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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
)
162 for (i
= a
->nlimbs
- 1; i
>= 0; i
--) {
164 #if BYTES_PER_MPI_LIMB == 4
169 #elif BYTES_PER_MPI_LIMB == 8
179 #error please implement for this limb size.
184 EXPORT_SYMBOL_GPL(mpi_read_buffer
);
187 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
188 * Caller must free the return string.
189 * This function does return a 0 byte buffer with nbytes set to zero if the
190 * value of A is zero.
192 * @a: a multi precision integer.
193 * @nbytes: receives the length of this buffer.
194 * @sign: if not NULL, it will be set to the sign of the a.
196 * Return: Pointer to MPI buffer or NULL on error
198 void *mpi_get_buffer(MPI a
, unsigned *nbytes
, int *sign
)
212 buf
= kmalloc(n
, GFP_KERNEL
);
217 ret
= mpi_read_buffer(a
, buf
, n
, nbytes
, sign
);
224 /* this is sub-optimal but we need to do the shift operation
225 * because the caller has to free the returned buffer */
226 for (p
= buf
; !*p
&& *nbytes
; p
++, --*nbytes
)
229 memmove(buf
, p
, *nbytes
);
233 EXPORT_SYMBOL_GPL(mpi_get_buffer
);
236 * Use BUFFER to update MPI.
238 int mpi_set_buffer(MPI a
, const void *xbuffer
, unsigned nbytes
, int sign
)
240 const uint8_t *buffer
= xbuffer
, *p
;
245 nlimbs
= DIV_ROUND_UP(nbytes
, BYTES_PER_MPI_LIMB
);
246 if (RESIZE_IF_NEEDED(a
, nlimbs
) < 0)
250 for (i
= 0, p
= buffer
+ nbytes
- 1; p
>= buffer
+ BYTES_PER_MPI_LIMB
;) {
251 #if BYTES_PER_MPI_LIMB == 4
252 alimb
= (mpi_limb_t
) *p
--;
253 alimb
|= (mpi_limb_t
) *p
-- << 8;
254 alimb
|= (mpi_limb_t
) *p
-- << 16;
255 alimb
|= (mpi_limb_t
) *p
-- << 24;
256 #elif BYTES_PER_MPI_LIMB == 8
257 alimb
= (mpi_limb_t
) *p
--;
258 alimb
|= (mpi_limb_t
) *p
-- << 8;
259 alimb
|= (mpi_limb_t
) *p
-- << 16;
260 alimb
|= (mpi_limb_t
) *p
-- << 24;
261 alimb
|= (mpi_limb_t
) *p
-- << 32;
262 alimb
|= (mpi_limb_t
) *p
-- << 40;
263 alimb
|= (mpi_limb_t
) *p
-- << 48;
264 alimb
|= (mpi_limb_t
) *p
-- << 56;
266 #error please implement for this limb size.
271 #if BYTES_PER_MPI_LIMB == 4
274 alimb
|= (mpi_limb_t
) *p
-- << 8;
276 alimb
|= (mpi_limb_t
) *p
-- << 16;
278 alimb
|= (mpi_limb_t
) *p
-- << 24;
279 #elif BYTES_PER_MPI_LIMB == 8
280 alimb
= (mpi_limb_t
) *p
--;
282 alimb
|= (mpi_limb_t
) *p
-- << 8;
284 alimb
|= (mpi_limb_t
) *p
-- << 16;
286 alimb
|= (mpi_limb_t
) *p
-- << 24;
288 alimb
|= (mpi_limb_t
) *p
-- << 32;
290 alimb
|= (mpi_limb_t
) *p
-- << 40;
292 alimb
|= (mpi_limb_t
) *p
-- << 48;
294 alimb
|= (mpi_limb_t
) *p
-- << 56;
296 #error please implement for this limb size.
303 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i
,
309 EXPORT_SYMBOL_GPL(mpi_set_buffer
);