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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/lib/crypto/mpi/mpi-inline.h
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/* SPDX-License-Identifier: GPL-2.0-or-later */

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/* mpi-inline.h  -  Internal to the Multi Precision Integers

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 *	Copyright (C) 1994, 1996, 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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 * Note: This code is heavily based on the GNU MP Library.

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 *	 Actually it's the same code with only minor changes in the

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 *	 way the data is stored; this is to support the abstraction

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 *	 of an optional secure memory allocation which may be used

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 *	 to avoid revealing of sensitive data due to paging etc.

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 *	 The GNU MP Library itself is published under the LGPL;

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 *	 however I decided to publish this code under the plain GPL.

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 */

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#ifndef G10_MPI_INLINE_H

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#define G10_MPI_INLINE_H

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#ifndef G10_MPI_INLINE_DECL

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#define G10_MPI_INLINE_DECL  static inline

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#endif

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G10_MPI_INLINE_DECL mpi_limb_t

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mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,

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	      mpi_size_t s1_size, mpi_limb_t s2_limb)

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{

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	mpi_limb_t x;

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	x = *s1_ptr++;

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	s2_limb += x;

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	*res_ptr++ = s2_limb;

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	if (s2_limb < x) {	/* sum is less than the left operand: handle carry */

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		while (--s1_size) {

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			x = *s1_ptr++ + 1;	/* add carry */

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			*res_ptr++ = x;	/* and store */

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			if (x)	/* not 0 (no overflow): we can stop */

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				goto leave;

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		}

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		return 1;	/* return carry (size of s1 to small) */

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	}

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leave:

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	if (res_ptr != s1_ptr) {	/* not the same variable */

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		mpi_size_t i;	/* copy the rest */

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		for (i = 0; i < s1_size - 1; i++)

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			res_ptr[i] = s1_ptr[i];

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	}

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	return 0;		/* no carry */

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}

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G10_MPI_INLINE_DECL mpi_limb_t

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mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,

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	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)

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{

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	mpi_limb_t cy = 0;

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	if (s2_size)

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		cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);

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	if (s1_size - s2_size)

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		cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,

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				   s1_size - s2_size, cy);

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	return cy;

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}

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G10_MPI_INLINE_DECL mpi_limb_t

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mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,

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	      mpi_size_t s1_size, mpi_limb_t s2_limb)

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{

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	mpi_limb_t x;

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	x = *s1_ptr++;

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	s2_limb = x - s2_limb;

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	*res_ptr++ = s2_limb;

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	if (s2_limb > x) {

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		while (--s1_size) {

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			x = *s1_ptr++;

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			*res_ptr++ = x - 1;

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			if (x)

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				goto leave;

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		}

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		return 1;

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	}

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leave:

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	if (res_ptr != s1_ptr) {

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		mpi_size_t i;

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		for (i = 0; i < s1_size - 1; i++)

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			res_ptr[i] = s1_ptr[i];

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	}

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	return 0;

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}

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G10_MPI_INLINE_DECL mpi_limb_t

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mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,

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	    mpi_ptr_t s2_ptr, mpi_size_t s2_size)

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{

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	mpi_limb_t cy = 0;

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	if (s2_size)

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		cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);

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	if (s1_size - s2_size)

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		cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,

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				   s1_size - s2_size, cy);

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	return cy;

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}

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#endif /*G10_MPI_INLINE_H */

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