Merge #13151: net: Serve blocks directly from disk when possible

0bf431870e45d8e20c4671e51a782ebf97b75fac net: Serve blocks directly from disk when possible (Wladimir J. van der Laan)

Pull request description:

  In `ProcessGetBlockData`, send the block data directly from disk if type MSG_WITNESS_BLOCK is requested. This is a valid shortcut as the on-disk format matches the network format.

  This is expected to increase performance because a deserialization and subsequent serialization roundtrip is avoided.

Tree-SHA512: 9a9500b4c1354eaae1a6f1c6ef2416c1c1985029852589266f3a70e808f6c7482c135e9ab251a527566935378ab7c32dba4ed43ba5451e802d8e72b77d1ba472

1 files changed, 46 insertions, 0 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 3971906424..9791d6e2d8 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1137,6 +1137,52 @@ bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus
     return true;
 }
 
+bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& message_start)
+{
+    CDiskBlockPos hpos = pos;
+    hpos.nPos -= 8; // Seek back 8 bytes for meta header
+    CAutoFile filein(OpenBlockFile(hpos, true), SER_DISK, CLIENT_VERSION);
+    if (filein.IsNull()) {
+        return error("%s: OpenBlockFile failed for %s", __func__, pos.ToString());
+    }
+
+    try {
+        CMessageHeader::MessageStartChars blk_start;
+        unsigned int blk_size;
+
+        filein >> blk_start >> blk_size;
+
+        if (memcmp(blk_start, message_start, CMessageHeader::MESSAGE_START_SIZE)) {
+            return error("%s: Block magic mismatch for %s: %s versus expected %s", __func__, pos.ToString(),
+                    HexStr(blk_start, blk_start + CMessageHeader::MESSAGE_START_SIZE),
+                    HexStr(message_start, message_start + CMessageHeader::MESSAGE_START_SIZE));
+        }
+
+        if (blk_size > MAX_SIZE) {
+            return error("%s: Block data is larger than maximum deserialization size for %s: %s versus %s", __func__, pos.ToString(),
+                    blk_size, MAX_SIZE);
+        }
+
+        block.resize(blk_size); // Zeroing of memory is intentional here
+        filein.read((char*)block.data(), blk_size);
+    } catch(const std::exception& e) {
+        return error("%s: Read from block file failed: %s for %s", __func__, e.what(), pos.ToString());
+    }
+
+    return true;
+}
+
+bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start)
+{
+    CDiskBlockPos block_pos;
+    {
+        LOCK(cs_main);
+        block_pos = pindex->GetBlockPos();
+    }
+
+    return ReadRawBlockFromDisk(block, block_pos, message_start);
+}
+
 CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
 {
     int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;