From 6853f8c05db6aa183e0dec674649f9508a937fc9 Mon Sep 17 00:00:00 2001
From: William Woodall <wjwwood@gmail.com>
Date: Sat, 4 Feb 2012 21:56:10 -0600
Subject: [PATCH] Fixing a reading buffer bug and expanding the example

---
 examples/serial_example.cc | 149 +++++++++++++++++++++++++++----------
 src/impl/unix.cc           |   3 +-
 2 files changed, 110 insertions(+), 42 deletions(-)

diff --git a/examples/serial_example.cc b/examples/serial_example.cc
index 3ba886b..93de9af 100644
--- a/examples/serial_example.cc
+++ b/examples/serial_example.cc
@@ -1,3 +1,21 @@
+/***
+ * This example expects the serial port has a loopback on it.
+ *
+ * Alternatively, you could use an Arduino:
+ * 
+ * <pre>
+ *  setup() {
+ *    Serial.begin(<insert your baudrate here>);
+ *  }
+ * 
+ *  loop() {
+ *    if (Serial.available()) {
+ *      Serial.write(Serial.read());
+ *    }
+ *  }
+ * </pre>
+ */
+
 #include <string>
 #include <iostream>
 #include <cstdio>
@@ -27,48 +45,97 @@ void my_sleep(unsigned long milliseconds) {
 
 int run(int argc, char **argv)
 {
-    if(argc < 3) {
-      cerr << "Usage: test_serial <serial port address> ";
-      cerr << "<baudrate> [test string]" << endl;
-      return 0;
-    }
-    // Argument 1 is the serial port
-    string port(argv[1]);
-
-    // Argument 2 is the baudrate
-    unsigned long baud = 0;
-    sscanf(argv[2], "%lu", &baud);
-
-    // port, baudrate, timeout in milliseconds
-    serial::Serial serial(port, baud, 1000);
-
-    cout << "Is the serial port open?";
-    if(serial.isOpen())
-        cout << " Yes." << endl;
-    else
-        cout << " No." << endl;
-
-    int count = 0;
-    string test_string;
-    if (argc == 4) {
-      test_string = argv[3];
-    } else {
-      test_string = "Testing.";
-    }
-    while (true) {
-      size_t bytes_wrote = serial.write(test_string);
-
-      string result = serial.read(test_string.length());
-
-      cout << "Iteration: " << count << ", Bytes written: ";
-      cout << bytes_wrote << ", Bytes read: ";
-      cout << result.length() << ", String read: " << result << endl;
-
-      count += 1;
-      my_sleep(10);
-    }
-    
+  if(argc < 3) {
+    cerr << "Usage: test_serial <serial port address> ";
+    cerr << "<baudrate> [test string]" << endl;
     return 0;
+  }
+  // Argument 1 is the serial port
+  string port(argv[1]);
+
+  // Argument 2 is the baudrate
+  unsigned long baud = 0;
+  sscanf(argv[2], "%lu", &baud);
+
+  // port, baudrate, timeout in milliseconds
+  serial::Serial my_serial(port, baud, 1000);
+
+  cout << "Is the serial port open?";
+  if(my_serial.isOpen())
+    cout << " Yes." << endl;
+  else
+    cout << " No." << endl;
+
+  // Get the Test string
+  int count = 0;
+  string test_string;
+  if (argc == 4) {
+    test_string = argv[3];
+  } else {
+    test_string = "Testing.";
+  }
+
+  // Test the timeout, there should be 1 second between prints
+  cout << "Timeout == 1000ms, asking for 1 more byte than written." << endl;
+  while (count < 10) {
+    size_t bytes_wrote = my_serial.write(test_string);
+
+    string result = my_serial.read(test_string.length()+1);
+
+    cout << "Iteration: " << count << ", Bytes written: ";
+    cout << bytes_wrote << ", Bytes read: ";
+    cout << result.length() << ", String read: " << result << endl;
+
+    count += 1;
+  }
+
+  // Test the timeout at 250ms
+  my_serial.setTimeout(250);
+  count = 0;
+  cout << "Timeout == 250ms, asking for 1 more byte than written." << endl;
+  while (count < 10) {
+    size_t bytes_wrote = my_serial.write(test_string);
+
+    string result = my_serial.read(test_string.length()+1);
+
+    cout << "Iteration: " << count << ", Bytes written: ";
+    cout << bytes_wrote << ", Bytes read: ";
+    cout << result.length() << ", String read: " << result << endl;
+
+    count += 1;
+  }
+
+  // Test the timeout at 250ms, but asking exactly for what was written
+  count = 0;
+  cout << "Timeout == 250ms, asking for exactly what was written." << endl;
+  while (count < 10) {
+    size_t bytes_wrote = my_serial.write(test_string);
+
+    string result = my_serial.read(test_string.length());
+
+    cout << "Iteration: " << count << ", Bytes written: ";
+    cout << bytes_wrote << ", Bytes read: ";
+    cout << result.length() << ", String read: " << result << endl;
+
+    count += 1;
+  }
+
+  // Test the timeout at 250ms, but asking for 1 less than what was written
+  count = 0;
+  cout << "Timeout == 250ms, asking for 1 less than was written." << endl;
+  while (count < 10) {
+    size_t bytes_wrote = my_serial.write(test_string);
+
+    string result = my_serial.read(test_string.length()-1);
+
+    cout << "Iteration: " << count << ", Bytes written: ";
+    cout << bytes_wrote << ", Bytes read: ";
+    cout << result.length() << ", String read: " << result << endl;
+
+    count += 1;
+  }
+
+  return 0;
 }
 
 int main(int argc, char **argv) {
diff --git a/src/impl/unix.cc b/src/impl/unix.cc
index cb84943..b8038a6 100644
--- a/src/impl/unix.cc
+++ b/src/impl/unix.cc
@@ -454,7 +454,8 @@ Serial::SerialImpl::read (unsigned char* buf, size_t size)
       if (FD_ISSET (fd_, &readfds)) {
         // This should be non-blocking returning only what is avaialble now
         //  Then returning so that select can block again.
-        ssize_t bytes_read_now = ::read (fd_, buf, size-bytes_read);
+        ssize_t bytes_read_now =
+          ::read (fd_, buf+bytes_read, size-bytes_read);
         // read should always return some data as select reported it was
         // ready to read when we get to this point.
         if (bytes_read_now < 1)