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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "net/base/dns_util.h"
      6 
      7 #include <cstring>
      8 
      9 namespace net {
     10 
     11 // Based on DJB's public domain code.
     12 bool DNSDomainFromDot(const base::StringPiece& dotted, std::string* out) {
     13   const char* buf = dotted.data();
     14   unsigned n = dotted.size();
     15   char label[63];
     16   unsigned int labellen = 0; /* <= sizeof label */
     17   char name[255];
     18   unsigned int namelen = 0; /* <= sizeof name */
     19   char ch;
     20 
     21   for (;;) {
     22     if (!n)
     23       break;
     24     ch = *buf++;
     25     --n;
     26     if (ch == '.') {
     27       if (labellen) {
     28         if (namelen + labellen + 1 > sizeof name)
     29           return false;
     30         name[namelen++] = labellen;
     31         memcpy(name + namelen, label, labellen);
     32         namelen += labellen;
     33         labellen = 0;
     34       }
     35       continue;
     36     }
     37     if (labellen >= sizeof label)
     38       return false;
     39     label[labellen++] = ch;
     40   }
     41 
     42   if (labellen) {
     43     if (namelen + labellen + 1 > sizeof name)
     44       return false;
     45     name[namelen++] = labellen;
     46     memcpy(name + namelen, label, labellen);
     47     namelen += labellen;
     48     labellen = 0;
     49   }
     50 
     51   if (namelen + 1 > sizeof name)
     52     return false;
     53   if (namelen == 0) // Empty names e.g. "", "." are not valid.
     54     return false;
     55   name[namelen++] = 0;  // This is the root label (of length 0).
     56 
     57   *out = std::string(name, namelen);
     58   return true;
     59 }
     60 
     61 std::string DNSDomainToString(const base::StringPiece& domain) {
     62   std::string ret;
     63 
     64   for (unsigned i = 0; i < domain.size() && domain[i]; i += domain[i] + 1) {
     65 #if CHAR_MIN < 0
     66     if (domain[i] < 0)
     67       return std::string();
     68 #endif
     69     if (domain[i] > 63)
     70       return std::string();
     71 
     72     if (i)
     73       ret += ".";
     74 
     75     if (static_cast<unsigned>(domain[i]) + i + 1 > domain.size())
     76       return std::string();
     77 
     78     domain.substr(i + 1, domain[i]).AppendToString(&ret);
     79   }
     80   return ret;
     81 }
     82 
     83 std::string TrimEndingDot(const base::StringPiece& host) {
     84   base::StringPiece host_trimmed = host;
     85   size_t len = host_trimmed.length();
     86   if (len > 1 && host_trimmed[len - 1] == '.') {
     87     host_trimmed.remove_suffix(1);
     88   }
     89   return host_trimmed.as_string();
     90 }
     91 
     92 }  // namespace net
     93