├── AUTHORS
├── CONTRIBUTING.md
├── CONTRIBUTORS
├── LICENSE
├── Makefile
├── README
└── dumpfp.cc


/AUTHORS:
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1 | # Copyright Holders.
2 | 
3 | Google, Inc.
4 | 


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/CONTRIBUTING.md:
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1 | ## <a name="cla"></a> Signing the CLA
2 | 
3 | Please sign the [Google Contributor License Agreement
4 | (CLA)](https://cla.developers.google.com/)
5 | before sending pull requests. For any code changes to be
6 | accepted, the CLA must be signed. It's a quick process, I
7 | promise!
8 | 


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/CONTRIBUTORS:
--------------------------------------------------------------------------------
1 | # People who have contributed code but are not copyright holders.
2 | 
3 | Joshua Haberman <jhaberman@gmail.com>
4 | 


--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
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--------------------------------------------------------------------------------
/Makefile:
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1 | 
2 | dumpfp: dumpfp.cc
3 | 	$(CXX) -o dumpfp dumpfp.cc -Wall -O3 -lm -lgmpxx -lgmp
4 | 


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/README:
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1 | 
2 | Tool for dumping floating-point numbers in their native
3 | representation.
4 | 
5 | For more info see: http://blog.reverberate.org/2012/11/dumpfp-tool-to-inspect-floating-point.html
6 | 


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/dumpfp.cc:
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  1 | 
  2 | #include <inttypes.h>
  3 | #include <math.h>
  4 | #include <stdbool.h>
  5 | #include <stdint.h>
  6 | #include <stdlib.h>
  7 | #include <string.h>
  8 | #include <iostream>
  9 | #include <iomanip>
 10 | #include <gmpxx.h>
 11 | 
 12 | using namespace std;
 13 | 
 14 | mpz_class bitat(int bit) { return mpz_class(1) << bit; }
 15 | mpz_class mask(int bits) { return bitat(bits) - 1; }
 16 | 
 17 | void dumpfp(mpz_class whole, mpz_class numer, int denom_lg2) {
 18 |   mpz_class denom = bitat(denom_lg2);
 19 | 
 20 |   // Reduce the fraction for nicer display.
 21 |   while ((numer & 0x1) == 0 && (denom & 0x1) == 0) {
 22 |     numer >>= 1;
 23 |     denom >>= 1;
 24 |     denom_lg2--;
 25 |   }
 26 | 
 27 |   // Pick the fewest number of digits that will precisely represent the value.
 28 |   int n = 1;
 29 |   mpz_class digits = 10;
 30 | again:
 31 |   mpz_class product = numer * digits;
 32 |   mpz_class fraction = product / denom;
 33 |   mpz_class product2 = fraction * denom;
 34 |   if (product2 != product) {
 35 |     digits *= 10;
 36 |     n += 1;
 37 |     goto again;
 38 |   }
 39 | 
 40 |   if (whole > 0)
 41 |     cout << whole;
 42 |   if (whole > 0 && numer > 0)
 43 |     cout << " + ";
 44 |   if (numer > 0)
 45 |     cout << numer << "/2^" << denom_lg2;
 46 | 
 47 |   gmp_printf("  (%Zd.%.*Zd)", whole.get_mpz_t(), n, fraction.get_mpz_t());
 48 | }
 49 | 
 50 | void dumpfp2(mpz_class raw, int sig_bits, int exp_bits) {
 51 |   // In these calculations we rely on the general properties of IEEE floating
 52 |   // point: X bits of significant, followed by an implicit "1", followed by
 53 |   // Y bits of exponent and a sign bit.  The exponent is expected to be biased
 54 |   // by half of the exponent's domain.
 55 |   //
 56 |   // Note that this will *not* work for "long double" because it does not use
 57 |   // an implicit 1 in its significand.
 58 |   mpz_class sig_scale = bitat(sig_bits),
 59 |             sig = raw & mask(sig_bits),
 60 |             sig2 = sig_scale + sig,
 61 |             expbias = mask(exp_bits - 1);
 62 |   int sign = mpz_class(raw >> (sig_bits + exp_bits)).get_si(),
 63 |       exp  = mpz_class(raw >> sig_bits & mask(exp_bits)).get_si(),
 64 |       exp2 = mpz_class(exp - expbias).get_si();
 65 | 
 66 |   cout << "           raw = 0x" << hex << raw << "\n";
 67 |   cout << "          sign = 0x" << hex << sign << "\n";
 68 | 
 69 |   if (exp2 == (expbias + 1)) {
 70 |     cout << "      exponent = 0x" << hex << exp << " (NaN or Infinity)\n";
 71 |     if (sig != 0)
 72 |       cout << "   significand = " << hex << sig << " (non-zero indicates NaN)\n";
 73 |     else
 74 |       cout << "   significand = " << hex << sig << " (zero indicates Infinity)\n";
 75 |   } else {
 76 |     cout << "      exponent = 0x" << hex << exp << " (" << dec << exp2 << ")\n";
 77 |     cout << "   significand = 0x" << hex << sig << dec << "\n";
 78 |     cout << "\n";
 79 | 
 80 |     cout << "   VALUE CALCULATION =\n";
 81 |     cout << "       significand   (";
 82 |     dumpfp(1, sig, sig_bits);
 83 |     cout << ")\n";
 84 |     cout << "     * 2^exponent    (2^" << exp2 << ")\n";
 85 |     cout << "     = VALUE         (";
 86 | 
 87 |     if (exp2 >= sig_bits) {
 88 |       cout << (sig2 << (exp2 - sig_bits));
 89 |     } else {
 90 |       int split = sig_bits - exp2;
 91 |       mpz_class whole = sig2 >> split;
 92 |       mpz_class frac = sig2 - (whole << split);
 93 |       dumpfp(whole, frac, split);
 94 |     }
 95 |     cout << ")\n";
 96 |   }
 97 | 
 98 |   cout << "\n";
 99 | }
100 | 
101 | // Gets an integer value corresponding to the given raw bytes.
102 | // The currently will only work on a little-endian machine.
103 | mpz_class getraw(void *val, size_t size) {
104 |   unsigned char bytes[128];
105 |   memcpy(bytes, val, size);
106 |   mpz_class raw(0);
107 |   for (size_t i = 0; i < size; i++) {
108 |     raw *= 256;
109 |     raw += bytes[size-i-1];
110 |   }
111 |   return raw;
112 | }
113 | 
114 | void dumpfloat(float x) {
115 |   printf("Single Precision (IEEE 32-bit):\n");
116 |   dumpfp2(getraw(&x, sizeof(float)), 23, 8);
117 | }
118 | 
119 | void dumpdouble(double x) {
120 |   printf("Double Precision (IEEE 64-bit):\n");
121 |   dumpfp2(getraw(&x, sizeof(double)), 52, 11);
122 | }
123 | 
124 | int main(int argc, char *argv[]) {
125 |   if (argc < 2) {
126 |     fprintf(stderr, "Usage: dumpfp 0.12345\n");
127 |     return 1;
128 |   }
129 | 
130 |   long double x = strtold(argv[1], NULL);
131 | 
132 |   dumpfloat(x);
133 |   dumpdouble(x);
134 | 
135 |   return 0;
136 | }
137 | 


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