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[Proposal] Clarify (the existence of) the constant empty String #5546

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[Proposal] Clarify (the existence of) the constant empty String #5546

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9335115
Clarify (the existence of) the constant empty String
Dec 23, 2018
28ca58f
Merge branch 'master' into clarify_const_empty_String
d-a-v Dec 26, 2018
6a41576
convert inline func `String::empty()` to constexpr `String::empty`
Jan 3, 2019
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2 changes: 1 addition & 1 deletion cores/esp8266/AddrList.h
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Expand Up @@ -123,7 +123,7 @@ struct netifWrapper

// common to all addresses of this interface
String ifname () const { return String(_netif->name[0]) + _netif->name[1]; }
const char* ifhostname () const { return _netif->hostname?: emptyString.c_str(); }
const char* ifhostname () const { return _netif->hostname?: String::empty.c_str(); }
const char* ifmac () const { return (const char*)_netif->hwaddr; }
int ifnumber () const { return _netif->num; }

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1 change: 1 addition & 0 deletions cores/esp8266/WString.cpp
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Expand Up @@ -800,3 +800,4 @@ float String::toFloat(void) const {
// global empty string to allow returning const String& with nothing

const String emptyString;
const String __emptyString __attribute__((alias("emptyString")));
8 changes: 7 additions & 1 deletion cores/esp8266/WString.h
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Expand Up @@ -39,6 +39,8 @@ class __FlashStringHelper;
#define F(string_literal) (FPSTR(PSTR(string_literal)))

// The string class
class String;
extern const String __emptyString;
class String {
// use a function pointer to allow for "if (s)" without the
// complications of an operator bool(). for more information, see:
Expand Down Expand Up @@ -70,6 +72,9 @@ class String {
explicit String(double, unsigned char decimalPlaces = 2);
~String(void);

// empty string singleton
static constexpr const String& empty = ::__emptyString;
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Please don't call the static member "empty". It should be ok to also call it "emptyString", because it is scoped, or call it something else (emptyStr, nullString, defString, etc)

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@devyte devyte Jan 3, 2019 •
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Given the deprecation, can this be implemented the other way around? make this member the "real" object, and make the global a reference to this one.


// memory management
// return true on success, false on failure (in which case, the string
// is left unchanged). reserve(0), if successful, will validate an
Expand Down Expand Up @@ -294,7 +299,8 @@ class StringSumHelper: public String {
}
};

extern const String emptyString;
// only for backward compatibility
extern const String emptyString __attribute__((deprecated("Use String::empty instead.")));

#endif // __cplusplus
#endif // String_class_h
8 changes: 4 additions & 4 deletions libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer.cpp
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Expand Up @@ -20,8 +20,8 @@ ESP8266HTTPUpdateServer::ESP8266HTTPUpdateServer(bool serial_debug)
{
_serial_output = serial_debug;
_server = NULL;
_username = emptyString;
_password = emptyString;
_username = String::empty;
_password = String::empty;
_authenticated = false;
}

Expand All @@ -33,7 +33,7 @@ void ESP8266HTTPUpdateServer::setup(ESP8266WebServer *server, const String& path

// handler for the /update form page
_server->on(path.c_str(), HTTP_GET, [&](){
if(_username != emptyString && _password != emptyString && !_server->authenticate(_username.c_str(), _password.c_str()))
if(_username != String::empty && _password != String::empty && !_server->authenticate(_username.c_str(), _password.c_str()))
return _server->requestAuthentication();
_server->send_P(200, PSTR("text/html"), serverIndex);
});
Expand Down Expand Up @@ -61,7 +61,7 @@ void ESP8266HTTPUpdateServer::setup(ESP8266WebServer *server, const String& path
if (_serial_output)
Serial.setDebugOutput(true);

_authenticated = (_username == emptyString || _password == emptyString || _server->authenticate(_username.c_str(), _password.c_str()));
_authenticated = (_username == String::empty || _password == String::empty || _server->authenticate(_username.c_str(), _password.c_str()));
if(!_authenticated){
if (_serial_output)
Serial.printf("Unauthenticated Update\n");
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4 changes: 2 additions & 2 deletions libraries/ESP8266HTTPUpdateServer/src/ESP8266HTTPUpdateServer.h
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Expand Up @@ -10,12 +10,12 @@ class ESP8266HTTPUpdateServer

void setup(ESP8266WebServer *server)
{
setup(server, emptyString, emptyString);
setup(server, String::empty, String::empty);
}

