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151 rivejä
2.9 KiB
151 rivejä
2.9 KiB
/* Display structure of floating-point numbers */
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#include <stdio.h>
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#include <stdlib.h>
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float strtof(const char *nptr, char **endptr);
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#define FLOAT_SIZE 32
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#define FRAC_SIZE 23
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#define EXP_SIZE 8
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#define BIAS ((1<<(EXP_SIZE-1))-1)
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#define FRAC_MASK ((1<<FRAC_SIZE)-1)
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#define EXP_MASK ((1<<EXP_SIZE)-1)
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/* Floating point helpers */
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unsigned f2u(float f)
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{
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union {
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unsigned u;
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float f;
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} v;
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v.u = 0;
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v.f = f;
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return v.u;
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}
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static float u2f(unsigned u)
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{
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union {
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unsigned u;
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float f;
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} v;
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v.u = u;
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return v.f;
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}
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/* Get exponent */
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unsigned get_exp(unsigned uf)
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{
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return (uf>>FRAC_SIZE) & EXP_MASK;
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}
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/* Get fraction */
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unsigned get_frac(unsigned uf)
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{
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return uf & FRAC_MASK;
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}
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/* Get sign */
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unsigned get_sign(unsigned uf)
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{
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return (uf>>(FLOAT_SIZE-1)) & 0x1;
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}
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void show_float(unsigned uf)
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{
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float f = u2f(uf);
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unsigned exp = get_exp(uf);
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unsigned frac = get_frac(uf);
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unsigned sign = get_sign(uf);
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printf("\nFloating point value %.10g\n", f);
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printf("Bit Representation 0x%.8x, sign = %x, exponent = 0x%.2x, fraction = 0x%.6x\n",
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uf, sign, exp, frac);
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if (exp == EXP_MASK) {
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if (frac == 0) {
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printf("%cInfinity\n", sign ? '-' : '+');
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} else
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printf("Not-A-Number\n");
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} else {
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int denorm = (exp == 0);
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int uexp = denorm ? 1-BIAS : exp - BIAS;
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int mantissa = denorm ? frac : frac + (1<<FRAC_SIZE);
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float fman = (float) mantissa / (float) (1<<FRAC_SIZE);
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printf("%s. %c%.10f X 2^(%d)\n",
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denorm ? "Denormalized" : "Normalized",
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sign ? '-' : '+',
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fman, uexp);
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}
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}
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/* Extract hex/decimal/or float value from string */
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static int get_num_val(char *sval, unsigned *valp) {
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char *endp;
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/* See if it's an integer or floating point */
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int ishex = 0;
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int isfloat = 0;
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int i;
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for (i = 0; sval[i]; i++) {
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switch (sval[i]) {
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case 'x':
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case 'X':
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ishex = 1;
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break;
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case 'e':
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case 'E':
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if (!ishex)
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isfloat = 1;
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break;
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case '.':
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isfloat = 1;
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break;
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default:
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break;
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}
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}
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if (isfloat) {
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float fval = strtof(sval, &endp);
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if (!*endp) {
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*valp = *(unsigned *) &fval;
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return 1;
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}
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return 0;
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} else {
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long long int llval = strtoll(sval, &endp, 0);
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long long int upperbits = llval >> 31;
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/* will give -1 for negative, 0 or 1 for positive */
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if (valp && (upperbits == 0 || upperbits == -1 || upperbits == 1)) {
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*valp = (unsigned) llval;
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return 1;
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}
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return 0;
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}
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}
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void usage(char *fname) {
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printf("Usage: %s val1 val2 ...\n", fname);
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printf("Values may be given as hex patterns or as floating point numbers\n");
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exit(0);
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}
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int main(int argc, char *argv[])
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{
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int i;
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unsigned uf;
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if (argc < 2)
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usage(argv[0]);
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for (i = 1; i < argc; i++) {
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char *sval = argv[i];
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if (get_num_val(sval, &uf)) {
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show_float(uf);
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} else {
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printf("Invalid 32-bit number: '%s'\n", sval);
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usage(argv[0]);
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}
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}
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return 0;
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}
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