Initial version of Blimp BlobCache.

blimp/common/blob_cache/in_memory_blob_cache.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "blimp/common/blob_cache/in_memory_blob_cache.h"
+
+#include "base/logging.h"
+#include "base/sha1.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+
+namespace blimp {
+
+InMemoryBlobCache::InMemoryBlobCache() {}
+
+InMemoryBlobCache::~InMemoryBlobCache() {}
+
+void InMemoryBlobCache::Put(const BlobId& id, BlobData data) {
+  if (Contains(id)) {
+    // In cases where the engine has miscalculated what is already available

[vmpstr, 2016/04/18 19:38:11]

I'm ok with leaving this as is, but this would seem like a bug in the engine?
That is, if this was all chromium code, then this should be a DCHECK. However,
because this is the client I don't know what should happen.

[nyquist, 2016/04/18 20:12:02]

When we deploy this for realz, there idea is to use a bloom filter to estimate
if the client has something or not. There might be issues with that, both races
and also not a perfect representation, so in practice this could happen. I guess
though, that in practice it might more often be the other way around, where the
client doesn't have something that the engine thinks it has.

I'll keep your comment in mind going forward when I start working on that.

+    // on the client, Put() might be called unnecessarily, which should be
+    // ignored.
+    VLOG(2) << "Item with ID " << id << " already exists in cache.";
+    return;
+  }
+  cache_.insert(std::make_pair(id, std::move(data)));
+}
+
+bool InMemoryBlobCache::Contains(const BlobId& id) const {
+  return cache_.find(id) != cache_.end();
+}
+
+BlobData InMemoryBlobCache::Get(const BlobId& id) const {
+  if (!Contains(id)) {

[vmpstr, 2016/04/18 19:38:11]

nit: braces optional

[nyquist, 2016/04/18 20:12:02]

The other reviewer pointed out to me that in //blimp we apparently use braces...

+    return nullptr;
+  }
+
+  return cache_.find(id)->second;
+}
+
+}  // namespace blimp