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2e328c8591
Since a is not a pointer, it is passed by value and declaring it const doesn’t make any sense and on the first read can make me miss the fact that a is not a pointer. Signed-off-by: Janos Follath <janos.follath@arm.com>
159 lines
6.0 KiB
C
159 lines
6.0 KiB
C
/**
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* Core bignum functions
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*
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* This interface should only be used by the legacy bignum module (bignum.h)
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* and the modular bignum modules (bignum_mod.c, bignum_mod_raw.c). All other
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* modules should use the high-level modular bignum interface (bignum_mod.h)
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* or the legacy bignum interface (bignum.h).
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef MBEDTLS_BIGNUM_CORE_H
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#define MBEDTLS_BIGNUM_CORE_H
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#include "common.h"
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#if defined(MBEDTLS_BIGNUM_C)
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#include "mbedtls/bignum.h"
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#endif
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/** Count leading zero bits in a given integer.
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*
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* \param a Integer to count leading zero bits.
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*
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* \return The number of leading zero bits in \p a.
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*/
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size_t mbedtls_mpi_core_clz( mbedtls_mpi_uint a );
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/** Return the minimum number of bits required to represent the value held
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* in the MPI.
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*
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* \note This function returns 0 if all the limbs of \p A are 0.
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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*
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* \return The number of bits in \p A.
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*/
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size_t mbedtls_mpi_core_bitlen( const mbedtls_mpi_uint *A, size_t A_limbs );
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/** Convert a big-endian byte array aligned to the size of mbedtls_mpi_uint
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* into the storage form used by mbedtls_mpi.
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*
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* \param[in,out] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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*/
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void mbedtls_mpi_core_bigendian_to_host( mbedtls_mpi_uint *A,
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size_t A_limbs );
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/** Import X from unsigned binary data, little-endian.
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*
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* The MPI needs to have enough limbs to store the full value (including any
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* most significant zero bytes in the input).
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*
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* \param[out] X The address of the MPI.
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* \param X_limbs The number of limbs of \p X.
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* \param[in] input The input buffer to import from.
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* \param input_length The length bytes of \p input.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
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* large enough to hold the value in \p input.
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*/
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int mbedtls_mpi_core_read_le( mbedtls_mpi_uint *X,
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size_t X_limbs,
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const unsigned char *input,
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size_t input_length );
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/** Import X from unsigned binary data, big-endian.
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*
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* The MPI needs to have enough limbs to store the full value (including any
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* most significant zero bytes in the input).
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*
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* \param[out] X The address of the MPI.
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* May only be #NULL if \X_limbs is 0 and \p input_length
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* is 0.
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* \param X_limbs The number of limbs of \p X.
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* \param[in] input The input buffer to import from.
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* May only be #NULL if \p input_length is 0.
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* \param input_length The length in bytes of \p input.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
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* large enough to hold the value in \p input.
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*/
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int mbedtls_mpi_core_read_be( mbedtls_mpi_uint *X,
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size_t X_limbs,
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const unsigned char *input,
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size_t input_length );
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/** Export A into unsigned binary data, little-endian.
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*
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* \note If \p output is shorter than \p A the export is still successful if the
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* value held in \p A fits in the buffer (that is, if enough of the most
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* significant bytes of \p A are 0).
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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* \param[out] output The output buffer to export to.
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* \param output_length The length in bytes of \p output.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p output isn't
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* large enough to hold the value of \p A.
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*/
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int mbedtls_mpi_core_write_le( const mbedtls_mpi_uint *A,
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size_t A_limbs,
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unsigned char *output,
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size_t output_length );
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/** Export A into unsigned binary data, big-endian.
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*
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* \note If \p output is shorter than \p A the export is still successful if the
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* value held in \p A fits in the buffer (that is, if enough of the most
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* significant bytes of \p A are 0).
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*
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* \param[in] A The address of the MPI.
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* \param A_limbs The number of limbs of \p A.
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* \param[out] output The output buffer to export to.
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* \param output_length The length in bytes of \p output.
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*
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* \return \c 0 if successful.
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* \return #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p output isn't
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* large enough to hold the value of \p A.
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*/
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int mbedtls_mpi_core_write_be( const mbedtls_mpi_uint *A,
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size_t A_limbs,
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unsigned char *output,
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size_t output_length );
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#define ciL ( sizeof(mbedtls_mpi_uint) ) /* chars in limb */
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#define biL ( ciL << 3 ) /* bits in limb */
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#define biH ( ciL << 2 ) /* half limb size */
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/*
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* Convert between bits/chars and number of limbs
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* Divide first in order to avoid potential overflows
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*/
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#define BITS_TO_LIMBS(i) ( (i) / biL + ( (i) % biL != 0 ) )
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#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
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/* Get a specific byte, without range checks. */
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#define GET_BYTE( X, i ) \
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( ( (X)[(i) / ciL] >> ( ( (i) % ciL ) * 8 ) ) & 0xff )
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#endif /* MBEDTLS_BIGNUM_CORE_H */
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