From 8734f66eacb9bbf807bbb77781c2f150f2fd3ccf Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Mon, 4 May 2020 14:40:03 +0200
Subject: Expose more fine grained control values & flags on the XZ compressor
This patch allows external users to fiddle with the XZ compressors
compression strength, alignment and other values.
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
include/sqfs/compressor.h | 69 +++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 67 insertions(+), 2 deletions(-)
(limited to 'include/sqfs')
diff --git a/include/sqfs/compressor.h b/include/sqfs/compressor.h
index 4190c67..af379e7 100644
--- a/include/sqfs/compressor.h
+++ b/include/sqfs/compressor.h
@@ -199,7 +199,50 @@ struct sqfs_compressor_config_t {
*/
sqfs_u32 dict_size;
- sqfs_u32 padd0[3];
+ /**
+ * @brief Compression level. Maximum 9, default is 6.
+ */
+ sqfs_u8 level;
+
+ /**
+ * @brief Number of literal context bits.
+ *
+ * How many of the highest bits of the previous
+ * uncompressed byte to take into account when
+ * predicting the bits of the next byte.
+ *
+ * The sum lc + lp must be at MOST 4. Default value of
+ * lc is 3.
+ */
+ sqfs_u8 lc;
+
+ /**
+ * @brief Number of literal position bits.
+ *
+ * lp affects what kind of alignment in the uncompressed
+ * data is assumed when encoding bytes.
+ * See pb below for more information about alignment.
+ *
+ * The sum lc + lp must be at MOST 4. Default value of
+ * lp is 0.
+ */
+ sqfs_u8 lp;
+
+ /**
+ * @brief Number of position bits.
+ *
+ * This is the log2 of the assumed underlying alignment
+ * of the input data, i.e. pb=0 means single byte
+ * allignment, pb=1 means 16 bit, 2 means 32 bit.
+ *
+ * When the alignment is known, setting pb may reduce
+ * the file size.
+ *
+ * The default value is 2, i.e. 32 bit alignment.
+ */
+ sqfs_u8 pb;
+
+ sqfs_u32 padd0[2];
} xz;
sqfs_u64 padd0[2];
@@ -247,7 +290,13 @@ typedef enum {
* @brief For LZMA, set this to select the Sparc BCJ filter.
*/
SQFS_COMP_FLAG_XZ_SPARC = 0x0020,
- SQFS_COMP_FLAG_XZ_ALL = 0x003F,
+
+ /**
+ * @brief Tell the LZMA compressor to try the "extreme" option.
+ */
+ SQFS_COMP_FLAG_XZ_EXTREME = 0x0100,
+
+ SQFS_COMP_FLAG_XZ_ALL = 0x013F,
/**
* @brief For zlib deflate, set this to try the default strategy.
@@ -316,6 +365,22 @@ typedef enum {
#define SQFS_GZIP_MIN_WINDOW (8)
#define SQFS_GZIP_MAX_WINDOW (15)
+#define SQFS_XZ_MIN_LEVEL (0)
+#define SQFS_XZ_MAX_LEVEL (9)
+#define SQFS_XZ_DEFAULT_LEVEL (6)
+
+#define SQFS_XZ_MIN_LC 0
+#define SQFS_XZ_MAX_LC 4
+#define SQFS_XZ_DEFAULT_LC 3
+
+#define SQFS_XZ_MIN_LP 0
+#define SQFS_XZ_MAX_LP 4
+#define SQFS_XZ_DEFAULT_LP 0
+
+#define SQFS_XZ_MIN_PB 0
+#define SQFS_XZ_MAX_PB 4
+#define SQFS_XZ_DEFAULT_PB 2
+
#ifdef __cplusplus
extern "C" {
#endif
--
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