-#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
* - 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[51] = {
- 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
+
+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 */
};
-const u32 lzx_position_base[51] = {
- 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
+#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
};
+#endif
+
+/* LZX window size must be a power of 2 between 2^15 and 2^21, inclusively. */
+bool
+lzx_window_size_valid(size_t window_size)
+{
+ if (window_size == 0 || (u32)window_size != window_size)
+ 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 a valid LZX window size, return the number of symbols that will exist
+ * in the main Huffman code. */
+unsigned
+lzx_get_num_main_syms(u32 window_size)
+{
+ /* NOTE: the calculation *should* be as follows:
+ *
+ * u32 max_offset = window_size - LZX_MIN_MATCH_LEN;
+ * u32 max_formatted_offset = max_offset + LZX_OFFSET_OFFSET;
+ * u32 num_position_slots = 1 + lzx_get_position_slot_raw(max_formatted_offset);
+ *
+ * However since LZX_MIN_MATCH_LEN == LZX_OFFSET_OFFSET, we would get
+ * max_formatted_offset == window_size, which would bump the number of
+ * position slots up by 1 since every valid LZX window size is equal to
+ * a position base value. The format doesn't do this, and instead
+ * disallows matches with minimum length and maximum offset. This sets
+ * max_formatted_offset = window_size - 1, so instead we must calculate:
+ *
+ * num_position_slots = 1 + lzx_get_position_slot_raw(window_size - 1);
+ *
+ * ... which is the same as
+ *
+ * num_position_slots = lzx_get_position_slot_raw(window_size);
+ *
+ * ... since every valid window size is equal to a position base value.
+ */
+ unsigned num_position_slots = lzx_get_position_slot_raw(window_size);
+ /* Now calculate the number of main symbols as LZX_NUM_CHARS literal
+ * symbols, plus 8 symbols per position slot (since there are 8 possible
+ * length headers, and we need all (position slot, length header)
+ * combinations). */
+ return LZX_NUM_CHARS + (num_position_slots << 3);
+}
git://wimlib.net / wimlib / blobdiff