Merge bitcoin/bitcoin#23438: refactor: Use spans of std::byte in serialize

fa5d2e678c809c26bd40d7e7c171529d3ffb5903 Remove unused char serialize (MarcoFalke)
fa24493d6394b3a477535f480664c9596f18e3c5 Use spans of std::byte in serialize (MarcoFalke)
fa65bbf217b725ada35107b4ad646d250228355c span: Add BytePtr helper (MarcoFalke)

Pull request description:

  This changes the serialize code (`.read()` and `.write()` functions) to take a `Span` instead of a pointer and size. This is a breaking change for the serialize interface, so at no additional cost we can also switch to `std::byte` (instead of using `char`).

  The benefits of using `Span`:
  * Less verbose and less fragile code when passing an already existing `Span`(-like) object to or from serialization

  The benefits of using `std::byte`:
  * `std::byte` can't accidentally be mistaken for an integer

  The goal here is to only change serialize to use spans of `std::byte`. If needed, `AsBytes`,  `MakeUCharSpan`, ... can be used (temporarily) to pass spans of the right type.

  Other changes that are included here:

  * [#22167](https://github.com/bitcoin/bitcoin/pull/22167) (refactor: Remove char serialize by MarcoFalke)
  * [#21906](https://github.com/bitcoin/bitcoin/pull/21906) (Preserve const in cast on CTransactionSignatureSerializer by promag)

ACKs for top commit:
  laanwj:
    Concept and code review ACK fa5d2e678c809c26bd40d7e7c171529d3ffb5903
  sipa:
    re-utACK fa5d2e678c809c26bd40d7e7c171529d3ffb5903

Tree-SHA512: 08ee9eced5fb777cedae593b11e33660bed9a3e1711a7451a87b835089a96c99ce0632918bb4666a4e859c4d020f88fb50f2dd734216b0c3d1a9a704967ece6f

2 files changed, 6 insertions, 6 deletions

diff --git a/src/bench/checkblock.cpp b/src/bench/checkblock.cpp
index a9f3f5f84d..52e5cb743f 100644
--- a/src/bench/checkblock.cpp
+++ b/src/bench/checkblock.cpp
@@ -17,8 +17,8 @@
 static void DeserializeBlockTest(benchmark::Bench& bench)
 {
     CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-    char a = '\0';
-    stream.write(&a, 1); // Prevent compaction
+    std::byte a{0};
+    stream.write({&a, 1}); // Prevent compaction
 
     bench.unit("block").run([&] {
         CBlock block;
@@ -31,8 +31,8 @@ static void DeserializeBlockTest(benchmark::Bench& bench)
 static void DeserializeAndCheckBlockTest(benchmark::Bench& bench)
 {
     CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-    char a = '\0';
-    stream.write(&a, 1); // Prevent compaction
+    std::byte a{0};
+    stream.write({&a, 1}); // Prevent compaction
 
     ArgsManager bench_args;
     const auto chainParams = CreateChainParams(bench_args, CBaseChainParams::MAIN);
diff --git a/src/bench/rpc_blockchain.cpp b/src/bench/rpc_blockchain.cpp
index 9bc31461d2..2143bcf950 100644
--- a/src/bench/rpc_blockchain.cpp
+++ b/src/bench/rpc_blockchain.cpp
@@ -23,8 +23,8 @@ struct TestBlockAndIndex {
     TestBlockAndIndex()
     {
         CDataStream stream(benchmark::data::block413567, SER_NETWORK, PROTOCOL_VERSION);
-        char a = '\0';
-        stream.write(&a, 1); // Prevent compaction
+        std::byte a{0};
+        stream.write({&a, 1}); // Prevent compaction
 
         stream >> block;