From 287b77720017d1cb5ddd8de8ca3ea28af1b34ec3 Mon Sep 17 00:00:00 2001
From: nekohkr <182421472+nekohkr@users.noreply.github.com>
Date: Sun, 5 Jul 2026 23:42:22 +0900
Subject: [PATCH] Optimize parser buffer handling

---
 src/dataUnit.cpp                | 19 ++++++++-----------
 src/dataUnit.h                  |  6 +++---
 src/fragmentAssembler.cpp       |  4 ++--
 src/fragmentAssembler.h         |  7 ++++---
 src/mmtTlvDemuxer.cpp           | 12 +++++-------
 src/mpu.cpp                     |  5 ++---
 src/mpu.h                       |  4 ++--
 src/mpuApplicationProcessor.cpp |  4 ++--
 src/mpuApplicationProcessor.h   |  4 ++--
 src/mpuAudioProcessor.cpp       |  4 ++--
 src/mpuAudioProcessor.h         |  4 ++--
 src/mpuProcessorBase.h          |  7 ++++---
 src/mpuSubtitleProcessor.cpp    |  4 ++--
 src/mpuSubtitleProcessor.h      |  4 ++--
 src/mpuVideoProcessor.cpp       |  4 ++--
 src/mpuVideoProcessor.h         |  4 ++--
 src/stream.cpp                  | 27 ++++++++++++++-------------
 src/stream.h                    | 32 ++++++++++++++++++++++++--------
 18 files changed, 84 insertions(+), 71 deletions(-)

diff --git a/src/dataUnit.cpp b/src/dataUnit.cpp
index a012f69..9e4f57c 100644
--- a/src/dataUnit.cpp
+++ b/src/dataUnit.cpp
@@ -2,8 +2,9 @@
 
 namespace MmtTlv {
 
-bool DataUnit::unpack(Common::ReadStream& stream, bool timedFlag, bool aggregateFlag) {
-	try {
+bool DataUnit::unpack(Common::ReadStream& stream, bool timedFlag, bool aggregateFlag) {
+	try {
+		data = {};
 		if (timedFlag) {
 			if (aggregateFlag == 0) {
 				movieFragmentSequenceNumber = stream.getBe32U();
@@ -12,8 +13,7 @@ bool DataUnit::unpack(Common::ReadStream& stream, bool timedFlag, bool aggregate
 				priority = stream.get8U();
 				dependencyCounter = stream.get8U();
 
-				data.resize(stream.leftBytes());
-				stream.read(data.data(), stream.leftBytes());
+				data = stream.readView(stream.leftBytes());
 			}
 			else {
 				dataUnitLength = stream.getBe16U();
@@ -29,22 +29,19 @@ bool DataUnit::unpack(Common::ReadStream& stream, bool timedFlag, bool aggregate
 					return false;
 				}
 
-				data.resize(dataUnitLength - 4 * 3 - 2);
-				stream.read(data.data(), dataUnitLength - 4 * 3 - 2);
+				data = stream.readView(dataUnitLength - 4 * 3 - 2);
 			}
 		}
 		else {
 			if (aggregateFlag == 0) {
 				itemId = stream.getBe32U();
 
-				data.resize(stream.leftBytes());
-				stream.read(data.data(), stream.leftBytes());
+				data = stream.readView(stream.leftBytes());
 			}
 			else {
 				dataUnitLength = stream.getBe16U();
 
