mirror of
https://github.com/simdjson/simdjson
synced 2026-06-08 17:27:07 +00:00
Paul Dreik
48 lines
1.4 KiB
C++
48 lines
1.4 KiB
C++
#ifndef SIMDJSON_FALLBACK_BITMANIPULATION_H
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#define SIMDJSON_FALLBACK_BITMANIPULATION_H
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#include "simdjson.h"
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#include <limits>
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namespace simdjson {
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namespace SIMDJSON_IMPLEMENTATION {
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namespace {
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#if defined(_MSC_VER) && !defined(_M_ARM64) && !defined(_M_X64)
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static inline unsigned char _BitScanForward64(unsigned long* ret, uint64_t x) {
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unsigned long x0 = (unsigned long)x, top, bottom;
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_BitScanForward(&top, (unsigned long)(x >> 32));
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_BitScanForward(&bottom, x0);
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*ret = x0 ? bottom : 32 + top;
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return x != 0;
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}
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static unsigned char _BitScanReverse64(unsigned long* ret, uint64_t x) {
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unsigned long x1 = (unsigned long)(x >> 32), top, bottom;
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_BitScanReverse(&top, x1);
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_BitScanReverse(&bottom, (unsigned long)x);
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*ret = x1 ? top + 32 : bottom;
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return x != 0;
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}
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#endif
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/* result might be undefined when input_num is zero */
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simdjson_really_inline int leading_zeroes(uint64_t input_num) {
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#ifdef _MSC_VER
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unsigned long leading_zero = 0;
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// Search the mask data from most significant bit (MSB)
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// to least significant bit (LSB) for a set bit (1).
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if (_BitScanReverse64(&leading_zero, input_num))
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return (int)(63 - leading_zero);
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else
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return 64;
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#else
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return __builtin_clzll(input_num);
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#endif// _MSC_VER
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}
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} // unnamed namespace
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} // namespace SIMDJSON_IMPLEMENTATION
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} // namespace simdjson
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#endif // SIMDJSON_FALLBACK_BITMANIPULATION_H
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