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path: root/lib/ieee754.c
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 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 ``` ``````/* * Shamelessly lifted from Beej's Guide to Network Programming, found here: * * http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#serialization * * Below code was granted to the public domain. */ #include "ieee754.h" uint64_t pack754(long double f, unsigned bits, unsigned expbits) { long double fnorm; int shift; long long sign, exp, significand; unsigned significandbits = bits - expbits - 1; // -1 for sign bit // get this special case out of the way if (f == 0.0) return 0; // check sign and begin normalization if (f < 0) { sign = 1; fnorm = -f; } else { sign = 0; fnorm = f; } // get the normalized form of f and track the exponent shift = 0; while (fnorm >= 2.0) { fnorm /= 2.0; shift++; } while (fnorm < 1.0) { fnorm *= 2.0; shift--; } fnorm = fnorm - 1.0; // calculate the binary form (non-float) of the significand data significand = fnorm * ((1LL << significandbits) + 0.5f); // get the biased exponent exp = shift + ((1 << (expbits - 1)) - 1); // shift + bias // return the final answer return (sign << (bits - 1)) | (exp << (bits-expbits - 1)) | significand; } long double unpack754(uint64_t i, unsigned bits, unsigned expbits) { long double result; long long shift; unsigned bias; unsigned significandbits = bits - expbits - 1; // -1 for sign bit if (i == 0) return 0.0; // pull the significand result = (i & ((1LL << significandbits) - 1)); // mask result /= (1LL << significandbits); // convert back to float result += 1.0f; // add the one back on // deal with the exponent bias = (1 << (expbits - 1)) - 1; shift = ((i >> significandbits) & ((1LL << expbits) - 1)) - bias; while (shift > 0) { result *= 2.0; shift--; } while (shift < 0) { result /= 2.0; shift++; } // sign it result *= (i >> (bits - 1)) & 1 ? -1.0 : 1.0; return result; } ``````