-				data.resize(dataUnitLength);
-				stream.read(data.data(), dataUnitLength);
+				data = stream.readView(dataUnitLength);
 			}
 		}
 	}
@@ -55,4 +52,4 @@ bool DataUnit::unpack(Common::ReadStream& stream, bool timedFlag, bool aggregate
 	return true;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/dataUnit.h b/src/dataUnit.h
index 6f10704..bbc2248 100644
--- a/src/dataUnit.h
+++ b/src/dataUnit.h
@@ -1,5 +1,5 @@
 #pragma once
-#include <vector>
+#include <span>
 #include "stream.h"
 
 namespace MmtTlv {
@@ -15,7 +15,7 @@ class DataUnit {
 	uint8_t priority;
 	uint8_t dependencyCounter;
 	uint32_t itemId;
-	std::vector<uint8_t> data;
+	std::span<const uint8_t> data;
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/fragmentAssembler.cpp b/src/fragmentAssembler.cpp
index f6efe00..1c6de2c 100644
--- a/src/fragmentAssembler.cpp
+++ b/src/fragmentAssembler.cpp
@@ -3,7 +3,7 @@
 
 namespace MmtTlv {
 
-bool FragmentAssembler::assemble(const std::vector<uint8_t>& fragment, FragmentationIndicator fragmentationIndicator, uint32_t packetSequenceNumber) {
+bool FragmentAssembler::assemble(std::span<const uint8_t> fragment, FragmentationIndicator fragmentationIndicator, uint32_t packetSequenceNumber) {
     switch (fragmentationIndicator) {
     case FragmentationIndicator::NotFragmented:
         if (state == State::InFragment) {
@@ -104,4 +104,4 @@ void FragmentValidator::clear() {
     state = State::NotStarted;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/fragmentAssembler.h b/src/fragmentAssembler.h
index 0691c83..48f4454 100644
--- a/src/fragmentAssembler.h
+++ b/src/fragmentAssembler.h
@@ -1,5 +1,6 @@
 #pragma once
-#include <vector>
+#include <vector>
+#include <span>
 #include <cstdint>
 #include "mmtFragment.h"
 
@@ -24,7 +25,7 @@ class FragmentValidator {
 
 class FragmentAssembler {
 public:
-	bool assemble(const std::vector<uint8_t>& fragment, FragmentationIndicator fragmentationIndicator, uint32_t packetSequenceNumber);
+	bool assemble(std::span<const uint8_t> fragment, FragmentationIndicator fragmentationIndicator, uint32_t packetSequenceNumber);
 	void checkState(uint32_t packetSequenceNumber);
 	void clear();
 
@@ -41,4 +42,4 @@ class FragmentAssembler {
 	uint32_t last_seq = 0;
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/mmtTlvDemuxer.cpp b/src/mmtTlvDemuxer.cpp
index 94f3948..d3b8d77 100644
--- a/src/mmtTlvDemuxer.cpp
+++ b/src/mmtTlvDemuxer.cpp
@@ -792,7 +792,7 @@ void MmtTlvDemuxer::processMpu(Common::ReadStream& stream) {
     }
 }
 
-void MmtTlvDemuxer::processMfuData(Common::ReadStream& stream) {
+void MmtTlvDemuxer::processMfuData(Common::ReadStream& stream) {
     MmtStream* mmtStream = getStream(mmtp.packetId);
     auto validator = getFragmentValidator(mmtp.packetId);
 
@@ -800,10 +800,8 @@ void MmtTlvDemuxer::processMfuData(Common::ReadStream& stream) {
         return;
     }
 
-    std::vector<uint8_t> data(stream.leftBytes());
-    stream.read(data.data(), stream.leftBytes());
-
-    const auto ret = mmtStream->mpuProcessor->process(*mmtStream, data, mpu.fragmentationIndicator);
+    const auto data = stream.readView(stream.leftBytes());
+    const auto ret = mmtStream->mpuProcessor->process(*mmtStream, data, mpu.fragmentationIndicator);
     if (ret) {
         const auto& mfuData = ret.value();
         auto* mmtStream = getStreamByIdx(mfuData.streamIndex);
@@ -864,7 +862,7 @@ void MmtTlvDemuxer::processSignalingMessages(Common::ReadStream& stream) {
 
             std::vector<uint8_t> message;
             message.resize(length);
-            stream.read(message.data(), length);
+            nstream.read(message.data(), length);
 
