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125 lines
4.5 KiB
C++
125 lines
4.5 KiB
C++
//
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// ██████ ██ ██ ██████ ██████
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// ██ ██ ██ ██ ██ ██ ** Classy Header-Only Classes **
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// ██ ███████ ██ ██ ██
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// ██ ██ ██ ██ ██ ██ https://github.com/Tracktion/choc
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// ██████ ██ ██ ██████ ██████
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//
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// CHOC is (C)2022 Tracktion Corporation, and is offered under the terms of the ISC license:
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//
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// Permission to use, copy, modify, and/or distribute this software for any purpose with or
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// without fee is hereby granted, provided that the above copyright notice and this permission
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// notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
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// WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
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// CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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// WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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#ifndef CHOC_MATH_HELPERS_HEADER_INCLUDED
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#define CHOC_MATH_HELPERS_HEADER_INCLUDED
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#include <cstdlib>
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#include <cstdint>
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#ifdef _MSC_VER
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#include <intrin.h>
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#pragma intrinsic (_BitScanReverse)
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#ifdef _WIN64
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#pragma intrinsic (_BitScanReverse64)
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#endif
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#if defined (_M_X64) && ! defined (_M_ARM64EC)
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#pragma intrinsic (_umul128)
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#define CHOC_HAS_UMUL128 1
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#endif
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#endif
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namespace choc::math
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{
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//==============================================================================
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/// Returns true if the given value is 2^something
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template <typename Integer>
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constexpr bool isPowerOf2 (Integer n) { return n > 0 && (n & (n - 1)) == 0; }
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// Returns the number of contiguously-clear upper bits in a 32-bit value
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/// Note this operation is undefined for value == 0!
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inline uint32_t countUpperClearBits (uint32_t value)
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{
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#ifdef _MSC_VER
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unsigned long result = 0;
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_BitScanReverse (&result, static_cast<unsigned long> (value));
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return static_cast<uint32_t> (31u - result);
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#else
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return static_cast<uint32_t> (__builtin_clz (value));
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#endif
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}
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/// Returns the number of contiguously-clear upper bits in a 64-bit value.
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/// Note this operation is undefined for value == 0!
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inline uint32_t countUpperClearBits (uint64_t value)
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{
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#ifdef _MSC_VER
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unsigned long result = 0;
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#ifdef _WIN64
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_BitScanReverse64 (&result, value);
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#else
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if (_BitScanReverse (&result, static_cast<unsigned long> (value >> 32))) return static_cast<uint32_t> (31u - result);
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_BitScanReverse (&result, static_cast<unsigned long> (value));
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#endif
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return static_cast<uint32_t> (63u - result);
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#else
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return static_cast<uint32_t> (__builtin_clzll (value));
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#endif
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}
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/// Returns the number of decimal digits required to print a given unsigned number
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inline int getNumDecimalDigits (uint32_t n)
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{
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return n < 1000 ? (n < 10 ? 1 : (n < 100 ? 2 : 3))
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: n < 1000000 ? (n < 10000 ? 4 : (n < 100000 ? 5 : 6))
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: n < 100000000 ? (n < 10000000 ? 7 : 8)
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: n < 1000000000 ? 9 : 10;
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}
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//==============================================================================
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/// Used as a return type for multiply128()
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struct Int128
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{
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uint64_t high, low;
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};
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/// A cross-platform function to multiply two 64-bit numbers and return a 128-bit result
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inline Int128 multiply128 (uint64_t a, uint64_t b)
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{
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#if CHOC_HAS_UMUL128
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Int128 result;
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result.low = _umul128 (a, b, &result.high);
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return result;
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#elif __LP64__
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#if __GNUC__
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wpedantic"
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#endif
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auto total = static_cast<unsigned __int128> (a) * static_cast<unsigned __int128> (b);
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#if __GNUC__
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#pragma GCC diagnostic pop
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#endif
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return { static_cast<uint64_t> (total >> 64), static_cast<uint64_t> (total) };
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#else
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uint64_t a0 = static_cast<uint32_t> (a), a1 = a >> 32,
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b0 = static_cast<uint32_t> (b), b1 = b >> 32;
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auto p10 = a1 * b0, p00 = a0 * b0,
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p11 = a1 * b1, p01 = a0 * b1;
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auto middleBits = p10 + static_cast<uint32_t> (p01) + (p00 >> 32);
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return { p11 + (middleBits >> 32) + (p01 >> 32), (middleBits << 32) | static_cast<uint32_t> (p00) };
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#endif
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}
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} // namespace choc::math
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#endif
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