[PATCH] Shoddy pack information tool

[Brian Downing <bdowning@lavos.net>]

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 pack | 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 pack | 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 pack | packinfo.pl -tree -filenames

It adds filenames to the tree.  Getting this information is somewhat
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 pack | 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.
---
 packinfo.pl |  141 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 141 insertions(+), 0 deletions(-)
 create mode 100644 packinfo.pl

diff --git a/packinfo.pl b/packinfo.pl
new file mode 100644
index 0000000..6abb7f2
--- /dev/null
+++ b/packinfo.pl
@@ -0,0 +1,141 @@
+#!/bin/perl
+
+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 && $tree) {
+    open(NAMES, "git-name-rev --all|");
+    while (<NAMES>) {
+        if (/^(\S+)\s+(.*)$/) {
+            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}\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);
+}
-- 
1.5.2.GIT