Reimplement decode_f4(). It uses RLE.

src/unpaker/decode.h

@@ -222,7 +222,7 @@ int decode_f3(char *input, int size, char *output)
                         v10 = v21;
                         memset32(v16, v18, v15 >> 1);
                         v19 = (int)((char *)v16 + 4 * (v15 >> 1));
-                        for (i = (v13 + 3) & 1; i; --i)
+                        for (i = v15 & 1; i; --i)
                         {
                             *(_WORD *)v19 = v18;
                             v19 += 2;
@@ -231,7 +231,10 @@ int decode_f3(char *input, int size, char *output)
                     }
                     goto LABEL_13;
                 }
-                *(_WORD *)v11 = *(_WORD *)&v4[2 * idx];
+                else
+                {
+                    *(_WORD *)v11 = *(_WORD *)&v4[2 * idx];
+                }
             }
             else
             {
@@ -307,3 +310,69 @@ int decode_f4(char *input, int size, char *output, int segment_offset)
     }
     return result;
 }
+
+void decode_rle(const short *input, const int size, short *output)
+{
+    if (size < 2)
+        return;
+
+    // input ptr, also rle_indicator
+    const auto rle_indicator = input++;
+    while (1)
+    {
+        auto c = *input++;
+        if ((c & 0xFF00) != (*rle_indicator << 8))
+            *output++ = c;
+        else
+        {
+            uint32_t count = (uint8_t)c;
+            if (count == (*rle_indicator << 8) + 255)
+                *output++ = c; // insert indicator byte itself
+            else
+            {
+                count += 3;
+                for (int i = 0; i < count / 2; i++)
+                {
+                    *output++ = *input;
+                    *output++ = *input;
+                }
+                for (int i = 0; i < ((count / 2) & 1); i++)
+                {
+                    *output++ = *input;
+                }
+            }
+        }
+
+        if (input >= rle_indicator + size)
+            return;
+    }
+}
+
+void decode_rle(const char *input, const int size, char *output)
+{
+    if (size < 2)
+        return;
+
+    // input ptr, also rle_indicator
+    const auto rle_indicator = input++;
+    while (1)
+    {
+        auto c = *input++;
+        if (c != *rle_indicator)
+            *output++ = c;
+        else
+        {
+            uint32_t count = (uint8_t)*input++;
+            if (count == 255)
+                *output++ = *rle_indicator; // insert indicator byte itself
+            else
+            {
+                memset(output, *input++, count += 3);
+                output += count;
+            }
+        }
+
+        if (input >= rle_indicator + size)
+            return;
+    }
+}

src/unpaker/pak.cpp

@@ -27,8 +27,6 @@
 
 #define FREAD(var) fread(&var, 1, sizeof(var), f)
 
-const int header_size = 0xC;
-
 void header::load(FILE *f)
 {
     FREAD(unk1);
@@ -42,7 +40,9 @@ void header::load(FILE *f)
 
 void record::load(FILE *f)
 {
-    FREAD(name);
+    char n[0x50];
+    FREAD(n);
+    name = n;
     FREAD(pos);
     FREAD(len);
 }
@@ -96,7 +96,7 @@ int record::read(pak *pak, void *output, int size)
 void segment::load_header(FILE *f)
 {
     FREAD(unk1);
-    FREAD(flags);
+    FREAD(algorithm);
     FREAD(offset);
 }
 
@@ -105,7 +105,7 @@ void segment::load_segment()
     auto f = file;
 
     fseek(f, offset, SEEK_SET);
-    if (flags == 0)
+    if (algorithm == 0)
     {
         std::cerr << "Something is wrong. Maybe you trying to open aim2 files?\n";
         std::cerr << "They can be opened with SDK extractor.\n";
@@ -114,7 +114,7 @@ void segment::load_segment()
 
     FREAD(size1);
     size2 = size1;
-    if ((flags & 0x3) && (flags & 0xC))
+    if ((algorithm & 0x3) && (algorithm & 0xC))
     {
         FREAD(size2);
         fread(&decoded[0], 1, size2, f);
@@ -129,19 +129,30 @@ void segment::decompress(int segment_id)
 {
     load_segment();
 
-    if (flags & 0xC)
+    if ((algorithm & DA_1) || (algorithm & DA_2))
     {
-        if (flags & 0x4)
+        if (algorithm & DA_1)
             decode_f1((char*)decoded, size2, (char*)encoded);
         else
             decode_f2((char*)decoded, size2, (char*)encoded);
     }
-    if (flags & 0x3)
+    if ((algorithm & RLE_1_byte) || (algorithm & RLE_2_bytes))
     {
-        if (flags & 0x1)
-            decode_f3((char*)encoded, size1, (char*)decoded);
+        if (algorithm & RLE_2_bytes)
+        {
+            //static std::vector<uint8_t> buf(4194432);
+            decode_f3((char*)encoded, size1, (char*)decoded/*buf.data()*/);
+            //decode_rle((short*)encoded, size1, (short*)decoded);
+            //assert(memcmp(decoded, buf.data(), size1) == 0);
+        }
         else
-            decode_f4((char*)encoded, size1, (char*)decoded, segment_id * header_size);
+        {
+            //static std::vector<uint8_t> buf(4194432);
+            //const int header_size = 0xC;
+            //decode_f4((char*)encoded, size1, (char*)buf.data(), segment_id * header_size);
+            decode_rle((char*)encoded, size1, (char*)decoded);
+            //assert(memcmp(decoded, buf.data(), size1) == 0);
+        }
     }
 }
 

src/unpaker/pak.h

@@ -40,7 +40,7 @@ struct header
 
 struct record
 {
-    char name[0x50];
+    std::string name;
     uint32_t pos;
     uint32_t len;
 
@@ -55,8 +55,16 @@ struct record
 
 struct segment
 {
+    enum decode_algorithm
+    {
+        RLE_2_bytes = 0x1,
+        RLE_1_byte  = 0x2,
+        DA_1 = 0x4,
+        DA_2 = 0x8,
+    };
+
     uint32_t unk1;
-    uint32_t flags;
+    decode_algorithm algorithm;
     uint32_t offset;
 
     uint32_t size1;

src/unpaker/unpaker.cpp

@@ -27,14 +27,19 @@ void unpak(string fn)
         return;
     pak p;
     p.load(f);
-    for (auto &f : p.files)
+
+    auto unpack = [&](auto &file)
     {
-        record &file = f.second;
         cout << "Unpacking " << file.name << "\n";
         vector<char> buf(file.len);
         file.read(&p, &buf[0], file.len);
         file.write(fn + ".dir", buf);
     };
+
+    unpack(p.files["arena.mmp"]);
+
+    //for (auto &[n,f] : p.files)
+        //unpack(f);
     fclose(f);
 }