Add brotli compressor

This commit is for the encoder for brotli compression format.
Brotli is a generic byte-level compression algorithm.

brotli/enc/find_match_length.h

@@ -0,0 +1,85 @@
+// Copyright 2010 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Function to find maximal matching prefixes of strings.
+
+#ifndef BROTLI_ENC_FIND_MATCH_LENGTH_H_
+#define BROTLI_ENC_FIND_MATCH_LENGTH_H_
+
+#include <stdint.h>
+
+#include "./port.h"
+
+namespace brotli {
+
+// Separate implementation for x86_64, for speed.
+#if defined(__GNUC__) && defined(ARCH_K8)
+
+static inline int FindMatchLengthWithLimit(const uint8_t* s1,
+                                           const uint8_t* s2,
+                                           size_t limit) {
+  int matched = 0;
+  size_t limit2 = (limit >> 3) + 1;  // + 1 is for pre-decrement in while
+  while (PREDICT_TRUE(--limit2)) {
+    if (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);
+      int matching_bits =  __builtin_ctzll(x);
+      matched += matching_bits >> 3;
+      return matched;
+    }
+  }
+  limit = (limit & 7) + 1;  // + 1 is for pre-decrement in while
+  while (--limit) {
+    if (PREDICT_TRUE(s1[matched] == *s2)) {
+      ++s2;
+      ++matched;
+    } else {
+      return matched;
+    }
+  }
+  return matched;
+}
+#else
+static inline int FindMatchLengthWithLimit(const uint8_t* s1,
+                                           const uint8_t* s2,
+                                           size_t limit) {
+  int 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
+
+}  // namespace brotli
+
+#endif  // BROTLI_ENC_FIND_MATCH_LENGTH_H_