             if (assembler->assemble(message, signalingMessage.fragmentationIndicator, mmtp.packetSequenceNumber)) {
                 Common::ReadStream messageStream(assembler->data);
@@ -913,4 +911,4 @@ bool MmtTlvDemuxer::isValidTlv(Common::ReadStream& stream) const {
     return true;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpu.cpp b/src/mpu.cpp
index e61c52e..c4d4aa3 100644
--- a/src/mpu.cpp
+++ b/src/mpu.cpp
@@ -18,8 +18,7 @@ bool Mpu::unpack(Common::ReadStream& stream)
 		fragmentCounter = stream.get8U();
 		mpuSequenceNumber = stream.getBe32U();
 
-		payload.resize(payloadLength - 6);
-		stream.read(payload.data(), payloadLength - 6);
+		payload = stream.readView(payloadLength - 6);
 
 	}
 	catch (const std::out_of_range&) {
@@ -29,4 +28,4 @@ bool Mpu::unpack(Common::ReadStream& stream)
 	return true;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpu.h b/src/mpu.h
index d15035d..ddaf419 100644
--- a/src/mpu.h
+++ b/src/mpu.h
@@ -1,5 +1,5 @@
 #pragma once
-#include <vector>
+#include <span>
 #include "stream.h"
 #include "mmtFragment.h"
 
@@ -16,7 +16,7 @@ class Mpu {
 	bool aggregateFlag;
 	uint8_t fragmentCounter;
 	uint32_t mpuSequenceNumber;
-	std::vector<uint8_t> payload;
+	std::span<const uint8_t> payload;
 };
 
 }
diff --git a/src/mpuApplicationProcessor.cpp b/src/mpuApplicationProcessor.cpp
index 402222a..21143d8 100644
--- a/src/mpuApplicationProcessor.cpp
+++ b/src/mpuApplicationProcessor.cpp
@@ -3,7 +3,7 @@
 
 namespace MmtTlv {
 
-std::optional<MfuData> MpuApplicationProcessor::process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) {
+std::optional<MfuData> MpuApplicationProcessor::process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) {
     Common::ReadStream stream(data);
     size_t size = stream.leftBytes();
     if (size == 0) {
@@ -19,4 +19,4 @@ std::optional<MfuData> MpuApplicationProcessor::process(MmtStream& mmtStream, co
     return mfuData;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuApplicationProcessor.h b/src/mpuApplicationProcessor.h
index c497b60..0c696b0 100644
--- a/src/mpuApplicationProcessor.h
+++ b/src/mpuApplicationProcessor.h
@@ -5,8 +5,8 @@ namespace MmtTlv {
 
 class MpuApplicationProcessor : public MpuProcessorTemplate<AssetType::aapp> {
 public:
-	std::optional<MfuData> process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) override;
+	std::optional<MfuData> process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) override;
 
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuAudioProcessor.cpp b/src/mpuAudioProcessor.cpp
index 550563d..5162355 100644
--- a/src/mpuAudioProcessor.cpp
+++ b/src/mpuAudioProcessor.cpp
@@ -7,7 +7,7 @@ namespace MmtTlv {
 
 constexpr int MAX_AAC_FRAME_SIZE = 1024 * 10;
 
-std::optional<MfuData> MpuAudioProcessor::process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) {
+std::optional<MfuData> MpuAudioProcessor::process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) {
     aacFragment.insert(aacFragment.end(), data.begin(), data.end());
 
     MfuData mfuData;
@@ -81,4 +81,4 @@ void MpuAudioProcessor::clear() {
     aacFragment.clear();
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuAudioProcessor.h b/src/mpuAudioProcessor.h
index d89f388..256ce46 100644
--- a/src/mpuAudioProcessor.h
+++ b/src/mpuAudioProcessor.h
@@ -5,7 +5,7 @@ namespace MmtTlv {
 
 class MpuAudioProcessor : public MpuProcessorTemplate<AssetType::mp4a> {
 public:
-	std::optional<MfuData> process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) override;
+	std::optional<MfuData> process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) override;
 	void clear() override;
 
 private:
@@ -15,4 +15,4 @@ class MpuAudioProcessor : public MpuProcessorTemplate<AssetType::mp4a> {
 
