Mercurial > dropbear
diff mtest/mpi.c @ 1:22d5cf7d4b1a libtommath
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| author | Matt Johnston <matt@ucc.asn.au> |
|---|---|
| date | Mon, 31 May 2004 18:23:46 +0000 |
| parents | |
| children | a96ff234ff19 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mtest/mpi.c Mon May 31 18:23:46 2004 +0000 @@ -0,0 +1,3981 @@ +/* + mpi.c + + by Michael J. Fromberger <[email protected]> + Copyright (C) 1998 Michael J. Fromberger, All Rights Reserved + + Arbitrary precision integer arithmetic library + + $Id: mpi.c,v 1.1.1.1 2003/05/19 04:01:19 matt Exp $ + */ + +#include "mpi.h" +#include <stdlib.h> +#include <string.h> +#include <ctype.h> + +#if MP_DEBUG +#include <stdio.h> + +#define DIAG(T,V) {fprintf(stderr,T);mp_print(V,stderr);fputc('\n',stderr);} +#else +#define DIAG(T,V) +#endif + +/* + If MP_LOGTAB is not defined, use the math library to compute the + logarithms on the fly. Otherwise, use the static table below. + Pick which works best for your system. + */ +#if MP_LOGTAB + +/* {{{ s_logv_2[] - log table for 2 in various bases */ + +/* + A table of the logs of 2 for various bases (the 0 and 1 entries of + this table are meaningless and should not be referenced). + + This table is used to compute output lengths for the mp_toradix() + function. Since a number n in radix r takes up about log_r(n) + digits, we estimate the output size by taking the least integer + greater than log_r(n), where: + + log_r(n) = log_2(n) * log_r(2) + + This table, therefore, is a table of log_r(2) for 2 <= r <= 36, + which are the output bases supported. + */ + +#include "logtab.h" + +/* }}} */ +#define LOG_V_2(R) s_logv_2[(R)] + +#else + +#include <math.h> +#define LOG_V_2(R) (log(2.0)/log(R)) + +#endif + +/* Default precision for newly created mp_int's */ +static unsigned int s_mp_defprec = MP_DEFPREC; + +/* {{{ Digit arithmetic macros */ + +/* + When adding and multiplying digits, the results can be larger than + can be contained in an mp_digit. Thus, an mp_word is used. These + macros mask off the upper and lower digits of the mp_word (the + mp_word may be more than 2 mp_digits wide, but we only concern + ourselves with the low-order 2 mp_digits) + + If your mp_word DOES have more than 2 mp_digits, you need to + uncomment the first line, and comment out the second. + */ + +/* #define CARRYOUT(W) (((W)>>DIGIT_BIT)&MP_DIGIT_MAX) */ +#define CARRYOUT(W) ((W)>>DIGIT_BIT) +#define ACCUM(W) ((W)&MP_DIGIT_MAX) + +/* }}} */ + +/* {{{ Comparison constants */ + +#define MP_LT -1 +#define MP_EQ 0 +#define MP_GT 1 + +/* }}} */ + +/* {{{ Constant strings */ + +/* Constant strings returned by mp_strerror() */ +static const char *mp_err_string[] = { + "unknown result code", /* say what? */ + "boolean true", /* MP_OKAY, MP_YES */ + "boolean false", /* MP_NO */ + "out of memory", /* MP_MEM */ + "argument out of range", /* MP_RANGE */ + "invalid input parameter", /* MP_BADARG */ + "result is undefined" /* MP_UNDEF */ +}; + +/* Value to digit maps for radix conversion */ + +/* s_dmap_1 - standard digits and letters */ +static const char *s_dmap_1 = + "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz+/"; + +#if 0 +/* s_dmap_2 - base64 ordering for digits */ +static const char *s_dmap_2 = + "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; +#endif + +/* }}} */ + +/* {{{ Static function declarations */ + +/* + If MP_MACRO is false, these will be defined as actual functions; + otherwise, suitable macro definitions will be used. This works + around the fact that ANSI C89 doesn't support an 'inline' keyword + (although I hear C9x will ... about bloody time). At present, the + macro definitions are identical to the function bodies, but they'll + expand in place, instead of generating a function call. + + I chose these particular functions to be made into macros because + some profiling showed they are called a lot on a typical workload, + and yet they are primarily housekeeping. + */ +#if MP_MACRO == 0 + void s_mp_setz(mp_digit *dp, mp_size count); /* zero digits */ + void s_mp_copy(mp_digit *sp, mp_digit *dp, mp_size count); /* copy */ + void *s_mp_alloc(size_t nb, size_t ni); /* general allocator */ + void s_mp_free(void *ptr); /* general free function */ +#else + + /* Even if these are defined as macros, we need to respect the settings + of the MP_MEMSET and MP_MEMCPY configuration options... + */ + #if MP_MEMSET == 0 + #define s_mp_setz(dp, count) \ + {int ix;for(ix=0;ix<(count);ix++)(dp)[ix]=0;} + #else + #define s_mp_setz(dp, count) memset(dp, 0, (count) * sizeof(mp_digit)) + #endif /* MP_MEMSET */ + + #if MP_MEMCPY == 0 + #define s_mp_copy(sp, dp, count) \ + {int ix;for(ix=0;ix<(count);ix++)(dp)[ix]=(sp)[ix];} + #else + #define s_mp_copy(sp, dp, count) memcpy(dp, sp, (count) * sizeof(mp_digit)) + #endif /* MP_MEMCPY */ + + #define s_mp_alloc(nb, ni) calloc(nb, ni) + #define s_mp_free(ptr) {if(ptr) free(ptr);} +#endif /* MP_MACRO */ + +mp_err s_mp_grow(mp_int *mp, mp_size min); /* increase allocated size */ +mp_err s_mp_pad(mp_int *mp, mp_size min); /* left pad with zeroes */ + +void s_mp_clamp(mp_int *mp); /* clip leading zeroes */ + +void s_mp_exch(mp_int *a, mp_int *b); /* swap a and b in place */ + +mp_err s_mp_lshd(mp_int *mp, mp_size p); /* left-shift by p digits */ +void s_mp_rshd(mp_int *mp, mp_size p); /* right-shift by p digits */ +void s_mp_div_2d(mp_int *mp, mp_digit d); /* divide by 2^d in place */ +void s_mp_mod_2d(mp_int *mp, mp_digit d); /* modulo 2^d in place */ +mp_err s_mp_mul_2d(mp_int *mp, mp_digit d); /* multiply by 2^d in place*/ +void s_mp_div_2(mp_int *mp); /* divide by 2 in place */ +mp_err s_mp_mul_2(mp_int *mp); /* multiply by 2 in place */ +mp_digit s_mp_norm(mp_int *a, mp_int *b); /* normalize for division */ +mp_err s_mp_add_d(mp_int *mp, mp_digit d); /* unsigned digit addition */ +mp_err s_mp_sub_d(mp_int *mp, mp_digit d); /* unsigned digit subtract */ +mp_err s_mp_mul_d(mp_int *mp, mp_digit d); /* unsigned digit multiply */ +mp_err s_mp_div_d(mp_int *mp, mp_digit d, mp_digit *r); + /* unsigned digit divide */ +mp_err s_mp_reduce(mp_int *x, mp_int *m, mp_int *mu); + /* Barrett reduction */ +mp_err s_mp_add(mp_int *a, mp_int *b); /* magnitude addition */ +mp_err s_mp_sub(mp_int *a, mp_int *b); /* magnitude subtract */ +mp_err s_mp_mul(mp_int *a, mp_int *b); /* magnitude multiply */ +#if 0 +void s_mp_kmul(mp_digit *a, mp_digit *b, mp_digit *out, mp_size len); + /* multiply buffers in place */ +#endif +#if MP_SQUARE +mp_err s_mp_sqr(mp_int *a); /* magnitude square */ +#else +#define s_mp_sqr(a) s_mp_mul(a, a) +#endif +mp_err s_mp_div(mp_int *a, mp_int *b); /* magnitude divide */ +mp_err s_mp_2expt(mp_int *a, mp_digit k); /* a = 2^k */ +int s_mp_cmp(mp_int *a, mp_int *b); /* magnitude comparison */ +int s_mp_cmp_d(mp_int *a, mp_digit d); /* magnitude digit compare */ +int s_mp_ispow2(mp_int *v); /* is v a power of 2? */ +int s_mp_ispow2d(mp_digit d); /* is d a power of 2? */ + +int s_mp_tovalue(char ch, int r); /* convert ch to value */ +char s_mp_todigit(int val, int r, int low); /* convert val to digit */ +int s_mp_outlen(int bits, int r); /* output length in bytes */ + +/* }}} */ + +/* {{{ Default precision manipulation */ + +unsigned int mp_get_prec(void) +{ + return s_mp_defprec; + +} /* end mp_get_prec() */ + +void mp_set_prec(unsigned int prec) +{ + if(prec == 0) + s_mp_defprec = MP_DEFPREC; + else + s_mp_defprec = prec; + +} /* end mp_set_prec() */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ mp_init(mp) */ + +/* + mp_init(mp) + + Initialize a new zero-valued mp_int. Returns MP_OKAY if successful, + MP_MEM if memory could not be allocated for the structure. + */ + +mp_err mp_init(mp_int *mp) +{ + return mp_init_size(mp, s_mp_defprec); + +} /* end mp_init() */ + +/* }}} */ + +/* {{{ mp_init_array(mp[], count) */ + +mp_err mp_init_array(mp_int mp[], int count) +{ + mp_err res; + int pos; + + ARGCHK(mp !=NULL && count > 0, MP_BADARG); + + for(pos = 0; pos < count; ++pos) { + if((res = mp_init(&mp[pos])) != MP_OKAY) + goto CLEANUP; + } + + return MP_OKAY; + + CLEANUP: + while(--pos >= 0) + mp_clear(&mp[pos]); + + return res; + +} /* end mp_init_array() */ + +/* }}} */ + +/* {{{ mp_init_size(mp, prec) */ + +/* + mp_init_size(mp, prec) + + Initialize a new zero-valued mp_int with at least the given + precision; returns MP_OKAY if successful, or MP_MEM if memory could + not be allocated for the structure. + */ + +mp_err mp_init_size(mp_int *mp, mp_size prec) +{ + ARGCHK(mp != NULL && prec > 0, MP_BADARG); + + if((DIGITS(mp) = s_mp_alloc(prec, sizeof(mp_digit))) == NULL) + return MP_MEM; + + SIGN(mp) = MP_ZPOS; + USED(mp) = 1; + ALLOC(mp) = prec; + + return MP_OKAY; + +} /* end mp_init_size() */ + +/* }}} */ + +/* {{{ mp_init_copy(mp, from) */ + +/* + mp_init_copy(mp, from) + + Initialize mp as an exact copy of from. Returns MP_OKAY if + successful, MP_MEM if memory could not be allocated for the new + structure. + */ + +mp_err mp_init_copy(mp_int *mp, mp_int *from) +{ + ARGCHK(mp != NULL && from != NULL, MP_BADARG); + + if(mp == from) + return MP_OKAY; + + if((DIGITS(mp) = s_mp_alloc(USED(from), sizeof(mp_digit))) == NULL) + return MP_MEM; + + s_mp_copy(DIGITS(from), DIGITS(mp), USED(from)); + USED(mp) = USED(from); + ALLOC(mp) = USED(from); + SIGN(mp) = SIGN(from); + + return MP_OKAY; + +} /* end mp_init_copy() */ + +/* }}} */ + +/* {{{ mp_copy(from, to) */ + +/* + mp_copy(from, to) + + Copies the mp_int 'from' to the mp_int 'to'. It is presumed that + 'to' has already been initialized (if not, use mp_init_copy() + instead). If 'from' and 'to' are identical, nothing happens. + */ + +mp_err mp_copy(mp_int *from, mp_int *to) +{ + ARGCHK(from != NULL && to != NULL, MP_BADARG); + + if(from == to) + return MP_OKAY; + + { /* copy */ + mp_digit *tmp; + + /* + If the allocated buffer in 'to' already has enough space to hold + all the used digits of 'from', we'll re-use it to avoid hitting + the memory allocater more than necessary; otherwise, we'd have + to grow anyway, so we just allocate a hunk and make the copy as + usual + */ + if(ALLOC(to) >= USED(from)) { + s_mp_setz(DIGITS(to) + USED(from), ALLOC(to) - USED(from)); + s_mp_copy(DIGITS(from), DIGITS(to), USED(from)); + + } else { + if((tmp = s_mp_alloc(USED(from), sizeof(mp_digit))) == NULL) + return MP_MEM; + + s_mp_copy(DIGITS(from), tmp, USED(from)); + + if(DIGITS(to) != NULL) { +#if MP_CRYPTO + s_mp_setz(DIGITS(to), ALLOC(to)); +#endif + s_mp_free(DIGITS(to)); + } + + DIGITS(to) = tmp; + ALLOC(to) = USED(from); + } + + /* Copy the precision and sign from the original */ + USED(to) = USED(from); + SIGN(to) = SIGN(from); + } /* end copy */ + + return MP_OKAY; + +} /* end mp_copy() */ + +/* }}} */ + +/* {{{ mp_exch(mp1, mp2) */ + +/* + mp_exch(mp1, mp2) + + Exchange mp1 and mp2 without allocating any intermediate memory + (well, unless you count the stack space needed for this call and the + locals it creates...). This cannot fail. + */ + +void mp_exch(mp_int *mp1, mp_int *mp2) +{ +#if MP_ARGCHK == 2 + assert(mp1 != NULL && mp2 != NULL); +#else + if(mp1 == NULL || mp2 == NULL) + return; +#endif + + s_mp_exch(mp1, mp2); + +} /* end mp_exch() */ + +/* }}} */ + +/* {{{ mp_clear(mp) */ + +/* + mp_clear(mp) + + Release the storage used by an mp_int, and void its fields so that + if someone calls mp_clear() again for the same int later, we won't + get tollchocked. + */ + +void mp_clear(mp_int *mp) +{ + if(mp == NULL) + return; + + if(DIGITS(mp) != NULL) { +#if MP_CRYPTO + s_mp_setz(DIGITS(mp), ALLOC(mp)); +#endif + s_mp_free(DIGITS(mp)); + DIGITS(mp) = NULL; + } + + USED(mp) = 0; + ALLOC(mp) = 0; + +} /* end mp_clear() */ + +/* }}} */ + +/* {{{ mp_clear_array(mp[], count) */ + +void mp_clear_array(mp_int mp[], int count) +{ + ARGCHK(mp != NULL && count > 0, MP_BADARG); + + while(--count >= 0) + mp_clear(&mp[count]); + +} /* end mp_clear_array() */ + +/* }}} */ + +/* {{{ mp_zero(mp) */ + +/* + mp_zero(mp) + + Set mp to zero. Does not change the allocated size of the structure, + and therefore cannot fail (except on a bad argument, which we ignore) + */ +void mp_zero(mp_int *mp) +{ + if(mp == NULL) + return; + + s_mp_setz(DIGITS(mp), ALLOC(mp)); + USED(mp) = 1; + SIGN(mp) = MP_ZPOS; + +} /* end mp_zero() */ + +/* }}} */ + +/* {{{ mp_set(mp, d) */ + +void mp_set(mp_int *mp, mp_digit d) +{ + if(mp == NULL) + return; + + mp_zero(mp); + DIGIT(mp, 0) = d; + +} /* end mp_set() */ + +/* }}} */ + +/* {{{ mp_set_int(mp, z) */ + +mp_err mp_set_int(mp_int *mp, long z) +{ + int ix; + unsigned long v = abs(z); + mp_err res; + + ARGCHK(mp != NULL, MP_BADARG); + + mp_zero(mp); + if(z == 0) + return MP_OKAY; /* shortcut for zero */ + + for(ix = sizeof(long) - 1; ix >= 0; ix--) { + + if((res = s_mp_mul_2d(mp, CHAR_BIT)) != MP_OKAY) + return res; + + res = s_mp_add_d(mp, + (mp_digit)((v >> (ix * CHAR_BIT)) & UCHAR_MAX)); + if(res != MP_OKAY) + return res; + + } + + if(z < 0) + SIGN(mp) = MP_NEG; + + return MP_OKAY; + +} /* end mp_set_int() */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ Digit arithmetic */ + +/* {{{ mp_add_d(a, d, b) */ + +/* + mp_add_d(a, d, b) + + Compute the sum b = a + d, for a single digit d. Respects the sign of + its primary addend (single digits are unsigned anyway). + */ + +mp_err mp_add_d(mp_int *a, mp_digit d, mp_int *b) +{ + mp_err res = MP_OKAY; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + if(SIGN(b) == MP_ZPOS) { + res = s_mp_add_d(b, d); + } else if(s_mp_cmp_d(b, d) >= 0) { + res = s_mp_sub_d(b, d); + } else { + SIGN(b) = MP_ZPOS; + + DIGIT(b, 0) = d - DIGIT(b, 0); + } + + return res; + +} /* end mp_add_d() */ + +/* }}} */ + +/* {{{ mp_sub_d(a, d, b) */ + +/* + mp_sub_d(a, d, b) + + Compute the difference b = a - d, for a single digit d. Respects the + sign of its subtrahend (single digits are unsigned anyway). + */ + +mp_err mp_sub_d(mp_int *a, mp_digit d, mp_int *b) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + if(SIGN(b) == MP_NEG) { + if((res = s_mp_add_d(b, d)) != MP_OKAY) + return res; + + } else if(s_mp_cmp_d(b, d) >= 0) { + if((res = s_mp_sub_d(b, d)) != MP_OKAY) + return res; + + } else { + mp_neg(b, b); + + DIGIT(b, 0) = d - DIGIT(b, 0); + SIGN(b) = MP_NEG; + } + + if(s_mp_cmp_d(b, 0) == 0) + SIGN(b) = MP_ZPOS; + + return MP_OKAY; + +} /* end mp_sub_d() */ + +/* }}} */ + +/* {{{ mp_mul_d(a, d, b) */ + +/* + mp_mul_d(a, d, b) + + Compute the product b = a * d, for a single digit d. Respects the sign + of its multiplicand (single digits are unsigned anyway) + */ + +mp_err mp_mul_d(mp_int *a, mp_digit d, mp_int *b) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if(d == 0) { + mp_zero(b); + return MP_OKAY; + } + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + res = s_mp_mul_d(b, d); + + return res; + +} /* end mp_mul_d() */ + +/* }}} */ + +/* {{{ mp_mul_2(a, c) */ + +mp_err mp_mul_2(mp_int *a, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if((res = mp_copy(a, c)) != MP_OKAY) + return res; + + return s_mp_mul_2(c); + +} /* end mp_mul_2() */ + +/* }}} */ + +/* {{{ mp_div_d(a, d, q, r) */ + +/* + mp_div_d(a, d, q, r) + + Compute the quotient q = a / d and remainder r = a mod d, for a + single digit d. Respects the sign of its divisor (single digits are + unsigned anyway). + */ + +mp_err mp_div_d(mp_int *a, mp_digit d, mp_int *q, mp_digit *r) +{ + mp_err res; + mp_digit rem; + int pow; + + ARGCHK(a != NULL, MP_BADARG); + + if(d == 0) + return MP_RANGE; + + /* Shortcut for powers of two ... */ + if((pow = s_mp_ispow2d(d)) >= 0) { + mp_digit mask; + + mask = (1 << pow) - 1; + rem = DIGIT(a, 0) & mask; + + if(q) { + mp_copy(a, q); + s_mp_div_2d(q, pow); + } + + if(r) + *r = rem; + + return MP_OKAY; + } + + /* + If the quotient is actually going to be returned, we'll try to + avoid hitting the memory allocator by copying the dividend into it + and doing the division there. This can't be any _worse_ than + always copying, and will sometimes be better (since it won't make + another copy) + + If it's not going to be returned, we need to allocate a temporary + to hold the quotient, which will just be discarded. + */ + if(q) { + if((res = mp_copy(a, q)) != MP_OKAY) + return res; + + res = s_mp_div_d(q, d, &rem); + if(s_mp_cmp_d(q, 0) == MP_EQ) + SIGN(q) = MP_ZPOS; + + } else { + mp_int qp; + + if((res = mp_init_copy(&qp, a)) != MP_OKAY) + return res; + + res = s_mp_div_d(&qp, d, &rem); + if(s_mp_cmp_d(&qp, 0) == 0) + SIGN(&qp) = MP_ZPOS; + + mp_clear(&qp); + } + + if(r) + *r = rem; + + return res; + +} /* end mp_div_d() */ + +/* }}} */ + +/* {{{ mp_div_2(a, c) */ + +/* + mp_div_2(a, c) + + Compute c = a / 2, disregarding the remainder. + */ + +mp_err mp_div_2(mp_int *a, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if((res = mp_copy(a, c)) != MP_OKAY) + return res; + + s_mp_div_2(c); + + return MP_OKAY; + +} /* end mp_div_2() */ + +/* }}} */ + +/* {{{ mp_expt_d(a, d, b) */ + +mp_err mp_expt_d(mp_int *a, mp_digit d, mp_int *c) +{ + mp_int s, x; + mp_err res; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if((res = mp_init(&s)) != MP_OKAY) + return res; + if((res = mp_init_copy(&x, a)) != MP_OKAY) + goto X; + + DIGIT(&s, 0) = 1; + + while(d != 0) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY) + goto CLEANUP; + } + + d >>= 1; + + if((res = s_mp_sqr(&x)) != MP_OKAY) + goto CLEANUP; + } + + s_mp_exch(&s, c); + +CLEANUP: + mp_clear(&x); +X: + mp_clear(&s); + + return res; + +} /* end mp_expt_d() */ + +/* }}} */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ Full arithmetic */ + +/* {{{ mp_abs(a, b) */ + +/* + mp_abs(a, b) + + Compute b = |a|. 'a' and 'b' may be identical. + */ + +mp_err mp_abs(mp_int *a, mp_int *b) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + SIGN(b) = MP_ZPOS; + + return MP_OKAY; + +} /* end mp_abs() */ + +/* }}} */ + +/* {{{ mp_neg(a, b) */ + +/* + mp_neg(a, b) + + Compute b = -a. 'a' and 'b' may be identical. + */ + +mp_err mp_neg(mp_int *a, mp_int *b) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + if(s_mp_cmp_d(b, 0) == MP_EQ) + SIGN(b) = MP_ZPOS; + else + SIGN(b) = (SIGN(b) == MP_NEG) ? MP_ZPOS : MP_NEG; + + return MP_OKAY; + +} /* end mp_neg() */ + +/* }}} */ + +/* {{{ mp_add(a, b, c) */ + +/* + mp_add(a, b, c) + + Compute c = a + b. All parameters may be identical. + */ + +mp_err mp_add(mp_int *a, mp_int *b, mp_int *c) +{ + mp_err res; + int cmp; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + if(SIGN(a) == SIGN(b)) { /* same sign: add values, keep sign */ + + /* Commutativity of addition lets us do this in either order, + so we avoid having to use a temporary even if the result + is supposed to replace the output + */ + if(c == b) { + if((res = s_mp_add(c, a)) != MP_OKAY) + return res; + } else { + if(c != a && (res = mp_copy(a, c)) != MP_OKAY) + return res; + + if((res = s_mp_add(c, b)) != MP_OKAY) + return res; + } + + } else if((cmp = s_mp_cmp(a, b)) > 0) { /* different sign: a > b */ + + /* If the output is going to be clobbered, we will use a temporary + variable; otherwise, we'll do it without touching the memory + allocator at all, if possible + */ + if(c == b) { + mp_int tmp; + + if((res = mp_init_copy(&tmp, a)) != MP_OKAY) + return res; + if((res = s_mp_sub(&tmp, b)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + + s_mp_exch(&tmp, c); + mp_clear(&tmp); + + } else { + + if(c != a && (res = mp_copy(a, c)) != MP_OKAY) + return res; + if((res = s_mp_sub(c, b)) != MP_OKAY) + return res; + + } + + } else if(cmp == 0) { /* different sign, a == b */ + + mp_zero(c); + return MP_OKAY; + + } else { /* different sign: a < b */ + + /* See above... */ + if(c == a) { + mp_int tmp; + + if((res = mp_init_copy(&tmp, b)) != MP_OKAY) + return res; + if((res = s_mp_sub(&tmp, a)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + + s_mp_exch(&tmp, c); + mp_clear(&tmp); + + } else { + + if(c != b && (res = mp_copy(b, c)) != MP_OKAY) + return res; + if((res = s_mp_sub(c, a)) != MP_OKAY) + return res; + + } + } + + if(USED(c) == 1 && DIGIT(c, 0) == 0) + SIGN(c) = MP_ZPOS; + + return MP_OKAY; + +} /* end mp_add() */ + +/* }}} */ + +/* {{{ mp_sub(a, b, c) */ + +/* + mp_sub(a, b, c) + + Compute c = a - b. All parameters may be identical. + */ + +mp_err mp_sub(mp_int *a, mp_int *b, mp_int *c) +{ + mp_err res; + int cmp; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + if(SIGN(a) != SIGN(b)) { + if(c == a) { + if((res = s_mp_add(c, b)) != MP_OKAY) + return res; + } else { + if(c != b && ((res = mp_copy(b, c)) != MP_OKAY)) + return res; + if((res = s_mp_add(c, a)) != MP_OKAY) + return res; + SIGN(c) = SIGN(a); + } + + } else if((cmp = s_mp_cmp(a, b)) > 0) { /* Same sign, a > b */ + if(c == b) { + mp_int tmp; + + if((res = mp_init_copy(&tmp, a)) != MP_OKAY) + return res; + if((res = s_mp_sub(&tmp, b)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + s_mp_exch(&tmp, c); + mp_clear(&tmp); + + } else { + if(c != a && ((res = mp_copy(a, c)) != MP_OKAY)) + return res; + + if((res = s_mp_sub(c, b)) != MP_OKAY) + return res; + } + + } else if(cmp == 0) { /* Same sign, equal magnitude */ + mp_zero(c); + return MP_OKAY; + + } else { /* Same sign, b > a */ + if(c == a) { + mp_int tmp; + + if((res = mp_init_copy(&tmp, b)) != MP_OKAY) + return res; + + if((res = s_mp_sub(&tmp, a)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + s_mp_exch(&tmp, c); + mp_clear(&tmp); + + } else { + if(c != b && ((res = mp_copy(b, c)) != MP_OKAY)) + return res; + + if((res = s_mp_sub(c, a)) != MP_OKAY) + return res; + } + + SIGN(c) = !SIGN(b); + } + + if(USED(c) == 1 && DIGIT(c, 0) == 0) + SIGN(c) = MP_ZPOS; + + return MP_OKAY; + +} /* end mp_sub() */ + +/* }}} */ + +/* {{{ mp_mul(a, b, c) */ + +/* + mp_mul(a, b, c) + + Compute c = a * b. All parameters may be identical. + */ + +mp_err mp_mul(mp_int *a, mp_int *b, mp_int *c) +{ + mp_err res; + mp_sign sgn; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + sgn = (SIGN(a) == SIGN(b)) ? MP_ZPOS : MP_NEG; + + if(c == b) { + if((res = s_mp_mul(c, a)) != MP_OKAY) + return res; + + } else { + if((res = mp_copy(a, c)) != MP_OKAY) + return res; + + if((res = s_mp_mul(c, b)) != MP_OKAY) + return res; + } + + if(sgn == MP_ZPOS || s_mp_cmp_d(c, 0) == MP_EQ) + SIGN(c) = MP_ZPOS; + else + SIGN(c) = sgn; + + return MP_OKAY; + +} /* end mp_mul() */ + +/* }}} */ + +/* {{{ mp_mul_2d(a, d, c) */ + +/* + mp_mul_2d(a, d, c) + + Compute c = a * 2^d. a may be the same as c. + */ + +mp_err mp_mul_2d(mp_int *a, mp_digit d, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if((res = mp_copy(a, c)) != MP_OKAY) + return res; + + if(d == 0) + return MP_OKAY; + + return s_mp_mul_2d(c, d); + +} /* end mp_mul() */ + +/* }}} */ + +/* {{{ mp_sqr(a, b) */ + +#if MP_SQUARE +mp_err mp_sqr(mp_int *a, mp_int *b) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if((res = mp_copy(a, b)) != MP_OKAY) + return res; + + if((res = s_mp_sqr(b)) != MP_OKAY) + return res; + + SIGN(b) = MP_ZPOS; + + return MP_OKAY; + +} /* end mp_sqr() */ +#endif + +/* }}} */ + +/* {{{ mp_div(a, b, q, r) */ + +/* + mp_div(a, b, q, r) + + Compute q = a / b and r = a mod b. Input parameters may be re-used + as output parameters. If q or r is NULL, that portion of the + computation will be discarded (although it will still be computed) + + Pay no attention to the hacker behind the curtain. + */ + +mp_err mp_div(mp_int *a, mp_int *b, mp_int *q, mp_int *r) +{ + mp_err res; + mp_int qtmp, rtmp; + int cmp; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + if(mp_cmp_z(b) == MP_EQ) + return MP_RANGE; + + /* If a <= b, we can compute the solution without division, and + avoid any memory allocation + */ + if((cmp = s_mp_cmp(a, b)) < 0) { + if(r) { + if((res = mp_copy(a, r)) != MP_OKAY) + return res; + } + + if(q) + mp_zero(q); + + return MP_OKAY; + + } else if(cmp == 0) { + + /* Set quotient to 1, with appropriate sign */ + if(q) { + int qneg = (SIGN(a) != SIGN(b)); + + mp_set(q, 1); + if(qneg) + SIGN(q) = MP_NEG; + } + + if(r) + mp_zero(r); + + return MP_OKAY; + } + + /* If we get here, it means we actually have to do some division */ + + /* Set up some temporaries... */ + if((res = mp_init_copy(&qtmp, a)) != MP_OKAY) + return res; + if((res = mp_init_copy(&rtmp, b)) != MP_OKAY) + goto CLEANUP; + + if((res = s_mp_div(&qtmp, &rtmp)) != MP_OKAY) + goto CLEANUP; + + /* Compute the signs for the output */ + SIGN(&rtmp) = SIGN(a); /* Sr = Sa */ + if(SIGN(a) == SIGN(b)) + SIGN(&qtmp) = MP_ZPOS; /* Sq = MP_ZPOS if Sa = Sb */ + else + SIGN(&qtmp) = MP_NEG; /* Sq = MP_NEG if Sa != Sb */ + + if(s_mp_cmp_d(&qtmp, 0) == MP_EQ) + SIGN(&qtmp) = MP_ZPOS; + if(s_mp_cmp_d(&rtmp, 0) == MP_EQ) + SIGN(&rtmp) = MP_ZPOS; + + /* Copy output, if it is needed */ + if(q) + s_mp_exch(&qtmp, q); + + if(r) + s_mp_exch(&rtmp, r); + +CLEANUP: + mp_clear(&rtmp); + mp_clear(&qtmp); + + return res; + +} /* end mp_div() */ + +/* }}} */ + +/* {{{ mp_div_2d(a, d, q, r) */ + +mp_err mp_div_2d(mp_int *a, mp_digit d, mp_int *q, mp_int *r) +{ + mp_err res; + + ARGCHK(a != NULL, MP_BADARG); + + if(q) { + if((res = mp_copy(a, q)) != MP_OKAY) + return res; + + s_mp_div_2d(q, d); + } + + if(r) { + if((res = mp_copy(a, r)) != MP_OKAY) + return res; + + s_mp_mod_2d(r, d); + } + + return MP_OKAY; + +} /* end mp_div_2d() */ + +/* }}} */ + +/* {{{ mp_expt(a, b, c) */ + +/* + mp_expt(a, b, c) + + Compute c = a ** b, that is, raise a to the b power. Uses a + standard iterative square-and-multiply technique. + */ + +mp_err mp_expt(mp_int *a, mp_int *b, mp_int *c) +{ + mp_int s, x; + mp_err res; + mp_digit d; + int dig, bit; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + if(mp_cmp_z(b) < 0) + return MP_RANGE; + + if((res = mp_init(&s)) != MP_OKAY) + return res; + + mp_set(&s, 1); + + if((res = mp_init_copy(&x, a)) != MP_OKAY) + goto X; + + /* Loop over low-order digits in ascending order */ + for(dig = 0; dig < (USED(b) - 1); dig++) { + d = DIGIT(b, dig); + + /* Loop over bits of each non-maximal digit */ + for(bit = 0; bit < DIGIT_BIT; bit++) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY) + goto CLEANUP; + } + + d >>= 1; + + if((res = s_mp_sqr(&x)) != MP_OKAY) + goto CLEANUP; + } + } + + /* Consider now the last digit... */ + d = DIGIT(b, dig); + + while(d) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY) + goto CLEANUP; + } + + d >>= 1; + + if((res = s_mp_sqr(&x)) != MP_OKAY) + goto CLEANUP; + } + + if(mp_iseven(b)) + SIGN(&s) = SIGN(a); + + res = mp_copy(&s, c); + +CLEANUP: + mp_clear(&x); +X: + mp_clear(&s); + + return res; + +} /* end mp_expt() */ + +/* }}} */ + +/* {{{ mp_2expt(a, k) */ + +/* Compute a = 2^k */ + +mp_err mp_2expt(mp_int *a, mp_digit k) +{ + ARGCHK(a != NULL, MP_BADARG); + + return s_mp_2expt(a, k); + +} /* end mp_2expt() */ + +/* }}} */ + +/* {{{ mp_mod(a, m, c) */ + +/* + mp_mod(a, m, c) + + Compute c = a (mod m). Result will always be 0 <= c < m. + */ + +mp_err mp_mod(mp_int *a, mp_int *m, mp_int *c) +{ + mp_err res; + int mag; + + ARGCHK(a != NULL && m != NULL && c != NULL, MP_BADARG); + + if(SIGN(m) == MP_NEG) + return MP_RANGE; + + /* + If |a| > m, we need to divide to get the remainder and take the + absolute value. + + If |a| < m, we don't need to do any division, just copy and adjust + the sign (if a is negative). + + If |a| == m, we can simply set the result to zero. + + This order is intended to minimize the average path length of the + comparison chain on common workloads -- the most frequent cases are + that |a| != m, so we do those first. + */ + if((mag = s_mp_cmp(a, m)) > 0) { + if((res = mp_div(a, m, NULL, c)) != MP_OKAY) + return res; + + if(SIGN(c) == MP_NEG) { + if((res = mp_add(c, m, c)) != MP_OKAY) + return res; + } + + } else if(mag < 0) { + if((res = mp_copy(a, c)) != MP_OKAY) + return res; + + if(mp_cmp_z(a) < 0) { + if((res = mp_add(c, m, c)) != MP_OKAY) + return res; + + } + + } else { + mp_zero(c); + + } + + return MP_OKAY; + +} /* end mp_mod() */ + +/* }}} */ + +/* {{{ mp_mod_d(a, d, c) */ + +/* + mp_mod_d(a, d, c) + + Compute c = a (mod d). Result will always be 0 <= c < d + */ +mp_err mp_mod_d(mp_int *a, mp_digit d, mp_digit *c) +{ + mp_err res; + mp_digit rem; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if(s_mp_cmp_d(a, d) > 0) { + if((res = mp_div_d(a, d, NULL, &rem)) != MP_OKAY) + return res; + + } else { + if(SIGN(a) == MP_NEG) + rem = d - DIGIT(a, 0); + else + rem = DIGIT(a, 0); + } + + if(c) + *c = rem; + + return MP_OKAY; + +} /* end mp_mod_d() */ + +/* }}} */ + +/* {{{ mp_sqrt(a, b) */ + +/* + mp_sqrt(a, b) + + Compute the integer square root of a, and store the result in b. + Uses an integer-arithmetic version of Newton's iterative linear + approximation technique to determine this value; the result has the + following two properties: + + b^2 <= a + (b+1)^2 >= a + + It is a range error to pass a negative value. + */ +mp_err mp_sqrt(mp_int *a, mp_int *b) +{ + mp_int x, t; + mp_err res; + + ARGCHK(a != NULL && b != NULL, MP_BADARG); + + /* Cannot take square root of a negative value */ + if(SIGN(a) == MP_NEG) + return MP_RANGE; + + /* Special cases for zero and one, trivial */ + if(mp_cmp_d(a, 0) == MP_EQ || mp_cmp_d(a, 1) == MP_EQ) + return mp_copy(a, b); + + /* Initialize the temporaries we'll use below */ + if((res = mp_init_size(&t, USED(a))) != MP_OKAY) + return