Added substring capability to ZString.

ZString.cpp

@@ -68,6 +68,10 @@ namespace coreutils {
       return (strncmp(data, valuex.data, valuex.length <= length ? valuex.length : length) == 0);
    }
 
+   bool ZString::operator==(const char *valuex) const {
+      return (strncmp(data, valuex, length) == 0);
+   }
+
    bool ZString::operator!=(const ZString &valuex) const {
 //      if(length != valuex.getLength())
 //	return false;
@@ -75,9 +79,8 @@ namespace coreutils {
    }
 
    bool ZString::operator!=(const char *valuex) const {
-      size_t len = strlen(valuex);
-      if(length != len)
-	return true;
+      if(strlen(valuex) != length)
+        return true;
       return (strncmp(data, valuex, length) != 0);
    }
 
@@ -124,6 +127,19 @@ namespace coreutils {
       cdata[length] = '\0';
       return cdata;
    }   
+
+   ZString ZString::substring(int start) {
+      char *end = data + length;
+      char *startChar = data + start;
+      if(startChar < end) {
+	 return ZString(startChar, end - startChar);
+      }
+      return ZString();
+   }
+   
+   ZString ZString::substring(int start, int len) {
+      return ZString();
+   }   
    
    std::vector<ZString> &ZString::split(std::string delimiter, size_t maxSize) {
       coreutils::ZString zDelimiter((char *)delimiter.c_str(), delimiter.size());