Clients/ClientCommon.c

   1 /* -*- Mode: C; tab-width: 4 -*-
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  40
  41 #include <ctype.h>
  42 #include <stdio.h>          // For stdout, stderr
  43
  44 #include "ClientCommon.h"
  45
  46 const char *GetNextLabel(const char *cstr, char label[64])
  47 {
  48     char *ptr = label;
  49     while (*cstr && *cstr != '.')               // While we have characters in the label...
  50     {
  51         char c = *cstr++;
  52         if (c == '\\')                          // If escape character, check next character
  53         {
  54             if (*cstr == '\0') break;           // If this is the end of the string, then break
  55             c = *cstr++;
  56             if (isdigit(cstr[-1]) && isdigit(cstr[0]) && isdigit(cstr[1]))
  57             {
  58                 int v0 = cstr[-1] - '0';                        // then interpret as three-digit decimal
  59                 int v1 = cstr[ 0] - '0';
  60                 int v2 = cstr[ 1] - '0';
  61                 int val = v0 * 100 + v1 * 10 + v2;
  62                 // If valid three-digit decimal value, use it
  63                 // Note that although ascii nuls are possible in DNS labels
  64                 // we're building a C string here so we have no way to represent that
  65                 if (val == 0) val = '-';
  66                 if (val <= 255) { c = (char)val; cstr += 2; }
  67             }
  68         }
  69         *ptr++ = c;
  70         if (ptr >= label+64) { label[63] = 0; return(NULL); }   // Illegal label more than 63 bytes
  71     }
  72     *ptr = 0;                                                   // Null-terminate label text
  73     if (ptr == label) return(NULL);                             // Illegal empty label
  74     if (*cstr) cstr++;                                          // Skip over the trailing dot (if present)
  75     return(cstr);
  76 }