1 files changed, 61 insertions, 0 deletions
diff --git a/neozip/compare256_rle.h b/neozip/compare256_rle.h
new file mode 100644
index 0000000000..02e6bd496a
--- /dev/null
+++ b/neozip/compare256_rle.h
@@ -0,0 +1,61 @@
+/* compare256_rle.h -- 256 byte run-length encoding comparison
+ * Copyright (C) 2022 Nathan Moinvaziri
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+#include "zbuild.h"
+#include "zendian.h"
+#include "zmemory.h"
+#include "fallback_builtins.h"
+
+typedef uint32_t (*compare256_rle_func)(const uint8_t* src0, const uint8_t* src1);
+
+/* 8-bit RLE comparison for hardware without unaligned loads */
+static inline uint32_t compare256_rle_8(const uint8_t *src0, const uint8_t *src1) {
+    uint32_t len = 0;
+    uint8_t val = *src0;
+
+    do {
+        if (val != src1[0])
+            return len;
+        if (val != src1[1])
+            return len + 1;
+        if (val != src1[2])
+            return len + 2;
+        if (val != src1[3])
+            return len + 3;
+        if (val != src1[4])
+            return len + 4;
+        if (val != src1[5])
+            return len + 5;
+        if (val != src1[6])
+            return len + 6;
+        if (val != src1[7])
+            return len + 7;
+        src1 += 8, len += 8;
+    } while (len < 256);
+
+    return 256;
+}
+
+/* 64-bit RLE comparison for hardware with unaligned loads */
+static inline uint32_t compare256_rle_64(const uint8_t *src0, const uint8_t *src1) {
+    uint32_t src0_cmp32, len = 0;
+    uint16_t src0_cmp;
+    uint64_t sv, mv, diff;
+
+    src0_cmp = zng_memread_2(src0);
+    src0_cmp32 = ((uint32_t)src0_cmp << 16) | src0_cmp;
+    sv = ((uint64_t)src0_cmp32 << 32) | src0_cmp32;
+
+    do {
+        mv = zng_memread_8(src1);
+        diff = sv ^ mv;
+        if (diff)
+            return len + zng_ctz64(Z_U64_TO_LE(diff)) / 8;
+
+        src1 += 8, len += 8;
+    } while (len < 256);
+
+    return 256;
+}