Move image encoding logic into a central EncodeManager class

This allows us to apply a lot more server logic
independently of which encoder is in use.

Most of this class are things moved over from the
Tight encoder.
diff --git a/common/rfb/ZRLEEncoderBPP.cxx b/common/rfb/ZRLEEncoderBPP.cxx
new file mode 100644
index 0000000..90f395b
--- /dev/null
+++ b/common/rfb/ZRLEEncoderBPP.cxx
@@ -0,0 +1,128 @@
+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * 
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#define CONCAT2(a,b) a##b
+#define CONCAT2E(a,b) CONCAT2(a,b)
+
+#define UBPP CONCAT2E(U,BPP)
+
+void ZRLEEncoder::writePaletteTile(int width, int height,
+                                   const rdr::UBPP* buffer, int stride,
+                                   const PixelFormat& pf,
+                                   const Palette& palette)
+{
+  const int bitsPerPackedPixel[] = {
+    0, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4
+  };
+
+  int bppp;
+  int pad;
+
+  assert(palette.size() > 1);
+  assert(palette.size() <= 16);
+
+  zos.writeU8(palette.size());
+  writePalette(pf, palette);
+
+  bppp = bitsPerPackedPixel[palette.size()-1];
+  pad = stride - width;
+
+  for (int i = 0; i < height; i++) {
+    int w;
+
+    rdr::U8 nbits = 0;
+    rdr::U8 byte = 0;
+
+    w = width;
+    while (w--) {
+      rdr::UBPP pix = *buffer++;
+      rdr::U8 index = palette.lookup(pix);
+      byte = (byte << bppp) | index;
+      nbits += bppp;
+      if (nbits >= 8) {
+        zos.writeU8(byte);
+        nbits = 0;
+      }
+    }
+    if (nbits > 0) {
+      byte <<= 8 - nbits;
+      zos.writeU8(byte);
+    }
+
+    buffer += pad;
+  }
+}
+
+void ZRLEEncoder::writePaletteRLETile(int width, int height,
+                                      const rdr::UBPP* buffer, int stride,
+                                      const PixelFormat& pf,
+                                      const Palette& palette)
+{
+  int pad;
+
+  rdr::UBPP prevColour;
+  int runLength;
+
+  assert(palette.size() > 1);
+  assert(palette.size() <= 127);
+
+  zos.writeU8(palette.size() | 0x80);
+  writePalette(pf, palette);
+
+  pad = stride - width;
+
+  prevColour = *buffer;
+  runLength = 0;
+
+  while (height--) {
+    int w = width;
+    while (w--) {
+      if (prevColour != *buffer) {
+        if (runLength == 1)
+          zos.writeU8(palette.lookup(prevColour));
+        else {
+          zos.writeU8(palette.lookup(prevColour) | 0x80);
+
+          while (runLength > 255) {
+            zos.writeU8(255);
+            runLength -= 255;
+          }
+          zos.writeU8(runLength - 1);
+        }
+
+        prevColour = *buffer;
+        runLength = 0;
+      }
+
+      runLength++;
+      buffer++;
+    }
+    buffer += pad;
+  }
+  if (runLength == 1)
+    zos.writeU8(palette.lookup(prevColour));
+  else {
+    zos.writeU8(palette.lookup(prevColour) | 0x80);
+
+    while (runLength > 255) {
+      zos.writeU8(255);
+      runLength -= 255;
+    }
+    zos.writeU8(runLength - 1);
+  }
+}