nixd/librpc: use exceptions for IO operations

nixd/librpc/include/nixd/rpc/IO.h

@@ -1,12 +1,12 @@
 #pragma once
 
-#include <cstdint>
-#include <string>
+#include <cstddef>
+
+#include <sys/types.h>
 
 namespace nixd::rpc {
 
 /// \brief Read N bytes from FD into Buf, block until N bytes are read.
-/// \returns the number of bytes read, or -1 on error. (errno is set)
-long readBytes(int FD, void *Buf, std::size_t N);
+size_t readBytes(int FD, void *Buf, std::size_t N);
 
 } // namespace nixd::rpc

nixd/librpc/include/nixd/rpc/Transport.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include "nixd/rpc/Protocol.h"
+
 #include <string_view>
 #include <vector>
 
@@ -10,9 +12,26 @@ class Transport {
   int OutboundFD;
 
 protected:
-  [[nodiscard]] int send(std::string_view Msg) const;
+  /// \brief Wraps a message with it's length, and then send it.
+  void send(std::string_view Msg) const;
+
+  /// \brief Read a message and then forms a packet.
+  [[nodiscard]] std::vector<char> recv() const;
+
+  template <class T> T recvPacket() const {
+    std::vector<char> Buf = recv();
+    T Data;
+    std::string_view D = {Buf.begin(), Buf.end()};
+    readBytecode(D, Data);
+    return Data;
+  }
+
+  template <class T> void sendPacket(const T &Data) {
+    auto Str = bc::toBytecode(Data);
+    send(Str);
+  }
 
-  [[nodiscard]] virtual int handleInbound(const std::vector<char> &Buf) = 0;
+  virtual void handleInbound(const std::vector<char> &Buf) = 0;
 
 public:
   [[nodiscard]] int run();

nixd/librpc/src/IO.cpp

@@ -1,18 +1,20 @@
 #include "nixd/rpc/IO.h"
 
+#include <system_error>
+
 #include <unistd.h>
 
 namespace nixd::rpc {
 
-long readBytes(int FD, void *Buf, std::size_t N) {
-  std::size_t Read = 0;
+size_t readBytes(int FD, void *Buf, std::size_t N) {
+  size_t Read = 0;
   while (Read < N) {
-    auto BytesRead = read(FD, static_cast<char *>(Buf) + Read, N - Read);
+    size_t BytesRead = read(FD, static_cast<char *>(Buf) + Read, N - Read);
     if (BytesRead <= 0)
-      return BytesRead;
+      throw std::system_error(std::make_error_code(std::errc(errno)));
     Read += BytesRead;
   }
-  return static_cast<long>(Read);
+  return Read;
 }
 
 } // namespace nixd::rpc

nixd/librpc/src/Transport.cpp

@@ -1,36 +1,37 @@
 #include "nixd/rpc/Transport.h"
 #include "nixd/rpc/IO.h"
 
-#include <unistd.h>
+#include <system_error>
 #include <vector>
 
+#include <unistd.h>
+
 namespace nixd::rpc {
 
 using MessageSizeT = std::size_t;
 
-int Transport::send(std::string_view Msg) const {
+void Transport::send(std::string_view Msg) const {
   MessageSizeT Size = Msg.size();
   if (write(OutboundFD, &Size, sizeof(MessageSizeT)) < 0)
-    return -1;
+    throw std::system_error(std::make_error_code(std::errc(errno)));
   if (write(OutboundFD, Msg.data(), Msg.size()) < 0)
-    return -1;
-  return 0;
+    throw std::system_error(std::make_error_code(std::errc(errno)));
+}
+
+std::vector<char> Transport::recv() const {
+  MessageSizeT Size;
+  readBytes(InboundFD, &Size, sizeof(Size));
+
+  // Collect a message
+  std::vector<char> Buf(Size);
+  readBytes(InboundFD, Buf.data(), Size);
+  return Buf;
 }
 
 int Transport::run() {
   for (;;) {
-    MessageSizeT Size;
-    if (readBytes(InboundFD, &Size, sizeof(Size)) <= 0) {
-      // Handle error
-    }
-
-    // Then read the message
-    // Collect a message
-    std::vector<char> Buf(Size);
-    if (readBytes(InboundFD, Buf.data(), Size) <= 0)
-      return -1;
-    if (handleInbound(Buf) != 0)
-      return -1;
+    std::vector<char> Buf = recv();
+    handleInbound(Buf);
   }
   return 0;
 }