Device/Port: Read() returns std::size_t

There are no error conditions, only an empty buffer.

src/Device/Port/BufferedPort.cpp

@@ -60,17 +60,14 @@ BufferedPort::StartRxThread()
   return true;
 }
 
-int
+std::size_t
 BufferedPort::Read(void *dest, std::size_t length)
 {
   assert(!running);
 
   std::lock_guard<Mutex> lock(mutex);
 
   auto r = buffer.Read();
-  if (r.size == 0)
-    return -1;
-
   std::size_t nbytes = std::min(length, r.size);
   std::copy_n(r.data, nbytes, (std::byte *)dest);
   buffer.Consume(nbytes);

src/Device/Port/BufferedPort.hpp

@@ -60,7 +60,7 @@ class BufferedPort : public Port, protected DataHandler {
 public:
   /* virtual methods from class Port */
   void Flush() override;
-  int Read(void *Buffer, std::size_t Size) override;
+  std::size_t Read(void *Buffer, std::size_t Size) override;
   void WaitRead(std::chrono::steady_clock::duration timeout) override;
   bool StopRxThread() override;
   bool StartRxThread() override;

src/Device/Port/DumpPort.cpp

@@ -143,17 +143,17 @@ DumpPort::StartRxThread()
   return port->StartRxThread();
 }
 
-int
+std::size_t
 DumpPort::Read(void *buffer, std::size_t size)
 {
   const bool enabled = CheckEnabled();
   if (enabled)
     LogFormat("Read(%u)", (unsigned)size);
 
-  int nbytes = port->Read(buffer, size);
+  auto nbytes = port->Read(buffer, size);
 
   if (enabled) {
-    LogFormat("Read(%u)=%d", (unsigned)size, nbytes);
+    LogFormat("Read(%u)=%u", (unsigned)size, (unsigned)nbytes);
     if (nbytes > 0)
       HexDump("R ", buffer, nbytes);
   }

src/Device/Port/DumpPort.hpp

@@ -90,7 +90,7 @@ class DumpPort final : public Port {
   void SetBaudrate(unsigned baud_rate) override;
   bool StopRxThread() override;
   bool StartRxThread() override;
-  int Read(void *buffer, std::size_t size) override;
+  std::size_t Read(void *buffer, std::size_t size) override;
   void WaitRead(std::chrono::steady_clock::duration timeout) override;
 };
 

src/Device/Port/K6BtPort.cpp

@@ -180,7 +180,7 @@ K6BtPort::StartRxThread(void)
   return port->StartRxThread();
 }
 
-int
+std::size_t
 K6BtPort::Read(void *Buffer, std::size_t Size)
 {
   return port->Read(Buffer, Size);

src/Device/Port/K6BtPort.hpp

@@ -63,7 +63,7 @@ class K6BtPort : public Port {
   unsigned GetBaudrate() const noexcept override;
   bool StopRxThread() override;
   bool StartRxThread() override;
-  int Read(void *Buffer, std::size_t Size) override;
+  std::size_t Read(void *Buffer, std::size_t Size) override;
   void WaitRead(std::chrono::steady_clock::duration timeout) override;
 };
 

src/Device/Port/NullPort.cpp

@@ -83,10 +83,10 @@ NullPort::SetBaudrate(unsigned)
 {
 }
 
-int
+std::size_t
 NullPort::Read(void *Buffer, std::size_t Size)
 {
-  return -1;
+  return 0;
 }
 
 void

src/Device/Port/NullPort.hpp

@@ -44,7 +44,7 @@ class NullPort : public Port, private DataHandler  {
   void SetBaudrate(unsigned baud_rate) override;
   bool StopRxThread() override;
   bool StartRxThread() override;
-  int Read(void *Buffer, std::size_t Size) override;
+  std::size_t Read(void *Buffer, std::size_t Size) override;
 
   [[noreturn]]
   void WaitRead(std::chrono::steady_clock::duration timeout) override;

src/Device/Port/Port.hpp

@@ -167,10 +167,11 @@ class Port {
    * Read data from the serial port
    * @param Buffer Pointer to the buffer
    * @param Size Size of the buffer
-   * @return Number of bytes read from the serial port or -1 on failure
+   * @return Number of bytes read from the port (0 if no data is
+   * available currently)
    */
   gcc_nonnull_all
-  virtual int Read(void *Buffer, std::size_t Size) = 0;
+  virtual std::size_t Read(void *Buffer, std::size_t Size) = 0;
 
   /**
    * Wait until data becomes available or the timeout expires.

test/src/FaultInjectionPort.hpp

@@ -79,9 +79,9 @@ class FaultInjectionPort : public Port {
     return true;
   }
 
-  int Read(void *Buffer, size_t Size) override {
+  std::size_t Read(void *Buffer, size_t Size) override {
     if (inject_port_fault == 0)
-      return -1;
+      return 0;
 
     if (--inject_port_fault == 0)
       StateChanged();

test/src/ReadPort.cpp

@@ -64,10 +64,7 @@ try {
       continue;
     }
 
-    int nbytes = port->Read(buffer, sizeof(buffer));
-    if (nbytes < 0)
-      break;
-
+    std::size_t nbytes = port->Read(buffer, sizeof(buffer));
     fwrite((const void *)buffer, 1, nbytes, stdout);
   }