Move string allocation to a point where get_ip_address() is called

This saves RAM/stack on typical socket usage where human readable
format is not exchanged so often.

features/netsocket/SocketAddress.cpp

@@ -106,35 +106,36 @@ static void ipv6_to_address(char *addr, const uint8_t *bytes)
 
 SocketAddress::SocketAddress(nsapi_addr_t addr, uint16_t port)
 {
-    _ip_address[0] = '\0';
+    _ip_address = NULL;
     set_addr(addr);
     set_port(port);
 }
 
 SocketAddress::SocketAddress(const char *addr, uint16_t port)
 {
-    _ip_address[0] = '\0';
+    _ip_address = NULL;
     set_ip_address(addr);
     set_port(port);
 }
 
 SocketAddress::SocketAddress(const void *bytes, nsapi_version_t version, uint16_t port)
 {
-    _ip_address[0] = '\0';
+    _ip_address = NULL;
     set_ip_bytes(bytes, version);
     set_port(port);
 }
 
 SocketAddress::SocketAddress(const SocketAddress &addr)
 {
-    _ip_address[0] = '\0';
+    _ip_address = NULL;
     set_addr(addr.get_addr());
     set_port(addr.get_port());
 }
 
 bool SocketAddress::set_ip_address(const char *addr)
 {
-    _ip_address[0] = '\0';
+    delete[] _ip_address;
+    _ip_address = NULL;
 
     if (addr && ipv4_is_valid(addr)) {
         _addr.version = NSAPI_IPv4;
@@ -166,7 +167,8 @@ void SocketAddress::set_ip_bytes(const void *bytes, nsapi_version_t version)
 
 void SocketAddress::set_addr(nsapi_addr_t addr)
 {
-    _ip_address[0] = '\0';
+    delete[] _ip_address;
+    _ip_address = NULL;
     _addr = addr;
 }
 
@@ -181,7 +183,8 @@ const char *SocketAddress::get_ip_address() const
         return NULL;
     }
 
-    if (!_ip_address[0]) {
+    if (!_ip_address) {
+        _ip_address = new char[NSAPI_IP_SIZE];
         if (_addr.version == NSAPI_IPv4) {
             ipv4_to_address(_ip_address, _addr.bytes);
         } else if (_addr.version == NSAPI_IPv6) {
@@ -235,6 +238,15 @@ SocketAddress::operator bool() const
     }
 }
 
+SocketAddress &SocketAddress::operator=(const SocketAddress &addr)
+{
+    delete[] _ip_address;
+    _ip_address = NULL;
+    set_addr(addr.get_addr());
+    set_port(addr.get_port());
+    return *this;
+}
+
 bool operator==(const SocketAddress &a, const SocketAddress &b)
 {
     if (!a && !b) {
@@ -257,7 +269,7 @@ bool operator!=(const SocketAddress &a, const SocketAddress &b)
 
 void SocketAddress::_SocketAddress(NetworkStack *iface, const char *host, uint16_t port)
 {
-    _ip_address[0] = '\0';
+    _ip_address = NULL;
 
     // gethostbyname must check for literals, so can call it directly
     int err = iface->gethostbyname(host, this);
@@ -267,3 +279,8 @@ void SocketAddress::_SocketAddress(NetworkStack *iface, const char *host, uint16
         _port = 0;
     }
 }
+
+SocketAddress::~SocketAddress()
+{
+    delete[] _ip_address;
+}

features/netsocket/SocketAddress.h

@@ -84,6 +84,9 @@ public:
      */
     SocketAddress(const SocketAddress &addr);
 
+    /** Destructor */
+    ~SocketAddress();
+
     /** Set the IP address
      *
      *  @param addr     Null-terminated represention of the IP address
@@ -111,7 +114,10 @@ public:
      */
     void set_port(uint16_t port);
 
-    /** Get the IP address
+    /** Get the human readable IP address
+     *
+     *  Allocates memory for a string and converts binary address to
+     *  human readable format. String is freed in the destructor.
      *
      *  @return         Null-terminated representation of the IP Address
      */
@@ -147,6 +153,12 @@ public:
      */
     operator bool() const;
 
+    /** Copy addres from another SocketAddress
+     *
+     * @param addr  SocketAddress to copy
+     */
+    SocketAddress &operator=(const SocketAddress &addr);
+
     /** Compare two addresses for equality
      *
      *  @return         True if both addresses are equal
@@ -162,7 +174,7 @@ public:
 private:
     void _SocketAddress(NetworkStack *iface, const char *host, uint16_t port);
 
-    mutable char _ip_address[NSAPI_IP_SIZE];
+    mutable char *_ip_address;
     nsapi_addr_t _addr;
     uint16_t _port;
 };