Merge bitcoin/bitcoin#21817: refactor: Replace &foo[0] with foo.data()

fac30eec42c486ec1bfd696293040a7aa0f04625 refactor: Replace &foo[0] with foo.data() (MarcoFalke)
faece47c4706783e0460ed977390a44630b2d44c refactor: Avoid &foo[0] on C-Style arrays (MarcoFalke)
face9611093377e8502d91f2ff56f9319a56357c refactor: Use only one temporary buffer in CreateObfuscateKey (MarcoFalke)
fa05dddc42770809fdae4d9c35155f8117960019 refactor: Use CPubKey vector constructor where possible (MarcoFalke)
fabb6dfe6e734eadd91448122f2ce8c1612c39a6 script: Replace address-of idiom with vector data() method (Guido Vranken)

Pull request description:

  The main theme of this refactor is to replace `&foo[0]` with `foo.data()`.

  The first commit is taken from #21781 with the rationale:

  * In CSignatureCache::ComputeEntryECDSA, change the way a vector pointer is resolved to prevent invoking undefined behavior if the vector is empty.

  The other commits aim to remove all `&foo[0]`, where `foo` is any kind of byte representation. The rationale:

  * Sometimes alternative code without any raw data pointers is easier to read (refer to the respective commit message for details)
  * If the raw data pointer is needed, `foo.data()` should be preferred, as pointed out in the developer notes. This addresses the instances that have been missed in commit 592404f03f2b734351d734f0c9ca1fdce997321b, and https://github.com/bitcoin/bitcoin/pull/9804

ACKs for top commit:
  laanwj:
    Code review ACK fac30eec42c486ec1bfd696293040a7aa0f04625
  practicalswift:
    cr ACK fac30eec42c486ec1bfd696293040a7aa0f04625: patch looks correct
  promag:
    Code review ACK fac30eec42c486ec1bfd696293040a7aa0f04625.

Tree-SHA512: e7e73146edbc78911a8e8c728b0a1c6b0ed9a88a008e650aa5dbffe72425bd42c76df70199a9cf7e02637448d7593e0eac52fd0f91f59240283e1390ee21bfa5

5 files changed, 12 insertions, 12 deletions

diff --git a/src/wallet/crypter.cpp b/src/wallet/crypter.cpp
index b50f00e7d1..251778e401 100644
--- a/src/wallet/crypter.cpp
+++ b/src/wallet/crypter.cpp
@@ -78,7 +78,7 @@ bool CCrypter::Encrypt(const CKeyingMaterial& vchPlaintext, std::vector<unsigned
     vchCiphertext.resize(vchPlaintext.size() + AES_BLOCKSIZE);
 
     AES256CBCEncrypt enc(vchKey.data(), vchIV.data(), true);
-    size_t nLen = enc.Encrypt(&vchPlaintext[0], vchPlaintext.size(), vchCiphertext.data());
+    size_t nLen = enc.Encrypt(vchPlaintext.data(), vchPlaintext.size(), vchCiphertext.data());
     if(nLen < vchPlaintext.size())
         return false;
     vchCiphertext.resize(nLen);
@@ -97,7 +97,7 @@ bool CCrypter::Decrypt(const std::vector<unsigned char>& vchCiphertext, CKeyingM
     vchPlaintext.resize(nLen);
 
     AES256CBCDecrypt dec(vchKey.data(), vchIV.data(), true);
-    nLen = dec.Decrypt(vchCiphertext.data(), vchCiphertext.size(), &vchPlaintext[0]);
+    nLen = dec.Decrypt(vchCiphertext.data(), vchCiphertext.size(), vchPlaintext.data());
     if(nLen == 0)
         return false;
     vchPlaintext.resize(nLen);
@@ -121,7 +121,7 @@ bool DecryptSecret(const CKeyingMaterial& vMasterKey, const std::vector<unsigned
     memcpy(chIV.data(), &nIV, WALLET_CRYPTO_IV_SIZE);
     if(!cKeyCrypter.SetKey(vMasterKey, chIV))
         return false;
-    return cKeyCrypter.Decrypt(vchCiphertext, *((CKeyingMaterial*)&vchPlaintext));
+    return cKeyCrypter.Decrypt(vchCiphertext, vchPlaintext);
 }
 
 bool DecryptKey(const CKeyingMaterial& vMasterKey, const std::vector<unsigned char>& vchCryptedSecret, const CPubKey& vchPubKey, CKey& key)
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 653dbdfc1d..a851765c57 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -469,7 +469,7 @@ RPCHelpMan importpubkey()
     if (!IsHex(request.params[0].get_str()))
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey must be a hex string");
     std::vector<unsigned char> data(ParseHex(request.params[0].get_str()));
-    CPubKey pubKey(data.begin(), data.end());
+    CPubKey pubKey(data);
     if (!pubKey.IsFullyValid())
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey is not a valid public key");
 
