correct availableForWrite signature

Author: hathach

cores/nRF5/Adafruit_TinyUSB_Core/Adafruit_USBD_CDC.cpp

@@ -97,7 +97,7 @@ int Adafruit_USBD_CDC::peek(void)
 
 int Adafruit_USBD_CDC::read(void)
 {
-  return tud_cdc_read_char();
+  return (int) tud_cdc_read_char();
 }
 
 void Adafruit_USBD_CDC::flush(void)
@@ -126,7 +126,7 @@ size_t Adafruit_USBD_CDC::write(const uint8_t *buffer, size_t size)
   return size - remain;
 }
 
-size_t Adafruit_USBD_CDC::availableForWrite(void)
+int Adafruit_USBD_CDC::availableForWrite(void)
 {
   return tud_cdc_write_available();
 }

cores/nRF5/Adafruit_TinyUSB_Core/Adafruit_USBD_CDC.h

@@ -51,7 +51,7 @@ class Adafruit_USBD_CDC : public Stream, Adafruit_USBD_Interface
 	size_t write(const char *buffer, size_t size) {
 	  return write((const uint8_t *)buffer, size);
 	}
-	size_t availableForWrite(void);
+	virtual int availableForWrite(void);
 	operator bool();
 };
 

cores/nRF5/Adafruit_TinyUSB_Core/tusb_config.h

@@ -72,7 +72,6 @@
 #define CFG_TUD_MIDI_TX_BUFSIZE     64
 
 // Vendor FIFO size of TX and RX
-// If not configured vendor endpoints will not be buffered
 #define CFG_TUD_VENDOR_RX_BUFSIZE   64
 #define CFG_TUD_VENDOR_TX_BUFSIZE   64
 

cores/nRF5/Print.h

@@ -55,6 +55,10 @@ class Print
       return write((const uint8_t *)buffer, size);
     }
 
+    // default to zero, meaning "a single write may block"
+    // should be overriden by subclasses with buffering
+    virtual int availableForWrite() { return 0; }
+
     size_t print(const __FlashStringHelper *);
     size_t print(const String &);
     size_t print(const char[]);