mpi_bin.c

#include "mpi_pvt.h"
#include <string.h>

int cry_mpi_load_bin(cry_mpi *x, const void *buf, size_t size)
{
    int res;
    size_t i, m;
    cry_mpi_digit d;
    unsigned char *p = (unsigned char *)buf;

    /* skip leading zeros */
    for (; size > 0 && *p == 0; p++, size--)
        NOP;
    if (size == 0) {
        cry_mpi_zero(x);
        return 0;
    }

    i = ((size - 1) / CRY_MPI_DIGIT_BYTES) + 1; /* Number of required octets */
    m =  (size - 1) % CRY_MPI_DIGIT_BYTES;      /* Remainder */

    if (x->alloc < i) {
        if ((res = cry_mpi_grow(x, i)) != 0)
            return res;
    }
    x->used = i;

    d = 0;
    while (size--) {
#if CRY_MPI_DIGIT_BITS > 8
        d <<= 8;
#endif
        d |= *p++;
        if (m-- == 0) {
            x->data[--i] = d;
            d = 0;
            m = CRY_MPI_DIGIT_BYTES - 1;
        }
    }
    return 0;
}

int cry_mpi_store_bin(const cry_mpi *x, void *buf,
                      size_t bufsiz, int pad)
{
    size_t i;
    cry_mpi_digit d;
    unsigned char *p = (unsigned char *)buf;

    i = cry_mpi_count_bytes(x);
    if (bufsiz < i)
        return CRY_ERROR_BAD_DATA;  /* Do not silently truncate */
    if (!pad)
        bufsiz = i;
    /* Add leading zeroes if necessary */
    if (bufsiz > i) {
        memset(p, 0, bufsiz - i);
        p += bufsiz - i;
    }
    while (i--) {
        d = x->data[i / CRY_MPI_DIGIT_BYTES];
        *p++ = (unsigned char)(d >> (8 * (i % CRY_MPI_DIGIT_BYTES))) & 0xff;
    }
    return 0;
}

int cry_mpi_init_bin(cry_mpi *x, const void *b, size_t size)
{
    int res;

    res = cry_mpi_init_size(x, CRY_MPI_BYTES_TO_DIGS(size));
    if (res == 0) {
        res = cry_mpi_load_bin(x, b, size);
        if (res != 0)
            cry_mpi_clear(x);
    }
    return res;
}