update readme

Update for Swift 4/5

README.md

@@ -1,5 +1,5 @@
 # SwiftSerial
-A Swift 3 Linux and Mac library for reading and writing to serial ports. This library has been tested to work on macOS Sierra, Linux Mint 18 (based on Ubuntu 16.04) and on the [Raspberry Pi 3 on Ubuntu 16.04](https://wiki.ubuntu.com/ARM/RaspberryPi). Other platforms using Ubuntu like the Beaglebone might work as well.
+A Swift Linux and Mac library for reading and writing to serial ports. This library has been tested to work on macOS Sierra, Linux Mint 18 (based on Ubuntu 16.04) and on the [Raspberry Pi 3 on Ubuntu 16.04](https://wiki.ubuntu.com/ARM/RaspberryPi). Other platforms using Ubuntu like the Beaglebone might work as well.
 
 This library is an improvement over my previous now deprecated library [SwiftLinuxSerial](https://github.com/yeokm1/SwiftLinuxSerial) which was less Swifty and supported only Linux. This library is thanks largely to [Jay Jun](https://github.com/jayjun). His original pull request can be found [here](https://github.com/yeokm1/SwiftLinuxSerial/pull/1).
 

Sources/SwiftSerial.swift

@@ -209,6 +209,8 @@ public enum PortError: Int32, Error {
     case mustReceiveOrTransmit
     case mustBeOpen
     case stringsMustBeUTF8
+    case unableToConvertByteToCharacter
+    case deviceNotConnected
 }
 
 public class SerialPort {
@@ -371,6 +373,12 @@ extension SerialPort {
             throw PortError.mustBeOpen
         }
 
+        var s: stat = stat()
+        fstat(fileDescriptor, &s)
+        if s.st_nlink != 1 {
+            throw PortError.deviceNotConnected
+        }
+
         let bytesRead = read(fileDescriptor, buffer, size)
         return bytesRead
     }
@@ -378,7 +386,7 @@ extension SerialPort {
     public func readData(ofLength length: Int) throws -> Data {
         let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: length)
         defer {
-            buffer.deallocate(capacity: length)
+            buffer.deallocate()
         }
 
         let bytesRead = try readBytes(into: buffer, size: length)
@@ -417,13 +425,16 @@ extension SerialPort {
         var data = Data()
         let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: 1)
         defer {
-            buffer.deallocate(capacity: 1)
+            buffer.deallocate()
         }
 
         while true {
             let bytesRead = try readBytes(into: buffer, size: 1)
 
             if bytesRead > 0 {
+                if ( buffer[0] > 127) {
+                    throw PortError.unableToConvertByteToCharacter
+                }
                 let character = CChar(buffer[0])
 
                 if character == terminator {
@@ -450,7 +461,7 @@ extension SerialPort {
         let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: 1)
 
         defer {
-            buffer.deallocate(capacity: 1)
+            buffer.deallocate()
         }
 
         while true {
@@ -487,7 +498,7 @@ extension SerialPort {
         let size = data.count
         let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: size)
         defer {
-            buffer.deallocate(capacity: size)
+            buffer.deallocate()
         }
 
         data.copyBytes(to: buffer, count: size)