Moving write errors out of return value into separate API methods.

write(), print(), println() now return size_t (and don't use negative values to signal errors).
Print adds writeError() for checking for write errors, clearWriteError() to reset the flag to false, and a protected setWriteError() for signalling errors.

http://code.google.com/p/arduino/issues/detail?id=598

hardware/arduino/cores/arduino/HardwareSerial.cpp

@@ -352,7 +352,7 @@ void HardwareSerial::flush()
     ;
 }
 
-ssize_t HardwareSerial::write(uint8_t c)
+size_t HardwareSerial::write(uint8_t c)
 {
   int i = (_tx_buffer->head + 1) % SERIAL_BUFFER_SIZE;
 	

hardware/arduino/cores/arduino/HardwareSerial.h

@@ -55,7 +55,7 @@ class HardwareSerial : public Stream
     virtual int peek(void);
     virtual int read(void);
     virtual void flush(void);
-    virtual ssize_t write(uint8_t);
+    virtual size_t write(uint8_t);
     using Print::write; // pull in write(str) and write(buf, size) from Print
 };
 

hardware/arduino/cores/arduino/Print.cpp

@@ -30,85 +30,80 @@
 // Public Methods //////////////////////////////////////////////////////////////
 
 /* default implementation: may be overridden */
-ssize_t Print::write(const char *str)
+size_t Print::write(const char *str)
 {
-  ssize_t n = 0;
+  size_t n = 0;
   while (*str) {
-    if (write(*str++) <= 0) break;
-    n++;
+    n += write(*str++);
   }
   return n;
 }
 
 /* default implementation: may be overridden */
-ssize_t Print::write(const uint8_t *buffer, size_t size)
+size_t Print::write(const uint8_t *buffer, size_t size)
 {
-  ssize_t n = 0;
+  size_t n = 0;
   while (size--) {
-    if (write(*buffer++) <= 0) break;
-    n++;
+    n += write(*buffer++);
   }
   return n;
 }
 
-ssize_t Print::print(const __FlashStringHelper *ifsh)
+size_t Print::print(const __FlashStringHelper *ifsh)
 {
   const prog_char *p = (const prog_char *)ifsh;
-  ssize_t n = 0;
+  size_t n = 0;
   while (1) {
     unsigned char c = pgm_read_byte(p++);
     if (c == 0) break;
-    if (write(c) <= 0) break;
-    n++;
+    n += write(c);
   }
   return n;
 }
 
-ssize_t Print::print(const String &s)
+size_t Print::print(const String &s)
 {
-  ssize_t n = 0;
+  size_t n = 0;
   for (int i = 0; i < s.length(); i++) {
-    if (write(s[i]) < 0) break;
-    n++;
+    n += write(s[i]);
   }
   return n;
 }
 
-ssize_t Print::print(const char str[])
+size_t Print::print(const char str[])
 {
   return write(str);
 }
 
-ssize_t Print::print(char c)
+size_t Print::print(char c)
 {
   return write(c);
 }
 
-ssize_t Print::print(unsigned char b, int base)
+size_t Print::print(unsigned char b, int base)
 {
   return print((unsigned long) b, base);
 }
 
-ssize_t Print::print(int n, int base)
+size_t Print::print(int n, int base)
 {
   return print((long) n, base);
 }
 
-ssize_t Print::print(unsigned int n, int base)
+size_t Print::print(unsigned int n, int base)
 {
   return print((unsigned long) n, base);
 }
 
-ssize_t Print::print(long n, int base)
+size_t Print::print(long n, int base)
 {
   if (base == 0) {
     return write(n);
   } else if (base == 10) {
     if (n < 0) {
       int t = print('-');
-      if (t <= 0) return t;
       n = -n;
-      return printNumber(n, 10) + 1;
+      return printNumber(n, 10) + t;
     }
     return printNumber(n, 10);
   } else {
@@ -116,110 +111,109 @@ ssize_t Print::print(long n, int base)
   }
 }
 
-ssize_t Print::print(unsigned long n, int base)
+size_t Print::print(unsigned long n, int base)
 {
   if (base == 0) return write(n);
   else return printNumber(n, base);
 }
 
-ssize_t Print::print(double n, int digits)
+size_t Print::print(double n, int digits)
 {
   return printFloat(n, digits);
 }
 
