Move crypto_helpers from sync to crypto

crypto_helpers only depends on resources in base and is used by sync and
password_manager.

BUG=
TEST=


Review URL: http://codereview.chromium.org/6873156

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@84223 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 33 insertions, 12 deletions

diff --git a/base/rand_util.cc b/base/rand_util.cc
index b823fa0..4140e9a 100644
--- a/base/rand_util.cc
+++ b/base/rand_util.cc
@@ -10,6 +10,7 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "base/string_util.h"
 
 namespace base {
 
@@ -47,19 +48,19 @@ uint64 RandGenerator(uint64 max) {
   return base::RandUint64() % max;
 }
 
-std::string RandBytesAsString(size_t length) {
-  const size_t kBitsPerChar = 8;
-  const int kCharsPerInt64 = sizeof(uint64)/sizeof(char);
-
-  std::string result(length, '\0');
-  uint64 entropy = 0;
-  for (size_t i = 0; i < result.size(); ++i) {
-    if (i % kCharsPerInt64 == 0)
-      entropy = RandUint64();
-    result[i] = static_cast<char>(entropy);
-    entropy >>= kBitsPerChar;
+void RandBytes(void* output, size_t output_length) {
+  uint64 random_int;
+  size_t random_int_size = sizeof(random_int);
+  for (size_t i = 0; i < output_length; i += random_int_size) {
+    random_int = base::RandUint64();
+    size_t copy_count = std::min(output_length - i, random_int_size);
+    memcpy(((uint8*)output) + i, &random_int, copy_count);
   }
+}
 
+std::string RandBytesAsString(size_t length) {
+  std::string result;
+  RandBytes(WriteInto(&result, length + 1), length);
   return result;
 }
 
diff --git a/base/rand_util.h b/base/rand_util.h
index d10cc8b..6bfbcb4 100644
--- a/base/rand_util.h
+++ b/base/rand_util.h
@@ -33,7 +33,14 @@ BASE_API double RandDouble();
 // the range [0, 1). Thread-safe.
 BASE_API double BitsToOpenEndedUnitInterval(uint64 bits);
 
-// Returns a random string of the specified length.
+// Fills |output_length| bytes of |output| with cryptographically strong random
+// data.
+BASE_API void RandBytes(void* output, size_t output_length);
+
+// Fills a string of length |length| with with cryptographically strong random
+// data and returns it.
+//
+// Not that this is a variation of |RandBytes| with a different return type.
 BASE_API std::string RandBytesAsString(size_t length);
 
 }  // namespace base
diff --git a/base/rand_util_unittest.cc b/base/rand_util_unittest.cc
index 3bdb815..d7fa37a 100644
--- a/base/rand_util_unittest.cc
+++ b/base/rand_util_unittest.cc
@@ -28,6 +28,19 @@ TEST(RandUtilTest, RandDouble) {
   EXPECT_LE(0.0, number);
 }
 
+TEST(RandUtilTest, RandBytes) {
+  const size_t buffer_size = 145;
+  char buffer[buffer_size];
+  memset(buffer, 0, buffer_size);
+  base::RandBytes(buffer, buffer_size);
+  char accumulator = 0;
+  for(size_t i = 0; i < buffer_size; ++i)
+    accumulator |= buffer[i];
+  // In theory this test can fail, but it won't before the universe dies of
+  // heat death.
+  EXPECT_NE(0, accumulator);
+}
+
 TEST(RandUtilTest, RandBytesAsString) {
   std::string random_string = base::RandBytesAsString(0);
   EXPECT_EQ(0U, random_string.size());