res; + + /* Compute an initial guess for the iteration as a itself */ + if((res = mp_init_copy(&x, a)) != MP_OKAY) + goto X; + +s_mp_rshd(&x, (USED(&x)/2)+1); +mp_add_d(&x, 1, &x); + + for(;;) { + /* t = (x * x) - a */ + mp_copy(&x, &t); /* can't fail, t is big enough for original x */ + if((res = mp_sqr(&t, &t)) != MP_OKAY || + (res = mp_sub(&t, a, &t)) != MP_OKAY) + goto CLEANUP; + + /* t = t / 2x */ + s_mp_mul_2(&x); + if((res = mp_div(&t, &x, &t, NULL)) != MP_OKAY) + goto CLEANUP; + s_mp_div_2(&x); + + /* Terminate the loop, if the quotient is zero */ + if(mp_cmp_z(&t) == MP_EQ) + break; + + /* x = x - t */ + if((res = mp_sub(&x, &t, &x)) != MP_OKAY) + goto CLEANUP; + + } + + /* Copy result to output parameter */ + mp_sub_d(&x, 1, &x); + s_mp_exch(&x, b); + + CLEANUP: + mp_clear(&x); + X: + mp_clear(&t); + + return res; + +} /* end mp_sqrt() */ + +/* }}} */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ Modular arithmetic */ + +#if MP_MODARITH +/* {{{ mp_addmod(a, b, m, c) */ + +/* + mp_addmod(a, b, m, c) + + Compute c = (a + b) mod m + */ + +mp_err mp_addmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG); + + if((res = mp_add(a, b, c)) != MP_OKAY) + return res; + if((res = mp_mod(c, m, c)) != MP_OKAY) + return res; + + return MP_OKAY; + +} + +/* }}} */ + +/* {{{ mp_submod(a, b, m, c) */ + +/* + mp_submod(a, b, m, c) + + Compute c = (a - b) mod m + */ + +mp_err mp_submod(mp_int *a, mp_int *b, mp_int *m, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG); + + if((res = mp_sub(a, b, c)) != MP_OKAY) + return res; + if((res = mp_mod(c, m, c)) != MP_OKAY) + return res; + + return MP_OKAY; + +} + +/* }}} */ + +/* {{{ mp_mulmod(a, b, m, c) */ + +/* + mp_mulmod(a, b, m, c) + + Compute c = (a * b) mod m + */ + +mp_err mp_mulmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && b != NULL && m != NULL && c != NULL, MP_BADARG); + + if((res = mp_mul(a, b, c)) != MP_OKAY) + return res; + if((res = mp_mod(c, m, c)) != MP_OKAY) + return res; + + return MP_OKAY; + +} + +/* }}} */ + +/* {{{ mp_sqrmod(a, m, c) */ + +#if MP_SQUARE +mp_err mp_sqrmod(mp_int *a, mp_int *m, mp_int *c) +{ + mp_err res; + + ARGCHK(a != NULL && m != NULL && c != NULL, MP_BADARG); + + if((res = mp_sqr(a, c)) != MP_OKAY) + return res; + if((res = mp_mod(c, m, c)) != MP_OKAY) + return res; + + return MP_OKAY; + +} /* end mp_sqrmod() */ +#endif + +/* }}} */ + +/* {{{ mp_exptmod(a, b, m, c) */ + +/* + mp_exptmod(a, b, m, c) + + Compute c = (a ** b) mod m. Uses a standard square-and-multiply + method with modular reductions at each step. (This is basically the + same code as mp_expt(), except for the addition of the reductions) + + The modular reductions are done using Barrett's algorithm (see + s_mp_reduce() below for details) + */ + +mp_err mp_exptmod(mp_int *a, mp_int *b, mp_int *m, mp_int *c) +{ + mp_int s, x, mu; + mp_err res; + mp_digit d, *db = DIGITS(b); + mp_size ub = USED(b); + int dig, bit; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + if(mp_cmp_z(b) < 0 || mp_cmp_z(m) <= 0) + return MP_RANGE; + + if((res = mp_init(&s)) != MP_OKAY) + return res; + if((res = mp_init_copy(&x, a)) != MP_OKAY) + goto X; + if((res = mp_mod(&x, m, &x)) != MP_OKAY || + (res = mp_init(&mu)) != MP_OKAY) + goto MU; + + mp_set(&s, 1); + + /* mu = b^2k / m */ + s_mp_add_d(&mu, 1); + s_mp_lshd(&mu, 2 * USED(m)); + if((res = mp_div(&mu, m, &mu, NULL)) != MP_OKAY) + goto CLEANUP; + + /* Loop over digits of b in ascending order, except highest order */ + for(dig = 0; dig < (ub - 1); dig++) { + d = *db++; + + /* Loop over the bits of the lower-order digits */ + for(bit = 0; bit < DIGIT_BIT; bit++) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY) + goto CLEANUP; + if((res = s_mp_reduce(&s, m, &mu)) != MP_OKAY) + goto CLEANUP; + } + + d >>= 1; + + if((res = s_mp_sqr(&x)) != MP_OKAY) + goto CLEANUP; + if((res = s_mp_reduce(&x, m, &mu)) != MP_OKAY) + goto CLEANUP; + } + } + + /* Now do the last digit... */ + d = *db; + + while(d) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY) + goto CLEANUP; + if((res = s_mp_reduce(&s, m, &mu)) != MP_OKAY) + goto CLEANUP; + } + + d >>= 1; + + if((res = s_mp_sqr(&x)) != MP_OKAY) + goto CLEANUP; + if((res = s_mp_reduce(&x, m, &mu)) != MP_OKAY) + goto CLEANUP; + } + + s_mp_exch(&s, c); + + CLEANUP: + mp_clear(&mu); + MU: + mp_clear(&x); + X: + mp_clear(&s); + + return res; + +} /* end mp_exptmod() */ + +/* }}} */ + +/* {{{ mp_exptmod_d(a, d, m, c) */ + +mp_err mp_exptmod_d(mp_int *a, mp_digit d, mp_int *m, mp_int *c) +{ + mp_int s, x; + mp_err res; + + ARGCHK(a != NULL && c != NULL, MP_BADARG); + + if((res = mp_init(&s)) != MP_OKAY) + return res; + if((res = mp_init_copy(&x, a)) != MP_OKAY) + goto X; + + mp_set(&s, 1); + + while(d != 0) { + if(d & 1) { + if((res = s_mp_mul(&s, &x)) != MP_OKAY || + (res = mp_mod(&s, m, &s)) != MP_OKAY) + goto CLEANUP; + } + + d /= 2; + + if((res = s_mp_sqr(&x)) != MP_OKAY || + (res = mp_mod(&x, m, &x)) != MP_OKAY) + goto CLEANUP; + } + + s_mp_exch(&s, c); + +CLEANUP: + mp_clear(&x); +X: + mp_clear(&s); + + return res; + +} /* end mp_exptmod_d() */ + +/* }}} */ +#endif /* if MP_MODARITH */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ Comparison functions */ + +/* {{{ mp_cmp_z(a) */ + +/* + mp_cmp_z(a) + + Compare a <=> 0. Returns <0 if a<0, 0 if a=0, >0 if a>0. + */ + +int mp_cmp_z(mp_int *a) +{ + if(SIGN(a) == MP_NEG) + return MP_LT; + else if(USED(a) == 1 && DIGIT(a, 0) == 0) + return MP_EQ; + else + return MP_GT; + +} /* end mp_cmp_z() */ + +/* }}} */ + +/* {{{ mp_cmp_d(a, d) */ + +/* + mp_cmp_d(a, d) + + Compare a <=> d. Returns <0 if a<d, 0 if a=d, >0 if a>d + */ + +int mp_cmp_d(mp_int *a, mp_digit d) +{ + ARGCHK(a != NULL, MP_EQ); + + if(SIGN(a) == MP_NEG) + return MP_LT; + + return s_mp_cmp_d(a, d); + +} /* end mp_cmp_d() */ + +/* }}} */ + +/* {{{ mp_cmp(a, b) */ + +int mp_cmp(mp_int *a, mp_int *b) +{ + ARGCHK(a != NULL && b != NULL, MP_EQ); + + if(SIGN(a) == SIGN(b)) { + int mag; + + if((mag = s_mp_cmp(a, b)) == MP_EQ) + return MP_EQ; + + if(SIGN(a) == MP_ZPOS) + return mag; + else + return -mag; + + } else if(SIGN(a) == MP_ZPOS) { + return MP_GT; + } else { + return MP_LT; + } + +} /* end mp_cmp() */ + +/* }}} */ + +/* {{{ mp_cmp_mag(a, b) */ + +/* + mp_cmp_mag(a, b) + + Compares |a| <=> |b|, and returns an appropriate comparison result + */ + +int mp_cmp_mag(mp_int *a, mp_int *b) +{ + ARGCHK(a != NULL && b != NULL, MP_EQ); + + return s_mp_cmp(a, b); + +} /* end mp_cmp_mag() */ + +/* }}} */ + +/* {{{ mp_cmp_int(a, z) */ + +/* + This just converts z to an mp_int, and uses the existing comparison + routines. This is sort of inefficient, but it's not clear to me how + frequently this wil get used anyway. For small positive constants, + you can always use mp_cmp_d(), and for zero, there is mp_cmp_z(). + */ +int mp_cmp_int(mp_int *a, long z) +{ + mp_int tmp; + int out; + + ARGCHK(a != NULL, MP_EQ); + + mp_init(&tmp); mp_set_int(&tmp, z); + out = mp_cmp(a, &tmp); + mp_clear(&tmp); + + return out; + +} /* end mp_cmp_int() */ + +/* }}} */ + +/* {{{ mp_isodd(a) */ + +/* + mp_isodd(a) + + Returns a true (non-zero) value if a is odd, false (zero) otherwise. + */ +int mp_isodd(mp_int *a) +{ + ARGCHK(a != NULL, 0); + + return (DIGIT(a, 0) & 1); + +} /* end mp_isodd() */ + +/* }}} */ + +/* {{{ mp_iseven(a) */ + +int mp_iseven(mp_int *a) +{ + return !mp_isodd(a); + +} /* end mp_iseven() */ + +/* }}} */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ Number theoretic functions */ + +#if MP_NUMTH +/* {{{ mp_gcd(a, b, c) */ + +/* + Like the old mp_gcd() function, except computes the GCD using the + binary algorithm due to Josef Stein in 1961 (via Knuth). + */ +mp_err mp_gcd(mp_int *a, mp_int *b, mp_int *c) +{ + mp_err res; + mp_int u, v, t; + mp_size k = 0; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + if(mp_cmp_z(a) == MP_EQ && mp_cmp_z(b) == MP_EQ) + return MP_RANGE; + if(mp_cmp_z(a) == MP_EQ) { + return mp_copy(b, c); + } else if(mp_cmp_z(b) == MP_EQ) { + return mp_copy(a, c); + } + + if((res = mp_init(&t)) != MP_OKAY) + return res; + if((res = mp_init_copy(&u, a)) != MP_OKAY) + goto U; + if((res = mp_init_copy(&v, b)) != MP_OKAY) + goto V; + + SIGN(&u) = MP_ZPOS; + SIGN(&v) = MP_ZPOS; + + /* Divide out common factors of 2 until at least 1 of a, b is even */ + while(mp_iseven(&u) && mp_iseven(&v)) { + s_mp_div_2(&u); + s_mp_div_2(&v); + ++k; + } + + /* Initialize t */ + if(mp_isodd(&u)) { + if((res = mp_copy(&v, &t)) != MP_OKAY) + goto CLEANUP; + + /* t = -v */ + if(SIGN(&v) == MP_ZPOS) + SIGN(&t) = MP_NEG; + else + SIGN(&t) = MP_ZPOS; + + } else { + if((res = mp_copy(&u, &t)) != MP_OKAY) + goto CLEANUP; + + } + + for(;;) { + while(mp_iseven(&t)) { + s_mp_div_2(&t); + } + + if(mp_cmp_z(&t) == MP_GT) { + if((res = mp_copy(&t, &u)) != MP_OKAY) + goto CLEANUP; + + } else { + if((res = mp_copy(&t, &v)) != MP_OKAY) + goto CLEANUP; + + /* v = -t */ + if(SIGN(&t) == MP_ZPOS) + SIGN(&v) = MP_NEG; + else + SIGN(&v) = MP_ZPOS; + } + + if((res = mp_sub(&u, &v, &t)) != MP_OKAY) + goto CLEANUP; + + if(s_mp_cmp_d(&t, 0) == MP_EQ) + break; + } + + s_mp_2expt(&v, k); /* v = 2^k */ + res = mp_mul(&u, &v, c); /* c = u * v */ + + CLEANUP: + mp_clear(&v); + V: + mp_clear(&u); + U: + mp_clear(&t); + + return res; + +} /* end mp_bgcd() */ + +/* }}} */ + +/* {{{ mp_lcm(a, b, c) */ + +/* We compute the least common multiple using the rule: + + ab = [a, b](a, b) + + ... by computing the product, and dividing out the gcd. + */ + +mp_err mp_lcm(mp_int *a, mp_int *b, mp_int *c) +{ + mp_int gcd, prod; + mp_err res; + + ARGCHK(a != NULL && b != NULL && c != NULL, MP_BADARG); + + /* Set up temporaries */ + if((res = mp_init(&gcd)) != MP_OKAY) + return res; + if((res = mp_init(&prod)) != MP_OKAY) + goto GCD; + + if((res = mp_mul(a, b, &prod)) != MP_OKAY) + goto CLEANUP; + if((res = mp_gcd(a, b, &gcd)) != MP_OKAY) + goto CLEANUP; + + res = mp_div(&prod, &gcd, c, NULL); + + CLEANUP: + mp_clear(&prod); + GCD: + mp_clear(&gcd); + + return res; + +} /* end mp_lcm() */ + +/* }}} */ + +/* {{{ mp_xgcd(a, b, g, x, y) */ + +/* + mp_xgcd(a, b, g, x, y) + + Compute g = (a, b) and values x and y satisfying Bezout's identity + (that is, ax + by = g). This uses the extended binary GCD algorithm + based on the Stein algorithm used for mp_gcd() + */ + +mp_err mp_xgcd(mp_int *a, mp_int *b, mp_int *g, mp_int *x, mp_int *y) +{ + mp_int gx, xc, yc, u, v, A, B, C, D; + mp_int *clean[9]; + mp_err res; + int last = -1; + + if(mp_cmp_z(b) == 0) + return MP_RANGE; + + /* Initialize all these variables we need */ + if((res = mp_init(&u)) != MP_OKAY) goto CLEANUP; + clean[++last] = &u; + if((res = mp_init(&v)) != MP_OKAY) goto CLEANUP; + clean[++last] = &v; + if((res = mp_init(&gx)) != MP_OKAY) goto CLEANUP; + clean[++last] = &gx; + if((res = mp_init(&A)) != MP_OKAY) goto CLEANUP; + clean[++last] = &A; + if((res = mp_init(&B)) != MP_OKAY) goto CLEANUP; + clean[++last] = &B; + if((res = mp_init(&C)) != MP_OKAY) goto CLEANUP; + clean[++last] = &C; + if((res = mp_init(&D)) != MP_OKAY) goto CLEANUP; + clean[++last] = &D; + if((res = mp_init_copy(&xc, a)) != MP_OKAY) goto CLEANUP; + clean[++last] = &xc; + mp_abs(&xc, &xc); + if((res = mp_init_copy(&yc, b)) != MP_OKAY) goto CLEANUP; + clean[++last] = &yc; + mp_abs(&yc, &yc); + + mp_set(&gx, 1); + + /* Divide by two until at least one of them is even */ + while(mp_iseven(&xc) && mp_iseven(&yc)) { + s_mp_div_2(&xc); + s_mp_div_2(&yc); + if((res = s_mp_mul_2(&gx)) != MP_OKAY) + goto CLEANUP; + } + + mp_copy(&xc, &u); + mp_copy(&yc, &v); + mp_set(&A, 1); mp_set(&D, 1); + + /* Loop through binary GCD algorithm */ + for(;;) { + while(mp_iseven(&u)) { + s_mp_div_2(&u); + + if(mp_iseven(&A) && mp_iseven(&B)) { + s_mp_div_2(&A); s_mp_div_2(&B); + } else { + if((res = mp_add(&A, &yc, &A)) != MP_OKAY) goto CLEANUP; + s_mp_div_2(&A); + if((res = mp_sub(&B, &xc, &B)) != MP_OKAY) goto CLEANUP; + s_mp_div_2(&B); + } + } + + while(mp_iseven(&v)) { + s_mp_div_2(&v); + + if(mp_iseven(&C) && mp_iseven(&D)) { + s_mp_div_2(&C); s_mp_div_2(&D); + } else { + if((res = mp_add(&C, &yc, &C)) != MP_OKAY) goto CLEANUP; + s_mp_div_2(&C); + if((res = mp_sub(&D, &xc, &D)) != MP_OKAY) goto CLEANUP; + s_mp_div_2(&D); + } + } + + if(mp_cmp(&u, &v) >= 0) { + if((res = mp_sub(&u, &v, &u)) != MP_OKAY) goto CLEANUP; + if((res = mp_sub(&A, &C, &A)) != MP_OKAY) goto CLEANUP; + if((res = mp_sub(&B, &D, &B)) != MP_OKAY) goto CLEANUP; + + } else { + if((res = mp_sub(&v, &u, &v)) != MP_OKAY) goto CLEANUP; + if((res = mp_sub(&C, &A, &C)) != MP_OKAY) goto CLEANUP; + if((res = mp_sub(&D, &B, &D)) != MP_OKAY) goto CLEANUP; + + } + + /* If we're done, copy results to output */ + if(mp_cmp_z(&u) == 0) { + if(x) + if((res = mp_copy(&C, x)) != MP_OKAY) goto CLEANUP; + + if(y) + if((res = mp_copy(&D, y)) != MP_OKAY) goto CLEANUP; + + if(g) + if((res = mp_mul(&gx, &v, g)) != MP_OKAY) goto CLEANUP; + + break; + } + } + + CLEANUP: + while(last >= 0) + mp_clear(clean[last--]); + + return res; + +} /* end mp_xgcd() */ + +/* }}} */ + +/* {{{ mp_invmod(a, m, c) */ + +/* + mp_invmod(a, m, c) + + Compute c = a^-1 (mod m), if there is an inverse for a (mod m). + This is equivalent to the question of whether (a, m) = 1. If not, + MP_UNDEF is returned, and there is no inverse. + */ + +mp_err mp_invmod(mp_int *a, mp_int *m, mp_int *c) +{ + mp_int g, x; + mp_err res; + + ARGCHK(a && m && c, MP_BADARG); + + if(mp_cmp_z(a) == 0 || mp_cmp_z(m) == 0) + return MP_RANGE; + + if((res = mp_init(&g)) != MP_OKAY) + return res; + if((res = mp_init(&x)) != MP_OKAY) + goto X; + + if((res = mp_xgcd(a, m, &g, &x, NULL)) != MP_OKAY) + goto CLEANUP; + + if(mp_cmp_d(&g, 1) != MP_EQ) { + res = MP_UNDEF; + goto CLEANUP; + } + + res = mp_mod(&x, m, c); + SIGN(c) = SIGN(a); + +CLEANUP: + mp_clear(&x); +X: + mp_clear(&g); + + return res; + +} /* end mp_invmod() */ + +/* }}} */ +#endif /* if MP_NUMTH */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ mp_print(mp, ofp) */ + +#if MP_IOFUNC +/* + mp_print(mp, ofp) + + Print a textual representation of the given mp_int on the output + stream 'ofp'. Output is generated using the internal radix. + */ + +void mp_print(mp_int *mp, FILE *ofp) +{ + int ix; + + if(mp == NULL || ofp == NULL) + return; + + fputc((SIGN(mp) == MP_NEG) ? '-' : '+', ofp); + + for(ix = USED(mp) - 1; ix >= 0; ix--) { + fprintf(ofp, DIGIT_FMT, DIGIT(mp, ix)); + } + +} /* end mp_print() */ + +#endif /* if MP_IOFUNC */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* {{{ More I/O Functions */ + +/* {{{ mp_read_signed_bin(mp, str, len) */ + +/* + mp_read_signed_bin(mp, str, len) + + Read in a raw value (base 256) into the given mp_int + */ + +mp_err mp_read_signed_bin(mp_int *mp, unsigned char *str, int len) +{ + mp_err res; + + ARGCHK(mp != NULL && str != NULL && len > 0, MP_BADARG); + + if((res = mp_read_unsigned_bin(mp, str + 1, len - 1)) == MP_OKAY) { + /* Get sign from first byte */ + if(str[0]) + SIGN(mp) = MP_NEG; + else + SIGN(mp) = MP_ZPOS; + } + + return res; + +} /* end mp_read_signed_bin() */ + +/* }}} */ + +/* {{{ mp_signed_bin_size(mp) */ + +int mp_signed_bin_size(mp_int *mp) +{ + ARGCHK(mp != NULL, 0); + + return mp_unsigned_bin_size(mp) + 1; + +} /* end mp_signed_bin_size() */ + +/* }}} */ + +/* {{{ mp_to_signed_bin(mp, str) */ + +mp_err mp_to_signed_bin(mp_int *mp, unsigned char *str) +{ + ARGCHK(mp != NULL && str != NULL, MP_BADARG); + + /* Caller responsible for allocating enough memory (use mp_raw_size(mp)) */ + str[0] = (char)SIGN(mp); + + return mp_to_unsigned_bin(mp, str + 1); + +} /* end mp_to_signed_bin() */ + +/* }}} */ + +/* {{{ mp_read_unsigned_bin(mp, str, len) */ + +/* + mp_read_unsigned_bin(mp, str, len) + + Read in an unsigned value (base 256) into the given mp_int + */ + +mp_err mp_read_unsigned_bin(mp_int *mp, unsigned char *str, int len) +{ + int ix; + mp_err res; + + ARGCHK(mp != NULL && str != NULL && len > 0, MP_BADARG); + + mp_zero(mp); + + for(ix = 0; ix < len; ix++) { + if((res = s_mp_mul_2d(mp, CHAR_BIT)) != MP_OKAY) + return res; + + if((res = mp_add_d(mp, str[ix], mp)) != MP_OKAY) + return res; + } + + return MP_OKAY; + +} /* end mp_read_unsigned_bin() */ + +/* }}} */ + +/* {{{ mp_unsigned_bin_size(mp) */ + +int mp_unsigned_bin_size(mp_int *mp) +{ + mp_digit topdig; + int count; + + ARGCHK(mp != NULL, 0); + + /* Special case for the value zero */ + if(USED(mp) == 1 && DIGIT(mp, 0) == 0) + return 1; + + count = (USED(mp) - 1) * sizeof(mp_digit); + topdig = DIGIT(mp, USED(mp) - 1); + + while(topdig != 0) { + ++count; + topdig >>= CHAR_BIT; + } + + return count; + +} /* end mp_unsigned_bin_size() */ + +/* }}} */ + +/* {{{ mp_to_unsigned_bin(mp, str) */ + +mp_err mp_to_unsigned_bin(mp_int *mp, unsigned char *str) +{ + mp_digit *dp, *end, d; + unsigned char *spos; + + ARGCHK(mp != NULL && str != NULL, MP_BADARG); + + dp = DIGITS(mp); + end = dp + USED(mp) - 1; + spos = str; + + /* Special case for zero, quick test */ + if(dp == end && *dp == 0) { + *str = '\0'; + return MP_OKAY; + } + + /* Generate digits in reverse order */ + while(dp < end) { + int ix; + + d = *dp; + for(ix = 0; ix < sizeof(mp_digit); ++ix) { + *spos = d & UCHAR_MAX; + d >>= CHAR_BIT; + ++spos; + } + + ++dp; + } + + /* Now handle last digit specially, high order zeroes are not written */ + d = *end; + while(d != 0) { + *spos = d & UCHAR_MAX; + d >>= CHAR_BIT; + ++spos; + } + + /* Reverse everything to get digits in the correct order */ + while(--spos > str) { + unsigned char t = *str; + *str = *spos; + *spos = t; + + ++str; + } + + return MP_OKAY; + +} /* end mp_to_unsigned_bin() */ + +/* }}} */ + +/* {{{ mp_count_bits(mp) */ + +int mp_count_bits(mp_int *mp) +{ + int len; + mp_digit d; + + ARGCHK(mp != NULL, MP_BADARG); + + len = DIGIT_BIT * (USED(mp) - 1); + d = DIGIT(mp, USED(mp) - 1); + + while(d != 0) { + ++len; + d >>= 1; + } + + return len; + +} /* end mp_count_bits() */ + +/* }}} */ + +/* {{{ mp_read_radix(mp, str, radix) */ + +/* + mp_read_radix(mp, str, radix) + + Read an integer from the given string, and set mp to the resulting + value. The input is presumed to be in base 10. Leading non-digit + characters are ignored, and the function reads until a non-digit + character or the end of the string. + */ + +mp_err mp_read_radix(mp_int *mp, unsigned char *str, int radix) +{ + int ix = 0, val = 0; + mp_err res; + mp_sign sig = MP_ZPOS; + + ARGCHK(mp != NULL && str != NULL && radix >= 2 && radix <= MAX_RADIX, + MP_BADARG); + + mp_zero(mp); + + /* Skip leading non-digit characters until a digit or '-' or '+' */ + while(str[ix] && + (s_mp_tovalue(str[ix], radix) < 0) && + str[ix] != '-' && + str[ix] != '+') { + ++ix; + } + + if(str[ix] == '-') { + sig = MP_NEG; + ++ix; + } else if(str[ix] == '+') { + sig = MP_ZPOS; /* this is the default anyway... */ + ++ix; + } + + while((val = s_mp_tovalue(str[ix], radix)) >= 0) { + if((res = s_mp_mul_d(mp, radix)) != MP_OKAY) + return res; + if((res = s_mp_add_d(mp, val)) != MP_OKAY) + return res; + ++ix; + } + + if(s_mp_cmp_d(mp, 0) == MP_EQ) + SIGN(mp) = MP_ZPOS; + else + SIGN(mp) = sig; + + return MP_OKAY; + +} /* end mp_read_radix() */ + +/* }}} */ + +/* {{{ mp_radix_size(mp, radix) */ + +int mp_radix_size(mp_int *mp, int radix) +{ + int len; + ARGCHK(mp != NULL, 0); + + len = s_mp_outlen(mp_count_bits(mp), radix) + 1; /* for NUL terminator */ + + if(mp_cmp_z(mp) < 0) + ++len; /* for sign */ + + return len; + +} /* end mp_radix_size() */ + +/* }}} */ + +/* {{{ mp_value_radix_size(num, qty, radix) */ + +/* num = number of digits + qty = number of bits per digit + radix = target base + + Return the number of digits in the specified radix that would be + needed to express 'num' digits of 'qty' bits each. + */ +int mp_value_radix_size(int num, int qty, int radix) +{ + ARGCHK(num >= 0 && qty > 0 && radix >= 2 && radix <= MAX_RADIX, 0); + + return s_mp_outlen(num * qty, radix); + +} /* end mp_value_radix_size() */ + +/* }}} */ + +/* {{{ mp_toradix(mp, str, radix) */ + +mp_err mp_toradix(mp_int *mp, unsigned char *str, int radix) +{ + int ix, pos = 0; + + ARGCHK(mp != NULL && str != NULL, MP_BADARG); + ARGCHK(radix > 1 && radix <= MAX_RADIX, MP_RANGE); + + if(mp_cmp_z(mp) == MP_EQ) { + str[0] = '0'; + str[1] = '\0'; + } else { + mp_err res; + mp_int tmp; + mp_sign sgn; + mp_digit rem, rdx = (mp_digit)radix; + char ch; + + if((res = mp_init_copy(&tmp, mp)) != MP_OKAY) + return res; + + /* Save sign for later, and take absolute value */ + sgn = SIGN(&tmp); SIGN(&tmp) = MP_ZPOS; + + /* Generate output digits in reverse order */ + while(mp_cmp_z(&tmp) != 0) { + if((res = s_mp_div_d(&tmp, rdx, &rem)) != MP_OKAY) { + mp_clear(&tmp); + return res; + } + + /* Generate digits, use capital letters */ + ch = s_mp_todigit(rem, radix, 0); + + str[pos++] = ch; + } + + /* Add - sign if original value was negative */ + if(sgn == MP_NEG) + str[pos++] = '-'; + + /* Add trailing NUL to end the string */ + str[pos--] = '\0'; + + /* Reverse the digits and sign indicator */ + ix = 0; + while(ix < pos) { + char tmp = str[ix]; + + str[ix] = str[pos]; + str[pos] = tmp; + ++ix; + --pos; + } + + mp_clear(&tmp); + } + + return MP_OKAY; + +} /* end mp_toradix() */ + +/* }}} */ + +/* {{{ mp_char2value(ch, r) */ + +int mp_char2value(char ch, int r) +{ + return s_mp_tovalue(ch, r); + +} /* end mp_tovalue() */ + +/* }}} */ + +/* }}} */ + +/* {{{ mp_strerror(ec) */ + +/* + mp_strerror(ec) + + Return a string describing the meaning of error code 'ec'. The + string returned is allocated in static memory, so the caller should + not attempt to modify or free the memory associated with this + string. + */ +const char *mp_strerror(mp_err ec) +{ + int aec = (ec < 0) ? -ec : ec; + + /* Code values are negative, so the senses of these comparisons + are accurate */ + if(ec < MP_LAST_CODE || ec > MP_OKAY) { + return mp_err_string[0]; /* unknown error code */ + } else { + return mp_err_string[aec + 1]; + } + +} /* end mp_strerror() */ + +/* }}} */ + +/*========================================================================*/ +/*------------------------------------------------------------------------*/ +/* Static function definitions (internal use only) */ + +/* {{{ Memory management */ + +/* {{{ s_mp_grow(mp, min) */ + +/* Make sure there are at least 'min' digits allocated to mp */ +mp_err s_mp_grow(mp_int *mp, mp_size min) +{ + if(min > ALLOC(mp)) { + mp_digit *tmp; + + /* Set min to next nearest default precision block size */ + min = ((min + (s_mp_defprec - 1)) / s_mp_defprec) * s_mp_defprec; + + if((tmp = s_mp_alloc(min, sizeof(mp_digit))) == NULL) + return MP_MEM; + + s_mp_copy(DIGITS(mp), tmp, USED(mp)); + +#if MP_CRYPTO + s_mp_setz(DIGITS(mp), ALLOC(mp)); +#endif + s_mp_free(DIGITS(mp)); + DIGITS(mp) = tmp; + ALLOC(mp) = min; + } + + return MP_OKAY; + +} /* end s_mp_grow() */ + +/* }}} */ + +/* {{{ s_mp_pad(mp, min) */ + +/* Make sure the used size of mp is at least 'min', growing if needed */ +mp_err s_mp_pad(mp_int *mp, mp_size min) +{ + if(min > USED(mp)) { + mp_err res; + + /* Make sure there is room to increase precision */ + if(min > ALLOC(mp) && (res = s_mp_grow(mp, min)) != MP_OKAY) + return res; + + /* Increase precision; should already be 0-filled */ + USED(mp) = min; + } + + return MP_OKAY; + +} /* end s_mp_pad() */ + +/* }}} */ + +/* {{{ s_mp_setz(dp, count) */ + +#if MP_MACRO == 0 +/* Set 'count' digits pointed to by dp to be zeroes */ +void s_mp_setz(mp_digit *dp, mp_size count) +{ +#if MP_MEMSET == 0 + int ix; + + for(ix = 0; ix < count; ix++) + dp[ix] = 0; +#else + memset(dp, 0, count * sizeof(mp_digit)); +#endif + +} /* end s_mp_setz() */ +#endif + +/* }}} */ + +/* {{{ s_mp_copy(sp, dp, count) */ + +#if MP_MACRO == 0 +/* Copy 'count' digits from sp to dp */ +void s_mp_copy(mp_digit *sp, mp_digit *dp, mp_size count) +{ +#if MP_MEMCPY == 0 + int ix; + + for(ix = 0; ix < count; ix++) + dp[ix] = sp[ix]; +#else + memcpy(dp, sp, count * sizeof(mp_digit)); +#endif + +} /* end s_mp_copy() */ +#endif + +/* }}} */ + +/* {{{ s_mp_alloc(nb, ni) */ + +#if MP_MACRO == 0 +/* Allocate ni records of nb bytes each, and return a pointer to that */ +void *s_mp_alloc(size_t nb, size_t ni) +{ + return calloc(nb, ni); + +} /* end s_mp_alloc() */ +#endif + +/* }}} */ + +/* {{{ s_mp_free(ptr) */ + +#if MP_MACRO == 0 +/* Free the memory pointed to by ptr */ +void s_mp_free(void *ptr) +{ + if(ptr) + free(ptr); + +} /* end s_mp_free() */ +#endif + +/* }}} */ + +/* {{{ s_mp_clamp(mp) */ + +/* Remove leading zeroes from the given value */ +void s_mp_clamp(mp_int *mp) +{ + mp_size du = USED(mp); + mp_digit *zp = DIGITS(mp) + du - 1; + + while(du > 1 && !*zp--) + --du; + + USED(mp) = du; + +} /* end s_mp_clamp() */ + + +/* }}} */ + +/* {{{ s_mp_exch(a, b) */ + +/* Exchange the data for a and b; (b, a) = (a, b) */ +void s_mp_exch(mp_int *a, mp_int *b) +{ + mp_int tmp; + + tmp = *a; + *a = *b; + *b = tmp; + +} /* end s_mp_exch() */ + +/* }}} */ + +/* }}} */ + +/* {{{ Arithmetic helpers */ + +/* {{{ s_mp_lshd(mp, p) */ + +/* + Shift mp leftward by p digits, growing if needed, and zero-filling + the in-shifted digits at the right end. This is a convenient + alternative to multiplication by powers of the radix + */ + +mp_err s_mp_lshd(mp_int *mp, mp_size p) +{ + mp_err res; + mp_size pos; + mp_digit *dp; + int ix; + + if(p == 0) + return MP_OKAY; + + if((res = s_mp_pad(mp, USED(mp) + p)) != MP_OKAY) + return res; + + pos = USED(mp) - 1; + dp = DIGITS(mp); + + /* Shift all the significant figures over as needed */ + for(ix = pos - p; ix >= 0; ix--) + dp[ix + p] = dp[ix]; + + /* Fill the bottom digits with zeroes */ + for(ix = 0; ix < p; ix++) + dp[ix] = 0; + + return MP_OKAY; + +} /* end s_mp_lshd() */ + +/* }}} */ + +/* {{{ s_mp_rshd(mp, p) */ + +/* + Shift mp rightward by p digits. Maintains the invariant that + digits above the precision are all zero. Digits shifted off the + end are lost. Cannot fail. + */ + +void s_mp_rshd(mp_int *mp, mp_size p) +{ + mp_size ix; + mp_digit *dp; + + if(p == 0) + return; + + /* Shortcut when all digits are to be shifted off */ + if(p >= USED(mp)) { + s_mp_setz(DIGITS(mp), ALLOC(mp)); + USED(mp) = 1; + SIGN(mp) = MP_ZPOS; + return; + } + + /* Shift all the significant figures over as needed */ + dp = DIGITS(mp); + for(ix = p; ix < USED(mp); ix++) + dp[ix - p] = dp[ix]; + + /* Fill the top digits with zeroes */ + ix -= p; + while(ix < USED(mp)) + dp[ix++] = 0; + + /* Strip off any leading zeroes */ + s_mp_clamp(mp); + +} /* end s_mp_rshd() */ + +/* }}} */ + +/* {{{ s_mp_div_2(mp) */ + +/* Divide by two -- take advantage of radix properties to do it fast */ +void s_mp_div_2(mp_int *mp) +{ + s_mp_div_2d(mp, 1); + +} /* end s_mp_div_2() */ + +/* }}} */ + +/* {{{ s_mp_mul_2(mp) */ + +mp_err s_mp_mul_2(mp_int *mp) +{ + int ix; + mp_digit kin = 0, kout, *dp = DIGITS(mp); + mp_err res; + + /* Shift digits leftward by 1 bit */ + for(ix = 0; ix < USED(mp); ix++) { + kout = (dp[ix] >> (DIGIT_BIT - 1)) & 1; + dp[ix] = (dp[ix] << 1) | kin; + + kin = kout; + } + + /* Deal with rollover from last digit */ + if(kin) { + if(ix >= ALLOC(mp)) { + if((res = s_mp_grow(mp, ALLOC(mp) + 1)) != MP_OKAY) + return res; + dp = DIGITS(mp); + } + + dp[ix] = kin; + USED(mp) += 1; + } + + return MP_OKAY; + +} /* end s_mp_mul_2() */ + +/* }}} */ + +/* {{{ s_mp_mod_2d(mp, d) */ + +/* + Remainder the integer by 2^d, where d is a number of bits. This + amounts to a bitwise AND of the value, and does not require the full + division code + */ +void s_mp_mod_2d(mp_int *mp, mp_digit d) +{ + unsigned int ndig = (d / DIGIT_BIT), nbit = (d % DIGIT_BIT); + unsigned int ix; + mp_digit dmask, *dp = DIGITS(mp); + + if(ndig >= USED(mp)) + return; + + /* Flush all the bits above 2^d in its digit */ + dmask = (1 << nbit) - 1; + dp[ndig] &= dmask; + + /* Flush all digits above the one with 2^d in it */ + for(ix = ndig + 1; ix < USED(mp); ix++) + dp[ix] = 0; + + s_mp_clamp(mp); + +} /* end s_mp_mod_2d() */ + +/* }}} */ + +/* {{{ s_mp_mul_2d(mp, d) */ + +/* + Multiply by the integer 2^d, where d is a number of bits. This + amounts to a bitwise shift of the value, and does not require the + full multiplication code. + */ +mp_err s_mp_mul_2d(mp_int *mp, mp_digit d) +{ + mp_err res; + mp_digit save, next, mask, *dp; + mp_size used; + int ix; + + if((res = s_mp_lshd(mp, d / DIGIT_BIT)) != MP_OKAY) + return res; + + dp = DIGITS(mp); used = USED(mp); + d %= DIGIT_BIT; + + mask = (1 << d) - 1; + + /* If the shift requires another digit, make sure we've got one to + work with */ + if((dp[used - 1] >> (DIGIT_BIT - d)) & mask) { + if((res = s_mp_grow(mp, used + 1)) != MP_OKAY) + return res; + dp = DIGITS(mp); + } + + /* Do the shifting... */ + save = 0; + for(ix = 0; ix < used; ix++) { + next = (dp[ix] >> (DIGIT_BIT - d)) & mask; + dp[ix] = (dp[ix] << d) | save; + save = next; + } + + /* If, at this point, we have a nonzero carryout into the next + digit, we'll increase the size by one digit, and store it... + */ + if(save) { + dp[used] = save; + USED(mp) += 1; + } + + s_mp_clamp(mp); + return MP_OKAY; + +} /* end s_mp_mul_2d() */ + +/* }}} */ + +/* {{{ s_mp_div_2d(mp, d) */ + +/* + Divide the integer by 2^d, where d is a number of bits. This + amounts to a bitwise shift of the value, and does not