From 33369b17753a051a6d89ba5135fb35ac46a89f44 Mon Sep 17 00:00:00 2001
From: James Grogan <grogan.ox@gmail.com>
Date: Thu, 24 Nov 2022 17:43:31 +0000
Subject: [PATCH] Toward first png.

---
 src/compression/CyclicRedundancyChecker.cpp | 42 +++++++++
 src/compression/CyclicRedundancyChecker.h   | 50 ++---------
 src/compression/ZlibEncoder.cpp             | 31 +++++--
 src/compression/ZlibEncoder.h               |  2 +-
 src/compression/deflate/DeflateBlock.cpp    |  4 +-
 src/compression/deflate/DeflateEncoder.cpp  |  2 +
 src/image/png/PngHeader.cpp                 | 18 ++--
 src/image/png/PngHeader.h                   |  4 +-
 src/image/png/PngReader.cpp                 | 95 +++++++++++++++------
 src/image/png/PngReader.h                   | 10 +--
 src/image/png/PngWriter.cpp                 | 30 ++++---
 test/image/TestPngReader.cpp                |  4 +-
 12 files changed, 190 insertions(+), 102 deletions(-)

diff --git a/src/compression/CyclicRedundancyChecker.cpp b/src/compression/CyclicRedundancyChecker.cpp
index e69de29..977ed97 100644
--- a/src/compression/CyclicRedundancyChecker.cpp
+++ b/src/compression/CyclicRedundancyChecker.cpp
@@ -0,0 +1,42 @@
+#include "CyclicRedundancyChecker.h"
+
+void CyclicRedundancyChecker::createTable()
+{
+    unsigned long c{0};
+    for (int n = 0; n < 256; n++)
+    {
+        c = (unsigned long) n;
+        for (int k = 0; k < 8; k++)
+        {
+            if (c & 1)
+            {
+                c = 0xedb88320L ^ (c >> 1);
+            }
+            else
+            {
+                c = c >> 1;
+            }
+        }
+        mTable[n] = c;
+    }
+    mTableComputed = true;
+}
+
+void CyclicRedundancyChecker::addValue(unsigned char val)
+{
+    if (!mTableComputed)
+    {
+        createTable();
+    }
+    mLastValue = mTable[(mLastValue ^ val) & 0xff] ^ (mLastValue >> 8);
+}
+
+uint32_t CyclicRedundancyChecker::getChecksum() const
+{
+    return mLastValue ^ 0xffffffffL;
+}
+
+void CyclicRedundancyChecker::reset()
+{
+    mLastValue = 0xffffffffL;
+}
diff --git a/src/compression/CyclicRedundancyChecker.h b/src/compression/CyclicRedundancyChecker.h
index 9d31d1e..fa6cd0e 100644
--- a/src/compression/CyclicRedundancyChecker.h
+++ b/src/compression/CyclicRedundancyChecker.h
@@ -1,52 +1,20 @@
 #pragma once
 
-class CyclicRedundancyChecker
+#include "AbstractChecksumCalculator.h"
+
+class CyclicRedundancyChecker : public AbstractChecksumCalculator
 {
 public:
+    void addValue(unsigned char val) override;
 
-    void createTable()
-    {
-        unsigned long c{0};
-        for (int n = 0; n < 256; n++)
-        {
-            c = (unsigned long) n;
-            for (int k = 0; k < 8; k++)
-            {
-                if (c & 1)
-                {
-                    c = 0xedb88320L ^ (c >> 1);
-                }
-                else
-                {
-                    c = c >> 1;
-                }
-            }
-            mTable[n] = c;
-        }
-        mTableComputed = true;
-        mTableComputed = 1;
-    }
+    uint32_t getChecksum() const override;
 
-    unsigned long updateCrc(unsigned long crc, unsigned char *buf, int len)
-    {
-        unsigned long c = crc;
-        if (!mTableComputed)
-        {
-            createTable();
-        }
-        for (int n = 0; n < len; n++)
-        {
-            c = mTable[(c ^ buf[n]) & 0xff] ^ (c >> 8);
-        }
-        return c;
-    }
-
-    unsigned long doCrc(unsigned char *buf, int len)
-    {
-        return updateCrc(0xffffffffL, buf, len) ^ 0xffffffffL;
-    }
+    void reset() override;
 
 private:
+    void createTable();
     bool mTableComputed{false};
+
+    uint32_t mLastValue{0xffffffffL};
     unsigned long mTable[256];
 };
diff --git a/src/compression/ZlibEncoder.cpp b/src/compression/ZlibEncoder.cpp
index 9a456e3..78764c2 100644
--- a/src/compression/ZlibEncoder.cpp
+++ b/src/compression/ZlibEncoder.cpp
@@ -61,10 +61,16 @@ void ZlibEncoder::parseCompressionMethod(unsigned char method)
     }
 }
 
