--- /dev/null
+// 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_
projects / apitrace / blobdiff