Starting to distinguish between empty strings and invalid (null) ones.

Author: damellis

hardware/arduino/cores/arduino/WString.cpp

@@ -114,7 +114,7 @@ inline void String::init(void)
 
 unsigned char String::reserve(unsigned int size)
 {
-	if (capacity >= size) return 1;
+	if (buffer && capacity >= size) return 1;
 	if (changeBuffer(size)) {
 		if (len == 0) buffer[0] = 0;
 		return 1;
@@ -139,11 +139,6 @@ unsigned char String::changeBuffer(unsigned int maxStrLen)
 
 String & String::copy(const char *cstr, unsigned int length)
 {
-	if (length == 0) {
-		if (buffer) buffer[0] = 0;
-		len = 0;
-		return *this;
-	}
 	if (!reserve(length)) {
 		if (buffer) {
 			free(buffer);
@@ -204,6 +199,11 @@ String & String::operator = (const char *cstr)
 	if (cstr) {
 		copy(cstr, strlen(cstr));
 	} else {
+		if (buffer) {
+			free(buffer);
+			capacity = 0;
+			buffer = NULL;
+		}
 		len = 0;
 	}
 	return *this;

hardware/arduino/cores/arduino/WString.h

@@ -43,7 +43,7 @@ class String
 {
 public:
 	// constructors
-	String(const char *cstr = NULL);
+	String(const char *cstr = "");
 	String(const String &str);
 	#ifdef __GXX_EXPERIMENTAL_CXX0X__
 	String(String &&rval);