-void ZlibEncoder::parseExtraFlags(unsigned char extraFlags)
+void ZlibEncoder::parseExtraFlags(unsigned char extraFlags, unsigned char compression_byte)
 {
     std::cout << "Got flags  " << static_cast<int>(extraFlags) << std::endl;
 
+    auto mod = ((static_cast<unsigned>(compression_byte) << 8) | extraFlags) % 31;
+    if (mod != 0)
+    {
+        std::cout << "Invalid header. Mod is " << mod << std::endl;
+    }
+
     mFlagCheck = ByteUtils::getLowerNBits(extraFlags, 5);
     mUseDictionary = bool(ByteUtils::getBitN(extraFlags, 5));
     mFlagLevel = static_cast<CompressionLevel>(ByteUtils::getHigherNBits(extraFlags, 2));
@@ -76,11 +82,10 @@ std::string ZlibEncoder::getData() const
     sstream << "ZlibEncoder data \n";
     sstream << "Compression method: " << toString(mCompressionMethod) << '\n';
     sstream << "Window size: " << mWindowSize << '\n';
-    sstream << "Flag check: " << mFlagCheck << '\n';
+    sstream << "Flag check: " << static_cast<int>(mFlagCheck) << '\n';
     sstream << "Use dictionary: " << mUseDictionary << '\n';
     sstream << "Flag level: " << toString(mFlagLevel) << '\n';
     return sstream.str();
-
 }
 
 bool ZlibEncoder::encode()
@@ -126,15 +131,17 @@ bool ZlibEncoder::encode()
     }
 
     const auto checksum = mChecksumCalculator->getChecksum();
-    std::cout << "ZlibEncoder Writing Checksum " << checksum << std::endl;
+    std::cout << "ZlibEncoder Writing Adler32 Checksum " << checksum << std::endl;
     mOutputStream->write(checksum);
     return true;
 }
 
 bool ZlibEncoder::decode()
 {
-    parseCompressionMethod(*mInputStream->readNextByte());
-    parseExtraFlags(*mInputStream->readNextByte());
+    auto compression_byte = *mInputStream->readNextByte();
+
+    parseCompressionMethod(compression_byte);
+    parseExtraFlags(*mInputStream->readNextByte(), compression_byte);
 
     if (!mWorkingEncoder)
     {
@@ -149,5 +156,15 @@ bool ZlibEncoder::decode()
         }
     }
 
-    return mWorkingEncoder->decode();
+    auto valid = mWorkingEncoder->decode();
+
+    unsigned char byte0 = *mInputStream->readNextByte();
+    unsigned char byte1 = *mInputStream->readNextByte();
+    unsigned char byte2 = *mInputStream->readNextByte();
+    unsigned char byte3 = *mInputStream->readNextByte();
+
+    uint32_t adler32 = (byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3;
+    std::cout << "Got adler 32 checksum " << adler32 << std::endl;
+
+    return valid;
 }
diff --git a/src/compression/ZlibEncoder.h b/src/compression/ZlibEncoder.h
index ec6653e..df898e8 100644
--- a/src/compression/ZlibEncoder.h
+++ b/src/compression/ZlibEncoder.h
@@ -40,7 +40,7 @@ public:
 
 private:
     void parseCompressionMethod(unsigned char method);
-    void parseExtraFlags(unsigned char extraFlags);
+    void parseExtraFlags(unsigned char extraFlags, unsigned char compression_byte);
 
