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