Pack information tool

This tool will print vaguely pretty information about a pack.  It
expects the output of "git-verify-pack -v" as input on stdin.

$ git-verify-pack -v | packinfo.pl

See the documentation in the script (contrib/stats/packinfo.pl)
for more information.

Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/stats/packinfo.pl b/contrib/stats/packinfo.pl
new file mode 100755 (executable)
index 0000000..792673a
--- /dev/null
+++ b/contrib/stats/packinfo.pl
@@ -0,0 +1,212 @@
+#!/bin/perl
+#
+# This tool will print vaguely pretty information about a pack.  It
+# expects the output of "git-verify-pack -v" as input on stdin.
+#
+# $ git-verify-pack -v | packinfo.pl
+#
+# This prints some full-pack statistics; currently "all sizes", "all
+# path sizes", "tree sizes", "tree path sizes", and "depths".
+#
+# * "all sizes" stats are across every object size in the file;
+#   full sizes for base objects, and delta size for deltas.
+# * "all path sizes" stats are across all object's "path sizes".
+#   A path size is the sum of the size of the delta chain, including the
+#   base object.  In other words, it's how many bytes need be read to
+#   reassemble the file from deltas.
+# * "tree sizes" are object sizes grouped into delta trees.
+# * "tree path sizes" are path sizes grouped into delta trees.
+# * "depths" should be obvious.
+#
+# When run as:
+#
+# $ git-verify-pack -v | packinfo.pl -tree
+#
+# the trees of objects are output along with the stats.  This looks
+# like:
+#
+#   0 commit 031321c6...      803      803
+#
+#   0   blob 03156f21...     1767     1767
+#   1    blob f52a9d7f...       10     1777
+#   2     blob a8cc5739...       51     1828
+#   3      blob 660e90b1...       15     1843
+#   4       blob 0cb8e3bb...       33     1876
+#   2     blob e48607f0...      311     2088
+#      size: count 6 total 2187 min 10 max 1767 mean 364.50 median 51 std_dev 635.85
+# path size: count 6 total 11179 min 1767 max 2088 mean 1863.17 median 1843 std_dev 107.26
+#
+# The first number after the sha1 is the object size, the second
+# number is the path size.  The statistics are across all objects in
+# the previous delta tree.  Obviously they are omitted for trees of
+# one object.
+#
+# When run as:
+#
+# $ git-verify-pack -v | packinfo.pl -tree -filenames
+#
+# it adds filenames to the tree.  Getting this information is slow:
+#
+#   0   blob 03156f21...     1767     1767 Documentation/git-lost-found.txt @ tags/v1.2.0~142
+#   1    blob f52a9d7f...       10     1777 Documentation/git-lost-found.txt @ tags/v1.5.0-rc1~74
+#   2     blob a8cc5739...       51     1828 Documentation/git-lost+found.txt @ tags/v0.99.9h^0
+#   3      blob 660e90b1...       15     1843 Documentation/git-lost+found.txt @ master~3222^2~2
+#   4       blob 0cb8e3bb...       33     1876 Documentation/git-lost+found.txt @ master~3222^2~3
+#   2     blob e48607f0...      311     2088 Documentation/git-lost-found.txt @ tags/v1.5.2-rc3~4
+#      size: count 6 total 2187 min 10 max 1767 mean 364.50 median 51 std_dev 635.85
+# path size: count 6 total 11179 min 1767 max 2088 mean 1863.17 median 1843 std_dev 107.26
+#
+# When run as:
+#
+# $ git-verify-pack -v | packinfo.pl -dump
+#
+# it prints out "sha1 size pathsize depth" for each sha1 in lexical
+# order.
+#
+# 000079a2eaef17b7eae70e1f0f635557ea67b644 30 472 7
+# 00013cafe6980411aa6fdd940784917b5ff50f0a 44 1542 4
+# 000182eacf99cde27d5916aa415921924b82972c 499 499 0
+# ...
+#
+# This is handy for comparing two packs.  Adding "-filenames" will add
+# filenames, as per "-tree -filenames" above.
+
+use strict;
+use Getopt::Long;
+
+my $filenames = 0;
+my $tree = 0;
+my $dump = 0;
