mdw@git.distorted.org.uk Git - become/blob - src/tx.c

   1 /* -*-c-*-
   2  *
   3  * $Id: tx.c,v 1.2 1997/08/04 10:24:25 mdw Exp $
   4  *
   5  * Transfer for keys and other large integers
   6  *
   7  * (c) 1997 Mark Wooding
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of `become'
  13  *
  14  * `Become' is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * `Become' is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with `become'; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: tx.c,v $
  32  * Revision 1.2  1997/08/04 10:24:25  mdw
  33  * Sources placed under CVS control.
  34  *
  35  * Revision 1.1  1997/07/21  13:47:43  mdw
  36  * Initial revision
  37  *
  38  */
  39
  40 /*----- Header files ------------------------------------------------------*/
  41
  42 /* --- ANSI headers --- */
  43
  44 #include <errno.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48
  49 /* --- Local headers --- */
  50
  51 #include "config.h"
  52 #include "tx.h"
  53
  54 /*----- Main code ---------------------------------------------------------*/
  55
  56 /* --- @tx_getBits@ --- *
  57  *
  58  * Arguments:   @unsigned char *k@ = pointer to key array to unpack into
  59  *              @size_t sz@ = number of bits to read (elements in array)
  60  *              @FILE *fp@ = stream to read from
  61  *
  62  * Returns:     ---
  63  *
  64  * Use:         Reads a number of bits into an array.  The least significant
  65  *              bits of the final word are cleared to zero.
  66  */
  67
  68 void tx_getBits(unsigned char *k, size_t sz, FILE *fp)
  69 {
  70   int i = 0;
  71   unsigned char a = 0;
  72   unsigned int ch;
  73   size_t wsz = (size_t)((sz + 7ul) & ~7ul);
  74   int t;
  75
  76   while ((t = getc(fp)) != EOF) {
  77
  78     /* --- Allow separators for readbility --- */
  79
  80     if (t == '-')
  81       continue;
  82
  83     /* --- Standard converting-from-hex-digit code --- *
  84      *
  85      * Assumes that 'a'--'f' and 'A'--'F' are contiguous and in order, in
  86      * addition to the guarantee that '0'--'9' are like this.  The assumption
  87      * is true in ASCII (and character sets based thereon) and EBCDIC.
  88      */
  89
  90     ch = (unsigned)t;
  91     ch -= '0';
  92     if (ch > 9) ch -= 'A' - '0' - 10;
  93     if (ch > 15) ch -= 'a' - 'A';
  94     if (ch > 15) break;
  95
  96     /* --- Accumulate and maybe store --- */
  97
  98     a = (a << 4) | ch;
  99     i++;
 100     sz -= 4, wsz -= 4;
 101     if ((i & 1) == 0)
 102       *k++ = a, a = 0;
 103     if (!sz)
 104       break;
 105   }
 106
 107   /* --- Pad the rest out with zeros --- */
 108
 109   while (wsz) {
 110     a <<= 4;
 111     i++;
 112     wsz -= 4;
 113     if ((i & 1) == 0)
 114       *k++ = a, a = 0;
 115   }
 116 }
 117
 118 /* --- @tx_putBits@ --- *
 119  *
 120  * Arguments:   @unsigned char *k@ = pointer to key block
 121  *              @size_t sz@ = number of bits to write
 122  *              @FILE *fp@ = pointer to stream to write on
 123  *
 124  * Returns:     ---
 125  *
 126  * Use:         Complements @tx_getBits@ above.  Writes a number of bits
 127  *              to a file in an easy-to-read and transportable format (hex!)
 128  */
 129
 130 void tx_putBits(unsigned char *k, size_t sz, FILE *fp)
 131 {
 132   const static char hex[16] = "0123456789abcdef";
 133   size_t dash;
 134   size_t d;
 135   unsigned char i;
 136
 137   /* --- Don't do anything unless we have to --- */
 138
 139   if (!sz)
 140     return;
 141
 142   /* --- Now decide where to `dash' the output --- */
 143
 144   if (sz % 32 == 0)
 145     dash = 4;
 146   else if (sz % 40 == 0)
 147     dash = 5;
 148   else
 149     dash = 0;
 150
 151   /* --- Start writing values out --- */
 152
 153   d = dash;
 154
 155   for (;;) {
 156
 157     /* --- Write next byte out --- */
 158
 159     i = *k++;
 160     putc(hex[(i >> 4) & 0x0fu], fp);
 161     putc(hex[(i >> 0) & 0x0fu], fp);
 162
 163     /* --- If done, stop now --- */
 164
 165     if (sz -= 8, sz == 0)
 166       break;
 167
 168     /* --- If need a dash, print one --- */
 169
 170     if (!--d) {
 171       putc('-', fp);
 172       d = dash;
 173     }
 174   }
 175
 176   /* --- Print the final newline --- */
 177
 178   fputc('\n', fp);
 179 }
 180
 181 /*----- That's all, folks -------------------------------------------------*/