rest: read raw block in rest_block and deserialize for json

Note that for speed this commit also removes the proof of work and
signet signature checks before returning the block in getblock.
It is assumed if a block is stored it will be valid.

src/rest.cpp

@@ -13,6 +13,7 @@
 #include <chain.h>
 #include <chainparams.h>
 #include <core_io.h>
+#include <flatfile.h>
 #include <httpserver.h>
 #include <index/blockfilterindex.h>
 #include <index/txindex.h>
@@ -34,7 +35,7 @@
 #include <validation.h>
 
 #include <any>
-#include <string>
+#include <vector>
 
 #include <univalue.h>
 
@@ -295,7 +296,7 @@ static bool rest_block(const std::any& context,
     if (!ParseHashStr(hashStr, hash))
         return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + hashStr);
 
-    CBlock block;
+    FlatFilePos pos{};
     const CBlockIndex* pblockindex = nullptr;
     const CBlockIndex* tip = nullptr;
     ChainstateManager* maybe_chainman = GetChainman(context, req);
@@ -311,32 +312,33 @@ static bool rest_block(const std::any& context,
         if (chainman.m_blockman.IsBlockPruned(*pblockindex)) {
             return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not available (pruned data)");
         }
+        pos = pblockindex->GetBlockPos();
     }
 
-    if (!chainman.m_blockman.ReadBlockFromDisk(block, *pblockindex)) {
+    std::vector<uint8_t> block_data{};
+    if (!chainman.m_blockman.ReadRawBlockFromDisk(block_data, pos)) {
         return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
     }
 
     switch (rf) {
     case RESTResponseFormat::BINARY: {
-        DataStream ssBlock;
-        ssBlock << TX_WITH_WITNESS(block);
-        std::string binaryBlock = ssBlock.str();
+        const std::string binaryBlock{block_data.begin(), block_data.end()};
         req->WriteHeader("Content-Type", "application/octet-stream");
         req->WriteReply(HTTP_OK, binaryBlock);
         return true;
     }
 
     case RESTResponseFormat::HEX: {
-        DataStream ssBlock;
-        ssBlock << TX_WITH_WITNESS(block);
-        std::string strHex = HexStr(ssBlock) + "\n";
+        const std::string strHex{HexStr(block_data) + "\n"};
         req->WriteHeader("Content-Type", "text/plain");
         req->WriteReply(HTTP_OK, strHex);
         return true;
     }
 
     case RESTResponseFormat::JSON: {
+        CBlock block{};
+        DataStream block_stream{block_data};
+        block_stream >> TX_WITH_WITNESS(block);
         UniValue objBlock = blockToJSON(chainman.m_blockman, block, *tip, *pblockindex, tx_verbosity);
         std::string strJSON = objBlock.write() + "\n";
         req->WriteHeader("Content-Type", "application/json");