NaCl Validation Cache: move browser implementation into its own file.

A few cleanups were also performed, such as encapsulating the UMA hooks.

BUG= http://code.google.com/p/nativeclient/issues/detail?id=2515
TEST= none

Review URL: https://chromiumcodereview.appspot.com/10377051

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@136085 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 71 insertions, 0 deletions

diff --git a/chrome/browser/nacl_host/nacl_validation_cache.cc b/chrome/browser/nacl_host/nacl_validation_cache.cc
new file mode 100644
index 0000000..5916b09
--- /dev/null
+++ b/chrome/browser/nacl_host/nacl_validation_cache.cc
@@ -0,0 +1,71 @@
+// Copyright (c) 2012 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 "chrome/browser/nacl_host/nacl_validation_cache.h"
+
+#include "base/metrics/histogram.h"
+#include "base/rand_util.h"
+
+namespace {
+
+// For the moment, choose an arbitrary cache size.
+const size_t kValidationCacheCacheSize = 200;
+// Key size is equal to the block size (not the digest size) of SHA256.
+const size_t kValidationCacheKeySize = 64;
+// Entry size is equal to the digest size of SHA256.
+const size_t kValidationCacheEntrySize = 32;
+
+enum ValidationCacheStatus {
+  CACHE_MISS = 0,
+  CACHE_HIT,
+  CACHE_ERROR,
+  CACHE_MAX
+};
+
+void LogCacheQuery(ValidationCacheStatus status) {
+  UMA_HISTOGRAM_ENUMERATION("NaCl.ValidationCache.Query", status, CACHE_MAX);
+}
+
+void LogCacheSet(ValidationCacheStatus status) {
+  // Bucket zero is reserved for future use.
+  UMA_HISTOGRAM_ENUMERATION("NaCl.ValidationCache.Set", status, CACHE_MAX);
+}
+
+}  // namespace
+
+NaClValidationCache::NaClValidationCache()
+    : validation_cache_(kValidationCacheCacheSize),
+      validation_cache_key_(base::RandBytesAsString(kValidationCacheKeySize)){
+}
+
+NaClValidationCache::~NaClValidationCache() {
+  // Make clang's style checking happy by adding a destructor.
+}
+
+bool NaClValidationCache::QueryKnownToValidate(const std::string& signature) {
+  bool result = false;
+  if (signature.length() != kValidationCacheEntrySize) {
+    // Signature is the wrong size, something is wrong.
+    LogCacheQuery(CACHE_ERROR);
+  } else {
+    ValidationCacheType::iterator iter = validation_cache_.Get(signature);
+    if (iter != validation_cache_.end()) {
+      result = iter->second;
+    }
+    LogCacheQuery(result ? CACHE_HIT : CACHE_MISS);
+  }
+  return result;
+}
+
+void NaClValidationCache::SetKnownToValidate(const std::string& signature) {
+  if (signature.length() != kValidationCacheEntrySize) {
+    // Signature is the wrong size, something is wrong.
+    LogCacheSet(CACHE_ERROR);
+  } else {
+    validation_cache_.Put(signature, true);
+    // The number of sets should be equal to the number of cache misses, minus
+    // validation failures and successful validations where stubout occurs.
+    LogCacheSet(CACHE_HIT);
+  }
+}