+++ /dev/null
-/* mpi-div.c - MPI functions
- * Copyright (C) 1994, 1996, 1998, 2001, 2002,
- * 2003 Free Software Foundation, Inc.
- *
- * This file is part of Libgcrypt.
- *
- * Note: This code is heavily based on the GNU MP Library.
- * Actually it's the same code with only minor changes in the
- * way the data is stored; this is to support the abstraction
- * of an optional secure memory allocation which may be used
- * to avoid revealing of sensitive data due to paging etc.
- */
-
-#include "mpi-internal.h"
-#include "longlong.h"
-
-void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den);
-void mpi_fdiv_qr(MPI quot, MPI rem, MPI dividend, MPI divisor);
-
-void mpi_fdiv_r(MPI rem, MPI dividend, MPI divisor)
-{
- int divisor_sign = divisor->sign;
- MPI temp_divisor = NULL;
-
- /* We need the original value of the divisor after the remainder has been
- * preliminary calculated. We have to copy it to temporary space if it's
- * the same variable as REM.
- */
- if (rem == divisor) {
- temp_divisor = mpi_copy(divisor);
- divisor = temp_divisor;
- }
-
- mpi_tdiv_r(rem, dividend, divisor);
-
- if (((divisor_sign?1:0) ^ (dividend->sign?1:0)) && rem->nlimbs)
- mpi_add(rem, rem, divisor);
-
- if (temp_divisor)
- mpi_free(temp_divisor);
-}
-
-void mpi_fdiv_q(MPI quot, MPI dividend, MPI divisor)
-{
- MPI tmp = mpi_alloc(mpi_get_nlimbs(quot));
- mpi_fdiv_qr(quot, tmp, dividend, divisor);
- mpi_free(tmp);
-}
-
-void mpi_fdiv_qr(MPI quot, MPI rem, MPI dividend, MPI divisor)
-{
- int divisor_sign = divisor->sign;
- MPI temp_divisor = NULL;
-
- if (quot == divisor || rem == divisor) {
- temp_divisor = mpi_copy(divisor);
- divisor = temp_divisor;
- }
-
- mpi_tdiv_qr(quot, rem, dividend, divisor);
-
- if ((divisor_sign ^ dividend->sign) && rem->nlimbs) {
- mpi_sub_ui(quot, quot, 1);
- mpi_add(rem, rem, divisor);
- }
-
- if (temp_divisor)
- mpi_free(temp_divisor);
-}
-
-/* If den == quot, den needs temporary storage.
- * If den == rem, den needs temporary storage.
- * If num == quot, num needs temporary storage.
- * If den has temporary storage, it can be normalized while being copied,
- * i.e no extra storage should be allocated.
- */
-
-void mpi_tdiv_r(MPI rem, MPI num, MPI den)
-{
- mpi_tdiv_qr(NULL, rem, num, den);
-}
-
-void mpi_tdiv_qr(MPI quot, MPI rem, MPI num, MPI den)
-{
- mpi_ptr_t np, dp;
- mpi_ptr_t qp, rp;
- mpi_size_t nsize = num->nlimbs;
- mpi_size_t dsize = den->nlimbs;
- mpi_size_t qsize, rsize;
- mpi_size_t sign_remainder = num->sign;
- mpi_size_t sign_quotient = num->sign ^ den->sign;
- unsigned int normalization_steps;
- mpi_limb_t q_limb;
- mpi_ptr_t marker[5];
- int markidx = 0;
-
- /* Ensure space is enough for quotient and remainder.
- * We need space for an extra limb in the remainder, because it's
- * up-shifted (normalized) below.
- */
- rsize = nsize + 1;
- mpi_resize(rem, rsize);
-
- qsize = rsize - dsize; /* qsize cannot be bigger than this. */
- if (qsize <= 0) {
- if (num != rem) {
- rem->nlimbs = num->nlimbs;
- rem->sign = num->sign;
- MPN_COPY(rem->d, num->d, nsize);
- }
- if (quot) {
- /* This needs to follow the assignment to rem, in case the
- * numerator and quotient are the same.
