third_party/re2/util/strutil.cc

   1 // Copyright 1999-2005 The RE2 Authors.  All Rights Reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 #include "util/util.h"
   6 #include "re2/stringpiece.h"
   7
   8 namespace re2 {
   9
  10 // ----------------------------------------------------------------------
  11 // CEscapeString()
  12 //    Copies 'src' to 'dest', escaping dangerous characters using
  13 //    C-style escape sequences.  'src' and 'dest' should not overlap.
  14 //    Returns the number of bytes written to 'dest' (not including the \0)
  15 //    or -1 if there was insufficient space.
  16 // ----------------------------------------------------------------------
  17 int CEscapeString(const char* src, int src_len, char* dest,
  18                   int dest_len) {
  19   const char* src_end = src + src_len;
  20   int used = 0;
  21
  22   for (; src < src_end; src++) {
  23     if (dest_len - used < 2)   // Need space for two letter escape
  24       return -1;
  25
  26     unsigned char c = *src;
  27     switch (c) {
  28       case '\n': dest[used++] = '\\'; dest[used++] = 'n';  break;
  29       case '\r': dest[used++] = '\\'; dest[used++] = 'r';  break;
  30       case '\t': dest[used++] = '\\'; dest[used++] = 't';  break;
  31       case '\"': dest[used++] = '\\'; dest[used++] = '\"'; break;
  32       case '\'': dest[used++] = '\\'; dest[used++] = '\''; break;
  33       case '\\': dest[used++] = '\\'; dest[used++] = '\\'; break;
  34       default:
  35         // Note that if we emit \xNN and the src character after that is a hex
  36         // digit then that digit must be escaped too to prevent it being
  37         // interpreted as part of the character code by C.
  38         if (c < ' ' || c > '~') {
  39           if (dest_len - used < 4) // need space for 4 letter escape
  40             return -1;
  41           sprintf(dest + used, "\\%03o", c);
  42           used += 4;
  43         } else {
  44           dest[used++] = c; break;
  45         }
  46     }
  47   }
  48
  49   if (dest_len - used < 1)   // make sure that there is room for \0
  50     return -1;
  51
  52   dest[used] = '\0';   // doesn't count towards return value though
  53   return used;
  54 }
  55
  56
  57 // ----------------------------------------------------------------------
  58 // CEscape()
  59 //    Copies 'src' to result, escaping dangerous characters using
  60 //    C-style escape sequences.  'src' and 'dest' should not overlap.
  61 // ----------------------------------------------------------------------
  62 string CEscape(const StringPiece& src) {
  63   const int dest_length = src.size() * 4 + 1; // Maximum possible expansion
  64   char* dest = new char[dest_length];
  65   const int len = CEscapeString(src.data(), src.size(),
  66                                 dest, dest_length);
  67   string s = string(dest, len);
  68   delete[] dest;
  69   return s;
  70 }
  71
  72 string PrefixSuccessor(const StringPiece& prefix) {
  73   // We can increment the last character in the string and be done
  74   // unless that character is 255, in which case we have to erase the
  75   // last character and increment the previous character, unless that
  76   // is 255, etc. If the string is empty or consists entirely of
  77   // 255's, we just return the empty string.
  78   bool done = false;
  79   string limit(prefix.data(), prefix.size());
  80   int index = limit.length() - 1;
  81   while (!done && index >= 0) {
  82     if ((limit[index]&255) == 255) {
  83       limit.erase(index);
  84       index--;
  85     } else {
  86       limit[index]++;
  87       done = true;
  88     }
  89   }
  90   if (!done) {
  91     return "";
  92   } else {
  93     return limit;
  94   }
  95 }
  96
  97 }  // namespace re2