Squashed 'src/leveldb/' changes from a31c8aa40..196962ff0

196962ff0 Add AcceleratedCRC32C to port_win.h
1bdf1c34c Merge upstream LevelDB v1.20
d31721eb0 Merge #17: Fixed file sharing errors
fecd44902 Fixed file sharing error in Win32Env::GetFileSize(), Win32SequentialFile::_Init(), Win32RandomAccessFile::_Init() Fixed error checking in Win32SequentialFile::_Init()
5b7510f1b Merge #14: Merge upstream LevelDB 1.19
0d969fd57 Merge #16: [LevelDB] Do no crash if filesystem can't fsync
c8c029b5b [LevelDB] Do no crash if filesystem can't fsync
a53934a3a Increase leveldb version to 1.20.
f3f139737 Separate Env tests from PosixEnv tests.
eb4f0972f leveldb: Fix compilation warnings in port_posix_sse.cc on x86 (32-bit).
d0883b600 Fixed path to doc file: index.md.
7fa20948d Convert documentation to markdown.
ea175e28f Implement support for Intel crc32 instruction (SSE 4.2)
95cd743e5 Including <limits> for std::numeric_limits.
646c3588d Limit the number of read-only files the POSIX Env will have open.
d40bc3fa5 Merge #13: Typo
ebbd772d3 Typo
a2fb086d0 Add option for max file size. The currend hard-coded value of 2M is inefficient in colossus.

git-subtree-dir: src/leveldb
git-subtree-split: 196962ff01c39b4705d8117df5c3f8c205349950

1 files changed, 18 insertions, 0 deletions

diff --git a/util/crc32c.cc b/util/crc32c.cc
index 6db9e77077..edd61cfd6f 100644
--- a/util/crc32c.cc
+++ b/util/crc32c.cc
@@ -8,6 +8,8 @@
 #include "util/crc32c.h"
 
 #include <stdint.h>
+
+#include "port/port.h"
 #include "util/coding.h"
 
 namespace leveldb {
@@ -283,7 +285,23 @@ static inline uint32_t LE_LOAD32(const uint8_t *p) {
   return DecodeFixed32(reinterpret_cast<const char*>(p));
 }
 
+// Determine if the CPU running this program can accelerate the CRC32C
+// calculation.
+static bool CanAccelerateCRC32C() {
+  // port::AcceleretedCRC32C returns zero when unable to accelerate.
+  static const char kTestCRCBuffer[] = "TestCRCBuffer";
+  static const char kBufSize = sizeof(kTestCRCBuffer) - 1;
+  static const uint32_t kTestCRCValue = 0xdcbc59fa;
+
+  return port::AcceleratedCRC32C(0, kTestCRCBuffer, kBufSize) == kTestCRCValue;
+}
+
 uint32_t Extend(uint32_t crc, const char* buf, size_t size) {
+  static bool accelerate = CanAccelerateCRC32C();
+  if (accelerate) {
+    return port::AcceleratedCRC32C(crc, buf, size);
+  }
+
   const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
   const uint8_t *e = p + size;
   uint32_t l = crc ^ 0xffffffffu;