require the + full division code (used in Barrett reduction, see below) + */ +void s_mp_div_2d(mp_int *mp, mp_digit d) +{ + int ix; + mp_digit save, next, mask, *dp = DIGITS(mp); + + s_mp_rshd(mp, d / DIGIT_BIT); + d %= DIGIT_BIT; + + mask = (1 << d) - 1; + + save = 0; + for(ix = USED(mp) - 1; ix >= 0; ix--) { + next = dp[ix] & mask; + dp[ix] = (dp[ix] >> d) | (save << (DIGIT_BIT - d)); + save = next; + } + + s_mp_clamp(mp); + +} /* end s_mp_div_2d() */ + +/* }}} */ + +/* {{{ s_mp_norm(a, b) */ + +/* + s_mp_norm(a, b) + + Normalize a and b for division, where b is the divisor. In order + that we might make good guesses for quotient digits, we want the + leading digit of b to be at least half the radix, which we + accomplish by multiplying a and b by a constant. This constant is + returned (so that it can be divided back out of the remainder at the + end of the division process). + + We multiply by the smallest power of 2 that gives us a leading digit + at least half the radix. By choosing a power of 2, we simplify the + multiplication and division steps to simple shifts. + */ +mp_digit s_mp_norm(mp_int *a, mp_int *b) +{ + mp_digit t, d = 0; + + t = DIGIT(b, USED(b) - 1); + while(t < (RADIX / 2)) { + t <<= 1; + ++d; + } + + if(d != 0) { + s_mp_mul_2d(a, d); + s_mp_mul_2d(b, d); + } + + return d; + +} /* end s_mp_norm() */ + +/* }}} */ + +/* }}} */ + +/* {{{ Primitive digit arithmetic */ + +/* {{{ s_mp_add_d(mp, d) */ + +/* Add d to |mp| in place */ +mp_err s_mp_add_d(mp_int *mp, mp_digit d) /* unsigned digit addition */ +{ + mp_word w, k = 0; + mp_size ix = 1, used = USED(mp); + mp_digit *dp = DIGITS(mp); + + w = dp[0] + d; + dp[0] = ACCUM(w); + k = CARRYOUT(w); + + while(ix < used && k) { + w = dp[ix] + k; + dp[ix] = ACCUM(w); + k = CARRYOUT(w); + ++ix; + } + + if(k != 0) { + mp_err res; + + if((res = s_mp_pad(mp, USED(mp) + 1)) != MP_OKAY) + return res; + + DIGIT(mp, ix) = k; + } + + return MP_OKAY; + +} /* end s_mp_add_d() */ + +/* }}} */ + +/* {{{ s_mp_sub_d(mp, d) */ + +/* Subtract d from |mp| in place, assumes |mp| > d */ +mp_err s_mp_sub_d(mp_int *mp, mp_digit d) /* unsigned digit subtract */ +{ + mp_word w, b = 0; + mp_size ix = 1, used = USED(mp); + mp_digit *dp = DIGITS(mp); + + /* Compute initial subtraction */ + w = (RADIX + dp[0]) - d; + b = CARRYOUT(w) ? 0 : 1; + dp[0] = ACCUM(w); + + /* Propagate borrows leftward */ + while(b && ix < used) { + w = (RADIX + dp[ix]) - b; + b = CARRYOUT(w) ? 0 : 1; + dp[ix] = ACCUM(w); + ++ix; + } + + /* Remove leading zeroes */ + s_mp_clamp(mp); + + /* If we have a borrow out, it's a violation of the input invariant */ + if(b) + return MP_RANGE; + else + return MP_OKAY; + +} /* end s_mp_sub_d() */ + +/* }}} */ + +/* {{{ s_mp_mul_d(a, d) */ + +/* Compute a = a * d, single digit multiplication */ +mp_err s_mp_mul_d(mp_int *a, mp_digit d) +{ + mp_word w, k = 0; + mp_size ix, max; + mp_err res; + mp_digit *dp = DIGITS(a); + + /* + Single-digit multiplication will increase the precision of the + output by at most one digit. However, we can detect when this + will happen -- if the high-order digit of a, times d, gives a + two-digit result, then the precision of the result will increase; + otherwise it won't. We use this fact to avoid calling s_mp_pad() + unless absolutely necessary. + */ + max = USED(a); + w = dp[max - 1] * d; + if(CARRYOUT(w) != 0) { + if((res = s_mp_pad(a, max + 1)) != MP_OKAY) + return res; + dp = DIGITS(a); + } + + for(ix = 0; ix < max; ix++) { + w = (dp[ix] * d) + k; + dp[ix] = ACCUM(w); + k = CARRYOUT(w); + } + + /* If there is a precision increase, take care of it here; the above + test guarantees we have enough storage to do this safely. + */ + if(k) { + dp[max] = k; + USED(a) = max + 1; + } + + s_mp_clamp(a); + + return MP_OKAY; + +} /* end s_mp_mul_d() */ + +/* }}} */ + +/* {{{ s_mp_div_d(mp, d, r) */ + +/* + s_mp_div_d(mp, d, r) + + Compute the quotient mp = mp / d and remainder r = mp mod d, for a + single digit d. If r is null, the remainder will be discarded. + */ + +mp_err s_mp_div_d(mp_int *mp, mp_digit d, mp_digit *r) +{ + mp_word w = 0, t; + mp_int quot; + mp_err res; + mp_digit *dp = DIGITS(mp), *qp; + int ix; + + if(d == 0) + return MP_RANGE; + + /* Make room for the quotient */ + if((res = mp_init_size(", USED(mp))) != MP_OKAY) + return res; + + USED(") = USED(mp); /* so clamping will work below */ + qp = DIGITS("); + + /* Divide without subtraction */ + for(ix = USED(mp) - 1; ix >= 0; ix--) { + w = (w << DIGIT_BIT) | dp[ix]; + + if(w >= d) { + t = w / d; + w = w % d; + } else { + t = 0; + } + + qp[ix] = t; + } + + /* Deliver the remainder, if desired */ + if(r) + *r = w; + + s_mp_clamp("); + mp_exch(", mp); + mp_clear("); + + return MP_OKAY; + +} /* end s_mp_div_d() */ + +/* }}} */ + +/* }}} */ + +/* {{{ Primitive full arithmetic */ + +/* {{{ s_mp_add(a, b) */ + +/* Compute a = |a| + |b| */ +mp_err s_mp_add(mp_int *a, mp_int *b) /* magnitude addition */ +{ + mp_word w = 0; + mp_digit *pa, *pb; + mp_size ix, used = USED(b); + mp_err res; + + /* Make sure a has enough precision for the output value */ + if((used > USED(a)) && (res = s_mp_pad(a, used)) != MP_OKAY) + return res; + + /* + Add up all digits up to the precision of b. If b had initially + the same precision as a, or greater, we took care of it by the + padding step above, so there is no problem. If b had initially + less precision, we'll have to make sure the carry out is duly + propagated upward among the higher-order digits of the sum. + */ + pa = DIGITS(a); + pb = DIGITS(b); + for(ix = 0; ix < used; ++ix) { + w += *pa + *pb++; + *pa++ = ACCUM(w); + w = CARRYOUT(w); + } + + /* If we run out of 'b' digits before we're actually done, make + sure the carries get propagated upward... + */ + used = USED(a); + while(w && ix < used) { + w += *pa; + *pa++ = ACCUM(w); + w = CARRYOUT(w); + ++ix; + } + + /* If there's an overall carry out, increase precision and include + it. We could have done this initially, but why touch the memory + allocator unless we're sure we have to? + */ + if(w) { + if((res = s_mp_pad(a, used + 1)) != MP_OKAY) + return res; + + DIGIT(a, ix) = w; /* pa may not be valid after s_mp_pad() call */ + } + + return MP_OKAY; + +} /* end s_mp_add() */ + +/* }}} */ + +/* {{{ s_mp_sub(a, b) */ + +/* Compute a = |a| - |b|, assumes |a| >= |b| */ +mp_err s_mp_sub(mp_int *a, mp_int *b) /* magnitude subtract */ +{ + mp_word w = 0; + mp_digit *pa, *pb; + mp_size ix, used = USED(b); + + /* + Subtract and propagate borrow. Up to the precision of b, this + accounts for the digits of b; after that, we just make sure the + carries get to the right place. This saves having to pad b out to + the precision of a just to make the loops work right... + */ + pa = DIGITS(a); + pb = DIGITS(b); + + for(ix = 0; ix < used; ++ix) { + w = (RADIX + *pa) - w - *pb++; + *pa++ = ACCUM(w); + w = CARRYOUT(w) ? 0 : 1; + } + + used = USED(a); + while(ix < used) { + w = RADIX + *pa - w; + *pa++ = ACCUM(w); + w = CARRYOUT(w) ? 0 : 1; + ++ix; + } + + /* Clobber any leading zeroes we created */ + s_mp_clamp(a); + + /* + If there was a borrow out, then |b| > |a| in violation + of our input invariant. We've already done the work, + but we'll at least complain about it... + */ + if(w) + return MP_RANGE; + else + return MP_OKAY; + +} /* end s_mp_sub() */ + +/* }}} */ + +mp_err s_mp_reduce(mp_int *x, mp_int *m, mp_int *mu) +{ + mp_int q; + mp_err res; + mp_size um = USED(m); + + if((res = mp_init_copy(&q, x)) != MP_OKAY) + return res; + + s_mp_rshd(&q, um - 1); /* q1 = x / b^(k-1) */ + s_mp_mul(&q, mu); /* q2 = q1 * mu */ + s_mp_rshd(&q, um + 1); /* q3 = q2 / b^(k+1) */ + + /* x = x mod b^(k+1), quick (no division) */ + s_mp_mod_2d(x, (mp_digit)(DIGIT_BIT * (um + 1))); + + /* q = q * m mod b^(k+1), quick (no division), uses the short multiplier */ +#ifndef SHRT_MUL + s_mp_mul(&q, m); + s_mp_mod_2d(&q, (mp_digit)(DIGIT_BIT * (um + 1))); +#else + s_mp_mul_dig(&q, m, um + 1); +#endif + + /* x = x - q */ + if((res = mp_sub(x, &q, x)) != MP_OKAY) + goto CLEANUP; + + /* If x < 0, add b^(k+1) to it */ + if(mp_cmp_z(x) < 0) { + mp_set(&q, 1); + if((res = s_mp_lshd(&q, um + 1)) != MP_OKAY) + goto CLEANUP; + if((res = mp_add(x, &q, x)) != MP_OKAY) + goto CLEANUP; + } + + /* Back off if it's too big */ + while(mp_cmp(x, m) >= 0) { + if((res = s_mp_sub(x, m)) != MP_OKAY) + break; + } + + CLEANUP: + mp_clear(&q); + + return res; + +} /* end s_mp_reduce() */ + + + +/* {{{ s_mp_mul(a, b) */ + +/* Compute a = |a| * |b| */ +mp_err s_mp_mul(mp_int *a, mp_int *b) +{ + mp_word w, k = 0; + mp_int tmp; + mp_err res; + mp_size ix, jx, ua = USED(a), ub = USED(b); + mp_digit *pa, *pb, *pt, *pbt; + + if((res = mp_init_size(&tmp, ua + ub)) != MP_OKAY) + return res; + + /* This has the effect of left-padding with zeroes... */ + USED(&tmp) = ua + ub; + + /* We're going to need the base value each iteration */ + pbt = DIGITS(&tmp); + + /* Outer loop: Digits of b */ + + pb = DIGITS(b); + for(ix = 0; ix < ub; ++ix, ++pb) { + if(*pb == 0) + continue; + + /* Inner product: Digits of a */ + pa = DIGITS(a); + for(jx = 0; jx < ua; ++jx, ++pa) { + pt = pbt + ix + jx; + w = *pb * *pa + k + *pt; + *pt = ACCUM(w); + k = CARRYOUT(w); + } + + pbt[ix + jx] = k; + k = 0; + } + + s_mp_clamp(&tmp); + s_mp_exch(&tmp, a); + + mp_clear(&tmp); + + return MP_OKAY; + +} /* end s_mp_mul() */ + +/* }}} */ + +/* {{{ s_mp_kmul(a, b, out, len) */ + +#if 0 +void s_mp_kmul(mp_digit *a, mp_digit *b, mp_digit *out, mp_size len) +{ + mp_word w, k = 0; + mp_size ix, jx; + mp_digit *pa, *pt; + + for(ix = 0; ix < len; ++ix, ++b) { + if(*b == 0) + continue; + + pa = a; + for(jx = 0; jx < len; ++jx, ++pa) { + pt = out + ix + jx; + w = *b * *pa + k + *pt; + *pt = ACCUM(w); + k = CARRYOUT(w); + } + + out[ix + jx] = k; + k = 0; + } + +} /* end s_mp_kmul() */ +#endif + +/* }}} */ + +/* {{{ s_mp_sqr(a) */ + +/* + Computes the square of a, in place. This can be done more + efficiently than a general multiplication, because many of the + computation steps are redundant when squaring. The inner product + step is a bit more complicated, but we save a fair number of + iterations of the multiplication loop. + */ +#if MP_SQUARE +mp_err s_mp_sqr(mp_int *a) +{ + mp_word w, k = 0; + mp_int tmp; + mp_err res; + mp_size ix, jx, kx, used = USED(a); + mp_digit *pa1, *pa2, *pt, *pbt; + + if((res = mp_init_size(&tmp, 2 * used)) != MP_OKAY) + return res; + + /* Left-pad with zeroes */ + USED(&tmp) = 2 * used; + + /* We need the base value each time through the loop */ + pbt = DIGITS(&tmp); + + pa1 = DIGITS(a); + for(ix = 0; ix < used; ++ix, ++pa1) { + if(*pa1 == 0) + continue; + + w = DIGIT(&tmp, ix + ix) + (*pa1 * *pa1); + + pbt[ix + ix] = ACCUM(w); + k = CARRYOUT(w); + + /* + The inner product is computed as: + + (C, S) = t[i,j] + 2 a[i] a[j] + C + + This can overflow what can be represented in an mp_word, and + since C arithmetic does not provide any way to check for + overflow, we have to check explicitly for overflow conditions + before they happen. + */ + for(jx = ix + 1, pa2 = DIGITS(a) + jx; jx < used; ++jx, ++pa2) { + mp_word u = 0, v; + + /* Store this in a temporary to avoid indirections later */ + pt = pbt + ix + jx; + + /* Compute the multiplicative step */ + w = *pa1 * *pa2; + + /* If w is more than half MP_WORD_MAX, the doubling will + overflow, and we need to record a carry out into the next + word */ + u = (w >> (MP_WORD_BIT - 1)) & 1; + + /* Double what we've got, overflow will be ignored as defined + for C arithmetic (we've already noted if it is to occur) + */ + w *= 2; + + /* Compute the additive step */ + v = *pt + k; + + /* If we do not already have an overflow carry, check to see + if the addition will cause one, and set the carry out if so + */ + u |= ((MP_WORD_MAX - v) < w); + + /* Add in the rest, again ignoring overflow */ + w += v; + + /* Set the i,j digit of the output */ + *pt = ACCUM(w); + + /* Save carry information for the next iteration of the loop. + This is why k must be an mp_word, instead of an mp_digit */ + k = CARRYOUT(w) | (u << DIGIT_BIT); + + } /* for(jx ...) */ + + /* Set the last digit in the cycle and reset the carry */ + k = DIGIT(&tmp, ix + jx) + k; + pbt[ix + jx] = ACCUM(k); + k = CARRYOUT(k); + + /* If we are carrying out, propagate the carry to the next digit + in the output. This may cascade, so we have to be somewhat + circumspect -- but we will have enough precision in the output + that we won't overflow + */ + kx = 1; + while(k) { + k = pbt[ix + jx + kx] + 1; + pbt[ix + jx + kx] = ACCUM(k); + k = CARRYOUT(k); + ++kx; + } + } /* for(ix ...) */ + + s_mp_clamp(&tmp); + s_mp_exch(&tmp, a); + + mp_clear(&tmp); + + return MP_OKAY; + +} /* end s_mp_sqr() */ +#endif + +/* }}} */ + +/* {{{ s_mp_div(a, b) */ + +/* + s_mp_div(a, b) + + Compute a = a / b and b = a mod b. Assumes b > a. + */ + +mp_err s_mp_div(mp_int *a, mp_int *b) +{ + mp_int quot, rem, t; + mp_word q; + mp_err res; + mp_digit d; + int ix; + + if(mp_cmp_z(b) == 0) + return MP_RANGE; + + /* Shortcut if b is power of two */ + if((ix = s_mp_ispow2(b)) >= 0) { + mp_copy(a, b); /* need this for remainder */ + s_mp_div_2d(a, (mp_digit)ix); + s_mp_mod_2d(b, (mp_digit)ix); + + return MP_OKAY; + } + + /* Allocate space to store the quotient */ + if((res = mp_init_size(", USED(a))) != MP_OKAY) + return res; + + /* A working temporary for division */ + if((res = mp_init_size(&t, USED(a))) != MP_OKAY) + goto T; + + /* Allocate space for the remainder */ + if((res = mp_init_size(&rem, USED(a))) != MP_OKAY) + goto REM; + + /* Normalize to optimize guessing */ + d = s_mp_norm(a, b); + + /* Perform the division itself...woo! */ + ix = USED(a) - 1; + + while(ix >= 0) { + /* Find a partial substring of a which is at least b */ + while(s_mp_cmp(&rem, b) < 0 && ix >= 0) { + if((res = s_mp_lshd(&rem, 1)) != MP_OKAY) + goto CLEANUP; + + if((res = s_mp_lshd(", 1)) != MP_OKAY) + goto CLEANUP; + + DIGIT(&rem, 0) = DIGIT(a, ix); + s_mp_clamp(&rem); + --ix; + } + + /* If we didn't find one, we're finished dividing */ + if(s_mp_cmp(&rem, b) < 0) + break; + + /* Compute a guess for the next quotient digit */ + q = DIGIT(&rem, USED(&rem) - 1); + if(q <= DIGIT(b, USED(b) - 1) && USED(&rem) > 1) + q = (q << DIGIT_BIT) | DIGIT(&rem, USED(&rem) - 2); + + q /= DIGIT(b, USED(b) - 1); + + /* The guess can be as much as RADIX + 1 */ + if(q >= RADIX) + q = RADIX - 1; + + /* See what that multiplies out to */ + mp_copy(b, &t); + if((res = s_mp_mul_d(&t, q)) != MP_OKAY) + goto CLEANUP; + + /* + If it's too big, back it off. We should not have to do this + more than once, or, in rare cases, twice. Knuth describes a + method by which this could be reduced to a maximum of once, but + I didn't implement that here. + */ + while(s_mp_cmp(&t, &rem) > 0) { + --q; + s_mp_sub(&t, b); + } + + /* At this point, q should be the right next digit */ + if((res = s_mp_sub(&rem, &t)) != MP_OKAY) + goto CLEANUP; + + /* + Include the digit in the quotient. We allocated enough memory + for any quotient we could ever possibly get, so we should not + have to check for failures here + */ + DIGIT(", 0) = q; + } + + /* Denormalize remainder */ + if(d != 0) + s_mp_div_2d(&rem, d); + + s_mp_clamp("); + s_mp_clamp(&rem); + + /* Copy quotient back to output */ + s_mp_exch(", a); + + /* Copy remainder back to output */ + s_mp_exch(&rem, b); + +CLEANUP: + mp_clear(&rem); +REM: + mp_clear(&t); +T: + mp_clear("); + + return res; + +} /* end s_mp_div() */ + +/* }}} */ + +/* {{{ s_mp_2expt(a, k) */ + +mp_err s_mp_2expt(mp_int *a, mp_digit k) +{ + mp_err res; + mp_size dig, bit; + + dig = k / DIGIT_BIT; + bit = k % DIGIT_BIT; + + mp_zero(a); + if((res = s_mp_pad(a, dig + 1)) != MP_OKAY) + return res; + + DIGIT(a, dig) |= (1 << bit); + + return MP_OKAY; + +} /* end s_mp_2expt() */ + +/* }}} */ + + +/* }}} */ + +/* }}} */ + +/* {{{ Primitive comparisons */ + +/* {{{ s_mp_cmp(a, b) */ + +/* Compare |a| <=> |b|, return 0 if equal, <0 if a<b, >0 if a>b */ +int s_mp_cmp(mp_int *a, mp_int *b) +{ + mp_size ua = USED(a), ub = USED(b); + + if(ua > ub) + return MP_GT; + else if(ua < ub) + return MP_LT; + else { + int ix = ua - 1; + mp_digit *ap = DIGITS(a) + ix, *bp = DIGITS(b) + ix; + + while(ix >= 0) { + if(*ap > *bp) + return MP_GT; + else if(*ap < *bp) + return MP_LT; + + --ap; --bp; --ix; + } + + return MP_EQ; + } + +} /* end s_mp_cmp() */ + +/* }}} */ + +/* {{{ s_mp_cmp_d(a, d) */ + +/* Compare |a| <=> d, return 0 if equal, <0 if a<d, >0 if a>d */ +int s_mp_cmp_d(mp_int *a, mp_digit d) +{ + mp_size ua = USED(a); + mp_digit *ap = DIGITS(a); + + if(ua > 1) + return MP_GT; + + if(*ap < d) + return MP_LT; + else if(*ap > d) + return MP_GT; + else + return MP_EQ; + +} /* end s_mp_cmp_d() */ + +/* }}} */ + +/* {{{ s_mp_ispow2(v) */ + +/* + Returns -1 if the value is not a power of two; otherwise, it returns + k such that v = 2^k, i.e. lg(v). + */ +int s_mp_ispow2(mp_int *v) +{ + mp_digit d, *dp; + mp_size uv = USED(v); + int extra = 0, ix; + + d = DIGIT(v, uv - 1); /* most significant digit of v */ + + while(d && ((d & 1) == 0)) { + d >>= 1; + ++extra; + } + + if(d == 1) { + ix = uv - 2; + dp = DIGITS(v) + ix; + + while(ix >= 0) { + if(*dp) + return -1; /* not a power of two */ + + --dp; --ix; + } + + return ((uv - 1) * DIGIT_BIT) + extra; + } + + return -1; + +} /* end s_mp_ispow2() */ + +/* }}} */ + +/* {{{ s_mp_ispow2d(d) */ + +int s_mp_ispow2d(mp_digit d) +{ + int pow = 0; + + while((d & 1) == 0) { + ++pow; d >>= 1; + } + + if(d == 1) + return pow; + + return -1; + +} /* end s_mp_ispow2d() */ + +/* }}} */ + +/* }}} */ + +/* {{{ Primitive I/O helpers */ + +/* {{{ s_mp_tovalue(ch, r) */ + +/* + Convert the given character to its digit value, in the given radix. + If the given character is not understood in the given radix, -1 is + returned. Otherwise the digit's numeric value is returned. + + The results will be odd if you use a radix < 2 or > 62, you are + expected to know what you're up to. + */ +int s_mp_tovalue(char ch, int r) +{ + int val, xch; + + if(r > 36) + xch = ch; + else + xch = toupper(ch); + + if(isdigit(xch)) + val = xch - '0'; + else if(isupper(xch)) + val = xch - 'A' + 10; + else if(islower(xch)) + val = xch - 'a' + 36; + else if(xch == '+') + val = 62; + else if(xch == '/') + val = 63; + else + return -1; + + if(val < 0 || val >= r) + return -1; + + return val; + +} /* end s_mp_tovalue() */ + +/* }}} */ + +/* {{{ s_mp_todigit(val, r, low) */ + +/* + Convert val to a radix-r digit, if possible. If val is out of range + for r, returns zero. Otherwise, returns an ASCII character denoting + the value in the given radix. + + The results may be odd if you use a radix < 2 or > 64, you are + expected to know what you're doing. + */ + +char s_mp_todigit(int val, int r, int low) +{ + char ch; + + if(val < 0 || val >= r) + return 0; + + ch = s_dmap_1[val]; + + if(r <= 36 && low) + ch = tolower(ch); + + return ch; + +} /* end s_mp_todigit() */ + +/* }}} */ + +/* {{{ s_mp_outlen(bits, radix) */ + +/* + Return an estimate for how long a string is needed to hold a radix + r representation of a number with 'bits' significant bits. + + Does not include space for a sign or a NUL terminator. + */ +int s_mp_outlen(int bits, int r) +{ + return (int)((double)bits * LOG_V_2(r)); + +} /* end s_mp_outlen() */ + +/* }}} */ + +/* }}} */ + +/*------------------------------------------------------------------------*/ +/* HERE THERE BE DRAGONS */ +/* crc==4242132123, version==2, Sat Feb 02 06:43:52 2002 */