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

   1 /* -*-c-*-
   2  *
   3  * $Id: tx.c,v 1.3 1998/01/12 16:46:31 mdw Exp $
   4  *
   5  * Transfer for keys and other large integers
   6  *
   7  * (c) 1998 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 1.3  1998/01/12 16:46:31  mdw
  33  * Fix copyright date.
  34  *
  35  * Revision 1.2  1997/08/04 10:24:25  mdw
  36  * Sources placed under CVS control.
  37  *
  38  * Revision 1.1  1997/07/21  13:47:43  mdw
  39  * Initial revision
  40  *
  41  */
  42
  43 /*----- Header files ------------------------------------------------------*/
  44
  45 /* --- ANSI headers --- */
  46
  47 #include <errno.h>
  48 #include <stdio.h>
  49 #include <stdlib.h>
  50 #include <string.h>
  51
  52 /* --- Local headers --- */
  53
  54 #include "config.h"
  55 #include "tx.h"
  56
  57 /*----- Main code ---------------------------------------------------------*/
  58
  59 /* --- @tx_getBits@ --- *
  60  *
  61  * Arguments:   @unsigned char *k@ = pointer to key array to unpack into
  62  *              @size_t sz@ = number of bits to read (elements in array)
  63  *              @FILE *fp@ = stream to read from
  64  *
  65  * Returns:     ---
  66  *
  67  * Use:         Reads a number of bits into an array.  The least significant
  68  *              bits of the final word are cleared to zero.
  69  */
  70
  71 void tx_getBits(unsigned char *k, size_t sz, FILE *fp)
  72 {
  73   int i = 0;
  74   unsigned char a = 0;
  75   unsigned int ch;
  76   size_t wsz = (size_t)((sz + 7ul) & ~7ul);
  77   int t;
  78
  79   while ((t = getc(fp)) != EOF) {
  80
  81     /* --- Allow separators for readbility --- */
  82
  83     if (t == '-')
  84       continue;
  85
  86     /* --- Standard converting-from-hex-digit code --- *
  87      *
  88      * Assumes that 'a'--'f' and 'A'--'F' are contiguous and in order, in
  89      * addition to the guarantee that '0'--'9' are like this.  The assumption
  90      * is true in ASCII (and character sets based thereon) and EBCDIC.
  91      */
  92
  93     ch = (unsigned)t;
  94     ch -= '0';
  95     if (ch > 9) ch -= 'A' - '0' - 10;
  96     if (ch > 15) ch -= 'a' - 'A';
  97     if (ch > 15) break;
  98
  99     /* --- Accumulate and maybe store --- */
 100
 101     a = (a << 4) | ch;
 102     i++;
 103     sz -= 4, wsz -= 4;
 104     if ((i & 1) == 0)
 105       *k++ = a, a = 0;
 106     if (!sz)
 107       break;
 108   }
 109
 110   /* --- Pad the rest out with zeros --- */
 111
 112   while (wsz) {
 113     a <<= 4;
 114     i++;
 115     wsz -= 4;
 116     if ((i & 1) == 0)
 117       *k++ = a, a = 0;
 118   }
 119 }
 120
 121 /* --- @tx_putBits@ --- *
 122  *
 123  * Arguments:   @unsigned char *k@ = pointer to key block
 124  *              @size_t sz@ = number of bits to write
 125  *              @FILE *fp@ = pointer to stream to write on
 126  *
 127  * Returns:     ---
 128  *
 129  * Use:         Complements @tx_getBits@ above.  Writes a number of bits
 130  *              to a file in an easy-to-read and transportable format (hex!)
 131  */
 132
 133 void tx_putBits(unsigned char *k, size_t sz, FILE *fp)
 134 {
 135   const static char hex[16] = "0123456789abcdef";
 136   size_t dash;
 137   size_t d;
 138   unsigned char i;
 139
 140   /* --- Don't do anything unless we have to --- */
 141
 142   if (!sz)
 143     return;
 144
 145   /* --- Now decide where to `dash' the output --- */
 146
 147   if (sz % 32 == 0)
 148     dash = 4;
 149   else if (sz % 40 == 0)
 150     dash = 5;
 151   else
 152     dash = 0;
 153
 154   /* --- Start writing values out --- */
 155
 156   d = dash;
 157
 158   for (;;) {
 159
 160     /* --- Write next byte out --- */
 161
 162     i = *k++;
 163     putc(hex[(i >> 4) & 0x0fu], fp);
 164     putc(hex[(i >> 0) & 0x0fu], fp);
 165
 166     /* --- If done, stop now --- */
 167
 168     if (sz -= 8, sz == 0)
 169       break;
 170
 171     /* --- If need a dash, print one --- */
 172
 173     if (!--d) {
 174       putc('-', fp);
 175       d = dash;
 176     }
 177   }
 178
 179   /* --- Print the final newline --- */
 180
 181   fputc('\n', fp);
 182 }
 183
 184 /*----- That's all, folks -------------------------------------------------*/