RAPPOR implementation

components/variations/metrics_util.cc

Index: components/variations/metrics_util.cc
diff --git a/components/variations/metrics_util.cc b/components/variations/metrics_util.cc
index 031c3d37a31311794a33aef7bc09497a0e0fa5f3..aeb62d47d319ab3e96c3e4a50789d8719a75b757 100644
--- a/components/variations/metrics_util.cc
+++ b/components/variations/metrics_util.cc
@@ -4,11 +4,25 @@
 
 #include "components/variations/metrics_util.h"
 
+#include "base/logging.h"
+#include "base/md5.h"
 #include "base/sha1.h"
 #include "base/sys_byteorder.h"
 
 namespace metrics {
 
+namespace {
+
+// Converts the 8-byte prefix of an MD5 hash into a uint64 value.
+inline uint64 HashToUInt64(const std::string& hash) {
+  uint64 value;
+  DCHECK_GE(hash.size(), sizeof(value));
+  memcpy(&value, hash.data(), sizeof(value));
+  return base::HostToNet64(value);
+}
+
+}  // namespace
+
 uint32 HashName(const std::string& name) {
   // SHA-1 is designed to produce a uniformly random spread in its output space,
   // even for nearly-identical inputs.
@@ -24,4 +38,20 @@ uint32 HashName(const std::string& name) {
   return base::ByteSwapToLE32(bits);
 }
 
+uint64 HashMetricName(const std::string& name) {
+  // Create an MD5 hash of the given |name|, represented as a byte buffer
+  // encoded as an std::string.
+  base::MD5Context context;
+  base::MD5Init(&context);
+  base::MD5Update(&context, name);
+
+  base::MD5Digest digest;
+  base::MD5Final(&digest, &context);
+
+  std::string hash_str(reinterpret_cast<char*>(digest.a), arraysize(digest.a));
+  uint64 hash = HashToUInt64(hash_str);

[Alexei Svitkine (slow), 2014/02/05 18:07:01]

Nit: Just return this directly.

[Steven Holte, 2014/02/05 22:44:37]

Done.

+
+  return hash;
+}
+
 }  // namespace metrics