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76 lines
2.0 KiB
C++
76 lines
2.0 KiB
C++
// platform.h
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//
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// Copyright 2015-2018 J. Andrew Rogers
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef METROHASH_PLATFORM_H
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#define METROHASH_PLATFORM_H
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#include <bit>
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#include <cstdint>
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#include <cstring>
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// rotate right idiom recognized by most compilers
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inline static uint64_t rotate_right(uint64_t v, unsigned k)
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{
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return (v >> k) | (v << (64 - k));
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}
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inline static uint64_t read_u64(const void * const ptr)
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{
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uint64_t result;
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// Assignment like `result = *reinterpret_cast<const uint64_t *>(ptr)` here would mean undefined behaviour (unaligned read),
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// so we use memcpy() which is the most portable. clang & gcc usually translates `memcpy()` into a single `load` instruction
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// when hardware supports it, so using memcpy() is efficient too.
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memcpy(&result, ptr, sizeof(result));
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#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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result = std::byteswap(result);
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#endif
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return result;
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}
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inline static uint64_t read_u32(const void * const ptr)
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{
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uint32_t result;
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memcpy(&result, ptr, sizeof(result));
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#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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result = std::byteswap(result);
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#endif
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return result;
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}
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inline static uint64_t read_u16(const void * const ptr)
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{
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uint16_t result;
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memcpy(&result, ptr, sizeof(result));
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#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
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result = std::byteswap(result);
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#endif
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return result;
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}
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inline static uint64_t read_u8 (const void * const ptr)
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{
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return static_cast<uint64_t>(*reinterpret_cast<const uint8_t *>(ptr));
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}
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#endif // #ifndef METROHASH_PLATFORM_H
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