mpf_cmp.c

   1 /* LibTomFloat, multiple-precision floating-point library
   2  *
   3  * LibTomFloat is a library that provides multiple-precision
   4  * floating-point artihmetic as well as trigonometric functionality.
   5  *
   6  * This library requires the public domain LibTomMath to be installed.
   7  *
   8  * This library is free for all purposes without any express
   9  * gurantee it works
  10  *
  11  * Tom St Denis, tomstdenis@iahu.ca, http://float.libtomcrypt.org
  12  */
  13 #include <tomfloat.h>
  14
  15 int  mpf_cmp(mp_float *a,   mp_float *b)
  16 {
  17    int za, zb, sa, sb;
  18
  19    /* if one is zero than we early out */
  20    za = mp_iszero(&(a->mantissa));
  21    sa = a->mantissa.sign;
  22    zb = mp_iszero(&(b->mantissa));
  23    sb = b->mantissa.sign;
  24
  25    if (za == MP_YES && zb == MP_NO) {
  26       /* result depends on b */
  27       if (sb == MP_NEG) {
  28          return MP_GT;
  29       } else {
  30          return MP_LT;
  31       }
  32    } else if (za == MP_NO && zb == MP_YES) {
  33       /* result depends on a */
  34       if (sa == MP_NEG) {
  35          return MP_LT;
  36       } else {
  37          return MP_GT;
  38       }
  39    }
  40
  41    /* compare the signs */
  42    if (sa == MP_NEG && sb == MP_ZPOS) {
  43       return MP_LT;
  44    } else if (sa == MP_ZPOS && sb == MP_NEG) {
  45       return MP_GT;
  46    }
  47
  48    /* they're both non-zero, the same sign and normalized, compare the exponents */
  49    if (a->exp > b->exp) {
  50       return (sa == MP_NEG) ? MP_LT : MP_GT;
  51    } else if (a->exp < b->exp) {
  52       return (sa == MP_NEG) ? MP_GT : MP_LT;
  53    }
  54
  55    /* same exponent and sign, compare mantissa */
  56    return mp_cmp(&(a->mantissa), &(b->mantissa));
  57 }
  58