/* mpicoder.c  -  Coder for the external representation of MPIs * Copyright (C) 1998, 1999 Free Software Foundation, Inc. * * This file is part of GnuPG. * * GnuPG is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * GnuPG is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA */ #include "mpi-internal.h" #define MAX_EXTERN_MPI_BITS 16384 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread){	const uint8_t *buffer = xbuffer;	int i, j;	unsigned nbits, nbytes, nlimbs, nread = 0;	mpi_limb_t a;	MPI val = NULL; 	if (*ret_nread < 2)		goto leave;	nbits = buffer[0] << 8 | buffer[1]; 	if (nbits > MAX_EXTERN_MPI_BITS) {		pr_info("MPI: mpi too large (%u bits)\n", nbits);		goto leave;	}	buffer += 2;	nread = 2; 	nbytes = (nbits + 7) / 8;	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;	val = mpi_alloc(nlimbs);	if (!val)		return NULL;	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;	i %= BYTES_PER_MPI_LIMB;	val->nbits = nbits;	j = val->nlimbs = nlimbs;	val->sign = 0;	for (; j > 0; j--) {		a = 0;		for (; i < BYTES_PER_MPI_LIMB; i++) {			if (++nread > *ret_nread) {				printk				    ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",				     nread, *ret_nread);				goto leave;			}			a <<= 8;			a |= *buffer++;		}		i = 0;		val->d[j - 1] = a;	} leave:	*ret_nread = nread;	return val;}EXPORT_SYMBOL_GPL(mpi_read_from_buffer); /**************** * Return an allocated buffer with the MPI (msb first). * NBYTES receives the length of this buffer. Caller must free the * return string (This function does return a 0 byte buffer with NBYTES * set to zero if the value of A is zero. If sign is not NULL, it will * be set to the sign of the A. */void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign){	uint8_t *p, *buffer;	mpi_limb_t alimb;	int i;	unsigned int n; 	if (sign)		*sign = a->sign;	*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;	if (!n)		n++;		/* avoid zero length allocation */	p = buffer = kmalloc(n, GFP_KERNEL);	if (!p)		return NULL; 	for (i = a->nlimbs - 1; i >= 0; i--) {		alimb = a->d[i];#if BYTES_PER_MPI_LIMB == 4		*p++ = alimb >> 24;		*p++ = alimb >> 16;		*p++ = alimb >> 8;		*p++ = alimb;#elif BYTES_PER_MPI_LIMB == 8		*p++ = alimb >> 56;		*p++ = alimb >> 48;		*p++ = alimb >> 40;		*p++ = alimb >> 32;		*p++ = alimb >> 24;		*p++ = alimb >> 16;		*p++ = alimb >> 8;		*p++ = alimb;#else#error please implement for this limb size.#endif	} 	/* this is sub-optimal but we need to do the shift operation	 * because the caller has to free the returned buffer */	for (p = buffer; !*p && *nbytes; p++, --*nbytes)		;	if (p != buffer)		memmove(buffer, p, *nbytes); 	return buffer;}EXPORT_SYMBOL_GPL(mpi_get_buffer); /**************** * Use BUFFER to update MPI. */int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign){	const uint8_t *buffer = xbuffer, *p;	mpi_limb_t alimb;	int nlimbs;	int i; 	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)		return -ENOMEM;	a->sign = sign; 	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {#if BYTES_PER_MPI_LIMB == 4		alimb = (mpi_limb_t) *p--;		alimb |= (mpi_limb_t) *p-- << 8;		alimb |= (mpi_limb_t) *p-- << 16;		alimb |= (mpi_limb_t) *p-- << 24;#elif BYTES_PER_MPI_LIMB == 8		alimb = (mpi_limb_t) *p--;		alimb |= (mpi_limb_t) *p-- << 8;		alimb |= (mpi_limb_t) *p-- << 16;		alimb |= (mpi_limb_t) *p-- << 24;		alimb |= (mpi_limb_t) *p-- << 32;		alimb |= (mpi_limb_t) *p-- << 40;		alimb |= (mpi_limb_t) *p-- << 48;		alimb |= (mpi_limb_t) *p-- << 56;#else#error please implement for this limb size.#endif		a->d[i++] = alimb;	}	if (p >= buffer) {#if BYTES_PER_MPI_LIMB == 4		alimb = *p--;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 8;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 16;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 24;#elif BYTES_PER_MPI_LIMB == 8		alimb = (mpi_limb_t) *p--;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 8;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 16;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 24;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 32;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 40;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 48;		if (p >= buffer)			alimb |= (mpi_limb_t) *p-- << 56;#else#error please implement for this limb size.#endif		a->d[i++] = alimb;	}	a->nlimbs = i; 	if (i != nlimbs) {		pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,		       nlimbs);		BUG();	}	return 0;}EXPORT_SYMBOL_GPL(mpi_set_buffer);