Add script to read git object files and print out their contents.

1 files changed, 53 insertions, 0 deletions

diff --git a/read_object.pl b/read_object.pl
new file mode 100755
index 0000000..8360882
--- /dev/null
+++ b/read_object.pl
@@ -0,0 +1,53 @@
+#!/usr/bin/env perl
+
+use Compress::Zlib;
+use Digest::SHA qw(sha1_hex);
+use File::Basename;
+use Data::Dumper;
+
+use strict;
+use warnings;
+
+my @filedata = <>;
+my ($signature, $type, $size, $data) = read_object(join('', @filedata));
+my $out = format_object($type, $data);
+
+print "signature: $signature\ntype: $type\nsize: $size\n"
+    . ("-" x 40) . "\n$out\n";
+
+sub read_object {
+    my ($zlib_data) = @_;
+
+    my $raw_data = uncompress($zlib_data)
+        || die "Couldn't uncompress zlib data.";
+    my $sig = sha1_hex($raw_data);
+    $raw_data =~ /(.*?) (.*?)\0(.*)/s || die "Invalid object format.";
+
+    my ($type, $size, $data) = ($1, $2, $3);
+    warn "Size mismatch: got $size, but was actually " . length($data)
+        unless length($data) == $size;
+
+    ($sig, $type, $size, $data);
+}
+
+sub format_object {
+    my ($type, $obj) = @_;
+
+    if ($type eq 'commit') {
+        $obj;
+    } elsif ($type eq 'tag') {
+        warn 'TODO - unimplemented';
+        join '', map { sprintf('%02x ', $_) } unpack('C*', $obj);
+    } elsif ($type eq 'tree') {
+        warn 'TODO - unimplemented';
+        join '', map { sprintf('%02x ', $_) } unpack('C*', $obj);
+    } elsif ($type eq 'blob') {
+        warn 'TODO - unimplemented';
+        join '', map { sprintf('%02x ', $_) } unpack('C*', $obj);
+    } else {
+        warn "Unknown object type, showing hex representation: $type.\n";
+        join '', map { sprintf('%02x', $_) } unpack('C*', $obj);
+    }
+}
+
+1;