-#ifndef _WIMLIB_LZ_HASH_H
-#define _WIMLIB_LZ_HASH_H
+/*
+ * lz_hash.h - hashing for Lempel-Ziv matchfinding
+ *
+ * The following copying information applies to this specific source code file:
+ *
+ * Written in 2014-2015 by Eric Biggers <ebiggers3@gmail.com>
+ *
+ * To the extent possible under law, the author(s) have dedicated all copyright
+ * and related and neighboring rights to this software to the public domain
+ * worldwide via the Creative Commons Zero 1.0 Universal Public Domain
+ * Dedication (the "CC0").
+ *
+ * This software 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 CC0 for more details.
+ *
+ * You should have received a copy of the CC0 along with this software; if not
+ * see <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
-#include "wimlib/compress_common.h"
+#ifndef _LZ_HASH_H
+#define _LZ_HASH_H
-struct lz_params {
- unsigned min_match;
- unsigned max_match;
- unsigned max_offset;
- unsigned nice_match;
- unsigned good_match;
- unsigned max_chain_len;
- unsigned max_lazy_match;
- unsigned too_far;
-};
+#include "wimlib/types.h"
-typedef void (*lz_record_match_t)(unsigned len, unsigned offset, void *ctx);
-typedef void (*lz_record_literal_t)(u8 lit, void *ctx);
+/*
+ * The hash function: given a sequence prefix held in the low-order bits of a
+ * 32-bit value, multiply by a carefully-chosen large constant. Discard any
+ * bits of the product that don't fit in a 32-bit value, but take the
+ * next-highest @num_bits bits of the product as the hash value, as those have
+ * the most randomness.
+ */
+static inline u32
+lz_hash(u32 seq, unsigned num_bits)
+{
+ return (u32)(seq * 0x1E35A7BD) >> (32 - num_bits);
+}
-extern void
-lz_analyze_block(const u8 window[restrict],
- input_idx_t window_size,
- lz_record_match_t record_match,
- lz_record_literal_t record_literal,
- void *record_ctx,
- const struct lz_params *params,
- input_idx_t prev_tab[restrict]);
-
-
-#endif /* _WIMLIB_LZ_HASH_H */
+#endif /* _LZ_HASH_H */
git://wimlib.net / wimlib / blobdiff