-ssize_t Print::println(const __FlashStringHelper *ifsh)
+size_t Print::println(const __FlashStringHelper *ifsh)
 {
-  ssize_t n = print(ifsh);
-  if (n >= 0) n += println();
+  size_t n = print(ifsh);
+  n += println();
   return n;
 }
 
-ssize_t Print::print(const Printable& x)
+size_t Print::print(const Printable& x)
 {
   return x.printTo(*this);
 }
 
-ssize_t Print::println(void)
+size_t Print::println(void)
 {
-  ssize_t t = print('\r');
-  if (t <= 0) return t;
-  if (print('\n') <= 0) return 1;
-  return 2;
-}
-
-ssize_t Print::println(const String &s)
-{
-  ssize_t n = print(s);
-  if (n >= 0) n += println();
+  size_t n = print('\r');
+  n += print('\n');
   return n;
 }
 
-ssize_t Print::println(const char c[])
+size_t Print::println(const String &s)
 {
-  ssize_t n = print(c);
-  if (n >= 0) n += println();
+  size_t n = print(s);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(char c)
+size_t Print::println(const char c[])
 {
-  ssize_t n = print(c);
-  if (n > 0) n += println();
+  size_t n = print(c);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(unsigned char b, int base)
+size_t Print::println(char c)
 {
-  ssize_t n = print(b, base);
-  if (n >= 0) n += println();
+  size_t n = print(c);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(int num, int base)
+size_t Print::println(unsigned char b, int base)
 {
-  ssize_t n = print(num, base);
-  if (n >= 0) n += println();
+  size_t n = print(b, base);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(unsigned int num, int base)
+size_t Print::println(int num, int base)
 {
-  ssize_t n = print(num, base);
-  if (n >= 0) n += println();
+  size_t n = print(num, base);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(long num, int base)
+size_t Print::println(unsigned int num, int base)
 {
-  ssize_t n = print(num, base);
-  if (n >= 0) n += println();
+  size_t n = print(num, base);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(unsigned long num, int base)
+size_t Print::println(long num, int base)
 {
-  ssize_t n = print(num, base);
-  if (n >= 0) n += println();
+  size_t n = print(num, base);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(double num, int digits)
+size_t Print::println(unsigned long num, int base)
 {
-  ssize_t n = print(num, digits);
-  if (n >= 0) n += println();
+  size_t n = print(num, base);
+  n += println();
   return n;
 }
 
-ssize_t Print::println(const Printable& x)
+size_t Print::println(double num, int digits)
 {
-  ssize_t n = print(x);
-  if (n >= 0) n += println();
+  size_t n = print(num, digits);
+  n += println();
+  return n;
+}
+
+size_t Print::println(const Printable& x)
+{
+  size_t n = print(x);
+  n += println();
   return n;
 }
 
 // Private Methods /////////////////////////////////////////////////////////////
 
-ssize_t Print::printNumber(unsigned long n, uint8_t base) {
+size_t Print::printNumber(unsigned long n, uint8_t base) {
   char buf[8 * sizeof(long) + 1]; // Assumes 8-bit chars plus zero byte.
   char *str = &buf[sizeof(buf) - 1];
 
@@ -238,14 +232,14 @@ ssize_t Print::printNumber(unsigned long n, uint8_t base) {
   return write(str);
 }
 
-ssize_t Print::printFloat(double number, uint8_t digits) 
+size_t Print::printFloat(double number, uint8_t digits) 
 { 
-  ssize_t n = 0, t;
+  size_t n = 0;
   
   // Handle negative numbers
   if (number < 0.0)
   {
-     if ((n = print('-')) <= 0) return n;
+     n += print('-');
      number = -number;
   }
 
@@ -259,15 +253,11 @@ ssize_t Print::printFloat(double number, uint8_t digits)
   // Extract the integer part of the number and print it
   unsigned long int_part = (unsigned long)number;
   double remainder = number - (double)int_part;
-  if ((t = print(int_part)) < 0) return n;
-  
-  n += t;
+  n += print(int_part);
 
   // Print the decimal point, but only if there are digits beyond
   if (digits > 0) {
-    t = print("."); 
-    if (t <= 0) return n;
-    n += t;
+    n += print("."); 
   }
 