@@ -871,7 +871,7 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
 
     switch (script_type) {
     case TxoutType::PUBKEY: {
-        CPubKey pubkey(solverdata[0].begin(), solverdata[0].end());
+        CPubKey pubkey(solverdata[0]);
         import_data.used_keys.emplace(pubkey.GetID(), false);
         return "";
     }
@@ -893,7 +893,7 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
     }
     case TxoutType::MULTISIG: {
         for (size_t i = 1; i + 1< solverdata.size(); ++i) {
-            CPubKey pubkey(solverdata[i].begin(), solverdata[i].end());
+            CPubKey pubkey(solverdata[i]);
             import_data.used_keys.emplace(pubkey.GetID(), false);
         }
         return "";
@@ -997,7 +997,7 @@ static UniValue ProcessImportLegacy(ImportData& import_data, std::map<CKeyID, CP
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" must be a hex string");
         }
         auto parsed_pubkey = ParseHex(str);
-        CPubKey pubkey(parsed_pubkey.begin(), parsed_pubkey.end());
+        CPubKey pubkey(parsed_pubkey);
         if (!pubkey.IsFullyValid()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Pubkey \"" + str + "\" is not a valid public key");
         }
diff --git a/src/wallet/salvage.cpp b/src/wallet/salvage.cpp
index 6d912be019..ea045eb6d8 100644
--- a/src/wallet/salvage.cpp
+++ b/src/wallet/salvage.cpp
@@ -154,8 +154,8 @@ bool RecoverDatabaseFile(const fs::path& file_path, bilingual_str& error, std::v
             warnings.push_back(strprintf(Untranslated("WARNING: WalletBatch::Recover skipping %s: %s"), strType, strErr));
             continue;
         }
-        Dbt datKey(&row.first[0], row.first.size());
-        Dbt datValue(&row.second[0], row.second.size());
+        Dbt datKey(row.first.data(), row.first.size());
+        Dbt datValue(row.second.data(), row.second.size());
         int ret2 = pdbCopy->put(ptxn, &datKey, &datValue, DB_NOOVERWRITE);
         if (ret2 > 0)
             fSuccess = false;
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 149549410c..2eb9ca5c6d 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -162,7 +162,7 @@ IsMineResult IsMineInner(const LegacyScriptPubKeyMan& keystore, const CScript& s
             break;
         }
         uint160 hash;
-        CRIPEMD160().Write(&vSolutions[0][0], vSolutions[0].size()).Finalize(hash.begin());
+        CRIPEMD160().Write(vSolutions[0].data(), vSolutions[0].size()).Finalize(hash.begin());
         CScriptID scriptID = CScriptID(hash);
         CScript subscript;
         if (keystore.GetCScript(scriptID, subscript)) {
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index f0aaee7e4e..3d0ef9f8c0 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -603,12 +603,12 @@ bool CWallet::EncryptWallet(const SecureString& strWalletPassphrase)
     CKeyingMaterial _vMasterKey;
 
     _vMasterKey.resize(WALLET_CRYPTO_KEY_SIZE);
-    GetStrongRandBytes(&_vMasterKey[0], WALLET_CRYPTO_KEY_SIZE);
+    GetStrongRandBytes(_vMasterKey.data(), WALLET_CRYPTO_KEY_SIZE);
 
     CMasterKey kMasterKey;
 
     kMasterKey.vchSalt.resize(WALLET_CRYPTO_SALT_SIZE);
-    GetStrongRandBytes(&kMasterKey.vchSalt[0], WALLET_CRYPTO_SALT_SIZE);
+    GetStrongRandBytes(kMasterKey.vchSalt.data(), WALLET_CRYPTO_SALT_SIZE);
 
     CCrypter crypter;
     int64_t nStartTime = GetTimeMillis();