1 files changed, 80 insertions, 0 deletions
diff --git a/c/enc/find_match_length.h b/c/enc/find_match_length.h
new file mode 100644
index 0000000..b3e3d80
--- /dev/null
+++ b/c/enc/find_match_length.h
@@ -0,0 +1,80 @@
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function to find maximal matching prefixes of strings. */
+
+#ifndef BROTLI_ENC_FIND_MATCH_LENGTH_H_
+#define BROTLI_ENC_FIND_MATCH_LENGTH_H_
+
+#include <brotli/types.h>
+#include "./port.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+/* Separate implementation for little-endian 64-bit targets, for speed. */
+#if defined(__GNUC__) && defined(_LP64) && defined(IS_LITTLE_ENDIAN)
+
+static BROTLI_INLINE size_t FindMatchLengthWithLimit(const uint8_t* s1,
+                                                     const uint8_t* s2,
+                                                     size_t limit) {
+  size_t matched = 0;
+  size_t limit2 = (limit >> 3) + 1;  /* + 1 is for pre-decrement in while */
+  while (BROTLI_PREDICT_TRUE(--limit2)) {
+    if (BROTLI_PREDICT_FALSE(BROTLI_UNALIGNED_LOAD64(s2) ==
+                      BROTLI_UNALIGNED_LOAD64(s1 + matched))) {
+      s2 += 8;
+      matched += 8;
+    } else {
+      uint64_t x =
+          BROTLI_UNALIGNED_LOAD64(s2) ^ BROTLI_UNALIGNED_LOAD64(s1 + matched);
+      size_t matching_bits = (size_t)__builtin_ctzll(x);
+      matched += matching_bits >> 3;
+      return matched;
+    }
+  }
+  limit = (limit & 7) + 1;  /* + 1 is for pre-decrement in while */
+  while (--limit) {
+    if (BROTLI_PREDICT_TRUE(s1[matched] == *s2)) {
+      ++s2;
+      ++matched;
+    } else {
+      return matched;
+    }
+  }
+  return matched;
+}
+#else
+static BROTLI_INLINE size_t FindMatchLengthWithLimit(const uint8_t* s1,
+                                                     const uint8_t* s2,
+                                                     size_t limit) {
+  size_t matched = 0;
+  const uint8_t* s2_limit = s2 + limit;
+  const uint8_t* s2_ptr = s2;
+  /* Find out how long the match is. We loop over the data 32 bits at a
+     time until we find a 32-bit block that doesn't match; then we find
+     the first non-matching bit and use that to calculate the total
+     length of the match. */
+  while (s2_ptr <= s2_limit - 4 &&
+         BROTLI_UNALIGNED_LOAD32(s2_ptr) ==
+         BROTLI_UNALIGNED_LOAD32(s1 + matched)) {
+    s2_ptr += 4;
+    matched += 4;
+  }
+  while ((s2_ptr < s2_limit) && (s1[matched] == *s2_ptr)) {
+    ++s2_ptr;
+    ++matched;
+  }
+  return matched;
+}
+#endif
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif
+
+#endif  /* BROTLI_ENC_FIND_MATCH_LENGTH_H_ */