   // Extract digits from the remainder one at a time
@@ -275,9 +265,7 @@ ssize_t Print::printFloat(double number, uint8_t digits)
   {
     remainder *= 10.0;
     int toPrint = int(remainder);
-    t = print(toPrint);
-    if (t <= 0) return n;
-    n += t;
+    n += print(toPrint);
     remainder -= toPrint; 
   } 
   

hardware/arduino/cores/arduino/Print.h

@@ -23,8 +23,6 @@
 #include <inttypes.h>
 #include <stdio.h> // for size_t
 
-typedef int ssize_t;
-
 #include "WString.h"
 #include "Printable.h"
 
@@ -36,37 +34,45 @@ typedef int ssize_t;
 class Print
 {
   private:
-    ssize_t printNumber(unsigned long, uint8_t);
-    ssize_t printFloat(double, uint8_t);
+    int write_error;
+    size_t printNumber(unsigned long, uint8_t);
+    size_t printFloat(double, uint8_t);
+  protected:
+    void setWriteError(int err = 1) { write_error = err; }
   public:
-    virtual ssize_t write(uint8_t) = 0;
-    virtual ssize_t write(const char *str);
-    virtual ssize_t write(const uint8_t *buffer, size_t size);
+    Print() : write_error(0) {}
   
-    ssize_t print(const __FlashStringHelper *);
-    ssize_t print(const String &);
-    ssize_t print(const char[]);
-    ssize_t print(char);
-    ssize_t print(unsigned char, int = DEC);
-    ssize_t print(int, int = DEC);
-    ssize_t print(unsigned int, int = DEC);
-    ssize_t print(long, int = DEC);
-    ssize_t print(unsigned long, int = DEC);
-    ssize_t print(double, int = 2);
-    ssize_t print(const Printable&);
+    int writeError() { return write_error; }
+    void clearWriteError() { setWriteError(0); }
   
-    ssize_t println(const __FlashStringHelper *);
-    ssize_t println(const String &s);
-    ssize_t println(const char[]);
-    ssize_t println(char);
-    ssize_t println(unsigned char, int = DEC);
-    ssize_t println(int, int = DEC);
-    ssize_t println(unsigned int, int = DEC);
-    ssize_t println(long, int = DEC);
-    ssize_t println(unsigned long, int = DEC);
-    ssize_t println(double, int = 2);
-    ssize_t println(const Printable&);
-    ssize_t println(void);
+    virtual size_t write(uint8_t) = 0;
+    virtual size_t write(const char *str);
+    virtual size_t write(const uint8_t *buffer, size_t size);
+    
+    size_t print(const __FlashStringHelper *);
+    size_t print(const String &);
+    size_t print(const char[]);
+    size_t print(char);
+    size_t print(unsigned char, int = DEC);
+    size_t print(int, int = DEC);
+    size_t print(unsigned int, int = DEC);
+    size_t print(long, int = DEC);
+    size_t print(unsigned long, int = DEC);
+    size_t print(double, int = 2);
+    size_t print(const Printable&);
+
+    size_t println(const __FlashStringHelper *);
+    size_t println(const String &s);
+    size_t println(const char[]);
+    size_t println(char);
+    size_t println(unsigned char, int = DEC);
+    size_t println(int, int = DEC);
+    size_t println(unsigned int, int = DEC);
+    size_t println(long, int = DEC);
+    size_t println(unsigned long, int = DEC);
+    size_t println(double, int = 2);
+    size_t println(const Printable&);
+    size_t println(void);
 };
 
 #endif

hardware/arduino/cores/arduino/Printable.h

@@ -30,7 +30,7 @@ class Print;
 class Printable
 {
   public:
-    virtual ssize_t printTo(Print& p) const = 0;
+    virtual size_t printTo(Print& p) const = 0;
 };
 
 #endif

libraries/Ethernet/Client.cpp

@@ -70,17 +70,23 @@ int Client::connect(IPAddress ip, uint16_t port) {
   return 1;
 }
 
-ssize_t Client::write(uint8_t b) {
+size_t Client::write(uint8_t b) {
   return write(&b, 1);
 }
 
-ssize_t Client::write(const char *str) {
+size_t Client::write(const char *str) {
   return write((const uint8_t *) str, strlen(str));
 }
 
