Merge bitcoin/bitcoin#27927: util: Allow std::byte and char Span serialization

fa38d862358b87219b12bf31236c52f28d9fc5d6 Use only Span{} constructor for byte-like types where possible (MarcoFalke)
fa257bc8312b91c2d281f48ca2500d9cba353cc5 util: Allow std::byte and char Span serialization (MarcoFalke)

Pull request description:

  Seems odd to require developers to cast all byte-like spans passed to serialization to `unsigned char`-spans. Fix that by passing and accepting byte-like spans as-is. Finally, add tests and update the code to use just `Span` where possible.

ACKs for top commit:
  sipa:
    utACK fa38d862358b87219b12bf31236c52f28d9fc5d6
  achow101:
    ACK fa38d862358b87219b12bf31236c52f28d9fc5d6
  ryanofsky:
    Code review ACK fa38d862358b87219b12bf31236c52f28d9fc5d6. This looks great. The second commit really removes a lot of boilerplate and shows why the first commit is useful.

Tree-SHA512: 788592d9ff515c3ebe73d48f9ecbb8d239f5b985af86f09974e508cafb0ca6d73a959350295246b4dfb496149bc56330a0b5d659fc434ba6723dbaba0b7a49e5

11 files changed, 36 insertions, 26 deletions

diff --git a/src/bench/load_external.cpp b/src/bench/load_external.cpp
index 2ff72a3012..1378a7b20a 100644
--- a/src/bench/load_external.cpp
+++ b/src/bench/load_external.cpp
@@ -34,7 +34,7 @@ static void LoadExternalBlockFile(benchmark::Bench& bench)
     ss << static_cast<uint32_t>(benchmark::data::block413567.size());
     // We can't use the streaming serialization (ss << benchmark::data::block413567)
     // because that first writes a compact size.
-    ss.write(MakeByteSpan(benchmark::data::block413567));
+    ss << Span{benchmark::data::block413567};
 
     // Create the test file.
     {
diff --git a/src/net.cpp b/src/net.cpp
index 0ac1586cfd..3cd06f44d6 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -2933,13 +2933,13 @@ void CaptureMessageToFile(const CAddress& addr,
     AutoFile f{fsbridge::fopen(path, "ab")};
 
     ser_writedata64(f, now.count());
-    f.write(MakeByteSpan(msg_type));
+    f << Span{msg_type};
     for (auto i = msg_type.length(); i < CMessageHeader::COMMAND_SIZE; ++i) {
         f << uint8_t{'\0'};
     }
     uint32_t size = data.size();
     ser_writedata32(f, size);
-    f.write(AsBytes(data));
+    f << data;
 }
 
 std::function<void(const CAddress& addr,
diff --git a/src/pubkey.h b/src/pubkey.h
index d8d5e3d85b..7d37504b01 100644
--- a/src/pubkey.h
+++ b/src/pubkey.h
@@ -142,14 +142,14 @@ public:
     {
         unsigned int len = size();
         ::WriteCompactSize(s, len);
-        s.write(AsBytes(Span{vch, len}));
+        s << Span{vch, len};
     }
     template <typename Stream>
     void Unserialize(Stream& s)
     {
         const unsigned int len(::ReadCompactSize(s));
         if (len <= SIZE) {
-            s.read(AsWritableBytes(Span{vch, len}));
+            s >> Span{vch, len};
             if (len != size()) {
                 Invalidate();
             }
diff --git a/src/serialize.h b/src/serialize.h
index 7bc7b10779..348a6ae4f1 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -188,6 +188,7 @@ template<typename X> const X& ReadWriteAsHelper(const X& x) { return x; }
     }                                                                               \
     FORMATTER_METHODS(cls, obj)
 
+// clang-format off
 #ifndef CHAR_EQUALS_INT8
 template <typename Stream> void Serialize(Stream&, char) = delete; // char serialization forbidden. Use uint8_t or int8_t
 #endif
@@ -201,8 +202,7 @@ template<typename Stream> inline void Serialize(Stream& s, int64_t a ) { ser_wri
 template<typename Stream> inline void Serialize(Stream& s, uint64_t a) { ser_writedata64(s, a); }
 template<typename Stream, int N> inline void Serialize(Stream& s, const char (&a)[N]) { s.write(MakeByteSpan(a)); }
 template<typename Stream, int N> inline void Serialize(Stream& s, const unsigned char (&a)[N]) { s.write(MakeByteSpan(a)); }
-template<typename Stream> inline void Serialize(Stream& s, const Span<const unsigned char>& span) { s.write(AsBytes(span)); }
-template<typename Stream> inline void Serialize(Stream& s, const Span<unsigned char>& span) { s.write(AsBytes(span)); }
+template <typename Stream, typename B> void Serialize(Stream& s, Span<B> span) { (void)/* force byte-type */UCharCast(span.data()); s.write(AsBytes(span)); }
 