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuProcessorBase.h b/src/mpuProcessorBase.h
index 9b9c751..8a02016 100644
--- a/src/mpuProcessorBase.h
+++ b/src/mpuProcessorBase.h
@@ -1,7 +1,8 @@
 #pragma once
 #include <vector>
 #include <optional>
-#include <memory>
+#include <memory>
+#include <span>
 #include "mmtp.h"
 #include "dataUnit.h"
 #include "mpu.h"
@@ -36,7 +37,7 @@ class MmtStream;
 class MpuProcessorBase {
 public:
 	virtual ~MpuProcessorBase() = default;
-	virtual std::optional<MfuData> process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) { return std::nullopt; }
+	virtual std::optional<MfuData> process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) { return std::nullopt; }
 	virtual void clear() {}
 
 };
@@ -50,4 +51,4 @@ class MpuProcessorTemplate : public MpuProcessorBase {
 
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuSubtitleProcessor.cpp b/src/mpuSubtitleProcessor.cpp
index e618dd1..86a2dbe 100644
--- a/src/mpuSubtitleProcessor.cpp
+++ b/src/mpuSubtitleProcessor.cpp
@@ -3,7 +3,7 @@
 
 namespace MmtTlv {
 
-std::optional<MfuData> MpuSubtitleProcessor::process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) {
+std::optional<MfuData> MpuSubtitleProcessor::process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) {
     Common::ReadStream stream(data);
 
     uint16_t subsampleNumber = stream.getBe16U();
@@ -50,4 +50,4 @@ std::optional<MfuData> MpuSubtitleProcessor::process(MmtStream& mmtStream, const
     return mfuData;
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuSubtitleProcessor.h b/src/mpuSubtitleProcessor.h
index 1d13a09..f7842bb 100644
--- a/src/mpuSubtitleProcessor.h
+++ b/src/mpuSubtitleProcessor.h
@@ -5,10 +5,10 @@ namespace MmtTlv {
 
 class MpuSubtitleProcessor : public MpuProcessorTemplate<AssetType::stpp> {
 public:
-	std::optional<MfuData> process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) override;
+	std::optional<MfuData> process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) override;
 
 private:
 	std::vector<uint8_t> pendingData;
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuVideoProcessor.cpp b/src/mpuVideoProcessor.cpp
index 9d1cef1..4333652 100644
--- a/src/mpuVideoProcessor.cpp
+++ b/src/mpuVideoProcessor.cpp
@@ -9,7 +9,7 @@ constexpr uint8_t CRA_NUT = 0x15;
 constexpr uint8_t NAL_AUD = 0x23;
 constexpr uint32_t MAX_NAL_SIZE = 1024 * 1024;
 
-std::optional<MfuData> MpuVideoProcessor::process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) {
+std::optional<MfuData> MpuVideoProcessor::process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) {
     Common::ReadStream stream(data);
     MfuData mfuData;
 
@@ -89,4 +89,4 @@ void MpuVideoProcessor::clear() {
 
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/mpuVideoProcessor.h b/src/mpuVideoProcessor.h
index 4dc5f59..3b90d92 100644
--- a/src/mpuVideoProcessor.h
+++ b/src/mpuVideoProcessor.h
@@ -5,7 +5,7 @@ namespace MmtTlv {
 
 class MpuVideoProcessor : public MpuProcessorTemplate<AssetType::hev1> {
 public:
-	std::optional<MfuData> process(MmtStream& mmtStream, const std::vector<uint8_t>& data, FragmentationIndicator fragmentationIndicator) override;
+	std::optional<MfuData> process(MmtStream& mmtStream, std::span<const uint8_t> data, FragmentationIndicator fragmentationIndicator) override;
 	void clear();
 
 private:
@@ -18,4 +18,4 @@ class MpuVideoProcessor : public MpuProcessorTemplate<AssetType::hev1> {
 
