Add fake-nvram daemon to persist NVRAM data

Create a daemon to host the access-controlled NVRAM backend used for
testing in the emulators. This makes access-controlled NVRAM data
persistent, which more closely resembles the behavior of a real
implementation.

BUG:27764637
Change-Id: Iaf1a44881527896628452810561e315c572be31c

3 files changed, 34 insertions, 0 deletions

diff --git a/messages/include/nvram/messages/io.h b/messages/include/nvram/messages/io.h
index 522469f..08c1091 100644
--- a/messages/include/nvram/messages/io.h
+++ b/messages/include/nvram/messages/io.h
@@ -144,6 +144,23 @@ class NVRAM_EXPORT OutputStreamBuffer {
   uint8_t* end_ = nullptr;
 };
 
+// An |OutputStreamBuffer| backed by a single data buffer.
+class NVRAM_EXPORT ArrayOutputStreamBuffer : public OutputStreamBuffer {
+ public:
+  ArrayOutputStreamBuffer() = default;
+  ArrayOutputStreamBuffer(void* data, size_t size)
+      : OutputStreamBuffer(data, size), data_(pos_) {}
+  ArrayOutputStreamBuffer(void* data, void* end)
+      : OutputStreamBuffer(data, end), data_(pos_) {}
+  ~ArrayOutputStreamBuffer() override = default;
+
+  // Returns the number of bytes already written.
+  size_t bytes_written() const { return pos_ - data_; }
+
+ private:
+  uint8_t* data_ = nullptr;
+};
+
 // An |OutputStream| implementation that doesn't write anything, but just counts
 // the number of bytes written.
 class NVRAM_EXPORT CountingOutputStreamBuffer : public OutputStreamBuffer {
diff --git a/messages/include/nvram/messages/nvram_messages.h b/messages/include/nvram/messages/nvram_messages.h
index b352d9f..e574707 100644
--- a/messages/include/nvram/messages/nvram_messages.h
+++ b/messages/include/nvram/messages/nvram_messages.h
@@ -162,6 +162,11 @@ struct Response {
 template <typename Message>
 bool Encode(const Message& msg, Blob* blob);
 
+// Encode |msg| to |buffer|, which is of size |*size|. Updates |*size| to
+// indicate the number of bytes written. Returns true on success.
+template <typename Message>
+bool Encode(const Message& msg, void* buffer, size_t* size);
+
 // Decode |msg| from the |data| buffer, which contains |size| bytes. Returns
 // true if successful.
 template <typename Message>
diff --git a/messages/nvram_messages.cpp b/messages/nvram_messages.cpp
index a984876..7b1cafb 100644
--- a/messages/nvram_messages.cpp
+++ b/messages/nvram_messages.cpp
@@ -159,6 +159,16 @@ bool Encode(const Message& msg, Blob* blob) {
 }
 
 template <typename Message>
+bool Encode(const Message& msg, void* buffer, size_t* size) {
+  ArrayOutputStreamBuffer stream(buffer, *size);
+  if (!nvram::proto::Encode(msg, &stream)) {
+    return false;
+  }
+  *size = stream.bytes_written();
+  return true;
+}
+
+template <typename Message>
 bool Decode(const uint8_t* data, size_t size, Message* msg) {
   InputStreamBuffer stream(data, size);
   return nvram::proto::Decode(msg, &stream) && stream.Done();
@@ -166,9 +176,11 @@ bool Decode(const uint8_t* data, size_t size, Message* msg) {
 
 // Instantiate the templates for the |Request| and |Response| message types.
 template NVRAM_EXPORT bool Encode<Request>(const Request&, Blob*);
+template NVRAM_EXPORT bool Encode<Request>(const Request&, void*, size_t*);
 template NVRAM_EXPORT bool Decode<Request>(const uint8_t*, size_t, Request*);
 
 template NVRAM_EXPORT bool Encode<Response>(const Response&, Blob*);
+template NVRAM_EXPORT bool Encode<Response>(const Response&, void*, size_t*);
 template NVRAM_EXPORT bool Decode<Response>(const uint8_t*, size_t, Response*);
 
 }  // namespace nvram