1 files changed, 34 insertions, 0 deletions

diff --git a/C/LzHash.h b/C/LzHash.h
new file mode 100644
index 0000000..77b898c
--- /dev/null
+++ b/C/LzHash.h
@@ -0,0 +1,34 @@
+/* LzHash.h -- HASH functions for LZ algorithms
+2019-10-30 : Igor Pavlov : Public domain */
+
+#ifndef __LZ_HASH_H
+#define __LZ_HASH_H
+
+/*
+  (kHash2Size >= (1 <<  8)) : Required
+  (kHash3Size >= (1 << 16)) : Required
+*/
+
+#define kHash2Size (1 << 10)
+#define kHash3Size (1 << 16)
+// #define kHash4Size (1 << 20)
+
+#define kFix3HashSize (kHash2Size)
+#define kFix4HashSize (kHash2Size + kHash3Size)
+// #define kFix5HashSize (kHash2Size + kHash3Size + kHash4Size)
+
+/*
+  We use up to 3 crc values for hash:
+    crc0
+    crc1 << Shift_1
+    crc2 << Shift_2
+  (Shift_1 = 5) and (Shift_2 = 10) is good tradeoff.
+  Small values for Shift are not good for collision rate.
+  Big value for Shift_2 increases the minimum size
+  of hash table, that will be slow for small files.
+*/
+
+#define kLzHash_CrcShift_1 5
+#define kLzHash_CrcShift_2 10
+
+#endif