implemented decoder from of p8.png together with code decompression

src/io/stegano.cpp

@@ -6,28 +6,25 @@
 using namespace retro8;
 using namespace io;
 
-constexpr size_t IMAGE_WIDTH = 160;
-constexpr size_t IMAGE_HEIGHT = 205;
-
 constexpr size_t RAW_DATA_LENGTH = 0x4300;
 
 uint8_t Stegano::assembleByte(const uint32_t v)
 {
-  constexpr uint32_t MASK_ALPHA = 0xff00000;
-  constexpr uint32_t MASK_RED = 0x000000ff;
+  constexpr uint32_t MASK_ALPHA = 0xff000000;
+  constexpr uint32_t MASK_RED = 0x00ff0000;
   constexpr uint32_t MASK_GREEN = 0x0000ff00;
-  constexpr uint32_t MASK_BLUE = 0x00ff0000;
+  constexpr uint32_t MASK_BLUE = 0x000000ff;
 
   constexpr uint32_t SHIFT_ALPHA = 24;
-  constexpr uint32_t SHIFT_RED = 0;
+  constexpr uint32_t SHIFT_RED = 16;
   constexpr uint32_t SHIFT_GREEN = 8;
-  constexpr uint32_t SHIFT_BLUE = 16;
+  constexpr uint32_t SHIFT_BLUE = 0;
 
   return
-    ((((v & MASK_ALPHA) >> SHIFT_ALPHA) & 0b11) ) |
-    ((((v & MASK_RED) >> SHIFT_RED) & 0b11) << 2) |
-    ((((v & MASK_GREEN) >> SHIFT_GREEN) & 0b11) << 4) |
-    ((((v & MASK_BLUE) >> SHIFT_BLUE) & 0b11) << 6);
+    ((((v & MASK_ALPHA) >> SHIFT_ALPHA) & 0b11) << 6) |
+    ((((v & MASK_RED) >> SHIFT_RED) & 0b11) << 0) |
+    ((((v & MASK_GREEN) >> SHIFT_GREEN) & 0b11) << 2) |
+    ((((v & MASK_BLUE) >> SHIFT_BLUE) & 0b11) << 4);
 }
 
 void Stegano::load(const PngData& data, Machine& m)
@@ -44,16 +41,65 @@ void Stegano::load(const PngData& data, Machine& m)
   static_assert(RAW_DATA_LENGTH == SPRITE_SHEET_SIZE + TILE_MAP_SIZE + SPRITE_FLAGS_SIZE + MUSIC_SIZE + SOUND_SIZE, "Must be equal");
   assert(data.length == IMAGE_WIDTH * IMAGE_HEIGHT);
 
+  auto* d = data.data;
+
   /* first 0x4300 are read directly into the cart */
   for (size_t i = 0; i < RAW_DATA_LENGTH; ++i)
-    m.memory().base()[i] = assembleByte(data.data[i]);
+    m.memory().base()[i] = assembleByte(d[i]);
 
   size_t o = RAW_DATA_LENGTH;
   std::array<uint8_t, 4> magic;
   std::array<uint8_t, 4> expected = { { ':', 'c', ':', '\0' } };
 
+  /* read magic code heaader */
   for (size_t i = 0; i < magic.size(); ++i)
-    magic[i] = assembleByte(data.data[o++]);
+    magic[i] = assembleByte(d[o++]);
 
   assert(magic == expected);
+
+  /* read uint6_t lsb compressed length*/
+  size_t compressedLength = assembleByte(d[o]) << 8 | assembleByte(d[o + 1]);
+  o += 2;
+  /* skip 2 null*/
+  o += 2;
+
+  const std::string lookup = "\n 0123456789abcdefghijklmnopqrstuvwxyz!#%(){}[]<>+=/*:;.,~_";
+  std::string code;
+
+  assert(0x3b == lookup.length());
+  //TODO: optimize concatenation on string by reserving space
+
+  for (size_t i = 0; i < compressedLength; ++i)
+  {
+    uint8_t v = assembleByte(d[o + i]);
+
+    /* copy next */
+    if (v == 0x00)
+    {
+      uint8_t vn = assembleByte(d[o + i + 1]);
+      code += vn;
+      ++i;
+    }
+    /* lookup */
+    else if (v <= 0x3b)
+    {
+      code += lookup[v - 1];
+    }
+    else
+    {
+      uint8_t vn = assembleByte(d[o + i + 1]);
+      
+      auto offset = ((v - 0x3c) << 4) + (vn & 0xf);
+      auto length = (vn >> 4) + 2;
+
+      const size_t start = code.length() - offset;
+      for (size_t j = 0; j < length; ++j)
+        code += code[start + j];
+
+      ++i;
+    }
+  }
+
+  m.code().initFromSource(code);
+
 }

src/io/stegano.h

@@ -16,6 +16,10 @@ namespace retro8
     
     class Stegano
     {
+    public:
+      static constexpr size_t IMAGE_WIDTH = 160;
+      static constexpr size_t IMAGE_HEIGHT = 205;
+
     private:
       uint8_t assembleByte(const uint32_t v);
     public:

src/views/game_view.cpp

@@ -107,9 +107,17 @@ void GameView::render()
     retro8::io::LoaderP8 loader;
 
     if (_path.empty())
-      _path = "pico-man.p8";
+      _path = "test.p8";
 
-    loader.load(_path, machine);
+    //loader.load(_path, machine);
+
+
+    /*SDL_Surface* surface = IMG_Load("pico-man.p8.png");
+    r8::io::PngData pngData = { static_cast<const uint32_t*>(surface->pixels), surface->h * surface->w };
+    assert(surface->pitch == r8::io::Stegano::IMAGE_WIDTH * sizeof(uint32_t));
+    assert(surface->format->BytesPerPixel == 4);
+    r8::io::Stegano stegano;
+    stegano.load(pngData, machine);*/
 
     manager->setFrameRate(machine.code().require60fps() ? 60 : 30);
 
@@ -120,11 +128,6 @@ void GameView::render()
     //machine.sound().init();
     //machine.sound().resume();
 
-    /*SDL_Surface* surface = IMG_Load("pico-man.p8.png");
-    r8::io::PngData pngData = { static_cast<const uint32_t*>(surface->pixels), surface->h * surface->w };
-    assert(surface->format->BytesPerPixel == 4);
-    r8::io::Stegano stegano;
-    stegano.load(pngData, machine);*/
 
     /*for (int i = 0; i < 32; ++i)
       machine.circ(64, 64, i+1, (r8::color_t)(i % 15 + 1));*/