+GetOptions("tree" => \$tree,
+           "filenames" => \$filenames,
+           "dump" => \$dump);
+
+my %parents;
+my %children;
+my %sizes;
+my @roots;
+my %paths;
+my %types;
+my @commits;
+my %names;
+my %depths;
+my @depths;
+
+while (<STDIN>) {
+    my ($sha1, $type, $size, $offset, $depth, $parent) = split(/\s+/, $_);
+    next unless ($sha1 =~ /^[0-9a-f]{40}$/);
+    $depths{$sha1} = $depth || 0;
+    push(@depths, $depth || 0);
+    push(@commits, $sha1) if ($type eq 'commit');
+    push(@roots, $sha1) unless $parent;
+    $parents{$sha1} = $parent;
+    $types{$sha1} = $type;
+    push(@{$children{$parent}}, $sha1);
+    $sizes{$sha1} = $size;
+}
+
+if ($filenames && ($tree || $dump)) {
+    open(NAMES, "git-name-rev --all|");
+    while (<NAMES>) {
+        if (/^(\S+)\s+(.*)$/) {
+            my ($sha1, $name) = ($1, $2);
+            $names{$sha1} = $name;
+        }
+    }
+    close NAMES;
+
+    for my $commit (@commits) {
+        my $name = $names{$commit};
+        open(TREE, "git-ls-tree -t -r $commit|");
+        print STDERR "Plumbing tree $name\n";
+        while (<TREE>) {
+            if (/^(\S+)\s+(\S+)\s+(\S+)\s+(.*)$/) {
+                my ($mode, $type, $sha1, $path) = ($1, $2, $3, $4);
+                $paths{$sha1} = "$path @ $name";
+            }
+        }
+        close TREE;
+    }
+}
+
+sub stats {
+    my @data = sort {$a <=> $b} @_;
+    my $min = $data[0];
+    my $max = $data[$#data];
+    my $total = 0;
+    my $count = scalar @data;
+    for my $datum (@data) {
+        $total += $datum;
+    }
+    my $mean = $total / $count;
+    my $median = $data[int(@data / 2)];
+    my $diff_sum = 0;
+    for my $datum (@data) {
+        $diff_sum += ($datum - $mean)**2;
+    }
+    my $std_dev = sqrt($diff_sum / $count);
+    return ($count, $total, $min, $max, $mean, $median, $std_dev);
+}
+
+sub print_stats {
+    my $name = shift;
+    my ($count, $total, $min, $max, $mean, $median, $std_dev) = stats(@_);
+    printf("%s: count %s total %s min %s max %s mean %.2f median %s std_dev %.2f\n",
+           $name, $count, $total, $min, $max, $mean, $median, $std_dev);
+}
+
+my @sizes;
+my @path_sizes;
+my @all_sizes;
+my @all_path_sizes;
+my %path_sizes;
+
+sub dig {
+    my ($sha1, $depth, $path_size) = @_;
+    $path_size += $sizes{$sha1};
+    push(@sizes, $sizes{$sha1});
+    push(@all_sizes, $sizes{$sha1});
+    push(@path_sizes, $path_size);
+    push(@all_path_sizes, $path_size);
+    $path_sizes{$sha1} = $path_size;
+    if ($tree) {
+        printf("%3d%s %6s %s %8d %8d %s\n",
+               $depth, (" " x $depth), $types{$sha1},
+               $sha1, $sizes{$sha1}, $path_size, $paths{$sha1});
+    }
+    for my $child (@{$children{$sha1}}) {
+        dig($child, $depth + 1, $path_size);
+    }
+}
+
+my @tree_sizes;
+my @tree_path_sizes;
+
+for my $root (@roots) {
+    undef @sizes;
+    undef @path_sizes;
+    dig($root, 0, 0);
+    my ($aa, $sz_total) = stats(@sizes);
+    my ($bb, $psz_total) = stats(@path_sizes);
+    push(@tree_sizes, $sz_total);
+    push(@tree_path_sizes, $psz_total);
+    if ($tree) {
+        if (@sizes > 1) {
+            print_stats("     size", @sizes);
+            print_stats("path size", @path_sizes);
+        }
+        print "\n";
+    }
+}
+
+if ($dump) {
+    for my $sha1 (sort keys %sizes) {
+        print "$sha1 $sizes{$sha1} $path_sizes{$sha1} $depths{$sha1} $paths{$sha1}\n";
+    }
+} else {
+    print_stats("      all sizes", @all_sizes);
+    print_stats(" all path sizes", @all_path_sizes);
+    print_stats("     tree sizes", @tree_sizes);
+    print_stats("tree path sizes", @tree_path_sizes);
+    print_stats("         depths", @depths);
+}