-ssize_t Client::write(const uint8_t *buf, size_t size) {
-  if (_sock == MAX_SOCK_NUM) return -1;
-  if (!send(_sock, buf, size)) return -2;
+size_t Client::write(const uint8_t *buf, size_t size) {
+  if (_sock == MAX_SOCK_NUM) {
+    setWriteError();
+    return 0;
+  }
+  if (!send(_sock, buf, size)) {
+    setWriteError();
+    return 0;
+  }
   return size;
 }
 

libraries/Ethernet/Client.h

@@ -12,9 +12,9 @@ public:
   uint8_t status();
   int connect(IPAddress ip, uint16_t port);
   int connect(const char *host, uint16_t port);
-  virtual ssize_t write(uint8_t);
-  virtual ssize_t write(const char *str);
-  virtual ssize_t write(const uint8_t *buf, size_t size);
+  virtual size_t write(uint8_t);
+  virtual size_t write(const char *str);
+  virtual size_t write(const uint8_t *buf, size_t size);
   virtual int available();
   virtual int read();
   virtual int read(uint8_t *buf, size_t size);

libraries/Ethernet/IPAddress.cpp

@@ -42,15 +42,15 @@ bool IPAddress::operator==(const uint8_t* addr)
     return memcmp(addr, _address, sizeof(_address)) == 0;
 }
 
-ssize_t IPAddress::printTo(Print& p) const
+size_t IPAddress::printTo(Print& p) const
 {
-    ssize_t n = 0, t;
+    size_t n = 0;
     for (int i =0; i < 3; i++)
     {
-        if ((t = p.print(_address[i], DEC)) > 0) n += t;
-        if ((t = p.print('.')) > 0) n+= t;
+        n += p.print(_address[i], DEC);
+        n += p.print('.');
     }
-    if ((t = p.print(_address[3], DEC)) > 0) n += t;
+    n += p.print(_address[3], DEC);
     return n;
 }
 

libraries/Ethernet/IPAddress.h

@@ -60,7 +60,7 @@ public:
     IPAddress& operator=(const uint8_t *address);
     IPAddress& operator=(uint32_t address);
 
-    virtual ssize_t printTo(Print& p) const;
+    virtual size_t printTo(Print& p) const;
 
     friend class EthernetClass;
     friend class UDP;

libraries/Ethernet/Server.cpp

@@ -67,19 +67,19 @@ Client Server::available()
   return Client(MAX_SOCK_NUM);
 }
 
-ssize_t Server::write(uint8_t b) 
+size_t Server::write(uint8_t b) 
 {
   write(&b, 1);
 }
 
-ssize_t Server::write(const char *str) 
+size_t Server::write(const char *str) 
 {
   write((const uint8_t *)str, strlen(str));
 }
 
-ssize_t Server::write(const uint8_t *buffer, size_t size) 
+size_t Server::write(const uint8_t *buffer, size_t size) 
 {
-  ssize_t n = 0;
+  size_t n = 0;
   
   accept();
 

libraries/Ethernet/Server.h

@@ -14,9 +14,9 @@ public:
   Server(uint16_t);
   Client available();
   void begin();
-  virtual ssize_t write(uint8_t);
-  virtual ssize_t write(const char *str);
-  virtual ssize_t write(const uint8_t *buf, size_t size);
+  virtual size_t write(uint8_t);
+  virtual size_t write(const char *str);
+  virtual size_t write(const uint8_t *buf, size_t size);
 };
 
 #endif

libraries/Ethernet/Udp.cpp

@@ -102,18 +102,18 @@ int UDP::endPacket()
   return sendUDP(_sock);
 }
 
-ssize_t UDP::write(uint8_t byte)
+size_t UDP::write(uint8_t byte)
 {
   return write(&byte, 1);
 }
 
-ssize_t UDP::write(const char *str)
+size_t UDP::write(const char *str)
 {
   size_t len = strlen(str);
   return write((const uint8_t *)str, len);
 }
 