     CompressionMethod mCompressionMethod{CompressionMethod::DEFLATE};
     Deflate::CompressionMethod mDeflateCompressionMethod{Deflate::CompressionMethod::NONE};
diff --git a/src/compression/deflate/DeflateBlock.cpp b/src/compression/deflate/DeflateBlock.cpp
index d178b53..5b07615 100644
--- a/src/compression/deflate/DeflateBlock.cpp
+++ b/src/compression/deflate/DeflateBlock.cpp
@@ -261,7 +261,7 @@ void DeflateBlock::write(uint16_t datalength)
 {
     unsigned char working_block{0};
     working_block |= static_cast<unsigned char>(mInFinalBlock);
-    working_block |= static_cast<unsigned char>(mCompressionMethod) << 1;
+    working_block |= (static_cast<unsigned char>(mCompressionMethod) << 1);
 
     if (mCompressionMethod == Deflate::CompressionMethod::NONE)
     {
@@ -277,7 +277,7 @@ void DeflateBlock::write(uint16_t datalength)
         for(unsigned idx=0; idx<datalength;idx++)
         {
             auto byte = *mInputStream->readNextByte();
-            std::cout << "Writing next byte " << static_cast<int>(byte) << std::endl;
+            //std::cout << "Writing next byte " << static_cast<int>(byte) << std::endl;
             mOutputStream->writeByte(byte);
         }
     }
diff --git a/src/compression/deflate/DeflateEncoder.cpp b/src/compression/deflate/DeflateEncoder.cpp
index c887b19..92d1dc8 100644
--- a/src/compression/deflate/DeflateEncoder.cpp
+++ b/src/compression/deflate/DeflateEncoder.cpp
@@ -66,6 +66,8 @@ bool DeflateEncoder::decode()
     auto working_block = std::make_unique<DeflateBlock>(mInputStream, mOutputStream);
     working_block->readHeader();
 
+    std::cout << working_block->getMetaData() << std::endl;
+
     DeflateBlock* raw_block = working_block.get();
 
     while(!raw_block->isFinalBlock())
diff --git a/src/image/png/PngHeader.cpp b/src/image/png/PngHeader.cpp
index b162e8e..b9fa13b 100644
--- a/src/image/png/PngHeader.cpp
+++ b/src/image/png/PngHeader.cpp
@@ -11,6 +11,8 @@ std::string PngHeader::toString() const
     sstr << "width: " << mWidth << "\n";
     sstr << "height: " << mHeight << "\n";
     sstr << "bitDepth: " << (int)mBitDepth << "\n";
+    sstr << "cached CRC: " << mCachedCrc << "\n";
+
     sstr << mPngInfo.toString();
     return sstr.str();
 }
@@ -66,14 +68,20 @@ void PngHeader::updateData()
     mData.push_back(static_cast<unsigned char>(mPngInfo.mInterlaceMethod));
 }
 
-uint32_t PngHeader::getCrc() const
+uint32_t PngHeader::getCrc()
 {
     CyclicRedundancyChecker crc_check;
     std::vector<unsigned char> char_data = StringUtils::toBytes(mName);
-    std::copy(mData.begin(), mData.end(), std::back_inserter(char_data));
-
-    auto result = crc_check.doCrc(char_data.data(), char_data.size());
-    return result;
+    for (auto c : char_data)
+    {
+        crc_check.addValue(c);
+    }
+    for (auto entry : mData)
+    {
+        crc_check.addValue(entry);
+    }
+    mCachedCrc = crc_check.getChecksum();
+    return mCachedCrc;
 }
 
 void PngHeader::setPngInfo(const PngInfo& info)
diff --git a/src/image/png/PngHeader.h b/src/image/png/PngHeader.h
index 05538a7..17ee0b4 100644
--- a/src/image/png/PngHeader.h
+++ b/src/image/png/PngHeader.h
@@ -9,7 +9,7 @@ class PngHeader
 public:
     uint32_t getLength() const;
 
-    uint32_t getCrc() const;
+    uint32_t getCrc();
 
     const std::vector<unsigned char>& getData() const;
 
@@ -36,5 +36,7 @@ private:
     PngInfo mPngInfo;
     std::string mName{"IHDR"};
 
+    uint32_t mCachedCrc{0};
+
     std::vector<unsigned char> mData;
 };
diff --git a/src/image/png/PngReader.cpp b/src/image/png/PngReader.cpp
index 522717b..0b8322d 100644
--- a/src/image/png/PngReader.cpp
+++ b/src/image/png/PngReader.cpp
@@ -5,6 +5,7 @@
 #include "BufferBitStream.h"
 
 #include "ZlibEncoder.h"
+#include "CyclicRedundancyChecker.h"
 
 #include <iostream>
 #include <sstream>
@@ -43,8 +44,6 @@ bool PngReader::checkSignature()
             return false;
         }
     }
-
-    mCurrentOffset += 8;
     return true;
 }
 
