| [25] | 1 | #include <tommath.h> |
|---|
| 2 | #ifdef BN_MP_RADIX_SIZE_C |
|---|
| 3 | /* LibTomMath, multiple-precision integer library -- Tom St Denis |
|---|
| 4 | * |
|---|
| 5 | * LibTomMath is a library that provides multiple-precision |
|---|
| 6 | * integer arithmetic as well as number theoretic functionality. |
|---|
| 7 | * |
|---|
| 8 | * The library was designed directly after the MPI library by |
|---|
| 9 | * Michael Fromberger but has been written from scratch with |
|---|
| 10 | * additional optimizations in place. |
|---|
| 11 | * |
|---|
| 12 | * The library is free for all purposes without any express |
|---|
| 13 | * guarantee it works. |
|---|
| 14 | * |
|---|
| 15 | * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com |
|---|
| 16 | */ |
|---|
| 17 | |
|---|
| 18 | /* returns size of ASCII reprensentation */ |
|---|
| 19 | int mp_radix_size (mp_int * a, int radix, int *size) |
|---|
| 20 | { |
|---|
| 21 | int res, digs; |
|---|
| 22 | mp_int t; |
|---|
| 23 | mp_digit d; |
|---|
| 24 | |
|---|
| 25 | *size = 0; |
|---|
| 26 | |
|---|
| 27 | /* special case for binary */ |
|---|
| 28 | if (radix == 2) { |
|---|
| 29 | *size = mp_count_bits (a) + (a->sign == MP_NEG ? 1 : 0) + 1; |
|---|
| 30 | return MP_OKAY; |
|---|
| 31 | } |
|---|
| 32 | |
|---|
| 33 | /* make sure the radix is in range */ |
|---|
| 34 | if (radix < 2 || radix > 64) { |
|---|
| 35 | return MP_VAL; |
|---|
| 36 | } |
|---|
| 37 | |
|---|
| 38 | if (mp_iszero(a) == MP_YES) { |
|---|
| 39 | *size = 2; |
|---|
| 40 | return MP_OKAY; |
|---|
| 41 | } |
|---|
| 42 | |
|---|
| 43 | /* digs is the digit count */ |
|---|
| 44 | digs = 0; |
|---|
| 45 | |
|---|
| 46 | /* if it's negative add one for the sign */ |
|---|
| 47 | if (a->sign == MP_NEG) { |
|---|
| 48 | ++digs; |
|---|
| 49 | } |
|---|
| 50 | |
|---|
| 51 | /* init a copy of the input */ |
|---|
| 52 | if ((res = mp_init_copy (&t, a)) != MP_OKAY) { |
|---|
| 53 | return res; |
|---|
| 54 | } |
|---|
| 55 | |
|---|
| 56 | /* force temp to positive */ |
|---|
| 57 | t.sign = MP_ZPOS; |
|---|
| 58 | |
|---|
| 59 | /* fetch out all of the digits */ |
|---|
| 60 | while (mp_iszero (&t) == MP_NO) { |
|---|
| 61 | if ((res = mp_div_d (&t, (mp_digit) radix, &t, &d)) != MP_OKAY) { |
|---|
| 62 | mp_clear (&t); |
|---|
| 63 | return res; |
|---|
| 64 | } |
|---|
| 65 | ++digs; |
|---|
| 66 | } |
|---|
| 67 | mp_clear (&t); |
|---|
| 68 | |
|---|
| 69 | /* |
|---|
| 70 | * return digs + 1, the 1 is for the NULL byte that would be required. |
|---|
| 71 | * mp_toradix_n requires a minimum of 3 bytes, so never report less than |
|---|
| 72 | * that. |
|---|
| 73 | */ |
|---|
| 74 | |
|---|
| 75 | if ( digs >= 2 ) { |
|---|
| 76 | *size = digs + 1; |
|---|
| 77 | } else { |
|---|
| 78 | *size = 3; |
|---|
| 79 | } |
|---|
| 80 | return MP_OKAY; |
|---|
| 81 | } |
|---|
| 82 | |
|---|
| 83 | #endif |
|---|
| 84 | |
|---|
| 85 | /* $Source: /cvsroot/tcl/libtommath/bn_mp_radix_size.c,v $ */ |
|---|
| 86 | /* Tom's revision is 1.4 */ |
|---|
| 87 | /* $Revision: 1.5 $ */ |
|---|
| 88 | /* $Date: 2006/12/01 00:31:32 $ */ |
|---|
