1 /* mpicoder.c - Coder for the external representation of MPIs
2 * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
4 * This file is part of GnuPG.
6 * GnuPG is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
21 #include <linux/bitops.h>
22 #include <asm-generic/bitops/count_zeros.h>
23 #include "mpi-internal.h"
25 #define MAX_EXTERN_MPI_BITS 16384
28 * mpi_read_raw_data - Read a raw byte stream as a positive integer
29 * @xbuffer: The data to read
30 * @nbytes: The amount of data to read
32 MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
34 const uint8_t *buffer = xbuffer;
36 unsigned nbits, nlimbs;
40 while (nbytes > 0 && buffer[0] == 0) {
46 if (nbits > MAX_EXTERN_MPI_BITS) {
47 pr_info("MPI: mpi too large (%u bits)\n", nbits);
51 nbits -= count_leading_zeros(buffer[0]);
55 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
56 val = mpi_alloc(nlimbs);
64 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
65 i %= BYTES_PER_MPI_LIMB;
66 for (j = nlimbs; j > 0; j--) {
68 for (; i < BYTES_PER_MPI_LIMB; i++) {
78 EXPORT_SYMBOL_GPL(mpi_read_raw_data);
80 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
82 const uint8_t *buffer = xbuffer;
84 unsigned nbits, nbytes, nlimbs, nread = 0;
90 nbits = buffer[0] << 8 | buffer[1];
92 if (nbits > MAX_EXTERN_MPI_BITS) {
93 pr_info("MPI: mpi too large (%u bits)\n", nbits);
99 nbytes = DIV_ROUND_UP(nbits, 8);
100 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
101 val = mpi_alloc(nlimbs);
104 i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
105 i %= BYTES_PER_MPI_LIMB;
107 j = val->nlimbs = nlimbs;
111 for (; i < BYTES_PER_MPI_LIMB; i++) {
112 if (++nread > *ret_nread) {
114 ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
129 EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
132 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
134 * @a: a multi precision integer
135 * @buf: bufer to which the output will be written to. Needs to be at
136 * leaset mpi_get_size(a) long.
137 * @buf_len: size of the buf.
138 * @nbytes: receives the actual length of the data written.
139 * @sign: if not NULL, it will be set to the sign of a.
141 * Return: 0 on success or error code in case of error
143 int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
148 unsigned int n = mpi_get_size(a);
151 if (buf_len < n || !buf || !nbytes)
157 p = (void *)&a->d[a->nlimbs] - 1;
159 for (i = a->nlimbs * sizeof(alimb) - 1; i >= 0; i--, p--) {
167 *nbytes = n - lzeros;
169 for (i = a->nlimbs - 1; i >= 0; i--) {
171 #if BYTES_PER_MPI_LIMB == 4
176 #elif BYTES_PER_MPI_LIMB == 8
186 #error please implement for this limb size.
190 if (lzeros >= sizeof(alimb)) {
193 mpi_limb_t *limb1 = (void *)p - sizeof(alimb);
194 mpi_limb_t *limb2 = (void *)p - sizeof(alimb)
199 lzeros -= sizeof(alimb);
204 EXPORT_SYMBOL_GPL(mpi_read_buffer);
207 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
208 * Caller must free the return string.
209 * This function does return a 0 byte buffer with nbytes set to zero if the
210 * value of A is zero.
212 * @a: a multi precision integer.
213 * @nbytes: receives the length of this buffer.
214 * @sign: if not NULL, it will be set to the sign of the a.
216 * Return: Pointer to MPI buffer or NULL on error
218 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
232 buf = kmalloc(n, GFP_KERNEL);
237 ret = mpi_read_buffer(a, buf, n, nbytes, sign);
245 EXPORT_SYMBOL_GPL(mpi_get_buffer);
248 * Use BUFFER to update MPI.
250 int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
252 const uint8_t *buffer = xbuffer, *p;
257 nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
258 if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
262 for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
263 #if BYTES_PER_MPI_LIMB == 4
264 alimb = (mpi_limb_t) *p--;
265 alimb |= (mpi_limb_t) *p-- << 8;
266 alimb |= (mpi_limb_t) *p-- << 16;
267 alimb |= (mpi_limb_t) *p-- << 24;
268 #elif BYTES_PER_MPI_LIMB == 8
269 alimb = (mpi_limb_t) *p--;
270 alimb |= (mpi_limb_t) *p-- << 8;
271 alimb |= (mpi_limb_t) *p-- << 16;
272 alimb |= (mpi_limb_t) *p-- << 24;
273 alimb |= (mpi_limb_t) *p-- << 32;
274 alimb |= (mpi_limb_t) *p-- << 40;
275 alimb |= (mpi_limb_t) *p-- << 48;
276 alimb |= (mpi_limb_t) *p-- << 56;
278 #error please implement for this limb size.
283 #if BYTES_PER_MPI_LIMB == 4
286 alimb |= (mpi_limb_t) *p-- << 8;
288 alimb |= (mpi_limb_t) *p-- << 16;
290 alimb |= (mpi_limb_t) *p-- << 24;
291 #elif BYTES_PER_MPI_LIMB == 8
292 alimb = (mpi_limb_t) *p--;
294 alimb |= (mpi_limb_t) *p-- << 8;
296 alimb |= (mpi_limb_t) *p-- << 16;
298 alimb |= (mpi_limb_t) *p-- << 24;
300 alimb |= (mpi_limb_t) *p-- << 32;
302 alimb |= (mpi_limb_t) *p-- << 40;
304 alimb |= (mpi_limb_t) *p-- << 48;
306 alimb |= (mpi_limb_t) *p-- << 56;
308 #error please implement for this limb size.
315 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
321 EXPORT_SYMBOL_GPL(mpi_set_buffer);