-ssize_t UDP::write(const uint8_t *buffer, size_t size)
+size_t UDP::write(const uint8_t *buffer, size_t size)
 {
   uint16_t bytes_written = bufferData(_sock, _offset, buffer, size);
   _offset += bytes_written;

libraries/Ethernet/Udp.h

@@ -67,11 +67,11 @@ public:
   // Returns 1 if the packet was sent successfully, 0 if there was an error
   int endPacket();
   // Write a single byte into the packet
-  virtual ssize_t write(uint8_t);
+  virtual size_t write(uint8_t);
   // Write a string of characters into the packet
-  virtual ssize_t write(const char *str);
+  virtual size_t write(const char *str);
   // Write size bytes from buffer into the packet
-  virtual ssize_t write(const uint8_t *buffer, size_t size);
+  virtual size_t write(const uint8_t *buffer, size_t size);
 
   // Start processing the next available incoming packet
   // Returns the size of the packet in bytes, or 0 if no packets are available

libraries/LiquidCrystal/LiquidCrystal.cpp

@@ -258,7 +258,7 @@ inline void LiquidCrystal::command(uint8_t value) {
   send(value, LOW);
 }
 
-inline ssize_t LiquidCrystal::write(uint8_t value) {
+inline size_t LiquidCrystal::write(uint8_t value) {
   send(value, HIGH);
   return 1; // assume sucess
 }

libraries/LiquidCrystal/LiquidCrystal.h

@@ -79,7 +79,7 @@ public:
 
   void createChar(uint8_t, uint8_t[]);
   void setCursor(uint8_t, uint8_t); 
-  virtual ssize_t write(uint8_t);
+  virtual size_t write(uint8_t);
   void command(uint8_t);
 private:
   void send(uint8_t, uint8_t);

libraries/SD/File.cpp

@@ -58,19 +58,26 @@ boolean File::isDirectory(void) {
 }
 
 
-ssize_t File::write(uint8_t val) {
+size_t File::write(uint8_t val) {
   return write(&val, 1);
 }
 
-ssize_t File::write(const char *str) {
+size_t File::write(const char *str) {
   return write((const uint8_t *) str, strlen(str));
 }
 
-ssize_t File::write(const uint8_t *buf, size_t size) {
-  ssize_t t;
-  if (!_file) return -1;
+size_t File::write(const uint8_t *buf, size_t size) {
+  size_t t;
+  if (!_file) {
+    setWriteError();
+    return 0;
+  }
+  _file->clearWriteError();
   t = _file->write(buf, size);
-  if (t < 0) return t - 1;
+  if (_file->writeError()) {
+    setWriteError();
+    return 0;
+  }
   return t;
 }
 

libraries/SD/SD.h

@@ -32,9 +32,9 @@ public:
   File(SdFile f, char *name);     // wraps an underlying SdFile
   File(void);      // 'empty' constructor
   ~File(void);     // destructor
-  virtual ssize_t write(uint8_t);
-  virtual ssize_t write(const char *str);
-  virtual ssize_t write(const uint8_t *buf, size_t size);
+  virtual size_t write(uint8_t);
+  virtual size_t write(const char *str);
+  virtual size_t write(const uint8_t *buf, size_t size);
   virtual int read();
   virtual int peek();
   virtual int available();

libraries/SD/utility/SdFat.h

@@ -141,7 +141,7 @@ class SdFile : public Print {
    * Set writeError to false before calling print() and/or write() and check
    * for true after calls to print() and/or write().
    */
-  bool writeError;
+  //bool writeError;
   /**
    * Cancel unbuffered reads for this file.
    * See setUnbufferedRead()
@@ -283,9 +283,9 @@ class SdFile : public Print {
   }
   /** \return SdVolume that contains this file. */
   SdVolume* volume(void) const {return vol_;}
-  ssize_t write(uint8_t b);
-  ssize_t write(const void* buf, uint16_t nbyte);
-  ssize_t write(const char* str);
+  size_t write(uint8_t b);
+  size_t write(const void* buf, uint16_t nbyte);
+  size_t write(const char* str);
   void write_P(PGM_P str);
   void writeln_P(PGM_P str);
 //------------------------------------------------------------------------------

libraries/SD/utility/SdFile.cpp

@@ -1121,7 +1121,7 @@ uint8_t SdFile::truncate(uint32_t length) {
  * for a read-only file, device is full, a corrupt file system or an I/O error.
  *
  */
-ssize_t SdFile::write(const void* buf, uint16_t nbyte) {
+size_t SdFile::write(const void* buf, uint16_t nbyte) {
   // convert void* to uint8_t*  -  must be before goto statements
   const uint8_t* src = reinterpret_cast<const uint8_t*>(buf);
 
