Generate Instance ID locally.

components/gcm_driver/instance_id/instance_id_impl.cc

Index: components/gcm_driver/instance_id/instance_id_impl.cc
diff --git a/components/gcm_driver/instance_id/instance_id_impl.cc b/components/gcm_driver/instance_id/instance_id_impl.cc
index 4d76ad2286cde3fddb590f048170526d1b93b50c..ad62823ec76a396a04a541e8317aa48f6fd33907 100644
--- a/components/gcm_driver/instance_id/instance_id_impl.cc
+++ b/components/gcm_driver/instance_id/instance_id_impl.cc
@@ -4,7 +4,12 @@
 
 #include "components/gcm_driver/instance_id/instance_id_impl.h"
 
+#include <algorithm>
+#include "base/base64.h"
+#include "base/bind.h"
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "crypto/random.h"
 
 namespace instance_id {
 
@@ -21,13 +26,12 @@ InstanceIDImpl::~InstanceIDImpl() {
 }
 
 std::string InstanceIDImpl::GetID() {
-  NOTIMPLEMENTED();
-  return std::string();
+  EnsureIDGenerated();
+  return id_;
 }
 
 base::Time InstanceIDImpl::GetCreationTime() {
-  NOTIMPLEMENTED();
-  return base::Time();
+  return creation_time_;
 }
 
 void InstanceIDImpl::GetToken(
@@ -45,7 +49,44 @@ void InstanceIDImpl::DeleteToken(const std::string& audience,
 }
 
 void InstanceIDImpl::DeleteID(const DeleteIDCallback& callback) {
-  NOTIMPLEMENTED();
+  // TODO(jianli): Delete the ID from the store.
+  id_.clear();
+  creation_time_ = base::Time();
+
+  base::MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(callback, this, InstanceID::SUCCESS));
+}
+
+void InstanceIDImpl::EnsureIDGenerated() {
+  if (!id_.empty())
+    return;
+
+  // Now produce the ID in the following steps:
+
+  // 1) Generates the cryptographically secure random number in 8 bytes.

[agl, 2015/05/04 21:55:54]

You can't have a cryptographically secure, 60-bit number. How about making
kInstanceIDByteLength 16? 124 is reasonable.

[jianli, 2015/05/04 22:07:20]

Updated the comment per discussion.

+  uint8 bytes[kInstanceIDByteLength];
+  crypto::RandBytes(bytes, kInstanceIDByteLength);

[agl, 2015/05/04 21:55:54]

s/kInstanceIDByteLength/sizeof(bytes)/

[jianli, 2015/05/04 22:07:20]

Done.

+
+  // 2) Transforms the first 4 bits to 0x7.

[agl, 2015/05/04 21:55:54]

Comment should explain why.

[jianli, 2015/05/04 22:07:20]

Done.

+  uint8 b0 = bytes[0];

[agl, 2015/05/04 21:55:54]

bytes[0] &= 0x0f;
bytes[0] |= 0x70;

?

[jianli, 2015/05/04 22:07:20]

Done.

+  b0 = 0x70 + (0xF & b0);
+  bytes[0] = b0 & 0xFF;
+
+  // 3) Encode the value in Android-compatible base64 scheme:
+  //    * URL safe: '/' replaced by '_' and '+' replaced by '-'.
+  //    * No padding: any trailing '=' will be removed.
+  base::Base64Encode(
+      base::StringPiece(reinterpret_cast<const char*>(bytes),
+                        kInstanceIDByteLength),
+      &id_);
+  std::replace(id_.begin(), id_.end(), '+', '-');
+  std::replace(id_.begin(), id_.end(), '/', '_');
+  id_.erase(std::remove(id_.begin(), id_.end(), '='), id_.end());
+
+  creation_time_ = base::Time::Now();
+
+  // TODO(jianli):  Save the ID to the store.
 }
 
 }  // namespace instance_id