void setup(ESP8266WebServer *server, const String& path)
{
setup(server, path, emptyString, emptyString);
setup(server, path, String::empty, String::empty);
}

void setup(ESP8266WebServer *server, const String& username, const String& password)
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18 changes: 9 additions & 9 deletions libraries/ESP8266WebServer/src/ESP8266WebServer.cpp
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Expand Up @@ -108,7 +108,7 @@ void ESP8266WebServer::begin(uint16_t port) {
String ESP8266WebServer::_extractParam(String& authReq,const String& param,const char delimit) const {
int _begin = authReq.indexOf(param);
if (_begin == -1)
return emptyString;
return String::empty;
return authReq.substring(_begin+param.length(),authReq.indexOf(delimit,_begin+param.length()));
}

Expand Down Expand Up @@ -486,7 +486,7 @@ void ESP8266WebServer::_streamFileCore(const size_t fileSize, const String & fil
contentType != String(FPSTR(mimeTable[none].mimeType))) {
sendHeader(F("Content-Encoding"), F("gzip"));
}
send(200, contentType, emptyString);
send(200, contentType, String::empty);
}


Expand All @@ -499,19 +499,19 @@ const String& ESP8266WebServer::arg(String name) const {
if ( _currentArgs[i].key == name )
return _currentArgs[i].value;
}
return emptyString;
return String::empty;
}

const String& ESP8266WebServer::arg(int i) const {
if (i >= 0 && i < _currentArgCount)
return _currentArgs[i].value;
return emptyString;
return String::empty;
}

const String& ESP8266WebServer::argName(int i) const {
if (i >= 0 && i < _currentArgCount)
return _currentArgs[i].key;
return emptyString;
return String::empty;
}

int ESP8266WebServer::args() const {
Expand All @@ -536,7 +536,7 @@ const String& ESP8266WebServer::header(String name) const {
if (_currentHeaders[i].key.equalsIgnoreCase(name))
return _currentHeaders[i].value;
}
return emptyString;
return String::empty;
}

void ESP8266WebServer::collectHeaders(const char* headerKeys[], const size_t headerKeysCount) {
Expand All @@ -553,13 +553,13 @@ void ESP8266WebServer::collectHeaders(const char* headerKeys[], const size_t hea
const String& ESP8266WebServer::header(int i) const {
if (i < _headerKeysCount)
return _currentHeaders[i].value;
return emptyString;
return String::empty;
}

const String& ESP8266WebServer::headerName(int i) const {
if (i < _headerKeysCount)
return _currentHeaders[i].key;
return emptyString;
return String::empty;
}

int ESP8266WebServer::headers() const {
Expand Down Expand Up @@ -619,7 +619,7 @@ void ESP8266WebServer::_handleRequest() {

void ESP8266WebServer::_finalizeResponse() {
if (_chunked) {
sendContent(emptyString);
sendContent(String::empty);
}
}

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2 changes: 1 addition & 1 deletion libraries/ESP8266WiFi/src/ESP8266WiFiAP.h
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Expand Up @@ -37,7 +37,7 @@ class ESP8266WiFiAPClass {
public:

bool softAP(const char* ssid, const char* passphrase = NULL, int channel = 1, int ssid_hidden = 0, int max_connection = 4);
bool softAP(const String& ssid,const String& passphrase = emptyString,int channel = 1,int ssid_hidden = 0,int max_connection = 4);
bool softAP(const String& ssid,const String& passphrase = String::empty,int channel = 1,int ssid_hidden = 0,int max_connection = 4);
bool softAPConfig(IPAddress local_ip, IPAddress gateway, IPAddress subnet);
bool softAPdisconnect(bool wifioff = false);

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2 changes: 1 addition & 1 deletion libraries/ESP8266WiFi/src/ESP8266WiFiSTA.h
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Expand Up @@ -38,7 +38,7 @@ class ESP8266WiFiSTAClass {

wl_status_t begin(const char* ssid, const char *passphrase = NULL, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
wl_status_t begin(char* ssid, char *passphrase = NULL, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
wl_status_t begin(const String& ssid, const String& passphrase = emptyString, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
wl_status_t begin(const String& ssid, const String& passphrase = String::empty, int32_t channel = 0, const uint8_t* bssid = NULL, bool connect = true);
wl_status_t begin();

//The argument order for ESP is not the same as for Arduino. However, there is compatibility code under the hood
Expand Down