorry - I thought I'd given you this in Re^4: Geo Package files

      Here you go, this is hex dump of the entirety of $geo from this script...the lengths are vastly different. I added the random order to see how varied the data actually is.

      
use DBD::SQLite;
use Data::Dumper;

use strict;
use warnings;

my $dbh = DBI->connect("dbi:SQLite:uri=file:osopenusrn_202203.gpkg?mod
+e=rwc");

my $tab = $dbh->prepare("SELECT * FROM openUSRN ORDER BY RANDOM() LIMI
+T 1");
$tab->execute;
my $data = $tab->fetchrow_hashref;

my $geo = $data->{'geometry'};

print join ' ', unpack '(H2)*', $geo;
exit;

47 50 00 05 34 6c 00 00 a0 70 3d 0a a6 be 14 41
00 2b 87 96 97 c9 14 41 20 b2 9d 6f 1a 03 1b 41
e0 ce f7 53 e7 0d 1b 41 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 01 ed 03 00 00 04 00 00
00 01 ea 03 00 00 0a 00 00 00 40 8b 6c e7 16 c1
14 41 20 87 16 d9 12 07 1b 41 00 00 00 00 00 00
00 00 90 6e 12 83 bf c1 14 41 40 62 10 d8 35 07
1b 41 00 00 00 00 00 00 00 00 90 ed 7c bf 18 c2
14 41 40 35 5e 3a 64 07 1b 41 00 00 00 00 00 00
00 00 a0 c4 20 b0 79 c2 14 41 00 fe d4 78 c3 07
1b 41 00 00 00 00 00 00 00 00 a0 9b c4 a0 1a c3
14 41 a0 47 e1 fa ab 08 1b 41 00 00 00 00 00 00
00 00 40 60 e5 d0 86 c4 14 41 c0 cc cc 4c 3e 09
1b 41 00 00 00 00 00 00 00 00 50 37 89 41 87 c6
14 41 00 2b 87 96 a0 0a 1b 41 00 00 00 00 00 00
00 00 a0 45 b6 f3 a5 c6 14 41 00 ac 1c da da 0a
1b 41 00 00 00 00 00 00 00 00 90 ed 7c bf a0 c6
14 41 00 d5 78 e9 a9 0b 1b 41 00 00 00 00 00 00
00 00 80 6a bc f4 61 c7 14 41 80 be 9f 1a 38 0c
1b 41 00 00 00 00 00 00 00 00 01 ea 03 00 00 04
00 00 00 40 8b 6c e7 16 c1 14 41 20 87 16 d9 12
07 1b 41 00 00 00 00 00 00 00 00 c0 20 b0 72 61
bf 14 41 e0 fb a9 f1 78 05 1b 41 00 00 00 00 00
00 00 00 90 97 6e 92 a7 be 14 41 20 5c 8f 42 5f
03 1b 41 00 00 00 00 00 00 00 00 a0 70 3d 0a a6
be 14 41 20 b2 9d 6f 1a 03 1b 41 00 00 00 00 00
00 00 00 01 ea 03 00 00 02 00 00 00 a0 70 3d 8a
8d c8 14 41 80 95 43 8b ea 0c 1b 41 00 00 00 00
00 00 00 00 00 2b 87 96 97 c9 14 41 e0 ce f7 53
e7 0d 1b 41 00 00 00 00 00 00 00 00 01 ea 03 00
00 02 00 00 00 80 6a bc f4 61 c7 14 41 80 be 9f
1a 38 0c 1b 41 00 00 00 00 00 00 00 00 a0 70 3d
8a 8d c8 14 41 80 95 43 8b ea 0c 1b 41 00 00 00
00 00 00 00 00

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        At least the envelope on that one makes more sense. 

