make_fp.c

早期freebsd实现

/*
 * $Source: /mit/kerberos/src/lib/des/RCS/make_fp.c,v $
 * $Author: jtkohl $
 *
 * Copyright 1988 by the Massachusetts Institute of Technology.
 *
 * For copying and distribution information,
 * please see the file <mit-copyright.h>.
 *
 * This file contains a generation routine for source code
 * implementing the final permutation of the DES.
 */

#include <mit-copyright.h>
#include <stdio.h>
#include "des_internal.h"
#include "tables.h"

extern unsigned int swap_bit_pos_0_to_ansi PROTOTYPE((unsigned int));
extern long swap_long_bytes();
extern void test_set PROTOTYPE((FILE *, char const *, int,
				char const *, int));

void gen (stream)
    FILE * stream;
{
    register    i;

    /* clear the output */
    fprintf(stream,"    L2 = 0; R2 = 0;\n");

    /*
     *  NOTE: As part of the final permutation, we also have to adjust
     *  for host bit order via "swap_bit_pos_0()".  Since L2,R2 are
     *  the output from this, we adjust the bit positions written into
     *  L2,R2.
     */

#define SWAP(i,j) \
    swap_long_bytes_bit_number(swap_bit_pos_0_to_ansi((unsigned)i)-j)

    /* first setup FP */
    fprintf(stream,
            "/* FP operations */\n/* first left to left */\n");

    /* first list mapping from left to left */
    for (i = 0; i <= 31; i++)
        if (FP[i] < 32)
            test_set(stream, "L1", FP[i], "L2", SWAP(i,0));

    /* now mapping from right to left */
    fprintf(stream,"\n\n/* now from right to left */\n");
    for (i = 0; i <= 31; i++)
        if (FP[i] >= 32)
            test_set(stream, "R1", FP[i]-32, "L2", SWAP(i,0));

    fprintf(stream,"\n/* now from left to right */\n");

    /*  list mapping from left to right */
    for (i = 32; i <= 63; i++)
        if (FP[i] <32)
            test_set(stream, "L1", FP[i], "R2", SWAP(i,32));

    /* now mapping from right to right */
    fprintf(stream,"\n/* last from right to right */\n");
    for (i = 32; i <= 63; i++)
        if (FP[i] >= 32)
            test_set(stream, "R1", FP[i]-32, "R2", SWAP(i,32));
}