perf: use small::max_size_vector in tr_torrentGetMetadataPiece() (#5768)

libtransmission/peer-msgs.cc

@@ -1880,8 +1880,8 @@ namespace peer_pulse_helpers
         return {};
     }
 
-    auto const data = tr_torrentGetMetadataPiece(msgs->torrent, *piece);
-    if (!data.has_value())
+    auto data = tr_metadata_piece{};
+    if (!tr_torrentGetMetadataPiece(msgs->torrent, *piece, data))
     {
         // send a reject
         auto tmp = tr_variant{};
@@ -1898,7 +1898,6 @@ namespace peer_pulse_helpers
     }
 
     // send the metadata
-    auto const data_sv = std::string_view{ reinterpret_cast<char const*>(std::data(*data)), std::size(*data) };
     auto tmp = tr_variant{};
     tr_variantInitDict(&tmp, 3);
     tr_variantDictAddInt(&tmp, TR_KEY_msg_type, MetadataMsgType::Data);
@@ -1909,7 +1908,7 @@ namespace peer_pulse_helpers
         BtPeerMsgs::Ltep,
         msgs->ut_metadata_id,
         tr_variantToStr(&tmp, TR_VARIANT_FMT_BENC),
-        data_sv);
+        data);
     tr_variantClear(&tmp);
     return n_bytes_written;
 }

libtransmission/torrent-magnet.cc

@@ -112,7 +112,7 @@ bool tr_torrentSetMetadataSizeHint(tr_torrent* tor, int64_t size)
     return true;
 }
 
-std::optional<std::vector<std::byte>> tr_torrentGetMetadataPiece(tr_torrent const* tor, int piece)
+bool tr_torrentGetMetadataPiece(tr_torrent const* tor, int piece, tr_metadata_piece& setme)
 {
     TR_ASSERT(tr_isTorrent(tor));
     TR_ASSERT(piece >= 0);
@@ -142,16 +142,10 @@ std::optional<std::vector<std::byte>> tr_torrentGetMetadataPiece(tr_torrent cons
         return {};
     }
 
-    auto buf = std::vector<std::byte>{};
     auto const piece_len = offset_in_info_dict + METADATA_PIECE_SIZE <= info_dict_size ? METADATA_PIECE_SIZE :
                                                                                          info_dict_size - offset_in_info_dict;
-    buf.resize(piece_len);
-    if (!in.read(reinterpret_cast<char*>(std::data(buf)), std::size(buf)))
-    {
-        return {};
-    }
-
-    return buf;
+    setme.resize(piece_len);
+    return !!in.read(reinterpret_cast<char*>(std::data(setme)), std::size(setme));
 }
 
 bool tr_torrentUseMetainfoFromFile(

libtransmission/torrent-magnet.h

@@ -15,6 +15,8 @@
 #include <optional>
 #include <vector>
 
+#include <small/vector.hpp>
+
 struct tr_error;
 struct tr_torrent;
 struct tr_torrent_metainfo;
@@ -22,7 +24,9 @@ struct tr_torrent_metainfo;
 // defined by BEP #9
 inline constexpr int METADATA_PIECE_SIZE = 1024 * 16;
 
-std::optional<std::vector<std::byte>> tr_torrentGetMetadataPiece(tr_torrent const* tor, int piece);
+using tr_metadata_piece = small::max_size_vector<std::byte, 1024U * 16U>;
+
+bool tr_torrentGetMetadataPiece(tr_torrent const* tor, int piece, tr_metadata_piece& setme);
 
 void tr_torrentSetMetadataPiece(tr_torrent* tor, int piece, void const* data, size_t len);
 

libtransmission/variant.cc

@@ -715,7 +715,7 @@ private:
 
     // When `v` is a dict, this is its children's indices sorted by key.
     // Bencoded dicts must be sorted, so this is useful when writing benc.
-    std::vector<size_t> sorted;
+    small::vector<size_t, 512> sorted;
 };
 
 class VariantWalker

tests/libtransmission/torrent-magnet-test.cc

@@ -28,16 +28,16 @@ TEST_F(TorrentMagnetTest, getMetadataPiece)
     };
     auto piece = int{ 0 };
     auto info_dict_size = size_t{ 0U };
+    auto data = tr_metadata_piece{};
     for (;;)
     {
-        auto const info_dict_data = tr_torrentGetMetadataPiece(tor, piece++);
-        if (!info_dict_data)
+        if (!tr_torrentGetMetadataPiece(tor, piece++, data))
         {
             break;
         }
 
-        benc.append(reinterpret_cast<char const*>(std::data(*info_dict_data)), std::size(*info_dict_data));
-        info_dict_size += std::size(*info_dict_data);
+        benc.append(reinterpret_cast<char const*>(std::data(data)), std::size(data));
+        info_dict_size += std::size(data);
     }
     benc.append("e");
     EXPECT_EQ(tor->info_dict_size(), info_dict_size);