@@ -54,45 +53,51 @@ bool PngReader::readChunk()
 
     std::string chunkType;
     BinaryStream::getNextString(mFile->GetInHandle(), chunkType, 4);
-    mCurrentOffset += 8;
 
     std::cout << "Got chunk with type: " << chunkType << " and length: " << length << std::endl;
     bool lastChunk = false;
     if (chunkType == "IHDR")
     {
-        readHeaderChunk();
+        if (!readHeaderChunk())
+        {
+            return false;
+        }
     }
     else if(chunkType == "IEND")
     {
         lastChunk = true;
+        if (mProcessingDatablocks)
+        {
+            decodeData();
+        }
+        unsigned crcCheck = *BinaryStream::getNextDWord(mFile->GetInHandle());
     }
     else if(chunkType == "IDAT")
     {
-        readIDATChunk(length);
+        mProcessingDatablocks = true;
+        if(!readIDATChunk(length))
+        {
+            return false;
+        }
     }
     else
     {
+        if (mProcessingDatablocks)
+        {
+            decodeData();
+        }
+
         for(unsigned idx=0;idx<length;idx++)
         {
             mFile->GetInHandle()->get();
         }
+
+        unsigned crcCheck = *BinaryStream::getNextDWord(mFile->GetInHandle());
     }
-
-    unsigned crcCheck = *BinaryStream::getNextDWord(mFile->GetInHandle());
-
-    mCurrentOffset += 4;
     return !lastChunk;
 }
 
-void PngReader::readIDATChunk(unsigned length)
-{
-    for(unsigned idx=0; idx<length; idx++)
-    {
-        mInputStream->writeByte(*mFile->readNextByte());
-    }
-}
-
-void PngReader::readHeaderChunk()
+bool PngReader::readHeaderChunk()
 {
     auto width = *BinaryStream::getNextDWord(mFile->GetInHandle());
     auto height = *BinaryStream::getNextDWord(mFile->GetInHandle());
@@ -106,15 +111,52 @@ void PngReader::readHeaderChunk()
     info.mFilterMethod = static_cast<PngInfo::FilterMethod>(mFile->GetInHandle()->get());
     info.mInterlaceMethod = static_cast<PngInfo::InterlaceMethod>(mFile->GetInHandle()->get());
     mHeader.setPngInfo(info);
+    mHeader.updateData();
 
-    mCurrentOffset += 13;
+    uint32_t file_crc = *BinaryStream::getNextDWord(mFile->GetInHandle());
+    auto crc_calc = mHeader.getCrc();
 
-    logHeader();
+    std::cout << mHeader.toString() << "*************\n";
+    if (file_crc != crc_calc)
+    {
+        std::cout << "Header crc calc does not match file value. File: " << file_crc << " Header: " << crc_calc << std::endl;;
+        return false;
+    }
+    else
+    {
+        return true;
+    }
 }
 
-void PngReader::logHeader()
+bool PngReader::readIDATChunk(unsigned length)
 {
-    std::cout << "IHDR\n" << mHeader.toString() << "*************\n";
+    auto crc_check = std::make_unique<CyclicRedundancyChecker>();
+
+    std::vector<unsigned char> char_data = StringUtils::toBytes("IDAT");
+    for (auto c : char_data)
+    {
+        crc_check->addValue(c);
+    }
+
+    mInputStream->setChecksumCalculator(crc_check.get());
+    for(unsigned idx=0; idx<length; idx++)
+    {
+        mInputStream->writeByte(*mFile->readNextByte());
+    }
+    mInputStream->clearChecksumCalculator();
+
+    uint32_t file_crc = *BinaryStream::getNextDWord(mFile->GetInHandle());
+    auto crc_calc = crc_check->getChecksum();
+
+    if (file_crc != crc_calc)
+    {
+        std::cout << "IDAT crc calc does not match file value. File: " << file_crc << " Header: " << crc_calc << std::endl;;
+        return false;
+    }
+    else
+    {
+        return true;
+    }
 }
 
 std::unique_ptr<Image<unsigned char> > PngReader::read()
@@ -138,8 +180,11 @@ std::unique_ptr<Image<unsigned char> > PngReader::read()
     {
 
     }
-
-    std::cout << mEncoder->getData() << std::endl;
-    mEncoder->decode();
     return std::move(image);
 }
+
+void PngReader::decodeData()
+{
+    mEncoder->decode();
+    std::cout << mEncoder->getData() << "***********" << std::endl;
+}
diff --git a/src/image/png/PngReader.h b/src/image/png/PngReader.h
index e657859..0dad321 100644
--- a/src/image/png/PngReader.h
+++ b/src/image/png/PngReader.h
@@ -24,15 +24,13 @@ public:
 private:
     bool readChunk();
 
