Use 64 bit shift when convert uint64_t to ByteVector

components/rappor/byte_vector_utils.cc

 // Copyright 2014 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 "components/rappor/byte_vector_utils.h"
 
 #include <string>
 
 #include "base/logging.h"
 #include "base/rand_util.h"
@@ skipping 60 matching lines @@
     return true;
   // 4. K = HMAC(K, V || 0x01 || provided_data)
   if (!HMAC_Rotate(*hmac2, Concat(*value, 0x01, provided_data), out_hmac))
     return false;
   // 5. V = HMAC(K, V)
   return HMAC_Rehash(*out_hmac, value);
 }
 
 }  // namespace
 
+void Uint64ToByteVector(uint64_t value, uint64_t size, ByteVector* output) {
+  DCHECK_LE(size, 8u);
+  DCHECK_EQ(size, output->size());
+  for (size_t i = 0; i < size; i++) {
+    // Get the value of the i-th smallest byte and copy it to the byte vector.
+    uint64_t shift = i * 8;

[brucedawson, 2015/04/29 18:21:51]

Why is shift a uint64_t? The legal values are from 0-63 so an int or unsigned is
more than sufficient.

+    uint64_t byte_mask = uint64_t(0xff) << shift;

[Alexei Svitkine (slow), 2015/04/29 15:01:07]

Our style guide prefers static_cast<uint64_t>().

[Steven Holte, 2015/04/29 18:18:56]

Done.

+    (*output)[i] = (value & byte_mask) >> shift;
+  }
+}
+
 ByteVector* ByteVectorAnd(const ByteVector& lhs, ByteVector* rhs) {
   DCHECK_EQ(lhs.size(), rhs->size());
   for (size_t i = 0; i < lhs.size(); ++i) {
     (*rhs)[i] = lhs[i] & (*rhs)[i];
   }
   return rhs;
 }
 
 ByteVector* ByteVectorOr(const ByteVector& lhs, ByteVector* rhs) {
   DCHECK_EQ(lhs.size(), rhs->size());
@@ skipping 125 matching lines @@
     bytes_to_go -= n;
     generated_bytes_ += n;
     // Check max_number_of_bits_per_request from 10.1 Table 2
     // max_number_of_bits_per_request == 2^19 bits == 2^16 bytes
     DCHECK_LT(generated_bytes_, 1U << 16);
   }
   return bytes;
 }
 
 }  // namespace rappor