Opaque Etags for compact index requests

This changes the CompactIndexClient to store etags received from the
compact index in separate files rather than relying on the MD5 checksum
of the file as the etag.

Smoothes the upgrade from md5 etags to opaque by generating them when no
etag file exists. This should reduce the initial impact of changing the
caching behavior by reducing cache misses when the MD5 etag is the same.

Eventually, the MD5 behavior should be retired and the etag should be
considered completely opaque with no assumption that MD5 would match.

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/bundler/shared_helpers.rb b/lib/bundler/shared_helpers.rb
index cccc2b63d9..fa7db1c09d 100644
--- a/lib/bundler/shared_helpers.rb
+++ b/lib/bundler/shared_helpers.rb
@@ -193,6 +193,21 @@ module Bundler
       Digest(name)
     end
 
+    def checksum_for_file(path, digest)
+      return unless path.file?
+      # This must use File.read instead of Digest.file().hexdigest
+      # because we need to preserve \n line endings on windows when calculating
+      # the checksum
+      SharedHelpers.filesystem_access(path, :read) do
+        File.open(path, "rb") do |f|
+          digest = SharedHelpers.digest(digest).new
+          buf = String.new(:capacity => 16_384, :encoding => Encoding::BINARY)
+          digest << buf while f.read(16_384, buf)
+          digest.hexdigest
+        end
+      end
+    end
+
     def write_to_gemfile(gemfile_path, contents)
       filesystem_access(gemfile_path) {|g| File.open(g, "w") {|file| file.puts contents } }
     end