-    void readHeaderChunk();
+    bool readHeaderChunk();
 
-    void readIDATChunk(unsigned length);
-
-    void logHeader();
+    bool readIDATChunk(unsigned length);
 
     bool checkSignature();
 
-    unsigned mCurrentOffset{0};
+    void decodeData();
 
     PngHeader mHeader;
 
@@ -43,5 +41,5 @@ private:
     std::unique_ptr<ZlibEncoder> mEncoder;
     std::unique_ptr<BitStream> mInputStream;
     std::unique_ptr<BitStream> mOutputStream;
-    bool mAwaitingDataBlock{true};
+    bool mProcessingDatablocks{false};
 };
diff --git a/src/image/png/PngWriter.cpp b/src/image/png/PngWriter.cpp
index 5c17a01..8811edd 100644
--- a/src/image/png/PngWriter.cpp
+++ b/src/image/png/PngWriter.cpp
@@ -83,9 +83,9 @@ void PngWriter::writeHeader()
     mPngHeader.updateData();
     mOutStream->writeBytes(mPngHeader.getData());
 
-    std::cout << "Writing header " << mPngHeader.toString() << std::endl;
-
     auto crc = mPngHeader.getCrc();
+
+    std::cout << mPngHeader.toString() << "*********" << std::endl;
     mOutStream->write(crc);
 }
 
@@ -98,7 +98,11 @@ void PngWriter::writeEndChunk()
     std::vector<unsigned char> char_data = StringUtils::toBytes("IEND");
 
     CyclicRedundancyChecker crc_check;
-    auto crc = crc_check.doCrc(char_data.data(), char_data.size());
+    for (auto c : char_data)
+    {
+        crc_check.addValue(c);
+    }
+    auto crc = crc_check.getChecksum();
     mOutStream->write(crc);
 
     std::cout << "Writing end chunk" << std::endl;
@@ -108,11 +112,6 @@ void PngWriter::writeDataChunks(const BufferBitStream& buffer)
 {
     auto num_bytes = buffer.getBuffer().size();
     auto max_bytes{32000};
-    std::vector<unsigned char> crc_buffer(num_bytes + 4, 0);
-    crc_buffer[0] = 'I';
-    crc_buffer[1] = 'D';
-    crc_buffer[2] = 'A';
-    crc_buffer[3] = 'T';
 
     unsigned num_dat_chunks = num_bytes/max_bytes + 1;
     unsigned offset = 0;
@@ -127,18 +126,23 @@ void PngWriter::writeDataChunks(const BufferBitStream& buffer)
         std::cout << "Writing idat length " << num_bytes << std::endl;
         mOutStream->write(num_bytes);
 
-        mOutStream->writeBytes(StringUtils::toBytes("IDAT"));
+        std::vector<unsigned char> char_data = StringUtils::toBytes("IDAT");
+        mOutStream->writeBytes(char_data);
+
+        CyclicRedundancyChecker crc_check;
+        for (auto c : char_data)
+        {
+            crc_check.addValue(c);
+        }
 
         for(unsigned jdx=0; jdx<num_bytes; jdx++)
         {
             auto val = buffer.getBuffer()[idx*max_bytes + jdx];
-            crc_buffer[jdx + 4] = val;
             mOutStream->writeByte(val);
+            crc_check.addValue(val);
         }
 
-        CyclicRedundancyChecker crc_check;
-        auto crc = crc_check.doCrc(crc_buffer.data(), crc_buffer.size());
-
+        auto crc = crc_check.getChecksum();
         std::cout << "Writing idat crc" << crc << std::endl;
         mOutStream->write(crc);
     }
diff --git a/test/image/TestPngReader.cpp b/test/image/TestPngReader.cpp
index d1f2cdb..b0458fd 100644
--- a/test/image/TestPngReader.cpp
+++ b/test/image/TestPngReader.cpp
@@ -9,7 +9,9 @@ int main()
 {
     //const auto path = "/home/jmsgrogan/Downloads/test.png";
 
-    const auto path = "/home/jmsgrogan/Downloads/index.png";
+    //const auto path = "/home/jmsgrogan/Downloads/index.png";
+
+    const auto path = "/home/jmsgrogan/code/MediaTool-build/bin/test.png";
 
     PngReader reader;
     reader.setPath(path);