 #ifndef CHAR_EQUALS_INT8
 template <typename Stream> void Unserialize(Stream&, char) = delete; // char serialization forbidden. Use uint8_t or int8_t
@@ -217,10 +217,11 @@ template<typename Stream> inline void Unserialize(Stream& s, int64_t& a ) { a =
 template<typename Stream> inline void Unserialize(Stream& s, uint64_t& a) { a = ser_readdata64(s); }
 template<typename Stream, int N> inline void Unserialize(Stream& s, char (&a)[N]) { s.read(MakeWritableByteSpan(a)); }
 template<typename Stream, int N> inline void Unserialize(Stream& s, unsigned char (&a)[N]) { s.read(MakeWritableByteSpan(a)); }
-template<typename Stream> inline void Unserialize(Stream& s, Span<unsigned char>& span) { s.read(AsWritableBytes(span)); }
+template <typename Stream, typename B> void Unserialize(Stream& s, Span<B> span) { (void)/* force byte-type */UCharCast(span.data()); s.read(AsWritableBytes(span)); }
 
 template <typename Stream> inline void Serialize(Stream& s, bool a) { uint8_t f = a; ser_writedata8(s, f); }
 template <typename Stream> inline void Unserialize(Stream& s, bool& a) { uint8_t f = ser_readdata8(s); a = f; }
+// clang-format on
 
 
 /**
diff --git a/src/test/fuzz/p2p_transport_serialization.cpp b/src/test/fuzz/p2p_transport_serialization.cpp
index ec3cdbff5a..a6fe3037e6 100644
--- a/src/test/fuzz/p2p_transport_serialization.cpp
+++ b/src/test/fuzz/p2p_transport_serialization.cpp
@@ -77,7 +77,7 @@ FUZZ_TARGET_INIT(p2p_transport_serialization, initialize_p2p_transport_serializa
             assert(msg.m_time == m_time);
 
             std::vector<unsigned char> header;
-            auto msg2 = CNetMsgMaker{msg.m_recv.GetVersion()}.Make(msg.m_type, MakeUCharSpan(msg.m_recv));
+            auto msg2 = CNetMsgMaker{msg.m_recv.GetVersion()}.Make(msg.m_type, Span{msg.m_recv});
             serializer.prepareForTransport(msg2, header);
         }
     }
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index 09f77d2b61..b445ff8ffc 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -186,32 +186,32 @@ BOOST_AUTO_TEST_CASE(noncanonical)
     std::vector<char>::size_type n;
 
     // zero encoded with three bytes:
-    ss.write(MakeByteSpan("\xfd\x00\x00").first(3));
+    ss << Span{"\xfd\x00\x00"}.first(3);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xfc encoded with three bytes:
-    ss.write(MakeByteSpan("\xfd\xfc\x00").first(3));
+    ss << Span{"\xfd\xfc\x00"}.first(3);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xfd encoded with three bytes is OK:
-    ss.write(MakeByteSpan("\xfd\xfd\x00").first(3));
+    ss << Span{"\xfd\xfd\x00"}.first(3);
     n = ReadCompactSize(ss);
     BOOST_CHECK(n == 0xfd);
 
     // zero encoded with five bytes:
-    ss.write(MakeByteSpan("\xfe\x00\x00\x00\x00").first(5));
+    ss << Span{"\xfe\x00\x00\x00\x00"}.first(5);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0xffff encoded with five bytes:
-    ss.write(MakeByteSpan("\xfe\xff\xff\x00\x00").first(5));
+    ss << Span{"\xfe\xff\xff\x00\x00"}.first(5);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // zero encoded with nine bytes:
-    ss.write(MakeByteSpan("\xff\x00\x00\x00\x00\x00\x00\x00\x00").first(9));
+    ss << Span{"\xff\x00\x00\x00\x00\x00\x00\x00\x00"}.first(9);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 
     // 0x01ffffff encoded with nine bytes:
-    ss.write(MakeByteSpan("\xff\xff\xff\xff\x01\x00\x00\x00\x00").first(9));
+    ss << Span{"\xff\xff\xff\xff\x01\x00\x00\x00\x00"}.first(9);
     BOOST_CHECK_EXCEPTION(ReadCompactSize(ss), std::ios_base::failure, isCanonicalException);
 }
 
