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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 // ----------------------------------------------------------------------
CEscapeString(const char * src,int src_len,char * dest,int dest_len)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 // ----------------------------------------------------------------------
CEscape(const StringPiece & src)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 
PrefixSuccessor(const StringPiece & prefix)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