        #!perl

use 5.012; # strict, //
use warnings;
use Data::Dump qw/dd/;
$Data::Dump::TRY_BASE64 = 0;

my $geo = do {
    local $/ = undef; # slurp
    local $\ = "\n";
    pack '(H2)*', split ' ', <DATA>;
};

my ($magic,$ver,$flag,$SRSID) = unpack 'nCCV', substr($geo,0,8);
printf "0x%04x v=%d f=%08b srsid=%d\n", $magic,$ver,$flag,$SRSID;
my $biglittle = ($flag & 0x1);  # 1 means little
my $eee = ($flag & 0xE)>>1;
my $envelope_count = (0,4,6,6,8)[$eee] // die "eee=$eee values 5-7 inv
+alid";
my $unpack_str = "d" . ($biglittle ? '<' : '>') . $envelope_count;
printf "envelope#%s -> %d elements, mode=%s-endian => '%s'\n", $eee, $
+envelope_count, (qw/big little/)[$biglittle], $unpack_str;
my @envelope = unpack $unpack_str, substr($geo, 8, 8*$envelope_count);
local $" = ", ";
print "@envelope\n";

__DATA__
47 50 00 05 34 6c 00 00 a0 70 3d 0a a6 be 14 41
00 2b 87 96 97 c9 14 41 20 b2 9d 6f 1a 03 1b 41
e0 ce f7 53 e7 0d 1b 41 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 01 ed 03 00 00 04 00 00
00 01 ea 03 00 00 0a 00 00 00 40 8b 6c e7 16 c1
14 41 20 87 16 d9 12 07 1b 41 00 00 00 00 00 00
00 00 90 6e 12 83 bf c1 14 41 40 62 10 d8 35 07
1b 41 00 00 00 00 00 00 00 00 90 ed 7c bf 18 c2
14 41 40 35 5e 3a 64 07 1b 41 00 00 00 00 00 00
00 00 a0 c4 20 b0 79 c2 14 41 00 fe d4 78 c3 07
1b 41 00 00 00 00 00 00 00 00 a0 9b c4 a0 1a c3
14 41 a0 47 e1 fa ab 08 1b 41 00 00 00 00 00 00
00 00 40 60 e5 d0 86 c4 14 41 c0 cc cc 4c 3e 09
1b 41 00 00 00 00 00 00 00 00 50 37 89 41 87 c6
14 41 00 2b 87 96 a0 0a 1b 41 00 00 00 00 00 00
00 00 a0 45 b6 f3 a5 c6 14 41 00 ac 1c da da 0a
1b 41 00 00 00 00 00 00 00 00 90 ed 7c bf a0 c6
14 41 00 d5 78 e9 a9 0b 1b 41 00 00 00 00 00 00
00 00 80 6a bc f4 61 c7 14 41 80 be 9f 1a 38 0c
1b 41 00 00 00 00 00 00 00 00 01 ea 03 00 00 04
00 00 00 40 8b 6c e7 16 c1 14 41 20 87 16 d9 12
07 1b 41 00 00 00 00 00 00 00 00 c0 20 b0 72 61
bf 14 41 e0 fb a9 f1 78 05 1b 41 00 00 00 00 00
00 00 00 90 97 6e 92 a7 be 14 41 20 5c 8f 42 5f
03 1b 41 00 00 00 00 00 00 00 00 a0 70 3d 0a a6
be 14 41 20 b2 9d 6f 1a 03 1b 41 00 00 00 00 00
00 00 00 01 ea 03 00 00 02 00 00 00 a0 70 3d 8a
8d c8 14 41 80 95 43 8b ea 0c 1b 41 00 00 00 00
00 00 00 00 00 2b 87 96 97 c9 14 41 e0 ce f7 53
e7 0d 1b 41 00 00 00 00 00 00 00 00 01 ea 03 00
00 02 00 00 00 80 6a bc f4 61 c7 14 41 80 be 9f
1a 38 0c 1b 41 00 00 00 00 00 00 00 00 a0 70 3d
8a 8d c8 14 41 80 95 43 8b ea 0c 1b 41 00 00 00
00 00 00 00 00

        [download]

        I get a decoding of the first 8 bites plus envelope of: 

        0x4750 v=0 f=00000101 srsid=27700
envelope#2 -> 6 elements, mode=little-endian => 'd<6'
339881.51, 340581.897, 442566.608999999, 443257.832, 0, 0

        [download]
        And the minx,miny are smaller than maxx,maxy -- so whether that's a good thing or not, I don't know.

        The main takeaways of my input is that you need to use the < for litte-endian and > for big-endian, and that way you won't be guessing in the future whether your system and/or perl have native big- or little-endianness. (Also, even if you'll always be on the same processor, having those directions explicit in the code will make future development/maintenance so much easier.)

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