[WIP] [PATCH v0.0-20200229 05/11] ez: lzma: add common header file

[Gao Xiang]

Note that meaningful names mentioned in LZMA implementation
keep in sync with LZMA SDK rather than XZ utils so that we
can follow latest offical LZMA SDK easily.

Apart from that, Linux kernel coding style is applied to
other parts of ez.

Signed-off-by: Gao Xiang <hsiangkao at aol.com>
---
 lzma/lzma_common.h | 59 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 lzma/lzma_common.h

diff --git a/lzma/lzma_common.h b/lzma/lzma_common.h
new file mode 100644
index 0000000..14df123
--- /dev/null
+++ b/lzma/lzma_common.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: Unlicense */
+/*
+ * ez/lzma/lzma_common.h - common definitions of LZMA encoder
+ *
+ * Copyright (C) 2019-2020 Gao Xiang <hsiangkao at aol.com>
+ *
+ * Authors: Igor Pavlov <http://7-zip.org/>
+ *          Gao Xiang <hsiangkao at aol.com>
+ */
+#ifndef __EZ_LZMA_LZMA_COMMON_H
+#define __EZ_LZMA_LZMA_COMMON_H
+
+#include <ez/defs.h>
+#include <ez/unaligned.h>
+
+/*
+ * LZMA Matchlength
+ */
+
+/* Minimum length of a match is two bytes. */
+#define kMatchMinLen	2
+
+/*
+ * Match length is encoded with 4, 5, or 10 bits.
+ *
+ * Length    Bits
+ *    2-9     4 = (Choice = 0) + 3 bits
+ *  10-17     5 = (Choice = 1) + (Choice2 = 0) + 3 bits
+ * 18-273    10 = (Choice = 1) + (Choice2 = 1) + 8 bits
+ */
+#define kLenNumLowBits		3
+#define kLenNumLowSymbols	(1 << kLenNumLowBits)
+#define kLenNumHighBits		8
+#define kLenNumHighSymbols	(1 << kLenNumHighBits)
+#define kLenNumSymbolsTotal	(kLenNumLowSymbols * 2 + kLenNumHighSymbols)
+
+/*
+ * Maximum length of a match is 273 which is a result
+ * of the encoding described above.
+ */
+#define kMatchMaxLen	(kMatchMinLen + kLenNumSymbolsTotal - 1)
+
+/*
+ * LZMA remembers the four most recent match distances.
+ * Reusing these distances tend to take less space than
+ * re-encoding the actual distance value.
+ */
+#define LZMA_NUM_REPS	4
+
+#define MARK_LIT ((uint32_t)-1)
+
+/*
+ * LZMA_REQUIRED_INPUT_MAX = number of required input bytes for worst case.
+ * Num bits = log2((2^11 / 31) ^ 22) + 26 < 134 + 26 = 160;
+ */
+#define LZMA_REQUIRED_INPUT_MAX 20
+
+#endif
+
-- 
2.20.1