[REST] improve performance for JSON calls

JSON calls do not use the raw data generated for
the .bin and .hex calls. By moving the raw data
creation into the .bin and .hex switch branches,
JSON calls become faster.

src/rest.cpp

@@ -157,13 +157,13 @@ static bool rest_headers(HTTPRequest* req,
         }
     }
 
-    CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
-    for (const CBlockIndex *pindex : headers) {
-        ssHeader << pindex->GetBlockHeader();
-    }
-
     switch (rf) {
     case RetFormat::BINARY: {
+        CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
+        for (const CBlockIndex *pindex : headers) {
+            ssHeader << pindex->GetBlockHeader();
+        }
+
         std::string binaryHeader = ssHeader.str();
         req->WriteHeader("Content-Type", "application/octet-stream");
         req->WriteReply(HTTP_OK, binaryHeader);
@@ -171,6 +171,11 @@ static bool rest_headers(HTTPRequest* req,
     }
 
     case RetFormat::HEX: {
+        CDataStream ssHeader(SER_NETWORK, PROTOCOL_VERSION);
+        for (const CBlockIndex *pindex : headers) {
+            ssHeader << pindex->GetBlockHeader();
+        }
+
         std::string strHex = HexStr(ssHeader.begin(), ssHeader.end()) + "\n";
         req->WriteHeader("Content-Type", "text/plain");
         req->WriteReply(HTTP_OK, strHex);
@@ -224,11 +229,10 @@ static bool rest_block(HTTPRequest* req,
             return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
     }
 
-    CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
-    ssBlock << block;
-
     switch (rf) {
     case RetFormat::BINARY: {
+        CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
+        ssBlock << block;
         std::string binaryBlock = ssBlock.str();
         req->WriteHeader("Content-Type", "application/octet-stream");
         req->WriteReply(HTTP_OK, binaryBlock);
@@ -236,6 +240,8 @@ static bool rest_block(HTTPRequest* req,
     }
 
     case RetFormat::HEX: {
+        CDataStream ssBlock(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
+        ssBlock << block;
         std::string strHex = HexStr(ssBlock.begin(), ssBlock.end()) + "\n";
         req->WriteHeader("Content-Type", "text/plain");
         req->WriteReply(HTTP_OK, strHex);
@@ -360,11 +366,11 @@ static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
     if (!GetTransaction(hash, tx, Params().GetConsensus(), hashBlock, true))
         return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
 
-    CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
-    ssTx << tx;
-
     switch (rf) {
     case RetFormat::BINARY: {
+        CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
+        ssTx << tx;
+
         std::string binaryTx = ssTx.str();
         req->WriteHeader("Content-Type", "application/octet-stream");
         req->WriteReply(HTTP_OK, binaryTx);
@@ -372,6 +378,9 @@ static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
     }
 
     case RetFormat::HEX: {
+        CDataStream ssTx(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
+        ssTx << tx;
+
         std::string strHex = HexStr(ssTx.begin(), ssTx.end()) + "\n";
         req->WriteHeader("Content-Type", "text/plain");
         req->WriteReply(HTTP_OK, strHex);