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 98