@@ -241,6 +241,15 @@ BOOST_AUTO_TEST_CASE(class_methods)
     ss2 << intval << boolval << stringval << charstrval << txval;
     ss2 >> methodtest3;
     BOOST_CHECK(methodtest3 == methodtest4);
+    {
+        DataStream ds;
+        const std::string in{"ab"};
+        ds << Span{in};
+        std::array<std::byte, 2> out;
+        ds >> Span{out};
+        BOOST_CHECK_EQUAL(out.at(0), std::byte{'a'});
+        BOOST_CHECK_EQUAL(out.at(1), std::byte{'b'});
+    }
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/uint256.h b/src/uint256.h
index dc8887287a..d35b3a66fa 100644
--- a/src/uint256.h
+++ b/src/uint256.h
@@ -78,7 +78,7 @@ public:
     template<typename Stream>
     void Serialize(Stream& s) const
     {
-        s.write(MakeByteSpan(m_data));
+        s << Span(m_data);
     }
 
     template<typename Stream>
diff --git a/src/wallet/dump.cpp b/src/wallet/dump.cpp
index 44c93eed7c..3ac5cf03b1 100644
--- a/src/wallet/dump.cpp
+++ b/src/wallet/dump.cpp
@@ -57,12 +57,12 @@ bool DumpWallet(const ArgsManager& args, CWallet& wallet, bilingual_str& error)
     // Write out a magic string with version
     std::string line = strprintf("%s,%u\n", DUMP_MAGIC, DUMP_VERSION);
     dump_file.write(line.data(), line.size());
-    hasher.write(MakeByteSpan(line));
+    hasher << Span{line};
 
     // Write out the file format
     line = strprintf("%s,%s\n", "format", db.Format());
     dump_file.write(line.data(), line.size());
-    hasher.write(MakeByteSpan(line));
+    hasher << Span{line};
 
     if (ret) {
 
@@ -83,7 +83,7 @@ bool DumpWallet(const ArgsManager& args, CWallet& wallet, bilingual_str& error)
             std::string value_str = HexStr(ss_value);
             line = strprintf("%s,%s\n", key_str, value_str);
             dump_file.write(line.data(), line.size());
-            hasher.write(MakeByteSpan(line));
+            hasher << Span{line};
         }
     }
 
@@ -160,7 +160,7 @@ bool CreateFromDump(const ArgsManager& args, const std::string& name, const fs::
         return false;
     }
     std::string magic_hasher_line = strprintf("%s,%s\n", magic_key, version_value);
-    hasher.write(MakeByteSpan(magic_hasher_line));
+    hasher << Span{magic_hasher_line};
 
     // Get the stored file format
     std::string format_key;
@@ -191,7 +191,7 @@ bool CreateFromDump(const ArgsManager& args, const std::string& name, const fs::
         warnings.push_back(strprintf(_("Warning: Dumpfile wallet format \"%s\" does not match command line specified format \"%s\"."), format_value, file_format));
     }
     std::string format_hasher_line = strprintf("%s,%s\n", format_key, format_value);
-    hasher.write(MakeByteSpan(format_hasher_line));
+    hasher << Span{format_hasher_line};
 
     DatabaseOptions options;
     DatabaseStatus status;
@@ -236,7 +236,7 @@ bool CreateFromDump(const ArgsManager& args, const std::string& name, const fs::
             }
 
             std::string line = strprintf("%s,%s\n", key, value);
-            hasher.write(MakeByteSpan(line));
+            hasher << Span{line};
 
             if (key.empty() || value.empty()) {
                 continue;
diff --git a/src/wallet/test/db_tests.cpp b/src/wallet/test/db_tests.cpp
index e0b4a1e74c..d341e84d9b 100644
--- a/src/wallet/test/db_tests.cpp
+++ b/src/wallet/test/db_tests.cpp
@@ -196,7 +196,7 @@ BOOST_AUTO_TEST_CASE(db_cursor_prefix_byte_test)
     for (const auto& database : TestDatabases(m_path_root)) {
         std::unique_ptr<DatabaseBatch> batch = database->MakeBatch();
         for (const auto& [k, v] : {e, p, ps, f, fs, ff, ffs}) {
-            batch->Write(MakeUCharSpan(k), MakeUCharSpan(v));
+            batch->Write(Span{k}, Span{v});
         }
         CheckPrefix(*batch, StringBytes(""), {e, p, ps, f, fs, ff, ffs});
         CheckPrefix(*batch, StringBytes("prefix"), {p, ps});
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index a1b26b139e..5d99fb92a2 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -3878,7 +3878,7 @@ bool CWallet::MigrateToSQLite(bilingual_str& error)
     bool began = batch->TxnBegin();
     assert(began); // This is a critical error, the new db could not be written to. The original db exists as a backup, but we should not continue execution.
     for (const auto& [key, value] : records) {
-        if (!batch->Write(MakeUCharSpan(key), MakeUCharSpan(value))) {
+        if (!batch->Write(Span{key}, Span{value})) {
             batch->TxnAbort();
             m_database->Close();
             fs::remove(m_database->Filename());
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 2aee750ced..ff0b83dc38 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -1392,7 +1392,7 @@ bool WalletBatch::EraseRecords(const std::unordered_set<std::string>& types)
         }
 
         // Make a copy of key to avoid data being deleted by the following read of the type
-        Span<const unsigned char> key_data = MakeUCharSpan(key);
+        Span key_data{key};
 
         std::string type;
         key >> type;