Compress as blocks.

The LZ77 compressor works with blocks. Each block is prefixed with
a header that defines the output size of the block being compressed.

1 files changed, 44 insertions, 57 deletions

diff --git a/rld-compression.cpp b/rld-compression.cpp
index 42c11fe..55e7a6c 100644
--- a/rld-compression.cpp
+++ b/rld-compression.cpp
@@ -53,6 +53,9 @@ namespace rld
         total (0),
         total_compressed (0)
     {
+      if (size > 0xffff)
+        throw rld::error ("Size too big, 16 bits only", "compression");
+
       buffer = new uint8_t[size];
       io = new uint8_t[size + (size / 10)];
     }
@@ -69,39 +72,21 @@ namespace rld
     {
       const uint8_t* data = static_cast <const uint8_t*> (data_);
 
-      if (compress)
+      while (length)
       {
-        while (length)
-        {
-          size_t appending;
-
-          if (length > (size - level))
-            appending = size - level;
-          else
-            appending = length;
-
-          ::memcpy ((void*) (buffer + level), data, appending);
+        size_t appending;
 
-          level += appending;
-          length -= appending;
-          total += appending;
+        if (length > (size - level))
+          appending = size - level;
+        else
+          appending = length;
 
-          if (level >= size)
-          {
-            int writing =
-              ::fastlz_compress (buffer, level, io);
+        ::memcpy ((void*) (buffer + level), data, appending);
 
-            image.write (io, writing);
+        level += appending;
+        length -= appending;
 
-            total_compressed += writing;
-            level = 0;
-          }
-        }
-      }
-      else
-      {
-        image.write (data, length);
-        total += length;
+        output ();
       }
     }
 
@@ -123,42 +108,15 @@ namespace rld
 
         level += appending;
         length -= appending;
-        total += appending;
-
-        if (level >= size)
-        {
-          if (compress)
-          {
-            int writing =
-              ::fastlz_compress (buffer, level, io);
-
-            image.write (io, writing);
-
-            total_compressed += writing;
-          }
-          else
-          {
-            image.write (buffer, length);
-          }
 
-          level = 0;
-        }
+        output ();
       }
     }
 
     void
     compressor::flush ()
     {
-      if (level)
-      {
-        int writing =
-          ::fastlz_compress (buffer, level, io);
-
-        image.write (io, writing);
-
-        total_compressed += writing;
-        level = 0;
-      }
+      output (true);
     }
 
     size_t
@@ -173,5 +131,34 @@ namespace rld
       return total_compressed;
     }
 
+    void
+    compressor::output (bool forced)
+    {
+      if ((forced && level) || (level >= size))
+      {
+        total += level;
+
+        if (compress)
+        {
+          int     writing = ::fastlz_compress (buffer, level, io);
+          uint8_t header[2];
+
+          header[0] = writing >> 8;
+          header[1] = writing;
+
+          image.write (header, 2);
+          image.write (io, writing);
+
+          total_compressed += 2 + writing;
+        }
+        else
+        {
+          image.write (buffer, level);
+        }
+
+        level = 0;
+      }
+    }
+
   }
 }