1 files changed, 52 insertions, 0 deletions
diff --git a/neozip/arch/generic/slide_hash_c.c b/neozip/arch/generic/slide_hash_c.c
new file mode 100644
index 0000000000..8345b9e36b
--- /dev/null
+++ b/neozip/arch/generic/slide_hash_c.c
@@ -0,0 +1,52 @@
+/* slide_hash.c -- slide hash table C implementation
+ *
+ * Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#include "zbuild.h"
+#include "deflate.h"
+
+/* ===========================================================================
+ * Slide the hash table when sliding the window down (could be avoided with 32
+ * bit values at the expense of memory usage). We slide even when level == 0 to
+ * keep the hash table consistent if we switch back to level > 0 later.
+ */
+static inline void slide_hash_c_chain(Pos *table, uint32_t entries, uint16_t wsize) {
+#ifdef NOT_TWEAK_COMPILER
+    table += entries;
+    do {
+        unsigned m;
+        m = *--table;
+        *table = (Pos)(m >= wsize ? m-wsize : 0);
+        /* If entries is not on any hash chain, prev[entries] is garbage but
+         * its value will never be used.
+         */
+    } while (--entries);
+#else
+    {
+    /* As of I make this change, gcc (4.8.*) isn't able to vectorize
+     * this hot loop using saturated-subtraction on x86-64 architecture.
+     * To avoid this defect, we can change the loop such that
+     *    o. the pointer advance forward, and
+     *    o. demote the variable 'm' to be local to the loop, and
+     *       choose type "Pos" (instead of 'unsigned int') for the
+     *       variable to avoid unnecessary zero-extension.
+     */
+        unsigned int i;
+        Pos *q = table;
+        for (i = 0; i < entries; i++) {
+            Pos m = *q;
+            Pos t = (Pos)wsize;
+            *q++ = (Pos)(m >= t ? m-t: 0);
+        }
+    }
+#endif /* NOT_TWEAK_COMPILER */
+}
+
+Z_INTERNAL void slide_hash_c(deflate_state *s) {
+    uint16_t wsize = (uint16_t)s->w_size;
+
+    slide_hash_c_chain(s->head, HASH_SIZE, wsize);
+    slide_hash_c_chain(s->prev, wsize, wsize);
+}