Fix issue with Packet::sideData(type)

Due to incorrect condition, for valid side data returns empty data set.

Added tests for this case.

Author: h4tr3d

src/avcpp/packet.cpp

@@ -371,18 +371,24 @@ void Packet::setTimeBase(const Rational &tb)
 #if AVCPP_HAS_PKT_SIDE_DATA
 using SideDataSize_t = std::conditional_t<AVCPP_API_AVBUFFER_SIZE_T, std::size_t, int>;
 
-std::span<const uint8_t> Packet::sideData(AVPacketSideDataType type) const
+static auto sideDataCommon(auto *pkt, AVPacketSideDataType type)
 {
+    using ResultType = std::conditional_t<std::is_const_v<decltype(pkt)>, std::span<const uint8_t>, std::span<uint8_t>>;
+    if (!pkt)
+        return ResultType{};
     SideDataSize_t size;
-    auto const data = av_packet_get_side_data(raw(), type, &size);
-    return data ? std::span<const uint8_t>{} : std::span<const uint8_t>{data, std::size_t(size)};
+    auto const data = av_packet_get_side_data(pkt, type, &size);
+    return data ? ResultType{data, std::size_t(size)} : ResultType{};
+}
+
+std::span<const uint8_t> Packet::sideData(AVPacketSideDataType type) const
+{
+    return sideDataCommon(raw(), type);
 }
 
 std::span<uint8_t> Packet::sideData(AVPacketSideDataType type)
 {
-    SideDataSize_t size;
-    auto const data = av_packet_get_side_data(raw(), type, &size);
-    return data ? std::span<uint8_t>{} : std::span<uint8_t>{data, std::size_t(size)};
+    return sideDataCommon(raw(), type);
 }
 
 PacketSideData Packet::sideData(std::size_t index) noexcept

tests/Packet.cpp

@@ -2,6 +2,7 @@
 
 #include <vector>
 
+#include "avcpp/avconfig.h"
 #include "avcpp/packet.h"
 
 #ifdef _MSC_VER
@@ -179,6 +180,74 @@ TEST_CASE("Packet define", "[Packet][Construct]")
         }
     }
 
+#if AVCPP_HAS_PKT_SIDE_DATA
+    SECTION("Packet side data")
+    {
+        const av::Rational tb{1000,1};
+        av::Packet in_pkt{pkt_data, sizeof(pkt_data)};
+        CHECK(in_pkt.timeBase() == av::Rational());
+        in_pkt.setTimeBase(tb);
+        CHECK(in_pkt.timeBase() == tb);
+
+        {
+            auto sd = in_pkt.sideData(AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL);
+            REQUIRE(sd.empty());
+        }
+
+        std::string meta = "field=val;field2=val2";
+
+        {
+            std::vector<uint8_t> side_block_adds(meta.size() + sizeof(uint64_t));
+            std::span out = side_block_adds;
+            uint64_t id = 100;
+            if (std::endian::native == std::endian::little)
+                id = av_bswap64(id);
+            memcpy(out.data(), &id, sizeof(id));
+            out = out.subspan(sizeof(id));
+            std::ranges::copy(meta, out.begin());
+
+            REQUIRE_NOTHROW(in_pkt.addSideData(AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL, side_block_adds));
+            REQUIRE(in_pkt.sideDataCount() == 1);
+        }
+
+        {
+            auto sd = in_pkt.sideData(AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL);
+            REQUIRE(!sd.empty());
+            REQUIRE(sd.size() == sizeof(uint64_t) + meta.size());
+
+            auto in = sd;
+            uint64_t id{};
+            memcpy(&id, in.data(), sizeof(uint64_t));
+            in = in.subspan(sizeof(uint64_t));
+            if (std::endian::native == std::endian::little)
+                id = av_bswap64(id);
+            REQUIRE(id == 100);
+
+            std::string_view meta_read{reinterpret_cast<const char*>(in.data()), in.size()};
+            REQUIRE(meta_read == meta);
+        }
+
+        {
+            auto const& pkt = in_pkt;
+            auto sd = pkt.sideData(AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL);
+            REQUIRE(!sd.empty());
+            REQUIRE(sd.size() == sizeof(uint64_t) + meta.size());
+
+            auto in = sd;
+            uint64_t id{};
+            memcpy(&id, in.data(), sizeof(uint64_t));
+            in = in.subspan(sizeof(uint64_t));
+            if (std::endian::native == std::endian::little)
+                id = av_bswap64(id);
+            REQUIRE(id == 100);
+
+            std::string_view meta_read{reinterpret_cast<const char*>(in.data()), in.size()};
+            REQUIRE(meta_read == meta);
+        }
+
+    }
+#endif
+
 #ifdef __cpp_lib_print
     SECTION("std::format formatter :: Side Data")
     {