sketch partial ipc payload

ipc.cc

@@ -2,6 +2,45 @@
 #include "serializer.h"
 
 namespace {
+  struct BufferBuilder {
+    void* memory;
+    size_t size;
+    size_t capacity;
+
+    BufferBuilder() {
+      memory = malloc(128);
+      size = 0;
+      capacity = 128;
+    }
+
+    ~BufferBuilder() {
+      free(memory);
+      size = 0;
+      capacity = 0;
+    }
+
+    void AppendToBuffer(void* content, size_t content_size) {
+      if (size + content_size > capacity) {
+        // Grow memory if needed.
+        size_t new_size = capacity * 2;
+        while (new_size < size + content_size)
+          new_size *= 2;
+        void* new_memory = malloc(capacity);
+        memcpy(new_memory, memory, size);
+        free(memory);
+        memory = new_memory;
+
+        // Append new content into memory.
+        memcpy((char*)memory + size, content, content_size);
+        size += content_size;
+      }
+    }
+
+    void Reset() {
+      size = 0;
+    }
+  };
+
   // JSON-encoded message that is passed across shared memory.
   //
   // Messages are funky objects. They contain potentially variable amounts of
@@ -85,6 +124,47 @@ struct IpcDirectionalChannel::MessageBuffer {
   JsonMessage* free_message() {
     return message_at_offset(metadata()->bytes_used);
   }
+
+  struct Iterator {
+    void* buffer;
+    size_t remaining_bytes;
+
+    Iterator(void* buffer, size_t remaining_bytes) : remaining_bytes(remaining_bytes) {}
+
+    JsonMessage* get() const {
+      assert(buffer);
+      return reinterpret_cast<JsonMessage*>(buffer);
+    }
+
+    JsonMessage* operator->() const {
+      return get();
+    }
+
+    Iterator operator++() const {
+      size_t next_message_offset = sizeof(JsonMessage) + get()->payload_size;
+      if (next_message_offset >= remaining_bytes) {
+        assert(next_message_offset == remaining_bytes);
+        return Iterator(nullptr, 0);
+      }
+
+      auto* next_message = (char*)buffer + next_message_offset;
+      return Iterator(next_message, remaining_bytes - next_message_offset);
+    }
+
+    bool operator==(const Iterator& other) const {
+      return buffer == other.buffer && remaining_bytes == other.remaining_bytes;
+    }
+    bool operator!=(const Iterator& other) const {
+      return !(*this == other);
+    }
+  };
+
+  Iterator begin() {
+    return Iterator(first_message(), metadata()->bytes_used);
+  }
+  Iterator end() {
+    return Iterator(nullptr, 0);
+  }
 };
 
 IpcDirectionalChannel::IpcDirectionalChannel(const std::string& name) {
@@ -170,19 +250,28 @@ std::vector<std::unique_ptr<IpcMessage>> IpcDirectionalChannel::TakeMessages() {
 
   std::vector<std::unique_ptr<IpcMessage>> result;
 
-  size_t offset = 0;
-  while (remaining_bytes > 0) {
-    JsonMessage* message = local_buffer->message_at_offset(offset);
-    std::cerr << "remaining_bytes=" << remaining_bytes << ", offset=" << offset << ", message->payload_size=" << message->payload_size << std::endl;
-    offset += message->payload_size;
-    remaining_bytes -= sizeof(JsonMessage) + message->payload_size;
-
+  // TODO
+  for (auto it = local_buffer->begin(); it != local_buffer->end(); ++it) {
+    // TODO: partial payload, maybe something like this:
+    //
+    //  if (it->partial_id != 0) {
+    //    auto* buf = CreateOrFindResizableBuffer(it->partial_id);
+    //    buf->Append(it->payload(), it->payload_size());
+    //    if (it->is_complete) {
+    //      Process(buf.payload(), buff.payload_size())
+    //      RemoveResizableBuffer(it->partial_id)
+    //    }
+    //  }
+    //  else {
+    //    Process(it->payload(), it->payload_size())
+    //  }
+    //
     rapidjson::Document document;
-    document.Parse(message->payload(), message->payload_size);
+    document.Parse(it->payload(), it->payload_size);
     bool has_error = document.HasParseError();
     auto error = document.GetParseError();
 
-    std::unique_ptr<IpcMessage> base_message = IpcRegistry::instance()->Allocate(message->ipc_id);
+    std::unique_ptr<IpcMessage> base_message = IpcRegistry::instance()->Allocate(it->ipc_id);
     base_message->Deserialize(document);
     result.emplace_back(std::move(base_message));
   }