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

   1 /* -*-c-*-
   2  *
   3  * $Id: tx.c,v 1.1 1997/07/21 13:47:43 mdw Exp $
   4  *
   5  * Transfer for keys and other large integers
   6  *
   7  * (c) 1997 Mark Wooding
   8  */
   9
  10 /*----- Licencing 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
  26  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  27  */
  28
  29 /*----- Revision history --------------------------------------------------*
  30  *
  31  * $Log: tx.c,v $
  32  * Revision 1.1  1997/07/21 13:47:43  mdw
  33  * Initial revision
  34  *
  35  */
  36
  37 /*----- Header files ------------------------------------------------------*/
  38
  39 /* --- ANSI headers --- */
  40
  41 #include <errno.h>
  42 #include <stdio.h>
  43 #include <stdlib.h>
  44 #include <string.h>
  45
  46 /* --- Local headers --- */
  47
  48 #include "config.h"
  49 #include "tx.h"
  50
  51 /*----- Main code ---------------------------------------------------------*/
  52
  53 /* --- @tx_getBits@ --- *
  54  *
  55  * Arguments:   @unsigned char *k@ = pointer to key array to unpack into
  56  *              @size_t sz@ = number of bits to read (elements in array)
  57  *              @FILE *fp@ = stream to read from
  58  *
  59  * Returns:     ---
  60  *
  61  * Use:         Reads a number of bits into an array.  The least significant
  62  *              bits of the final word are cleared to zero.
  63  */
  64
  65 void tx_getBits(unsigned char *k, size_t sz, FILE *fp)
  66 {
  67   int i = 0;
  68   unsigned char a = 0;
  69   unsigned int ch;
  70   size_t wsz = (size_t)((sz + 7ul) & ~7ul);
  71   int t;
  72
  73   while ((t = getc(fp)) != EOF) {
  74
  75     /* --- Allow separators for readbility --- */
  76
  77     if (t == '-')
  78       continue;
  79
  80     /* --- Standard converting-from-hex-digit code --- *
  81      *
  82      * Assumes that 'a'--'f' and 'A'--'F' are contiguous and in order, in
  83      * addition to the guarantee that '0'--'9' are like this.  The assumption
  84      * is true in ASCII (and character sets based thereon) and EBCDIC.
  85      */
  86
  87     ch = (unsigned)t;
  88     ch -= '0';
  89     if (ch > 9) ch -= 'A' - '0' - 10;
  90     if (ch > 15) ch -= 'a' - 'A';
  91     if (ch > 15) break;
  92
  93     /* --- Accumulate and maybe store --- */
  94
  95     a = (a << 4) | ch;
  96     i++;
  97     sz -= 4, wsz -= 4;
  98     if ((i & 1) == 0)
  99       *k++ = a, a = 0;
 100     if (!sz)
 101       break;
 102   }
 103
 104   /* --- Pad the rest out with zeros --- */
 105
 106   while (wsz) {
 107     a <<= 4;
 108     i++;
 109     wsz -= 4;
 110     if ((i & 1) == 0)
 111       *k++ = a, a = 0;
 112   }
 113 }
 114
 115 /* --- @tx_putBits@ --- *
 116  *
 117  * Arguments:   @unsigned char *k@ = pointer to key block
 118  *              @size_t sz@ = number of bits to write
 119  *              @FILE *fp@ = pointer to stream to write on
 120  *
 121  * Returns:     ---
 122  *
 123  * Use:         Complements @tx_getBits@ above.  Writes a number of bits
 124  *              to a file in an easy-to-read and transportable format (hex!)
 125  */
 126
 127 void tx_putBits(unsigned char *k, size_t sz, FILE *fp)
 128 {
 129   const static char hex[16] = "0123456789abcdef";
 130   size_t dash;
 131   size_t d;
 132   unsigned char i;
 133
 134   /* --- Don't do anything unless we have to --- */
 135
 136   if (!sz)
 137     return;
 138
 139   /* --- Now decide where to `dash' the output --- */
 140
 141   if (sz % 32 == 0)
 142     dash = 4;
 143   else if (sz % 40 == 0)
 144     dash = 5;
 145   else
 146     dash = 0;
 147
 148   /* --- Start writing values out --- */
 149
 150   d = dash;
 151
 152   for (;;) {
 153
 154     /* --- Write next byte out --- */
 155
 156     i = *k++;
 157     putc(hex[(i >> 4) & 0x0fu], fp);
 158     putc(hex[(i >> 0) & 0x0fu], fp);
 159
 160     /* --- If done, stop now --- */
 161
 162     if (sz -= 8, sz == 0)
 163       break;
 164
 165     /* --- If need a dash, print one --- */
 166
 167     if (!--d) {
 168       putc('-', fp);
 169       d = dash;
 170     }
 171   }
 172
 173   /* --- Print the final newline --- */
 174
 175   fputc('\n', fp);
 176 }
 177
 178 /*----- That's all, folks -------------------------------------------------*/