Do not allocate another std::vector to append hex string

lib/libpcsc-cpp/include/pcsc-cpp/pcsc-cpp.hpp

@@ -81,6 +81,9 @@ constexpr uint16_t toSW(byte_type sw1, byte_type sw2) noexcept
     return uint16_t(sw1 << 8) | sw2;
 }
 
+/** Convert bytes to hex string. */
+std::string bytes2hexstr(const byte_vector& bytes);
+
 /** Struct that wraps response APDUs. */
 struct ResponseApdu
 {
@@ -120,22 +123,14 @@ struct ResponseApdu
         return {sw1, sw2, std::move(data)};
     }
 
-    byte_vector toBytes() const
-    {
-        // makes a copy, valid both if data is empty or full
-        auto bytes = data;
-
-        bytes.push_back(sw1);
-        bytes.push_back(sw2);
-
-        return bytes;
-    }
-
     constexpr uint16_t toSW() const noexcept { return pcsc_cpp::toSW(sw1, sw2); }
 
     constexpr bool isOK() const noexcept { return sw1 == OK && sw2 == 0x00; }
 
-    // TODO: friend function toString() in utilities.hpp
+    friend std::string operator+(std::string&& lhs, const ResponseApdu& rhs)
+    {
+        return lhs + pcsc_cpp::bytes2hexstr(rhs.data) + pcsc_cpp::bytes2hexstr({rhs.sw1, rhs.sw2});
+    }
 };
 
 /** Struct that wraps command APDUs. */
@@ -270,9 +265,6 @@ std::vector<Reader> listReaders();
 
 // Utility functions.
 
-/** Convert bytes to hex string. */
-std::string bytes2hexstr(const byte_vector& bytes);
-
 /** Transmit APDU command and verify that expected response is received. */
 void transmitApduWithExpectedResponse(const SmartCard& card, const CommandApdu& command);
 

lib/libpcsc-cpp/src/SmartCard.cpp

@@ -243,8 +243,7 @@ class CardImpl
             break;
         default:
             THROW(Error,
-                  "Error response: '" + bytes2hexstr({response.sw1, response.sw2}) + "', protocol "
-                      + std::to_string(protocol()));
+                  "Error response: '" + response + "', protocol " + std::to_string(protocol()));
         }
 
         if (response.sw1 == ResponseApdu::WRONG_LE_LENGTH) {

lib/libpcsc-cpp/src/utils.cpp

@@ -58,9 +58,9 @@ class UnexpectedResponseError : public Error
                                      const char* file, const int line,
                                      const char* callerFunctionName) :
         Error("transmitApduWithExpectedResponse(): Unexpected response to command '"s
-              + bytes2hexstr(command) + "' - expected '9000', got '"s
-              + bytes2hexstr(response.toBytes()) + "' in " + removeAbsolutePathPrefix(file) + ':'
-              + std::to_string(line) + ':' + callerFunctionName)
+              + bytes2hexstr(command) + "' - expected '9000', got '"s + response + "' in "
+              + removeAbsolutePathPrefix(file) + ':' + std::to_string(line) + ':'
+              + callerFunctionName)
     {
     }
 };

src/electronic-id.cpp

@@ -289,7 +289,7 @@ AutoSelectFailed::AutoSelectFailed(Reason r) :
 VerifyPinFailed::VerifyPinFailed(const Status s, const observer_ptr<pcsc_cpp::ResponseApdu> ra,
                                  const int8_t r) :
     Error(std::string("Verify PIN failed, status: ") + std::string(magic_enum::enum_name(s))
-          + (ra ? ", response: " + pcsc_cpp::bytes2hexstr(ra->toBytes()) : "")),
+          + (ra ? ", response: " + *ra : "")),
     _status(s), _retries(r)
 {
 }

src/electronic-ids/pcsc/EIDIDEMIA.cpp

@@ -152,9 +152,7 @@ ElectronicID::PinRetriesRemainingAndMax EIDIDEMIA::pinRetriesLeft(byte_type pinR
         0x00};
     const auto response = card->transmit(GET_DATA_ODD);
     if (!response.isOK()) {
-        THROW(SmartCardError,
-              "Command GET DATA ODD failed with error "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+        THROW(SmartCardError, "Command GET DATA ODD failed with error " + response);
     }
     if (response.data.size() < 14) {
         THROW(SmartCardError,

