external/ibm-public/postfix/dist/src/global/off_cvt.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      off_cvt 3
   6 /* SUMMARY
   7 /*      off_t conversions
   8 /* SYNOPSIS
   9 /*      #include <off_cvt.h>
  10 /*
  11 /*      off_t   off_cvt_string(string)
  12 /*      const char *string;
  13 /*
  14 /*      VSTRING *off_cvt_number(result, offset)
  15 /*      VSTRING *result;
  16 /*      off_t   offset;
  17 /* DESCRIPTION
  18 /*      This module provides conversions between \fIoff_t\fR and string.
  19 /*
  20 /*      off_cvt_string() converts a string, containing a non-negative
  21 /*      offset, to numerical form. The result is -1 in case of problems.
  22 /*
  23 /*      off_cvt_number() converts a non-negative offset to string form.
  24 /*
  25 /*      Arguments:
  26 /* .IP string
  27 /*      String with non-negative number to be converted to off_t.
  28 /* .IP result
  29 /*      Buffer for storage of the result of conversion to string.
  30 /* .IP offset
  31 /*      Non-negative off_t value to be converted to string.
  32 /* DIAGNOSTICS
  33 /*      Panic: negative offset
  34 /* LICENSE
  35 /* .ad
  36 /* .fi
  37 /*      The Secure Mailer license must be distributed with this software.
  38 /* AUTHOR(S)
  39 /*      Wietse Venema
  40 /*      IBM T.J. Watson Research
  41 /*      P.O. Box 704
  42 /*      Yorktown Heights, NY 10598, USA
  43 /*--*/
  44
  45 /* System library. */
  46
  47 #include <sys_defs.h>
  48 #include <ctype.h>
  49
  50 /* Utility library. */
  51
  52 #include <msg.h>
  53 #include <vstring.h>
  54
  55 /* Global library. */
  56
  57 #include "off_cvt.h"
  58
  59 /* Application-specific. */
  60
  61 #define STR     vstring_str
  62 #define END     vstring_end
  63 #define SWAP(type, a, b) { type temp; temp = a; a = b; b = temp; }
  64
  65 /* off_cvt_string - string to number */
  66
  67 off_t   off_cvt_string(const char *str)
  68 {
  69     int     ch;
  70     off_t   result;
  71     off_t   res2;
  72     off_t   res4;
  73     off_t   res8;
  74     off_t   res10;
  75
  76     /*
  77      * Multiplication by numbers > 2 can overflow without producing a smaller
  78      * result mod 2^N (where N is the number of bits in the result type).
  79      * (Victor Duchovni, Morgan Stanley).
  80      */
  81     for (result = 0; (ch = *(unsigned char *) str) != 0; str++) {
  82         if (!ISDIGIT(ch))
  83             return (-1);
  84         if ((res2 = result + result) < result)
  85             return (-1);
  86         if ((res4 = res2 + res2) < res2)
  87             return (-1);
  88         if ((res8 = res4 + res4) < res4)
  89             return (-1);
  90         if ((res10 = res8 + res2) < res8)
  91             return (-1);
  92         if ((result = res10 + ch - '0') < res10)
  93             return (-1);
  94     }
  95     return (result);
  96 }
  97
  98 /* off_cvt_number - number to string */
  99
 100 VSTRING *off_cvt_number(VSTRING *buf, off_t offset)
 101 {
 102     static char digs[] = "0123456789";
 103     char   *start;
 104     char   *last;
 105     int     i;
 106
 107     /*
 108      * Sanity checks
 109      */
 110     if (offset < 0)
 111         msg_panic("off_cvt_number: negative offset -%s",
 112                   STR(off_cvt_number(buf, -offset)));
 113
 114     /*
 115      * First accumulate the result, backwards.
 116      */
 117     VSTRING_RESET(buf);
 118     while (offset != 0) {
 119         VSTRING_ADDCH(buf, digs[offset % 10]);
 120         offset /= 10;
 121     }
 122     VSTRING_TERMINATE(buf);
 123
 124     /*
 125      * Then, reverse the result.
 126      */
 127     start = STR(buf);
 128     last = END(buf) - 1;
 129     for (i = 0; i < VSTRING_LEN(buf) / 2; i++)
 130         SWAP(int, start[i], last[-i]);
 131     return (buf);
 132 }
 133
 134 #ifdef TEST
 135
 136  /*
 137   * Proof-of-concept test program. Read a number from stdin, convert to
 138   * off_t, back to string, and print the result.
 139   */
 140 #include <vstream.h>
 141 #include <vstring_vstream.h>
 142
 143 int     main(int unused_argc, char **unused_argv)
 144 {
 145     VSTRING *buf = vstring_alloc(100);
 146     off_t   offset;
 147
 148     while (vstring_fgets_nonl(buf, VSTREAM_IN)) {
 149         if ((offset = off_cvt_string(STR(buf))) < 0) {
 150             msg_warn("bad input %s", STR(buf));
 151         } else {
 152             vstream_printf("%s\n", STR(off_cvt_number(buf, offset)));
 153         }
 154         vstream_fflush(VSTREAM_OUT);
 155     }
 156     vstring_free(buf);
 157     return (0);
 158 }
 159
 160 #endif