The Tor Browser: comparison other-licenses/snappy/src/snappy-internal.h

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+// Copyright 2008 Google Inc. All Rights Reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Internals shared between the Snappy implementation and its unittest.
+#ifndef UTIL_SNAPPY_SNAPPY_INTERNAL_H_
+#define UTIL_SNAPPY_SNAPPY_INTERNAL_H_
+#include "snappy-stubs-internal.h"
+namespace snappy {
+namespace internal {
+class WorkingMemory {
+public:
+WorkingMemory() : large_table_(NULL) { }
+~WorkingMemory() { delete[] large_table_; }
+// Allocates and clears a hash table using memory in "*this",
+// stores the number of buckets in "*table_size" and returns a pointer to
+// the base of the hash table.
+uint16* GetHashTable(size_t input_size, int* table_size);
+private:
+uint16 small_table_[1<<10];    // 2KB
+uint16* large_table_;          // Allocated only when needed
+DISALLOW_COPY_AND_ASSIGN(WorkingMemory);
+};
+// Flat array compression that does not emit the "uncompressed length"
+// prefix. Compresses "input" string to the "*op" buffer.
+//
+// REQUIRES: "input_length <= kBlockSize"
+// REQUIRES: "op" points to an array of memory that is at least
+// "MaxCompressedLength(input_length)" in size.
+// REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+// REQUIRES: "table_size" is a power of two
+//
+// Returns an "end" pointer into "op" buffer.
+// "end - op" is the compressed size of "input".
+char* CompressFragment(const char* input,
+size_t input_length,
+char* op,
+uint16* table,
+const int table_size);
+// Return the largest n such that
+//
+//   s1[0,n-1] == s2[0,n-1]
+//   and n <= (s2_limit - s2).
+//
+// Does not read *s2_limit or beyond.
+// Does not read *(s1 + (s2_limit - s2)) or beyond.
+// Requires that s2_limit >= s2.
+//
+// Separate implementation for x86_64, for speed.  Uses the fact that
+// x86_64 is little endian.
+#if defined(ARCH_K8)
+static inline int FindMatchLength(const char* s1,
+const char* s2,
+const char* s2_limit) {
+DCHECK_GE(s2_limit, s2);
+int matched = 0;
+// Find out how long the match is. We loop over the data 64 bits at a
+// time until we find a 64-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 (PREDICT_TRUE(s2 <= s2_limit - 8)) {
+if (PREDICT_FALSE(UNALIGNED_LOAD64(s2) == UNALIGNED_LOAD64(s1 + matched))) {
+s2 += 8;
+matched += 8;
+} else {
+// On current (mid-2008) Opteron models there is a 3% more
+// efficient code sequence to find the first non-matching byte.
+// However, what follows is ~10% better on Intel Core 2 and newer,
+// and we expect AMD's bsf instruction to improve.
+uint64 x = UNALIGNED_LOAD64(s2) ^ UNALIGNED_LOAD64(s1 + matched);
+int matching_bits = Bits::FindLSBSetNonZero64(x);
+matched += matching_bits >> 3;
+return matched;
+}
+}
+while (PREDICT_TRUE(s2 < s2_limit)) {
+if (PREDICT_TRUE(s1[matched] == *s2)) {
+++s2;
+++matched;
+} else {
+return matched;
+}
+}
+return matched;
+}
+#else
+static inline int FindMatchLength(const char* s1,
+const char* s2,
+const char* s2_limit) {
+// Implementation based on the x86-64 version, above.
+DCHECK_GE(s2_limit, s2);
+int matched = 0;
+while (s2 <= s2_limit - 4 &&
+UNALIGNED_LOAD32(s2) == UNALIGNED_LOAD32(s1 + matched)) {
+s2 += 4;
+matched += 4;
+}
+if (LittleEndian::IsLittleEndian() && s2 <= s2_limit - 4) {
+uint32 x = UNALIGNED_LOAD32(s2) ^ UNALIGNED_LOAD32(s1 + matched);
+int matching_bits = Bits::FindLSBSetNonZero(x);
+matched += matching_bits >> 3;
+} else {
+while ((s2 < s2_limit) && (s1[matched] == *s2)) {
+++s2;
+++matched;
+}
+}
+return matched;
+}
+#endif
+}  // end namespace internal
+}  // end namespace snappy
+#endif  // UTIL_SNAPPY_SNAPPY_INTERNAL_H_

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comparison: other-licenses/snappy/src/snappy-internal.h

other-licenses/snappy/src/snappy-internal.h