261 строка
6.2 KiB
C
261 строка
6.2 KiB
C
/* mpicoder.c - Coder for the external representation of MPIs
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* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <linux/bitops.h>
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#include <asm-generic/bitops/count_zeros.h>
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#include "mpi-internal.h"
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#define MAX_EXTERN_MPI_BITS 16384
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/**
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* mpi_read_raw_data - Read a raw byte stream as a positive integer
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* @xbuffer: The data to read
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* @nbytes: The amount of data to read
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*/
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MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
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{
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const uint8_t *buffer = xbuffer;
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int i, j;
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unsigned nbits, nlimbs;
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mpi_limb_t a;
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MPI val = NULL;
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while (nbytes > 0 && buffer[0] == 0) {
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buffer++;
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nbytes--;
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}
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nbits = nbytes * 8;
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if (nbits > MAX_EXTERN_MPI_BITS) {
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pr_info("MPI: mpi too large (%u bits)\n", nbits);
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return NULL;
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}
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if (nbytes > 0)
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nbits -= count_leading_zeros(buffer[0]);
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else
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nbits = 0;
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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val = mpi_alloc(nlimbs);
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if (!val)
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return NULL;
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val->nbits = nbits;
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val->sign = 0;
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val->nlimbs = nlimbs;
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if (nbytes > 0) {
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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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for (j = nlimbs; j > 0; j--) {
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a = 0;
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for (; i < BYTES_PER_MPI_LIMB; i++) {
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a <<= 8;
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a |= *buffer++;
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}
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i = 0;
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val->d[j - 1] = a;
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}
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}
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return val;
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}
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EXPORT_SYMBOL_GPL(mpi_read_raw_data);
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MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
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{
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const uint8_t *buffer = xbuffer;
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int i, j;
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unsigned nbits, nbytes, nlimbs, nread = 0;
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mpi_limb_t a;
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MPI val = NULL;
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if (*ret_nread < 2)
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goto leave;
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nbits = buffer[0] << 8 | buffer[1];
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if (nbits > MAX_EXTERN_MPI_BITS) {
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pr_info("MPI: mpi too large (%u bits)\n", nbits);
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goto leave;
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}
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buffer += 2;
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nread = 2;
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nbytes = DIV_ROUND_UP(nbits, 8);
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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val = mpi_alloc(nlimbs);
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if (!val)
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return NULL;
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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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val->nbits = nbits;
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j = val->nlimbs = nlimbs;
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val->sign = 0;
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for (; j > 0; j--) {
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a = 0;
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for (; i < BYTES_PER_MPI_LIMB; i++) {
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if (++nread > *ret_nread) {
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printk
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("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
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nread, *ret_nread);
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goto leave;
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}
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a <<= 8;
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a |= *buffer++;
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}
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i = 0;
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val->d[j - 1] = a;
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}
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leave:
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*ret_nread = nread;
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return val;
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}
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EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
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/****************
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* Return an allocated buffer with the MPI (msb first).
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* NBYTES receives the length of this buffer. Caller must free the
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* return string (This function does return a 0 byte buffer with NBYTES
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* set to zero if the value of A is zero. If sign is not NULL, it will
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* be set to the sign of the A.
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*/
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void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
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{
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uint8_t *p, *buffer;
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mpi_limb_t alimb;
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int i;
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unsigned int n;
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if (sign)
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*sign = a->sign;
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*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
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if (!n)
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n++; /* avoid zero length allocation */
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p = buffer = kmalloc(n, GFP_KERNEL);
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if (!p)
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return NULL;
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for (i = a->nlimbs - 1; i >= 0; i--) {
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alimb = a->d[i];
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#if BYTES_PER_MPI_LIMB == 4
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*p++ = alimb >> 24;
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*p++ = alimb >> 16;
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*p++ = alimb >> 8;
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*p++ = alimb;
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#elif BYTES_PER_MPI_LIMB == 8
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*p++ = alimb >> 56;
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*p++ = alimb >> 48;
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*p++ = alimb >> 40;
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*p++ = alimb >> 32;
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*p++ = alimb >> 24;
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*p++ = alimb >> 16;
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*p++ = alimb >> 8;
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*p++ = alimb;
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#else
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#error please implement for this limb size.
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#endif
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}
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/* this is sub-optimal but we need to do the shift operation
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* because the caller has to free the returned buffer */
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for (p = buffer; !*p && *nbytes; p++, --*nbytes)
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;
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if (p != buffer)
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memmove(buffer, p, *nbytes);
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return buffer;
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}
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EXPORT_SYMBOL_GPL(mpi_get_buffer);
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/****************
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* Use BUFFER to update MPI.
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*/
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int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
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{
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const uint8_t *buffer = xbuffer, *p;
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mpi_limb_t alimb;
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int nlimbs;
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int i;
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
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return -ENOMEM;
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a->sign = sign;
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for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = (mpi_limb_t) *p--;
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alimb |= (mpi_limb_t) *p-- << 8;
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alimb |= (mpi_limb_t) *p-- << 16;
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alimb |= (mpi_limb_t) *p-- << 24;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = (mpi_limb_t) *p--;
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alimb |= (mpi_limb_t) *p-- << 8;
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alimb |= (mpi_limb_t) *p-- << 16;
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alimb |= (mpi_limb_t) *p-- << 24;
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alimb |= (mpi_limb_t) *p-- << 32;
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alimb |= (mpi_limb_t) *p-- << 40;
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alimb |= (mpi_limb_t) *p-- << 48;
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alimb |= (mpi_limb_t) *p-- << 56;
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#else
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#error please implement for this limb size.
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#endif
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a->d[i++] = alimb;
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}
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if (p >= buffer) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = *p--;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 8;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 16;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 24;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = (mpi_limb_t) *p--;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 8;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 16;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 24;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 32;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 40;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 48;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 56;
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#else
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#error please implement for this limb size.
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#endif
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a->d[i++] = alimb;
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}
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a->nlimbs = i;
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if (i != nlimbs) {
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pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
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nlimbs);
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BUG();
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(mpi_set_buffer);
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