src/electronic-ids/pcsc/FinEID.cpp

@@ -148,25 +148,20 @@ byte_vector FinEIDv3::sign(const HashAlgorithm hashAlgo, const byte_vector& hash
 
     if (response.sw1 == ResponseApdu::WRONG_LENGTH) {
         THROW(SmartCardError,
-              "Wrong data length in command COMPUTE SIGNATURE argument: "
-                  + bytes2hexstr(response.toBytes()));
+              "Wrong data length in command COMPUTE SIGNATURE argument: " + response);
     }
     if (!response.isOK()) {
-        THROW(SmartCardError,
-              "Command COMPUTE SIGNATURE failed with error " + bytes2hexstr(response.toBytes()));
+        THROW(SmartCardError, "Command COMPUTE SIGNATURE failed with error " + response);
     }
 
     const CommandApdu getSignature {0x00, 0x2A, 0x9E, 0x9A, LE};
     const auto signature = card->transmit(getSignature);
 
     if (signature.sw1 == ResponseApdu::WRONG_LENGTH) {
-        THROW(SmartCardError,
-              "Wrong data length in command GET SIGNATURE argument: "
-                  + bytes2hexstr(response.toBytes()));
+        THROW(SmartCardError, "Wrong data length in command GET SIGNATURE argument: " + response);
     }
     if (!signature.isOK()) {
-        THROW(SmartCardError,
-              "Command GET SIGNATURE failed with error " + bytes2hexstr(signature.toBytes()));
+        THROW(SmartCardError, "Command GET SIGNATURE failed with error " + signature);
     }
 
     return signature.data;
@@ -178,8 +173,7 @@ ElectronicID::PinRetriesRemainingAndMax FinEIDv3::pinRetriesLeft(byte_type pinRe
         0x00, 0xCB, 0x00, 0xFF, {0xA0, 0x03, 0x83, 0x01, pinReference}};
     const auto response = card->transmit(GET_DATA);
     if (!response.isOK()) {
-        THROW(SmartCardError,
-              "Command GET DATA failed with error " + pcsc_cpp::bytes2hexstr(response.toBytes()));
+        THROW(SmartCardError, "Command GET DATA failed with error " + response);
     }
     if (response.data.size() < 21) {
         THROW(SmartCardError,

src/electronic-ids/pcsc/pcsc-common.hpp

@@ -123,13 +123,12 @@ inline pcsc_cpp::byte_vector internalAuthenticate(pcsc_cpp::SmartCard& card,
 
     if (response.sw1 == pcsc_cpp::ResponseApdu::WRONG_LENGTH) {
         THROW(SmartCardError,
-              cardType + ": Wrong data length in command INTERNAL AUTHENTICATE argument: "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+              cardType
+                  + ": Wrong data length in command INTERNAL AUTHENTICATE argument: " + response);
     }
     if (!response.isOK()) {
         THROW(SmartCardError,
-              cardType + ": Command INTERNAL AUTHENTICATE failed with error "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+              cardType + ": Command INTERNAL AUTHENTICATE failed with error " + response);
     }
 
     return response.data;
@@ -144,13 +143,11 @@ inline pcsc_cpp::byte_vector computeSignature(pcsc_cpp::SmartCard& card,
 
     if (response.sw1 == pcsc_cpp::ResponseApdu::WRONG_LENGTH) {
         THROW(SmartCardError,
-              cardType + ": Wrong data length in command COMPUTE SIGNATURE argument: "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+              cardType + ": Wrong data length in command COMPUTE SIGNATURE argument: " + response);
     }
     if (!response.isOK()) {
         THROW(SmartCardError,
-              cardType + ": Command COMPUTE SIGNATURE failed with error "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+              cardType + ": Command COMPUTE SIGNATURE failed with error " + response);
     }
 
     return response.data;
@@ -165,9 +162,7 @@ inline pcsc_cpp::byte_type selectSecurityEnv(pcsc_cpp::SmartCard& card, pcsc_cpp
         {0x00, 0x22, 0x41, env, {0x80, 0x01, signatureAlgo, 0x84, 0x01, keyReference}});
 
     if (!response.isOK()) {
-        THROW(SmartCardError,
-              cardType + ": Command SET ENV failed with error "
-                  + pcsc_cpp::bytes2hexstr(response.toBytes()));
+        THROW(SmartCardError, cardType + ": Command SET ENV failed with error " + response);
     }
     return signatureAlgo;
 }