Added --disk-cache option

This option enables disk cache. If SIZE is 0, the disk cache is
disabled. This feature caches the downloaded data in memory, which
grows to at most SIZE bytes. The cache storage is created for aria2
instance and shared by all downloads. The one advantage of the disk
cache is reduce the disk seek time because the data is written in
larger unit and it is reordered by the offset of the file. If the
underlying file is heavily fragmented it is not the case.

1 files changed, 129 insertions, 0 deletions

diff --git a/src/WrDiskCache.cc b/src/WrDiskCache.cc
new file mode 100644
index 00000000..79af80e9
--- /dev/null
+++ b/src/WrDiskCache.cc
@@ -0,0 +1,129 @@
+/* <!-- copyright */
+/*
+ * aria2 - The high speed download utility
+ *
+ * Copyright (C) 2012 Tatsuhiro Tsujikawa
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * In addition, as a special exception, the copyright holders give
+ * permission to link the code of portions of this program with the
+ * OpenSSL library under certain conditions as described in each
+ * individual source file, and distribute linked combinations
+ * including the two.
+ * You must obey the GNU General Public License in all respects
+ * for all of the code used other than OpenSSL.  If you modify
+ * file(s) with this exception, you may extend this exception to your
+ * version of the file(s), but you are not obligated to do so.  If you
+ * do not wish to do so, delete this exception statement from your
+ * version.  If you delete this exception statement from all source
+ * files in the program, then also delete it here.
+ */
+/* copyright --> */
+#include "WrDiskCache.h"
+#include "WrDiskCacheEntry.h"
+#include "LogFactory.h"
+#include "fmt.h"
+
+namespace aria2 {
+
+WrDiskCache::WrDiskCache(size_t limit)
+  : limit_(limit),
+    total_(0),
+    clock_(0)
+{}
+
+WrDiskCache::~WrDiskCache()
+{
+  if(total_) {
+    A2_LOG_WARN(fmt("Write disk cache is not empty size=%lu",
+                    static_cast<unsigned long>(total_)));
+  }
+}
+
+bool WrDiskCache::add(WrDiskCacheEntry* ent)
+{
+  ent->setSizeKey(ent->getSize());
+  ent->setLastUpdate(++clock_);
+  std::pair<EntrySet::iterator, bool> rv = set_.insert(ent);
+  if(rv.second) {
+    total_ += ent->getSize();
+    ensureLimit();
+    return true;
+  } else {
+    A2_LOG_WARN(fmt("Found duplicate cache entry a.{size=%lu,clock=%"PRId64
+                    "} b{size=%lu,clock=%"PRId64"}",
+                    static_cast<unsigned long>((*rv.first)->getSize()),
+                    (*rv.first)->getLastUpdate(),
+                    static_cast<unsigned long>(ent->getSize()),
+                    ent->getLastUpdate()));
+    return false;
+  }
+}
+
+bool WrDiskCache::remove(WrDiskCacheEntry* ent)
+{
+  if(set_.erase(ent)) {
+    A2_LOG_DEBUG(fmt("Removed cache entry size=%lu, clock=%"PRId64,
+                     static_cast<unsigned long>(ent->getSize()),
+                     ent->getLastUpdate()));
+    total_ -= ent->getSize();
+    return true;
+  } else {
+    return false;
+  }
+}
+
+bool WrDiskCache::update(WrDiskCacheEntry* ent, ssize_t delta)
+{
+  if(!set_.erase(ent)) {
+    return false;
+  }
+  A2_LOG_DEBUG(fmt("Update cache entry size=%lu, delta=%ld, clock=%"PRId64,
+                   static_cast<unsigned long>(ent->getSize()),
+                   static_cast<long>(delta),
+                   ent->getLastUpdate()));
+
+  ent->setSizeKey(ent->getSize());
+  ent->setLastUpdate(++clock_);
+  set_.insert(ent);
+
+  if(delta < 0) {
+    assert(total_ >= static_cast<size_t>(-delta));
+  }
+  total_ += delta;
+  ensureLimit();
+  return true;
+}
+
+void WrDiskCache::ensureLimit()
+{
+  while(total_ > limit_) {
+    EntrySet::iterator i = set_.begin();
+    total_ -= (*i)->getSize();
+    (*i)->writeToDisk();
+    WrDiskCacheEntry* ent = *i;
+    A2_LOG_DEBUG(fmt("Force flush cache entry size=%lu, clock=%"PRId64,
+                     static_cast<unsigned long>(ent->getSizeKey()),
+                     ent->getLastUpdate()));
+    set_.erase(i);
+
+    ent->setSizeKey(ent->getSize());
+    ent->setLastUpdate(++clock_);
+    set_.insert(ent);
+  }
+}
+
+} // namespace aria2