@@ -1210,8 +1210,9 @@ ssize_t SdFile::write(const void* buf, uint16_t nbyte) {
 
  writeErrorReturn:
   // return for write error
-  writeError = true;
-  return -1;
+  //writeError = true;
+  setWriteError();
+  return 0;
 }
 //------------------------------------------------------------------------------
 /**
@@ -1219,7 +1220,7 @@ ssize_t SdFile::write(const void* buf, uint16_t nbyte) {
  *
  * Use SdFile::writeError to check for errors.
  */
-ssize_t SdFile::write(uint8_t b) {
+size_t SdFile::write(uint8_t b) {
   return write(&b, 1);
 }
 //------------------------------------------------------------------------------
@@ -1228,7 +1229,7 @@ ssize_t SdFile::write(uint8_t b) {
  *
  * Use SdFile::writeError to check for errors.
  */
-ssize_t SdFile::write(const char* str) {
+size_t SdFile::write(const char* str) {
   return write(str, strlen(str));
 }
 //------------------------------------------------------------------------------

libraries/SoftwareSerial/SoftwareSerial.cpp

@@ -440,10 +440,12 @@ int SoftwareSerial::available()
   return (_receive_buffer_tail + _SS_MAX_RX_BUFF - _receive_buffer_head) % _SS_MAX_RX_BUFF;
 }
 
-ssize_t SoftwareSerial::write(uint8_t b)
+size_t SoftwareSerial::write(uint8_t b)
 {
-  if (_tx_delay == 0)
-    return -1;
+  if (_tx_delay == 0) {
+    setWriteError();
+    return 0;
+  }
 
   uint8_t oldSREG = SREG;
   cli();  // turn off interrupts for a clean txmit

libraries/SoftwareSerial/SoftwareSerial.h

@@ -89,7 +89,7 @@ public:
   bool overflow() { bool ret = _buffer_overflow; _buffer_overflow = false; return ret; }
   int peek();
 
-  virtual ssize_t write(uint8_t byte);
+  virtual size_t write(uint8_t byte);
   virtual int read();
   virtual int available();
   virtual void flush();

libraries/Wire/Wire.cpp

@@ -124,13 +124,14 @@ uint8_t TwoWire::endTransmission(void)
 // must be called in:
 // slave tx event callback
 // or after beginTransmission(address)
-ssize_t TwoWire::write(uint8_t data)
+size_t TwoWire::write(uint8_t data)
 {
   if(transmitting){
   // in master transmitter mode
     // don't bother if buffer is full
     if(txBufferLength >= BUFFER_LENGTH){
-      return -1;
+      setWriteError();
+      return 0;
     }
     // put byte in tx buffer
     txBuffer[txBufferIndex] = data;
@@ -148,12 +149,12 @@ ssize_t TwoWire::write(uint8_t data)
 // must be called in:
 // slave tx event callback
 // or after beginTransmission(address)
-ssize_t TwoWire::write(const uint8_t *data, size_t quantity)
+size_t TwoWire::write(const uint8_t *data, size_t quantity)
 {
   if(transmitting){
   // in master transmitter mode
     for(size_t i = 0; i < quantity; ++i){
-      if (write(data[i]) < 0) return i;
+      write(data[i]);
     }
   }else{
   // in slave send mode
@@ -166,7 +167,7 @@ ssize_t TwoWire::write(const uint8_t *data, size_t quantity)
 // must be called in:
 // slave tx event callback
 // or after beginTransmission(address)
-ssize_t TwoWire::write(const char *data)
+size_t TwoWire::write(const char *data)
 {
   return write((uint8_t*)data, strlen(data));
 }

libraries/Wire/Wire.h

@@ -52,9 +52,9 @@ class TwoWire : public Stream
     uint8_t endTransmission(void);
     uint8_t requestFrom(uint8_t, uint8_t);
     uint8_t requestFrom(int, int);
-    virtual ssize_t write(uint8_t);
-    virtual ssize_t write(const char *);
-    virtual ssize_t write(const uint8_t *, size_t);
+    virtual size_t write(uint8_t);
+    virtual size_t write(const char *);
+    virtual size_t write(const uint8_t *, size_t);
     virtual int available(void);
     virtual int read(void);
     virtual int peek(void);