forked from GitHub/gf-core
77 lines
1.3 KiB
C
77 lines
1.3 KiB
C
#include <gu/bits.h>
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#include <limits.h>
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#include <inttypes.h>
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <math.h>
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GU_INTERNAL unsigned
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gu_ceil2e(unsigned u)
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{
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u--;
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u |= u >> 1;
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u |= u >> 2;
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u |= u >> 4;
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u |= u >> 8;
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#if UINT_MAX > UINT16_MAX
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u |= u >> 16;
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#endif
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#if UINT_MAX > UINT32_MAX
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u |= u >> 32;
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#endif
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u++;
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return u;
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}
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GU_INTERNAL double
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gu_decode_double(uint64_t u)
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{
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bool sign = u >> 63;
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unsigned rawexp = u >> 52 & 0x7ff;
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uint64_t mantissa = u & 0xfffffffffffff;
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double ret;
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if (rawexp == 0x7ff) {
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ret = (mantissa == 0) ? INFINITY : NAN;
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} else {
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uint64_t m = rawexp ? 1ULL << 52 | mantissa : mantissa << 1;
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ret = ldexp((double) m, rawexp - 1075);
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}
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return sign ? copysign(ret, -1.0) : ret;
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}
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GU_INTERNAL uint64_t
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gu_encode_double(double d)
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{
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int sign = signbit(d) > 0;
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unsigned rawexp;
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uint64_t mantissa;
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switch (fpclassify(d)) {
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case FP_NAN:
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rawexp = 0x7ff;
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mantissa = 1;
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break;
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case FP_INFINITE:
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rawexp = 0x7ff;
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mantissa = 0;
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break;
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default: {
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int exp;
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mantissa = (uint64_t) scalbn(frexp(d, &exp), 53);
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mantissa &= ~ (1ULL << 52);
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exp -= 53;
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rawexp = exp + 1075;
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}
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}
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uint64_t u = (((uint64_t) sign) << 63) |
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(((uint64_t) rawexp & 0x7ff) << 52) |
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mantissa;
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return u;
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}
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