Variable LZX window sizes

[wimlib] / src / lzx-common.c

diff --git a/src/lzx-common.c b/src/lzx-common.c
index 9da4ddb069ca46fba21291f31c434f56d2536a28..547059e7b93268c8cc9af73e635ada28ec5594fa 100644 (file)
--- a/src/lzx-common.c
+++ b/src/lzx-common.c
@@ -1,4 +1,32 @@
-#include "lzx.h"
+/*
+ * lzx-common.c - Common data for LZX compression and decompression.
+ */
+
+/*
+ * Copyright (C) 2012, 2013 Eric Biggers
+ *
+ * This file is part of wimlib, a library for working with WIM files.
+ *
+ * wimlib 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 3 of the License, or (at your option)
+ * any later version.
+ *
+ * wimlib 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 wimlib; if not, see http://www.gnu.org/licenses/.
+ */
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "wimlib/lzx.h"
+#include "wimlib/util.h"
 
 /* LZX uses what it calls 'position slots' to represent match offsets.
  * What this means is that a small 'position slot' number and a small
@@ -7,31 +35,55 @@
  * - lzx_position_base is an index to the position slot bases
  * - lzx_extra_bits states how many bits of offset-from-base data is needed.
  */
-const u8 lzx_extra_bits[LZX_NUM_POSITION_SLOTS] = {
+
+const u32 lzx_position_base[LZX_MAX_POSITION_SLOTS] = {
+       0      , 1      , 2      , 3      , 4      ,    /* 0  --- 4  */
+       6      , 8      , 12     , 16     , 24     ,    /* 5  --- 9  */
+       32     , 48     , 64     , 96     , 128    ,    /* 10 --- 14 */
+       192    , 256    , 384    , 512    , 768    ,    /* 15 --- 19 */
+       1024   , 1536   , 2048   , 3072   , 4096   ,    /* 20 --- 24 */
+       6144   , 8192   , 12288  , 16384  , 24576  ,    /* 25 --- 29 */
+       32768  , 49152  , 65536  , 98304  , 131072 ,    /* 30 --- 34 */
+       196608 , 262144 , 393216 , 524288 , 655360 ,    /* 35 --- 39 */
+       786432 , 917504 , 1048576, 1179648, 1310720,    /* 40 --- 44 */
+       1441792, 1572864, 1703936, 1835008, 1966080,    /* 45 --- 49 */
+       2097152                                         /* 50        */
+};
+
+#ifdef USE_LZX_EXTRA_BITS_ARRAY
+const u8 lzx_extra_bits[LZX_MAX_POSITION_SLOTS] = {
        0 , 0 , 0 , 0 , 1 ,
        1 , 2 , 2 , 3 , 3 ,
        4 , 4 , 5 , 5 , 6 ,
        6 , 7 , 7 , 8 , 8 ,
        9 , 9 , 10, 10, 11,
        11, 12, 12, 13, 13,
-       /*14, 14, 15, 15, 16,*/
-       /*16, 17, 17, 17, 17,*/
-       /*17, 17, 17, 17, 17,*/
-       /*17, 17, 17, 17, 17,*/
-       /*17*/
+       14, 14, 15, 15, 16,
+       16, 17, 17, 17, 17,
+       17, 17, 17, 17, 17,
+       17, 17, 17, 17, 17,
+       17
 };
+#endif
 
-const u32 lzx_position_base[LZX_NUM_POSITION_SLOTS] = {
-       0      , 1      , 2      , 3      , 4      ,
-       6      , 8      , 12     , 16     , 24     ,
-       32     , 48     , 64     , 96     , 128    ,
-       192    , 256    , 384    , 512    , 768    ,
-       1024   , 1536   , 2048   , 3072   , 4096   ,
-       6144   , 8192   , 12288  , 16384  , 24576  ,
-       /*32768  , 49152  , 65536  , 98304  , 131072 ,*/
-       /*196608 , 262144 , 393216 , 524288 , 655360 ,*/
-       /*786432 , 917504 , 1048576, 1179648, 1310720,*/
-       /*1441792, 1572864, 1703936, 1835008, 1966080,*/
-       /*2097152*/
-};
+/* LZX window size can be between 2^15 and 2^21, inclusively.  */
+bool
+lzx_window_size_valid(u32 window_size)
+{
+       if (window_size == 0)
+               return false;
+       u32 order = bsr32(window_size);
+       if (window_size != 1U << order)
+               return false;
+       return (order >= LZX_MIN_WINDOW_ORDER && order <= LZX_MAX_WINDOW_ORDER);
+}
 
+/* Given the specified valid window size, return the number of LZX main symbols
+ * that will be needed.  (This depends on the number of position slots, which
+ * itself depends on the window size.)  */
+unsigned
+lzx_get_num_main_syms(u32 window_size)
+{
+       unsigned num_position_slots = lzx_get_position_slot_raw(window_size);
+       return LZX_NUM_CHARS + (num_position_slots << 3);
+}