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99 lines
2 KiB
C
99 lines
2 KiB
C
/*
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* PROJECT: ReactOS CRT library
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* LICENSE: MIT (https://spdx.org/licenses/MIT)
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* PURPOSE: Integer to float conversion (__i64tod/u64tod/i64tos/u64tos)
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* COPYRIGHT: Copyright 2021 Roman Masanin <36927roma@gmail.com>
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*/
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#ifdef _USE_64_BITS_
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typedef double FLOAT_TYPE;
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typedef unsigned long long FINT_TYPE;
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#define FRACTION_LEN 52
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#define EXPONENT_LEN 11
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#define SHIFT_OFFSET EXPONENT_LEN
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#else
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typedef float FLOAT_TYPE;
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typedef unsigned int FINT_TYPE;
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#define FRACTION_LEN 23
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#define EXPONENT_LEN 8
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#define SHIFT_OFFSET (EXPONENT_LEN + 32)
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#endif
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#ifdef _USE_SIGNED_
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typedef long long INT64SU;
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#else
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typedef unsigned long long INT64SU;
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#endif
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typedef union _FLOAT_RESULT
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{
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FLOAT_TYPE value;
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FINT_TYPE raw;
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} FLOAT_RESULT;
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#define SIGN_MASK 0x8000000000000000ULL
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#define EXPONENT_ZERO ((1 << (EXPONENT_LEN - 1)) - 1)
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#define NEGATE(x) (~(x) + 1)
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FLOAT_TYPE
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__64tof(INT64SU value)
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{
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FLOAT_RESULT result;
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FINT_TYPE exponent = EXPONENT_ZERO + FRACTION_LEN;
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int count = 0;
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unsigned long long mask = SIGN_MASK;
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if (value == 0)
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return (FLOAT_TYPE)0;
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#ifdef _USE_SIGNED_
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if (value & SIGN_MASK)
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{
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value = NEGATE(value);
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/* set Sign bit using exponent */
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exponent |= 1 << EXPONENT_LEN;
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}
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#endif
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for (; count < 64; count++)
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{
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if (value & mask)
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break;
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mask = mask >> 1;
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}
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count -= SHIFT_OFFSET;
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/* exponent is FRACTION_LEN - count */
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exponent -= count;
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result.raw = exponent << FRACTION_LEN;
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mask--;
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value = value & mask;
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if (value == 0)
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return result.value;
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if (count == 0)
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{
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result.raw |= value;
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}
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else if (count < 0)
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{
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count = NEGATE(count) - 1;
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value = value >> count;
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mask = value & 1;
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result.raw |= value >> 1;
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/* round up if left most bit of lost data is 1 */
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if (mask)
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result.raw++;
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}
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else
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{
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result.raw |= value << count;
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}
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return result.value;
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}
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