[RFC PATCHv4 12/17] gitweb/lib - Use CHI compatibile (compute method) caching interface

[Jakub Narebski <jnareb@gmail.com>]

If $cache provides CHI compatible ->compute($key, $code) method, use it
instead of Cache::Cache compatible ->get($key) and ->set($key, $data).

GitwebCache::SimpleFileCache provides 'compute' method, which currently
simply use 'get' and 'set' methods in proscribed manner.  Nevertheless
'compute' method can be more flexible in choosing when to refresh cache,
and which process is to refresh/(re)generate cache entry.  This method
would use (advisory) locking to prevent 'cache miss stampede' (aka
'stampeding herd') problem in the next commit.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
 gitweb/lib/GitwebCache/CacheOutput.pm |   31 +++++++++++++++++++++++++++++++
 1 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/gitweb/lib/GitwebCache/CacheOutput.pm b/gitweb/lib/GitwebCache/CacheOutput.pm
index 8195f0b..de4bd4d 100644
--- a/gitweb/lib/GitwebCache/CacheOutput.pm
+++ b/gitweb/lib/GitwebCache/CacheOutput.pm
@@ -35,6 +35,37 @@ our $CAPTURE_CLASS = 'GitwebCache::Capture::SelectFH';
 sub cache_output {
 	my ($cache, $key, $code) = @_;
 
+	if ($cache->can('compute')) {
+		#other solution: goto &cache_output_compute;
+		return cache_output_compute($cache, $key, $code);
+	} else {
+		#other solution: goto &cache_output_get_set;
+		return cache_output_get_set($cache, $key, $code);
+	}
+}
+
+# for $cache which can ->compute($key, $code)
+sub cache_output_compute {
+	my ($cache, $key, $code) = @_;
+
+	my $capture = $CAPTURE_CLASS;
+	setup_capture($capture);
+
+	my $data = $cache->compute($key, sub { &capture_block($code) });
+
+	if (defined $data) {
+		# select() instead of STDOUT is here for t9503 test:
+		binmode select(), ':raw';
+		print $data;
+	}
+
+	return $data;
+}
+
+# for $cache which can ->get($key) and ->set($key, $data)
+sub cache_output_get_set {
+	my ($cache, $key, $code) = @_;
+
 	my $data = $cache->get($key);
 
 	# capture and cache output, if there was nothing in the cache
-- 
1.7.0.1