 };
 
-}
\ No newline at end of file
+}
diff --git a/src/stream.cpp b/src/stream.cpp
index 811f5c2..73c4e99 100644
--- a/src/stream.cpp
+++ b/src/stream.cpp
@@ -2,19 +2,20 @@
 
 namespace MmtTlv {
     
-namespace Common {
-
-ReadStream::ReadStream(const std::vector<uint8_t>& buffer)
-    : buffer(buffer)
-{
-    this->hasSize = true;
-    this->size = buffer.size();
-}
+namespace Common {
+
+ReadStream::ReadStream(std::span<const uint8_t> buffer)
+    : buffer(buffer), hasSize(true), size(buffer.size())
+{
+}
+
+ReadStream::ReadStream(const std::vector<uint8_t>& buffer)
+    : ReadStream(std::span<const uint8_t>(buffer)) {}
 
 ReadStream::ReadStream(const std::vector<uint8_t>& buffer, size_t size)
-    : buffer(buffer)
+    : buffer(buffer)
 {
-    if (buffer.size() < size) {
+    if (this->buffer.size() < size) {
         throw std::out_of_range("Access out of bounds");
     }
 
@@ -22,10 +23,10 @@ ReadStream::ReadStream(const std::vector<uint8_t>& buffer, size_t size)
     this->size = size;
 }
 
-ReadStream::ReadStream(ReadStream& stream, size_t size)
+ReadStream::ReadStream(ReadStream& stream, size_t size)
     : buffer(stream.buffer)
 {
-    if (stream.buffer.size() < stream.pos + size) {
+    if (stream.size < stream.pos + size) {
         throw std::out_of_range("Access out of bounds");
     }
 
@@ -44,4 +45,4 @@ ReadStream::ReadStream(ReadStream& stream)
 
 }
 
-}
\ No newline at end of file
+}
diff --git a/src/stream.h b/src/stream.h
index ee092e2..12ebe45 100644
--- a/src/stream.h
+++ b/src/stream.h
@@ -9,9 +9,10 @@ namespace MmtTlv {
 
 namespace Common {
 
-class ReadStream final {
-public:
-    explicit ReadStream(const std::vector<uint8_t>& data);
+class ReadStream final {
+public:
+    explicit ReadStream(std::span<const uint8_t> data);
+    explicit ReadStream(const std::vector<uint8_t>& data);
     explicit ReadStream(const std::vector<uint8_t>& data, size_t size);
     explicit ReadStream(ReadStream& stream, size_t size);
     explicit ReadStream(ReadStream& stream);
@@ -24,7 +25,20 @@ class ReadStream final {
 
     bool isEof() const { return size == pos; }
     size_t leftBytes() const { return size - pos; }
-    size_t getPos() const { return pos; }
+    size_t getPos() const { return pos; }
+
+    [[nodiscard]] std::span<const uint8_t> remaining() const noexcept {
+        return buffer.subspan(pos, size - pos);
+    }
+
+    std::span<const uint8_t> readView(size_t count) {
+        if (count > leftBytes()) {
+            throw std::out_of_range("Access out of bounds");
+        }
+        const auto view = buffer.subspan(pos, count);
+        pos += count;
+        return view;
+    }
 
     void seek(size_t pos) {
         if (size < pos) {
@@ -116,10 +130,12 @@ class ReadStream final {
         if (size < pos + sizeof(T)) {
             throw std::out_of_range("Access out of bounds");
         }
-        return *reinterpret_cast<const T*>(buffer.data() + pos);
-    }
-
-    const std::vector<uint8_t>& buffer;
+        T value{};
+        memcpy(&value, buffer.data() + pos, sizeof(T));
+        return value;
+    }
+
+    std::span<const uint8_t> buffer;
     bool hasSize = false;
     mutable size_t size = 0;
     mutable size_t pos = 0;