costan ea175e28f8 Implement support for Intel crc32 instruction (SSE 4.2)
This change authored by vadimskipin and submitted via:

    https://github.com/google/leveldb/pull/309

Changes made to support iOS builds and other architectures
without support for SSE 4.2.

db_bench reports original crc32 speed at:

    crc32c : 3.610 micros/op; 1082.0 MB/s (4K per op)

with this change performance has increased to:

    crc32c : 0.843 micros/op; 4633.6 MB/s (4K per op)

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=148694935
2017-02-28 14:08:46 -08:00
..
2014-12-17 14:18:54 -05:00
2014-09-16 14:19:52 -07:00

This directory contains interfaces and implementations that isolate the
rest of the package from platform details.

Code in the rest of the package includes "port.h" from this directory.
"port.h" in turn includes a platform specific "port_<platform>.h" file
that provides the platform specific implementation.

See port_posix.h for an example of what must be provided in a platform
specific header file.