packbytes.c: Packbyte compression for Apple Prefered Format (Apple 2GS)

src/2gsformats.c

@@ -20,6 +20,7 @@
 
 ///@file 2gsformats.c
 /// Formats for the Apple II GS
+/// Support APF = Apple Preferred Format
 
 #include <stdio.h>
 #include <string.h>

src/Makefile

@@ -820,7 +820,7 @@ OBJS = main.o init.o graph.o $(APIOBJ) misc.o osdep.o special.o \
        loadsave.o loadsavefuncs.o \
        pngformat.o motoformats.o stformats.o c64formats.o cpcformats.o \
        ifformat.o msxformats.o packbits.o giformat.o \
-       2gsformats.o \
+       2gsformats.o packbytes.o \
        fileformats.o miscfileformats.o libraw2crtc.o \
        brush_ops.o buttons_effects.o layers.o \
        oldies.o tiles.o colorred.o unicode.o gfx2surface.o \

src/packbytes.c

@@ -0,0 +1,154 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+	Copyright owned by various GrafX2 authors, see COPYRIGHT.txt for details.
+
+    Grafx2 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; version 2
+    of the License.
+
+    Grafx2 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 Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+///@file packbytes.c
+/// Packbytes compression as used in Apple Preferred Format
+
+#include <stdio.h>
+#include <string.h>
+#include "struct.h"
+#include "io.h"
+#include "gfx2log.h"
+#include "packbytes.h"
+
+void PackBytes_pack_init(T_PackBytes_data * data, FILE * f)
+{
+  memset(data, 0, sizeof(T_PackBytes_data));
+  data->f = f;
+}
+
+int PackBytes_pack_add(T_PackBytes_data * data, byte b)
+{
+  switch (data->list_size)
+  {
+    case 0 : // First color
+      data->list[0] = b;
+      data->list_size = 1;
+      break;
+    case 1 : // second color
+      data->repetition_mode = (data->list[0] == b);
+      data->list[1] = b;
+      data->list_size = 2;
+      break;
+    default: // next colors
+      if (data->list[data->list_size - 1] == b)  // repeat detected
+      {
+        if ( !data->repetition_mode && data->list_size >= 63)
+        {
+          // diff mode with 126 bytes then 2 identical bytes
+          data->list_size--;
+          if (PackBytes_pack_flush(data) < 0)
+            return -1;
+          data->list[0] = b;
+          data->list[1] = b;
+          data->list_size = 2;
+          data->repetition_mode = 1;
+        }
+        else if ((data->repetition_mode) || (data->list[data->list_size - 2] != b))
+        {
+          // same mode is kept
+          if (data->list_size == 64)
+          {
+            if (PackBytes_pack_flush(data) < 0)
+              return -1;
+          }
+          data->list[data->list_size++] = b;
+        }
+        else
+        {
+          // diff mode and 3 identical bytes
+          data->list_size -= 2;
+          if (PackBytes_pack_flush(data) < 0)
+            return -1;
+          data->list[0] = b;
+          data->list[1] = b;
+          data->list[2] = b;
+          data->list_size = 3;
+          data->repetition_mode = 1;
+        }
+      }
+      else // the color is different from the previous one
+      {
+        if (!data->repetition_mode)                 // keep mode
+        {
+          if (data->list_size == 64)
+          {
+            if (PackBytes_pack_flush(data) < 0)
+              return -1;
+          }
+          data->list[data->list_size++] = b;
+        }
+        else                                        // change mode
+        {
+          if (PackBytes_pack_flush(data) < 0)
+            return -1;
+          data->list[data->list_size++] = b;
+        }
+      }
+  }
+  return 0; // OK
+}
+
+int PackBytes_pack_flush(T_PackBytes_data * data)
+{
+  if (data->list_size > 0)
+  {
+    if (data->list_size > 64)
+    {
+      GFX2_Log(GFX2_ERROR, "PackBytes_pack_flush() list_size=%d !\n", data->list_size);
+    }
+    if (data->repetition_mode)
+    {
+      if (data->f != NULL)
+      {
+        if (!Write_byte(data->f, 0x40 + data->list_size - 1) ||
+            !Write_byte(data->f, data->list[0]))
+          return -1;
+      }
+      data->output_count += 2;
+    }
+    else
+    {
+      if (data->f != NULL)
+      {
+        if (!Write_byte(data->f, data->list_size - 1) ||
+            !Write_bytes(data->f, data->list, data->list_size))
+          return -1;
+      }
+      data->output_count += 1 + data->list_size;
+    }
+    data->list_size = 0;
+    data->repetition_mode = 0;
+  }
+  return data->output_count;
+}
+
+int PackBytes_pack_buffer(FILE * f, const byte * buffer, size_t size)
+{
+  T_PackBytes_data pb_data;
+
+  PackBytes_pack_init(&pb_data, f);
+  while (size-- > 0)
+  {
+    if (PackBytes_pack_add(&pb_data, *buffer++))
+      return -1;
+  }
+  return PackBytes_pack_flush(&pb_data);
+}

src/packbytes.h

@@ -0,0 +1,68 @@
+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+
+	Copyright owned by various GrafX2 authors, see COPYRIGHT.txt for details.
+
+    Grafx2 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; version 2
+    of the License.
+
+    Grafx2 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 Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+///@file packbytes.h
+/// Packbytes is used in Apple Preferred Format
+
+#ifndef PACKBYTES_H_INCLUDED
+#define PACKBYTES_H_INCLUDED
+
+/**
+ * Data used by the PackBytes packer
+ */
+typedef struct {
+  FILE * f;
+  int output_count;
+  byte list_size;
+  byte repetition_mode;
+  byte list[65];
+} T_PackBytes_data;
+
+/**
+ * init before packing
+ *
+ * @param data storage for packbits data
+ * @param f FILE output or NULL (for no output)
+ */
+void PackBytes_pack_init(T_PackBytes_data * data, FILE * f);
+
+/**
+ * Add a byte to the packbits stream
+ * @return -1 for error, 0 if OK
+ */
+int PackBytes_pack_add(T_PackBytes_data * data, byte b);
+
+/**
+ * Flush the packed data to the file
+ *
+ * @return -1 for error, or the size of the packed stream so far
+ */
+int PackBytes_pack_flush(T_PackBytes_data * data);
+
+/**
+ * Pack a full buffer to FILE
+ * @param f FILE output or NULL (for no output)
+ * @param buffer input buffer
+ * @param size byte size of input buffer
+ * @return -1 for error, or the size of the packed stream so far
+ */
+int PackBytes_pack_buffer(FILE * f, const byte * buffer, size_t size);
+
+#endif