- */
- quot->nlimbs = 0;
- quot->sign = 0;
- }
- return;
- }
-
- if (quot)
- mpi_resize(quot, qsize);
-
- /* Read pointers here, when reallocation is finished. */
- np = num->d;
- dp = den->d;
- rp = rem->d;
-
- /* Optimize division by a single-limb divisor. */
- if (dsize == 1) {
- mpi_limb_t rlimb;
- if (quot) {
- qp = quot->d;
- rlimb = mpihelp_divmod_1(qp, np, nsize, dp[0]);
- qsize -= qp[qsize - 1] == 0;
- quot->nlimbs = qsize;
- quot->sign = sign_quotient;
- } else
- rlimb = mpihelp_mod_1(np, nsize, dp[0]);
- rp[0] = rlimb;
- rsize = rlimb != 0?1:0;
- rem->nlimbs = rsize;
- rem->sign = sign_remainder;
- return;
- }
-
-
- if (quot) {
- qp = quot->d;
- /* Make sure QP and NP point to different objects. Otherwise the
- * numerator would be gradually overwritten by the quotient limbs.
- */
- if (qp == np) { /* Copy NP object to temporary space. */
- np = marker[markidx++] = mpi_alloc_limb_space(nsize);
- MPN_COPY(np, qp, nsize);
- }
- } else /* Put quotient at top of remainder. */
- qp = rp + dsize;
-
- normalization_steps = count_leading_zeros(dp[dsize - 1]);
-
- /* Normalize the denominator, i.e. make its most significant bit set by
- * shifting it NORMALIZATION_STEPS bits to the left. Also shift the
- * numerator the same number of steps (to keep the quotient the same!).
- */
- if (normalization_steps) {
- mpi_ptr_t tp;
- mpi_limb_t nlimb;
-
- /* Shift up the denominator setting the most significant bit of
- * the most significant word. Use temporary storage not to clobber
- * the original contents of the denominator.
- */
- tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
- mpihelp_lshift(tp, dp, dsize, normalization_steps);
- dp = tp;
-
- /* Shift up the numerator, possibly introducing a new most
- * significant word. Move the shifted numerator in the remainder
- * meanwhile.
- */
- nlimb = mpihelp_lshift(rp, np, nsize, normalization_steps);
- if (nlimb) {
- rp[nsize] = nlimb;
- rsize = nsize + 1;
- } else
- rsize = nsize;
- } else {
- /* The denominator is already normalized, as required. Copy it to
- * temporary space if it overlaps with the quotient or remainder.
- */
- if (dp == rp || (quot && (dp == qp))) {
- mpi_ptr_t tp;
-
- tp = marker[markidx++] = mpi_alloc_limb_space(dsize);
- MPN_COPY(tp, dp, dsize);
- dp = tp;
- }
-
- /* Move the numerator to the remainder. */
- if (rp != np)
- MPN_COPY(rp, np, nsize);
-
- rsize = nsize;
- }
-
- q_limb = mpihelp_divrem(qp, 0, rp, rsize, dp, dsize);
-
- if (quot) {
- qsize = rsize - dsize;
- if (q_limb) {
- qp[qsize] = q_limb;
- qsize += 1;
- }
-
- quot->nlimbs = qsize;
- quot->sign = sign_quotient;
- }
-
- rsize = dsize;
- MPN_NORMALIZE(rp, rsize);
-
- if (normalization_steps && rsize) {
- mpihelp_rshift(rp, rp, rsize, normalization_steps);
- rsize -= rp[rsize - 1] == 0?1:0;
- }
-
- rem->nlimbs = rsize;
- rem->sign = sign_remainder;
- while (markidx) {
- markidx--;
- mpi_free_limb_space(marker[markidx]);
- }
-}
projects / linux-2.6-microblaze.git / blobdiff